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Running one on a 10.25:1 L31 with a aftermarket Vortecs with beehive springs, GM 6492 cam, 1.6 rockers and used all the Proflow 4150 parts on the manifold itself. Thorley tri-ys into a dual 2.5" exhaust. It is all in a 1987 G20 van with a TH400 that has the stock converter and a 3.08 gear. The Mercruiser manifold makes more torque than the Proflow 4150 manifold ever thought about. By comparison the single plane was horrible.
Here is a screen shot launching that van about as hard as I could without a smoke show from the right rear do to the open differential. Brought it up on the converter, walked it off the line, then hammered it. With the gearing it will run ~60 mph in 1st. So roughly a 0-60. I found I can use a screen capture app to record the PF4 Tuner data screen and capture the interior audio at the same time. Kind of slick because you can hear how the engine sounds in realtime with the recorded data which is a step up from a normal datalog.
Was able to get some mandrel bent 2.5" tailpipes over the axle this morning. The L31 350 sounds pretty darn good now too and fairly quiet cruising around with the windows up and the ac cranked up.
The duty cycle is only hitting 60% - ish. Which isnt bad but I would have expected higher. What are the port sizes on that intake? Any pics?
Many of these L31 Vortec head port injected builds run around 0.400 BSFC rather than the rule of thumb 0.450, so lower injector duty cycle is kind of expected to me. The stock 22.1# MPFI upgrade spider from my L31 running 70 psi for 24.6#, supported ~450 hp on my 383, feeding it up to ~5,000 rpm.
Not sure if I have any but will look. The ports match very well to the Etec170 fiber gaskets and the manifold design itself is virtually identical to a square bore vortec performer rpm. It actually looks like a performer rpm cast in cast iron with injector bungs added to the casting.
The Mercruiser manifold makes more torque than the Proflow 4150 manifold ever thought about. By comparison the single plane was horrible.
There is no magic in the "mercruiser" dual plane intake. Where's the before and after dyno graphs?? Why'd you use Vortec's when 113's are vastly superior to 4500? I don't get it.
There is no magic in the "mercruiser" dual plane intake. Where's the before and after dyno graphs?? Why'd you use Vortec's when 113's are vastly superior to 4500? I don't get it.
Because I did not have a good set of 113s laying around. I had a good set of 180cc aftermarket vortecs laying around. I was initially going to run this engine with a L31 injection system on it and even had it bolted on and started re-working a later model P59 Astro van harness before I found the PF4 system.
There absolutely is a big difference in the dual plane manifold, much more torque than the single plane. It is stalling the same converter over 200 rpm higher. The manifold dynamics in regard to the airflow inertia and resonance tuning effects do not magically change when you put injector bungs in the end of the ports. Dual plane makes more torque than a single plane regardless if it is a wet manifold or a dry one.
This was a comparison of a dual plane vs single plane on a LS, both with port injection. The dual plane had dual 1,000 cfm 4150 throttle bodies on it and the single plane had a single 1,000 cfm 4150, not that it mattered at that power level. That is a victor jr vs holley dual quad dual plane manifold. That LS is down 60 ft/lbs at 3,000 rpm with the victor jr compared to the dual plane, so I am not the only claim of this! After the big fat torque gain in the midrange, the dual plane still effectively matched the single plane through 6,500.
The old SBC saw an almost identical change dual plane mercruiser vs the junk 4150 single plane. The dual plane is better everywhere under 5,000 rpm and much more responsive at part-throttle off-idle when accelerating from a stop. Under 3,000 rpm it is a night and day difference in how the engine runs, similar to the difference between the manifolds and the tri-ys. With the dual plane and tri-ys it is a completely different engine. From a stop it absolutely anhilates the right rear tire now if you jump on the throttle too hard.
I have printouts from the runs, but not going to post them because it was an under the table set of runs and the printouts have the shop name in the background of the graphs. I do not want to get my dyno operater friend in trouble for messing with my stuff on a day off while the shop was closed. He has permission to run the dyno tuning his stuff but mine was on a day the shop was closed and he was working up there, the owner probably does not care but I am not willing to take that chance and mess up his ability to work on a day the shop is closed or my avenue for dyno tuning my stuff.
Before I found the PF4 system this is how I had already set up the engine, it has an EFI Connection 24x reluctor behind the timing cover as well. I was going to run CNP to start with, then bounced between it and the L31 distributor.
Awww.... I wanted to see YOUR b4 and after....not some graph of who know's what (looks like it says "Dual Quad" and "Vic Jr"), off the 'net. As you were.
Last edited by Tom 400 CFI; 04-25-2024 at 03:54 PM.
Awww.... I wanted to see YOUR b4 and after....not some graph of who know's what (looks like it says "Dual Quad" and "Vic Jr"), off the 'net. As you were.
My gain was 40 tq at the tire at 2,500 and the dual plane had more torque to 5,000 rpm, then pretty much overlayed the single plane to 5,800 rpm. I also played with a taper spacer on the dual plane. Upside down it was worth about 8 whp compared to the TB bolted right on to the dual plane manifold and no loss of torque anywhere because it did not change the air/fuel ratio unlike spacers under a carb. Dual plane plus spacer had equal power to the single plane from 5,000-5,800 rpm. I do not care about anything over 5,800 rpm because the cam is done well before that.
