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Tech / General EngineIs your car making a strange sound or won't start? Thinking of adding power with a new combination? Need other technical information or engine specific advice? Don't see another board for your problem? Post it here!
After reading the article in the link I became seriously interested in building an aluminum headed 406"+ with 10.5:1 compression and hydraulic roller cam that would produce 15"+ of vacuum. Please note that I intend to paint entire engine
305? Maybe or Maybe Not? 😎😎😎
black and top it off with my black ported and polished ZZ4 intake, Cliff's Performance prepared CC Quadrajet, then hide it under my L69 air cleaner and emissions equipment.
I realize that this type of engine build isn't popular, but at my age driveability and air conditioning are mandatory.
I say go for it. Quality parts, big engine and driveability big yes. I would probably also upgrade to a 4bbl EFI system so you cna keep the cleaner and have better driveability
Most of your fairly modern lobe hyd rollers in the 230 deg range at .050” will get that kind of vacuum and be very smooth idle. With a dual plane intake it also will be a good match rpm wise to the combo.
The big cubes and restricted induction wont need alot of cam anyway. It will make tons of off idle torque
I had a afr 195 head 9:1 400” with a lazier 233 deg lobe and it idled near 14-15” from what i remember. My big head 400” with a 246 deg hyd roller made 10-11”
Most of your fairly modern lobe hyd rollers in the 230 deg range at .050” will get that kind of vacuum and be very smooth idle. With a dual plane intake it also will be a good match rpm wise to the combo.
The big cubes and restricted induction wont need alot of cam anyway. It will make tons of off idle torque
I had a afr 195 head 9:1 400” with a lazier 233 deg lobe and it idled near 14-15” from what i remember. My big head 400” with a 246 deg hyd roller made 10-11”
Excellent advice thank you. I am strongly considering a Comp XE276HR.....your opinion please
Yeah that would work and be mild driving. Proven to be a good cam in alot of applications from 350 to 400+, although most common in a 350-383. It will idle very smooth especially if you get the 112 lsa vs 110 but either is fine on big cubes
Yeah that would work and be mild driving. Proven to be a good cam in alot of applications from 350 to 400+, although most common in a 350-383. It will idle very smooth especially if you get the 112 lsa vs 110 but either is fine on big cubes
Nothing wrong with wanting a smooth idle and good street manners. I'm only 44, but loud mufflers, smelly exhaust and rumpity cams are no longer my thing anymore either... Which is why eventually I want to get in to the 427 sbc club... huge power but mild manners.
Back when I had my old speed shop, we offered three series of engines, the Street Sleeper, the Street Stalker, and the Street Killer. The 406 Street Sleeper with 10.89:1 and TFS G1 aluminum heads ran on 93 octane (in 1997) pump gas, idled smoothly at 650rpm with the custom hydraulic flat tappet (268/276 218/228 .489/.506 on a 110 spread) and pulled 17”. That was with a vacuum advance distributor with 12-degrees base timing. It could easily pass as a 305 HO with headers and exhaust until you stepped on the gas.
I used that same cam in a 9.8:1, 355 and was able to pull 18” of vacuum at 700rpm with a little creative timing around idle from a self-burned chip for the electronically controlled ignition. While I’d still call the idle smooth, you could tell the 355 had a mild cam in it.
I think the code has been busted for the computer controlled carbs and if that’s the case, and you can burn your own chips, you should be able to make in excess of 17” with the HR276 you posted in a 10+:1 406. I used to "super-tune" those CCC back in the day and was very successfully getting them to run well on 406s with cams in the 230 duration range without having to do a lot of modifications on the carb.
Back when I had my old speed shop, we offered three series of engines, the Street Sleeper, the Street Stalker, and the Street Killer. The 406 Street Sleeper with 10.89:1 and TFS G1 aluminum heads ran on 93 octane (in 1997) pump gas, idled smoothly at 650rpm with the custom hydraulic flat tappet (268/276 218/228 .489/.506 on a 110 spread) and pulled 17”. That was with a vacuum advance distributor with 12-degrees base timing. It could easily pass as a 305 HO with headers and exhaust until you stepped on the gas.
I used that same cam in a 9.8:1, 355 and was able to pull 18” of vacuum at 700rpm with a little creative timing around idle from a self-burned chip for the electronically controlled ignition. While I’d still call the idle smooth, you could tell the 355 had a mild cam in it.
I think the code has been busted for the computer controlled carbs and if that’s the case, and you can burn your own chips, you should be able to make in excess of 17” with the HR276 you posted in a 10+:1 406. I used to "super-tune" those CCC back in the day and was very successfully getting them to run well on 406s with cams in the 230 duration range without having to do a lot of modifications on the carb.
Cliffs Performance prepared my CC Quadrajet. I am seriously considering XE276HR on a 112 or a very similar grind from Howards. Your Street Sleeper biild is definitely the type of engine combination that I have in mind.