Graphs. I'm a visual guy so I LOVE graphs! Graphs are fun. Colorful. Interesting. I dig 'em.
It's incredible that OEM's started designing all new, single plane intakes w/the advent of MPFI....when they already had these massive TORK MONSTAH intakes already on their shelves! Crazy.
Graphs. I'm a visual guy so I LOVE graphs! Graphs are fun. Colorful. Interesting. I dig 'em.
It's incredible that OEM's started designing all new, single plane intakes w/the advent of MPFI....when they already had these massive TORK MONSTAH intakes already on their shelves! Crazy.
Its funny that a marine engine that actually requires torque never uses a single plane either. They are always using some kind of dual plane or port fuel injected manifold with longer runners. Even the Indmar manifold I have that has tunnel ram style ports has runners substantially longer than other similar offerings like say a LT1 or Ramjet manifold. The later GM marine manifold is virtually identical to a L31 truck manifold and has runners longer than a crossfire manifold because it promotes torque.
I actually decided to find one of the dual plane MPFI manifolds after a Gearhead-EFI member used one on his S10 build. More than one marine engine owner has made 450+ hp and loads of torque using the dual plane MPFI manifolds as well. Saw a 9:1 marine 383 build with Etec 170s make over 500 ft/lbs with one a couple of years ago.
The S10 guy had a L31 350 with some head work and a Comp 08-502-8 in it. Claimed 389 rwhp and 422 rwtq on a Dynojet with the combination.
Mine through a TH400 in 2nd gear, screaming a clutch fan still put down 348 rwhp @ 5,300 and 387 rwtq @ 3,100 rpm. My GM 6492 cam is a lot smaller as well than that 08-502-8. I need to get it back on the dyno with the tri-ys. Just need to come up with an air cleaner duct for the 454 TBI air cleaner I have to get it plenty of nice cool air. The TBI SBC air cleaner and intake duct are restricting it with 1.6 in/hg of manifold vacuum built at 5,500 rpm.
A buddy of mine is running the first merc dual plane, along with an Edelbrock plenum I also had to run a 92mm LS throttle body on his L31 350 that has a 3.50" stroke crank in place of the stock one that had spun a couple of rod bearings. Has some ported vortecs, a LT4 hotcam and 1.6 rockers. The truck makes gobs of torque across the whole RPM range. He plans to turbo it at some point.
Wait. 113’s are superior to Vortec heads?? When did this happen? Or are you being facetious?
Right?? It's pretty mind blowing, isn't it? He (fast) actually believes this stuff. Or pretends to? Hard to say. Whatever the motive, it's material that's pretty hard to swallow. GM had a head (the 113) that "made more tq than anything ever in history from 0-4500 RPM....so they went and designed a head w/clean sheet port design, that makes LESS tq from 0-4500....for a 0-4500 truck motor. Makes sense!....doesn't it....?
Originally Posted by Fast355
Its funny that a marine engine that actually requires torque never uses a single plane either.
It's not funny, b/c it's not true. Marine engines almost exclusively use a "single plane" intake. They used (recycled) dual planes for a short time. Likely for economic reasons and ease of getting to market w/"EFI".
Originally Posted by Fast355
The later GM marine manifold is virtually identical to a L31 truck manifold and has runners longer than a crossfire manifold because it promotes torque.
Wait....WHUT!?? I thought the CFI was ALL about "low end tork"...it's not good for anything else. Ignore that. The "Marine L31" has what we'd call "mid length runner". Very much like HSR length, and way, WAY shorter than TPI. Shouldn't the marine industry have used a TPI intake on Marine engines??
BTW, nearly all MPFI intakes ARE, single plane intakes. They're packaged/configured/different looking than yer typical old-skool thinking mind goes to when you see "single plane", but they are, single plane intakes.
Last edited by Tom 400 CFI; 04-25-2024 at 10:26 PM.
Wait. 113’s are superior to Vortec heads?? When did this happen? Or are you being facetious?
The 113s ARE superior to Vortecs under 4,500 rpm on the same short block. Hell TBI heads even make more torque than the Vortecs do under ~4,500 rpm.
You would have had to read the thread. I suggested 113s for an 1987 LG4 build because they work very well with their 58cc chambers.
Find the Goodwrench Quest article CHP did around 2000. The L98 aluminum heads had 4% more average torque than the GOOD production Vortecs did and only lost out power wise to them over about 4,500-5,000 rpm. By comparison the Mexican Vortecs are down everywhere.
Right?? It's pretty mind blowing, isn't it? He (fast) actually believes this stuff. Or pretends to? Hard to say. Whatever the motive, it's material that's pretty hard to swallow. GM had a head (the 113) that "made more tq than anything ever in history from 0-4500 RPM....so they went and designed a head w/clean sheet port design, that makes LESS tq from 0-4500....for a 0-4500 truck motor. Makes sense!....doesn't it....?
It's not funny, b/c it's not true. Marine engines almost exclusively use a "single plane" intake. They used (recycled) dual planes for a short time. Likely for economic reasons and ease of getting to market w/"EFI".
Wait....WHUT!?? I thought the CFI was ALL about "low end tork"...it's not good for anything else. Ignore that. The "Marine L31" has what we'd call "mid length runner". Very much like HSR length, and way, WAY shorter than TPI. Shouldn't the marine industry have used a TPI intake on Marine engines??
BTW, nearly all MPFI intakes ARE, single plane intakes. They're packaged/configured/different looking than yer typical old-skool thinking mind goes to when you see "single plane", but they are, single plane intakes.
Well think what you want. IDGAF to be honest. The dual plane far outperforms the single plane in the RPM range I am using it in. Even gave you the dyno chart of a head to head manifold comparison on a Holley dual plane vs victor jr on a LS with both being MPFI and the dual plane blew the single plane away in that test too.
Since you are so smart, if the dual plane approach did not work, why does Holley build and offer one and rate it with a a 1,000 rpm lower starting rpm range than the single plane. The dual plane is rated 1,500-7,000 rpm and the single plane 2,500-7,000. Dyno testing of the Holley single plane showed 24 ft/lbs more torque at lower rpm than the Victor Jr as well in that manifold shootout I pulled that chart from. Maybe you can take Holleys word for it and not mine.
Since you like colorful, squigly lines I remembered another dual plane MPFI manifold that has been tested against a single plane MPFI manifold on a 360 Magnum. Mopar Performance sold the M1 single plane that was allegidly performance oriented to replace the stock long runner barrel intake that had sealing issues in the belly pan. Hughes performance came out with a dual plane similar to the performer rpm air gap after Mopar discontinued the M1s. They have been tested back to back on the same engine and dyno. The M1 was available as both a 2bbl and 4bbl flange. The stock kegger manifold is also on this graph. Hughes dual plane MPFI air gap manifold beat out all of them and it was not even close. At 3,000 rpm on the stock 360 magnum that closely matches the L31 350 in overall setup and power, the dual plane made more than the long runner truck manifold and was nearly 40 hp up at the wheels up on the Mopar Performance single planes. 40 hp @ 3,000 rpm is ~70 ft/lbs of torque more than the single plane. On the 360 magnum with the stock roller cam the dual plane even made more peak HP than the single plane. As I said before the single vs dual plane characteristics do not suddenly change when fuel injectors are hung on the end of the ports. The 4bbl single plane and the dual plane were also still dead even in power production at 5,500. My brothers 98 R/T Dakota had the M1 2bbl on it when he purchased it. We moded a stock kegger from the local junkyard, added a hughes aluminum belly pan and it was a much torquier truck to drive and fuel mileage improved substantially. Out of those intake choices on the 360, I can tell you which one is going to get the truck down the track the quickest and it is not the single planes or the long runner stock manifold. The kegger even modified also suffers from a case of asthma like a stock TPI does at higher rpm.
The Mercruiser dual plane also kicks the PF4 4150 single plane manifold in the pants torque wise and it is not even close. Big gain in useable torque.
Well Fast....at least your providing good, solid, objective data for us. Internet graphs of who-knows-what, Misguided terminology (understanding of single plane (360*) and dual plane (180*) intakes), "some other guy's truck" producing who-knows-what....and best of all, the end results! The "Gobs of tork-o-meter". The "It RIPS-o-meter". The "kicks in the pants-o-meter". And lets not for get...the famous....PEEL-O-METER! How far you were able to do a 1 tire fryer.
The random pictures of random "things" really help drive your points home, too. A random intake, taken of the 'net. Some junky looking van, from somewhere? A video of a tachometer going...up? A pic of "this guy's engine" in a truck....it's all clear now! It's a LOT of rhetoric...that's for sure.
Why didn't the Marine biz put TPI on 113's in boats? Thing would have ripped the outdrives right off the transoms! How come they're not still using dual planes? They're giving up all that pants-kicking TORK!! :bigears:
Last edited by Tom 400 CFI; 04-26-2024 at 09:10 AM.
Well Fast....at least your providing good, solid, objective data for us. Internet graphs of who-knows-what, Misguided terminology (understanding of single plane (360*) and dual plane (180*) intakes), "some other guy's truck" producing who-knows-what....and best of all, the end results! The "Gobs of tork-o-meter". The "It RIPS-o-meter". The "kicks in the pants-o-meter". And lets not for get...the famous....PEEL-O-METER! How far you were able to do a 1 tire fryer.
The random pictures of random "things" really help drive your points home, too. A random intake, taken of the 'net. Some junky looking van, from somewhere? A video of a tachometer going...up? A pic of "this guy's engine" in a truck....it's all clear now! It's a LOT of rhetoric...that's for sure.
Why didn't the Marine biz put TPI on 113's in boats? Thing would have ripped the outdrives right off the transoms! How come they're not still using dual planes? They're giving up all that pants-kicking TORK!! :bigears:
Marine engines did use 113s but only with closed cooling systems.