If you change the LSA for a given cam grind, then you change more than that regarding the cam specs.
I think you will find that spreading the LSA will give you the opposite results of what you're looking for. Typically the larger the cubic inches for a given cylinder head, the tighter you want the LSA. The 110° listed in Comps catalogue is very general. You can get specific with your combination. Your 406 would probably like 106° to make the most peak torque.
Now having said that, if you like the XR2786HR, (which I ran with a Vortec headed 353 for quite a while) then work with the overlap that cam has. The overlap will determine where the torque peak is and will also give you the idle quality you're after both in terms of the amount of lope and the vacuum produced. There's obviously more to it than that, ignition timing specifically, but it's a starting point.
The 276 has ~ 60° overlap. Take the 106 LSA and using this equation: 2(106 + (60/2)) = the duration value you're after. Result: 272°. Whether you choose a single pattern cam vs a split will depend on the efficiency of your exhaust system. That being the exhaust port right through to the tailpipes. If you have weak cylinder heads on the exhaust (e.g. Vortec) or a crappy small diameter single muffler (like me) then a split duration may add something.
This is along the lines of what Mike Jones or Terry Walter (via David Vizard) might spec for you torque monster. At least as far as the anecdotal information I've gathered over the years and my own experiences.
EDIT: This is Gen 1 SBC OEM valve angle with 2.02" intake and decent valve seat angles.
Back when I had my old speed shop, we offered three series of engines, the Street Sleeper, the Street Stalker, and the Street Killer. The 406 Street Sleeper with 10.89:1 and TFS G1 aluminum heads ran on 93 octane (in 1997) pump gas, idled smoothly at 650rpm with the custom hydraulic flat tappet (268/276 218/228 .489/.506 on a 110 spread) and pulled 17”. That was with a vacuum advance distributor with 12-degrees base timing. It could easily pass as a 305 HO with headers and exhaust until you stepped on the gas.
I used that same cam in a 9.8:1, 355 and was able to pull 18” of vacuum at 700rpm with a little creative timing around idle from a self-burned chip for the electronically controlled ignition. While I’d still call the idle smooth, you could tell the 355 had a mild cam in it.
I think the code has been busted for the computer controlled carbs and if that’s the case, and you can burn your own chips, you should be able to make in excess of 17” with the HR276 you posted in a 10+:1 406. I used to "super-tune" those CCC back in the day and was very successfully getting them to run well on 406s with cams in the 230 duration range without having to do a lot of modifications on the carb.
Were you running a carb on that 355 with 18" Hg vacuum? If not, what manifold?
With my miniram and a 262 cam I can barely muster 15" at 700 in neutral. It idles smooth though but I'm still surprised you were able to get that much vacuum with s bigger cam.
Ignition timing has a lot to do with it too. Any cammed SBC can easily absorb 25° of idle timing. The difference in idle: quality, reduced RPM, engine temps and vacuum is noteworthy.
Were you running a carb on that 355 with 18" Hg vacuum? If not, what manifold?
With my miniram and a 262 cam I can barely muster 15" at 700 in neutral. It idles smooth though but I'm still surprised you were able to get that much vacuum with s bigger cam.
The 355 was fuel injected and pulled the same vacuum running a ported stock base with SLP runner, the FIRST, and a StealthRam. I could break out the old laptop to make sure, but seems like I had a total of around 19-degrees timing plugged in at idle and had to add and bring total timing in a lot faster with the StealthRam compared to the LTR intakes.
Comp's web page on the XE262 gives an example of it in a 9.25:1, 356 with a 3310, 750 Holley making 17.5" vacuum at 800rpm. Mine had a little more compression and while it doesn't indicate the ignition system or settings, I'd venture to say I probably had a little more timing than their example. http://www.compcams.com/v002/Pages/387/XE262H-10.aspx
If you change the LSA for a given cam grind, then you change more than that regarding the cam specs.
I think you will find that spreading the LSA will give you the opposite results of what you're looking for. Typically the larger the cubic inches for a given cylinder head, the tighter you want the LSA. Your 406 would probably like 106°.
Now having said that, if you like the XR2786HR, (which I ran with a Vortec headed 353 for quite a while) then work with the overlap that cam has. The overlap will determine where the torque peak is and will also give you the idle quality you're after both in terms of the amount of lope and the vacuum produced. There's obviously more to it than that, ignition timing specifically, but it's a starting point.
The 276 has ~ 60° overlap. Take the 106 LSA and using this equation: 2(106 + (60/2)) = the duration value you're after. That value being 272°. Whether you choose a single pattern cam will depend on the efficiency of your exhaust system. That being from the exhaust port CFM right through to the tailpipes. If you have weak cylinder heads on the exhaust (like the Vortec) or a crappy small diameter single muffler (like me) then a split duration may add something.