Get over yourself Tom. I gave you two solid dyno graphs of dual planes making substantially more torque than single planes with port injection on the same engine. They were not random images, they were exact tests on what your refuse to want to believe. Not my loss! Test one yourself sometime or STFU and stop chasing me thread to thread.
Also consider what you are saying is totally wrong. If the runner design and resonance tuning effect did not change the torque production, your mini-ram test should have made equal torque to your Super Ram test and it did not. The dual plane has a resonance effect within the runners, making the overall runner length much longer than a single plane. The reflected wave on the dual plane runners is what helps them boost torque.
All "your" internet-sourced graphs on irrelevant engines are....worthless. This **** is cookoo.
I've shown how to test intakes, in my thread; my dyno sheets, my tests, same engine, back to back. No hyperbole. Back to "story time".
Dual plane vs single plane is fairly the same regardless what engine you test it on. The dual plane MPFI manifold has a very flat torque curve compared to a single plane. Not a ton of data on them for a SBC since the only way to get one is from an old boat. They work, you are just afraid to admit you are wrong.
Here is a dual plane MPFI on a 360 Magnum with a 236/242 on a 110 with nearly 0.600 lift cam. Torque curve of the MPFI dual plane based off the rpm airgap is table top flat. I may have to pickup an air gap and build my own MPFI conversion of one by adding injector bungs seeing the results of the Mopar unit. I am driving a 4,500 lbs box on wheels with a TH400, stock torque converter and 3.08 gears and it is still getting to 60 mph in under 6 seconds with a mild L31 350. It is making torque.
Dual plane vs single plane is fairly the same regardless what engine you test it on. The dual plane MPFI manifold has a very flat torque curve compared to a single plane. Not a ton of data on them for a SBC since the only way to get one is from an old boat. They work, you are just afraid to admit you are wrong.
I'm not "afraid" of anything. I know dual plane intakes work. They've worked, just "fine" for nearly 100 years. What I also know, is that they don't do what you portray them as being able to do. Along w/most of the other outlandish claims that you make....then back up with OTHER PEOPLE's crap. Crap which we and you know nothing about. Questionable case study...at BEST. Totally irrelevant, in most cases. See below....
Originally Posted by Fast355
Here is a dual plane MPFI on a 360 Magnum with a 236/242 on a 110 with nearly 0.600 lift cam. Torque curve of the MPFI dual plane based off the rpm airgap is table top flat. I may have to pickup an air gap and build my own MPFI conversion of one by adding injector bungs seeing the results of the Mopar unit. I am driving a 4,500 lbs box on wheels with a TH400, stock torque converter and 3.08 gears and it is still getting to 60 mph in under 6 seconds with a mild L31 350. It is making torque.
^There we go.^ Random dude, random truck. Just pick some YT vid and throw it up there to make what point? What ever the alternative reality, assertion-of-the-day is, I guess. Whatever. Give'r hell dude. Van the **** out of it.
Last edited by Tom 400 CFI; 04-26-2024 at 03:08 PM.
Same engine -a Chevy, in this 'net sourced pair of vids. Both making just about the exact same tq at the start of the pull, ~2900-3000....not surprisingly, the MID length dual plane make ~15 more peak/midrange tq.....buuuuut...then (also not surprisingly), by ~4300 it's game over for the dual plane and from there on out, the stock, single plane kicks the dual plane in the pants. RIPS it a new one. More area under the curve. Absolutely destroys it! And just look at that "Table top flat" tork curve for the single plane....finishing w/a decimating, 27hp over the dual plane.
Yep, there is no "magic" in a dual plane intake; not even a super-special, used boat one. Dual planes do what they've always done; proved a better signal to CARBS, at lower RPM. Take the carb out of the pic and there is no reason to run a dual plane (because it's a dual plane) over any other similar runner length intake. All you're doing is cutting your available throttle body to any given cylinder, in 1/2.
Same engine -a Chevy, in this 'net sourced pair of vids. Both making just about the exact same tq at the start of the pull, ~2900-3000....not surprisingly, the MID length dual plane make ~15 more peak/midrange tq.....buuuuut...then (also not surprisingly), by ~4300 it's game over for the dual plane and from there on out, the stock, single plane kicks the dual plane in the pants. RIPS it a new one. More area under the curve. Absolutely destroys it! And just look at that "Table top flat" tork curve for the single plane....finishing w/a decimating, 27hp over the dual plane.
Yep, there is no "magic" in a dual plane intake; not even a super-special, used boat one. Dual planes do what they've always done; proved a better signal to CARBS, at lower RPM. Take the carb out of the pic and there is no reason to run a dual plane (because it's a dual plane) over any other similar runner length intake. All you're doing is cutting your available throttle body to any given cylinder, in 1/2.
Not with a tapered spacer. A spacer allows both plenums of the manifold to be fed by the whole throttle body.There is a good reason to run a dual plane. Not everyone blast down the road everywhere at 4,300+ rpm all time. The dual plane with the spacer matched the single plane until fuel kill on this engine, dual plane gained 40 ft/lbs at the tires at 2,500. Guess which intake is staying on the van. The dual plane, it has noticeably better low-speed torque and makes the combination much more responsive especially off-idle. You mention runner length, a dual plane has substantially longer effective runner length than a single plane does. The reflected tuning wave is not largely dissapated in the plenum area like it is on an open plenum single plane. It bounces from end to end and makes the effective runner length 2-3x longer than a single plane, hence the added low speed torque. In that test a MPFI dual plane would also benifit by having an ECM control the mixture and timing. The 8 LS coils also offer more spark energy and could be adding some additional hp at high rpm.
The dual plane a full 1/2 second off the 0-60 in a 4,500 lbs G-van with a TH400 and a 3.08 gear.
You mention runner length, a dual plane has substantially longer effective runner length than a single plane does.
Yeah? You sure about that? What's the runner length on your "marine" dual plane? What's the runner length on TPI?
Originally Posted by Fast355
In that test a MPFI dual plane would also benifit by having an ECM control the mixture and timing.
Probably not. It's a WOT pull. I have confidence that RH did the jetting and set the timing for max peaks...at least. Wishful thinking.
Originally Posted by Fast355
The 8 LS coils also offer more spark energy and could be adding some additional hp at high rpm.
No. Ignition doesn't add ****. That's just desparately grabbing at straws, there, buddy. We already know that from 100+ years of engines with ignitions, on planet earth. BTW, both engines used a single coil and distributor...so...where's this LS coil thing coming from, anyway?? Cookoo.
Originally Posted by Fast355
The dual plane a full 1/2 second off the 0-60 in a 4,500 lbs G-van with a TH400 and a 3.08 gear.
Awesome. No one here GAF about vans, TH400's or crappy gears. There is no magic in the dual plane. It's a nearly 100 year old design that is good at some stuff.
Last edited by Tom 400 CFI; 05-12-2024 at 12:07 PM.
Yeah? You sure about that? What's the runner length on your "marine" dual plane? What's the runner length on TPI?
Probably not. It's a WOT pull. I have confidence that RH did the jetting and set the timing for max peaks...at least. Wishful thinking.
No. Ignition doesn't add ****. That's just desparately grabbing at straws, there, buddy. We already know that from 100+ years of engines with ignitions, on planet earth. BTW, both engines used a single coil and distributor...so...where's this LS coil thing coming from, anyway?? Cookoo.
Awesome. No one here GAF about vans, TH400's or crappy gears. There is no magic in the dual plane. It's a nearly 100 year old design that is good at some stuff.
To be honest, I do not GAF what you think you know. Fact remains the dual plane made substantially more torque at lower rpm than a single plane both with MPFI. The dual plane unlike TPI is also not a tuned length runner, so each runner has a different RPM where it resonates, which flattens the overall torque curve compared to TPI that peaks at a tuned RPM range. Most of these cars had a 2.73 or 3.08 gear and are not the lightest vehicles on the road either and added low-speed torque will make the car feel lighter and more responsive. The added low-speed torque means the engine spends less time in the lower gears to get the same acceleration rate which saves fuel.
It has also been proven numerous times that the CNP substantially improves HP vs a single coil. A single coil does not have adequate time to fully charge at high rpm where 8 individual coils do. CD will increase the voltage but does nothing for the spark duration. Here is an actual test showing a dramatic improvement from the CNP swap.
Sure thing bud! I just posted to help the unwitting who might have the misfortune of reading this crap, and fall for your "marine minutiae". Keep up the stories about the "One Tire Fryers"
Sure thing bud! I just posted to help the unwitting who might have the misfortune of reading this crap, and fall for your "marine minutiae". Keep up the stories about the "One Tire Fryers"
Those of us that actually know about intake design and how an engine actually works laugh at your lack of knowledge. Those of us that actually tune GM ECMs laugh at your lack of understanding there too.
A single plane and dual plane manifold does exactly what it does with a carb with injection bungs on the end of either. The booster signal is not the only reason the dual plane works better at lower engine speeds.
OK. Here's a question that seems on topic. And it's it's not asked for any other reason than gathering opinions.
Case in point. My 357. Carbureted.
I've flowed the heads (the head porters flow bench). Measured all the critical dimensions in them as well as the shortblock. They're small but tick all of the boxes for this engine size and application.
Had my cam spec'd by Jones Cams with a converter that should stall around 4000 and have a predicted peak HP RPM at or around 6200. It's a drag racing deal where whatever happens at RPMs less than the stall are inconsequential. Best estimates, through Jones, is that it should carry well to 6500 (as I requested).
This is all based on running an RPM Air Gap dual plane manifold.
Would I see a benefit with a single plane? My take on that is torque would be down at the stall RPM, so less stall as a result and less TQ to get the car moving. It may however carry a little better past the targeted shift point.
That's the traditional perspective anyway. Many racers I've chatted with have demonstrated more trap speed with a open spacer on the dual plane and in back to backs, outperform the single plane tested within the rev range I've presented.
OK. Here's a question that seems on topic. And it's it's not asked for any other reason than gathering opinions.
Case in point. My 357. Carbureted.
I've flowed the heads. Measured all the critical in them as well as the shortblock. Had my cam spec'd by Jones Cams with a converter that should stall around 4000 and have a predicted peak HP RPM at or around 6200. It's a drag racing deal where whatever happens at RPMs less than the stall are inconsequential. Best estimates, through Jones is that it should well to 6500.
This is all based on running an RPM Air Gap dual plane manifold.
Would I see a benefit with a single plane? My take on that is that torque would be down at the stall RPM, so less stall as a result and less TQ to get the car moving. It may however carry a little better past the targeted shift point.
That's the traditional perspective anyway. Many racers I've chatted with have demonstrated more trap speed with a open spacer on the dual plane and in back to backs, outperform the single plane tested within the rev range I've presented.
What the thinking here?
I have seen a good dual plane like you mention typically outperform any single plane under 6,500. Eric Weingarner has some interestings tests and findings on the engine dyno with multiple intakes on the same engine.
Those of us that actually know about intake design and how an engine actually works laugh at your lack of knowledge. Those of us that actually tune GM ECMs laugh at your lack of understanding there too.
A single plane and dual plane manifold does exactly what it does with a carb with injection bungs on the end of either. The booster signal is not the only reason the dual plane works better at lower engine speeds.
what’s laughable is the very thing you accuse me of, lack of knowledge of how components work, you reinforce in yourself, every time you post to the Forum. It’s pretty bad. Then you back up your data with videos of attack, bragging rights of one tire, peel, outs, and other worthless junk like that. Those are the metrics we all used when we were 18 years old. Most of us moved onto dynamometers, or at least the dragstrip…. and most of the people who know what they’re doing back up their claims with real data. You should check it out.😂👍
OK. Here's a question that seems on topic. And it's it's not asked for any other reason than gathering opinions.
Case in point. My 357. Carbureted.
I've flowed the heads (the head porters flow bench). Measured all the critical dimensions in them as well as the shortblock. They're small but tick all of the boxes for this engine size and application.
Had my cam spec'd by Jones Cams with a converter that should stall around 4000 and have a predicted peak HP RPM at or around 6200. It's a drag racing deal where whatever happens at RPMs less than the stall are inconsequential. Best estimates, through Jones, is that it should carry well to 6500 (as I requested).
This is all based on running an RPM Air Gap dual plane manifold.
Would I see a benefit with a single plane? My take on that is torque would be down at the stall RPM, so less stall as a result and less TQ to get the car moving. It may however carry a little better past the targeted shift point.
That's the traditional perspective anyway. Many racers I've chatted with have demonstrated more trap speed with a open spacer on the dual plane and in back to backs, outperform the single plane tested within the rev range I've presented.
What the thinking here?
I would run the dual plan RPM intake on your combo with the carburetor.
I have seen a good dual plane like you mention typically outperform any single plane under 6,500. Eric Weingarner has some interestings tests and findings on the engine dyno with multiple intakes on the same engine.
This I'm hopeful for. The dragstrip will tell the tale but then again, I'm not breaking new territory here. I've confidence in that my heap will on par with the guys that tested this kind of combination before. There'll be spacer test for sure. I'm somewhat hesitant to invest in and possbily no use a single plane intake but that's always an option.
As for Weingartner, I read his test results with great interest. He almost tested my combination but just fell short with his selection of dual planes (IIRC).
I would run the dual plan RPM intake on your combo with the carburetor.
That's the plan. As mentioned above, a spacer test even if it's just to say I did it.
Carb is arguably on the small at 750 CFM. Being an original Barry Grant, that may be spec'd on the low side though. Some will argue the vacuum secondary isn't ideal but that's where I've my own results that indicate that isn't necessarily the case. There's just another level of tuning involved.
Anyway, thanks for that gentlemen.
Back to our regularly scheduled discussion...
what’s laughable is the very thing you accuse me of, lack of knowledge of how components work, you reinforce in yourself, every time you post to the Forum. It’s pretty bad. Then you back up your data with videos of attack, bragging rights of one tire, peel, outs, and other worthless junk like that. Those are the metrics we all used when we were 18 years old. Most of us moved onto dynamometers, or at least the dragstrip…. and most of the people who know what they’re doing back up their claims with real data. You should check it out.😂👍
Except I did do the dyno testing and know exactly where it gained and how much it gained. I also made some 0-60 mph tests and it is 1/2 second quicker to 60 than it was with the single plane.
I also find it interesting that the test Holdener made on the dual plane vs LT1 short runner EFI manifold offered a drastically different result than the 383 test you referenced earlier. On a cammed L99 the dual plane was worth a huge improvement in torque.
Buddy of mine just acquired one of these manifolds and put it on his 1998 K1500 in place of the stock Vortec manifold. He has a fresh flat top piston L31 with a 6492 cam, 1.6 rockers and long tubes. Manifold woke that truck up everywhere. Loaded up with tools it is about 7,000 lbs and the manifold knocked a good bit off the 0-60 time. The MAF is reading nearly 30 gms/sec more airflow from 3,500+. The 6492 cam does not really wake up fully until 2,500+ but the manifold added torque and hp everywhere compared to the stock crossram manifold with the injector spider inside.
Man, that sounds awesome. What was GM thinking, throwing away the dual planes they'd used for 45+ years, and replacing them all with single planes/tuned length runner intakes??
Originally Posted by Fast355
Buddy of mine.... woke that truck up everywhere.
knocked a good bit off the 0-60 time.
the manifold added torque and hp everywhere
Awesome metrics. Gotta love the good 'ol SOTP meter!!.....
Man, that sounds awesome. What was GM thinking, throwing away the dual planes they'd used for 45+ years, and replacing them all with single planes/tuned length runner intakes??
Maybe it IS faster w/that intake. Who knows? Doesn't seem like you know. We don't know. Makes for a great car-guy/beers story, though.
I know it is quicker because I have seen numerous datalogs of both. Even at 1/2 throttle the engine is making a lot more torque. Same throttle body and same air intake the dual plane is moving over 40 gms/sec more airflow while making 10 kpa more manifold vacuum at basically the same throttle opening. At WOT it stalls the same torque converter over 300 rpm higher from a stop.
Up for grabs! The TOWAH, of POWAH! The TOWAK MONSTAH of the TOW BOATS! The WINNAH of the WATTAH WAYS!!
Even though every marine engine OE has switched to MPFI, it is actually this thing, that is the KING OF THE KASTLE!! Just look at it....drool over it.....LUST FOR IT!!!
This thing is the real deal guys. It's got a little hair on it's ***, It's got a boater's body, good face, good jaw, the thing has an attitude an attitude is good, I mean, this is the kind of intake that when it walks in to a room.... This is the eye-candy intake that snuck past all of us! We should put this thing into the 10 X THE TORK TEST where it can smoke 'em all! The intake from the '90's that no one knew they wanted!
Last edited by Tom 400 CFI; 08-08-2024 at 09:23 PM.
Up for grabs! The TOWAH, of POWAH! The TOWAK MONSTAH of the TOW BOATS! The WINNAH of the WATTAH WAYS!!
Even though every marine engine OE has switched to MPFI, it is actually this thing, that is the KING OF THE KASTLE!! Just look at it....drool over it.....LUST FOR IT!!!
This thing is the real deal guys. It's got a little hair on it's ***, It's got a boater's body, good face, good jaw, the thing has an attitude an attitude is good, I mean, this is the kind of intake that when it walks in to a room.... This is the eye-candy intake that snuck past all of us! We should put this thing into the 10 X THE TORK TEST where it can smoke 'em all! The intake from the '90's that no one knew they wanted!
Laugh if you want that is actually a very good intake manifold you have there. It is worth some money with the dirt track guys. Probably $250-350 the way it sits without the carb. The manifold I am running is MPFI.
They actually are a very good intake if you want or need to run a cast iron intake. Two versions of this intake with the same part number. One for 1955 to 1986/91 bolt pattern and one for the 1987 to 1995 bolt pattern. Cash in hand no shipping involved realistic price is about $225 to $250. I sure price varies by region too. That's about what one goes for around here in the Southeast.
Yeah? How good is "very good"? What'll it do? And I'm not talking how long it'll one-wheel-peel....
I have no doubt that "if you need a Iron intake" (class racing), it's may be one of the best options for an artificially limited class (?). Is it better than all the single plane, equal length/tuned length runner MPFI (since that apparently has to be clarified) intakes that came after it? 'Cause that's what's being played in this thread. I'd bet.....no.
People around here that want them is because of the "cast iron intake" rule.
This is what the Internet says about them.
"This Bow Tie part is the best stock cast iron (casting #14096242) 4 barrel manifold available.
In stock form it will produce more power between 4500 and 7000 rpm than any other stock Chevy manifold. Commonly referred to as a “Marine” intake, this manifold is a cast-iron copy of a LT-1 high rise aluminum intake. The marine intake is equipped with both carburetor bolt patterns, is 1.250" taller than regular intakes and was not available – in cast iron form – on any production cars.
In stock form this intake will out perform stock Q-Jet and 2 barrel manifolds in most applications where the engine is running between 4500 and 7000 rpm. Because of its huge internal volume, the Marine Intake lacks throttle response below 4500 rpm compared to other stock intakes."
Interesting. That doesn't appear to match up to claims earlier in the thread about "more tq everywhere", and "boats need tq". Sounds great for dirt track'n though.
Well...someone who loves marine parts and old-tech dual planes should buy this thing. No doubt it's a legend!
I actually decided to find one of the dual plane MPFI manifolds after a Gearhead-EFI member used one on his S10 build. More than one marine engine owner has made 450+ hp and loads of torque using the dual plane MPFI manifolds as well. Saw a 9:1 marine 383 build with Etec 170s make over 500 ft/lbs with one a couple of years ago.
The S10 guy had a L31 350 with some head work and a Comp 08-502-8 in it. Claimed 389 rwhp and 422 rwtq on a Dynojet with the combination.
Mine through a TH400 in 2nd gear, screaming a clutch fan still put down 348 rwhp @ 5,300 and 387 rwtq @ 3,100 rpm. My GM 6492 cam is a lot smaller as well than that 08-502-8. I need to get it back on the dyno with the tri-ys. Just need to come up with an air cleaner duct for the 454 TBI air cleaner I have to get it plenty of nice cool air. The TBI SBC air cleaner and intake duct are restricting it with 1.6 in/hg of manifold vacuum built at 5,500 rpm.
Ayyyyyy....I'm that S10 guy. Btw, I've dyno'd a bunch of different intakes on my setup now, including a Chinese knock off 4150 single plane. My motor is the exact same still, minus now being a 383.
That single plane made 20+ more TQ across the ENTIRE RPM band after tuning. Running the same tune as that dual plane it was down almost 60tq but HP was comparable. Injector timing made the biggest difference while tuning that knockoff single plane.
I've dyno'd the following intakes on my setup: Stock spider injector intake(350)
Proform junk short runner single plane(350)
Mercruiser dual plane(350 and 383)
Holley 300-263 short runner single plane(383)
Edelbrock Pro Flow XT tunnel ram style.(383)
Edelbrock Victor E-Tec short runner single plane(383)
And the one that made the most power, both in peak and average HP and TQ across the entire RPM band with the 383, the MasterCraft MCX Vortec H.O. manifold. This one's another boat intake, but is a long runner single plane with a big open plenum.
I'm sure if I was turning more RPM than 5800-6000 those short runner single plane intakes would take the lead for peak numbers.
But for my very mild build, this one works the best.
Ayyyyyy....I'm that S10 guy. Btw, I've dyno'd a bunch of different intakes on my setup now, including a Chinese knock off 4150 single plane. My motor is the exact same still, minus now being a 383.
That single plane made 20+ more TQ across the ENTIRE RPM band after tuning. Running the same tune as that dual plane it was down almost 60tq but HP was comparable. Injector timing made the biggest difference while tuning that knockoff single plane.
I've dyno'd the following intakes on my setup: Stock spider injector intake(350)
Proform junk short runner single plane(350)
Mercruiser dual plane(350 and 383)
Holley 300-263 short runner single plane(383)
Edelbrock Pro Flow XT tunnel ram style.(383)
Edelbrock Victor E-Tec short runner single plane(383)
And the one that made the most power, both in peak and average HP and TQ across the entire RPM band with the 383, the MasterCraft MCX Vortec H.O. manifold. This one's another boat intake, but is a long runner single plane with a big open plenum.
I'm sure if I was turning more RPM than 5800-6000 those short runner single plane intakes would take the lead for peak numbers.
But for my very mild build, this one works the best.
I have that same intake as well with the 90mm 4-bolt LS style lid. I have messed around with injection timing changes on multiple setups. I have yet to see it make any real difference on any setup except in idle and low load, part throttle drivability. WOT it made ZERO change for me after adjusting the AFR to match what it was. I have run them with the Boundary as low as 5.5 and as high as 7.5. I have found setting for 6.5 boundary and a 6.3 Normal/Makeup warmed up has worked well on numerous setups. 6.5 boundary is BDC on the intake stroke for reference. I have used the same value as the boundary to as much as 1.0 difference in the Normal and Makeup tables. Would love to hear what the magic formula is there to gain nearly 60 ft/lbs from injection timing because I have just not even seen a 10 ft/lb difference on anything with a huge range of change in the adjustments and that was easily brought back tp the baseline value adjusting the fueling for the change that the injection timing made. Over 6.5 on the Boundary tends to cause a massive lean tip-in as well while the calculators show I should be over 7.5 with my cam profile. I am not calling you a liar by any means but I want to know how you realized those gains and take another stab at it myself if it in fact made that much of a difference. I feel like it maybe so numb to change on the setups I have tested it on because the duty cycle on the ones I have tested is fairly high, in the 60-75% range. Past 3,000-3,500 rpm the duty cycle pushes the injection timing values into the overlap period anyway. Idle and low load I have seen it shift fueling 10-15% or even more optimizing the values to deliver the target air/fuel ratio on the least amount of fuel though.
Single plane out performing the dual plane across the whole RPM range on a 350 is NOT happening. If you are starting a pull at perhaps 3,500 rpm on a healthy 383 I could see the single plane doing as you claim, lock the converter and start the pull at 1,500 rpm, not a chance in the world the single plane is doing better. I pulled a single plane off and put a dual plane in its place and instantly had a lot more torque with nothing else changed. Off-Idle to 4,000+ RPM it is a completely different engine and even flash stalls the same converter to a higher rpm. With a TH400 and a 3.08 gear the torque was a welcomed addition. I have both manifolds and have run both, not like I have a dozen of the dual plane manifolds I am trying to sell someone either. I am going to a single plane on a 383 but that is a different story entirely and for a different reason. I am purposely trying to kill off some low-midrange cylinder pressure in that setup. This is what it cranks with the other 7 plugs still in it even after removing the Rhoads V-Max lifters it had in it. The new cam going into this engine also has a later IVC. I moved from an area that had cheap, plentiful E70 testing E85 to one that 91+ is $4.00/gal. My goal is to be able to run 89 at most.
04-22-2024, 08:34 PM
This is the eye-candy intake that snuck past all of us! We should put this thing into the 10 X THE TORK TEST where it can smoke 'em all! The intake from the '90's that no one knew they wanted! 