This is along the lines of what Mike Jones or Terry Walter (via David Vizard) might spec for you torque monster. At least as far as the anecdotal information I've gathered over the years.
Excellent advice thank you Sir!! I have read a couple David Vizards books and utilized one of his recipes for an incredible 496. Believe me when I say that I will be exchanging emails with David before final cam selection.
If you change the LSA for a given cam grind, then you change more than that regarding the cam specs.
I think you will find that spreading the LSA will give you the opposite results of what you're looking for. Typically the larger the cubic inches for a given cylinder head, the tighter you want the LSA. The 110° listed in Comps catalogue is very general. You can get specific with your combination. Your 406 would probably like 106° to make the most peak torque.
Now having said that, if you like the XR2786HR, (which I ran with a Vortec headed 353 for quite a while) then work with the overlap that cam has. The overlap will determine where the torque peak is and will also give you the idle quality you're after both in terms of the amount of lope and the vacuum produced. There's obviously more to it than that, ignition timing specifically, but it's a starting point.
The 276 has ~ 60° overlap. Take the 106 LSA and using this equation: 2(106 + (60/2)) = the duration value you're after. Result: 272°. Whether you choose a single pattern cam vs a split will depend on the efficiency of your exhaust system. That being the exhaust port right through to the tailpipes. If you have weak cylinder heads on the exhaust (e.g. Vortec) or a crappy small diameter single muffler (like me) then a split duration may add something.
This is along the lines of what Mike Jones or Terry Walter (via David Vizard) might spec for you torque monster. At least as far as the anecdotal information I've gathered over the years and my own experiences.
EDIT: This is Gen 1 SBC OEM valve angle with 2.02" intake and decent valve seat angles.
Skinny knows what he's talking about on this topic. EVERY WORD.
Skinny knows what he's talking about on this topic. EVERY WORD.
First, unless I missed something, it appears that Skinny is suggesting that going to a 272/272-219/219-106 cam with it's tighter lobe spread and equal overlap would be more beneficial than the 276/282-224/230-110 cam in a 406.
Have either you or Skinny ever run a 272/272-106 in a 406?
I'm curious because when people would come in my old speed shop wanting a choppy idle for their basically stock 350s I’d turn them on to the 274/274-218/218-106 Crane. So I have firsthand experience with a very similar “106” cam.
We sold a lot of them and I tuned on a lot of them as well. The cam sounded great and was a perfect fit for what we called “the posers” (by their own admission) because it had the sound and wouldn’t really run,,, but it wasn’t a total dog either compared to most other “poser” cams.
As a rule of thumb, I like to go with the tightest lobe spread, the least duration, and the most lift possible for any given application. The problem is typically there are many factors and compromises that must be met and that typically involves a wider spread than deemed "optimal" or actually is optimal in regard to average power. That said,,,, I never spec’ed that 274/274-106 cam for anyone looking to make good vacuum AND performance because it didn’t really do a good job at either. Not in a 350 and certainly not in a 406. It’s way too small for a 406 and will kill a lot of upper RPM power compared to the 276/282-110.
It seems that we're taking about different results here.
This is not a "What's the best cam for my 406" question.
Originally Posted by Ja85z28
... interested in building an aluminum headed 406"+ with 10.5:1 compression and hydraulic roller cam that would produce 15"+ of vacuum.
I realize that this type of engine build isn't popular, but at my age driveability and air conditioning are mandatory.
Based on that I offered up overlap specs similar to the XR276HR mentioned, with an LSA better suited to the larger cubes. The 276 has 59°. With a 106 LSA and about the same overlap gets you 272° of adv duration.
Is that going to produce the most power? I would certainly think not. Will it idle well, (or well enough) and produce 15" of idle vacuum? I would think so.
Originally Posted by BadSS
Have either you or Skinny ever run a 272/272-106 in a 406?
I'm curious because when people would come in my old speed shop wanting a choppy idle for their basically stock 350s I’d turn them on to the 274/274-218/218-106 Crane.
I wouldn't build a 406 to use a 272/272-106. Comps XR282HR on a 106 is a good choice. Then again I'm building for maximum power and torque and not highest idle vacuum and driveability. Driveability being subjective here.
As for the old Crane grind, with 274 adv and 218 at .050", that makes it pretty slow as cam profiles go. With about 62° of overlap, I can see how it would produce a distinct idle quality though. At least the 106 LSA was better than 110. If it were a more modern grind, maybe 274 adv with 224 at 050", it would be a decent performer. Give that 10:1 with a decent cylinder head and it would be a great daily driver and be reasonably quick. (One of my first flat tappet cams was Clevite's 284/218. That was even slower.)
Originally Posted by BadSS
As a rule of thumb, I like to go with the tightest lobe spread, the least duration, and the most lift possible for any given application. The problem is typically there are many factors and compromises that must be met and that typically involves a wider spread than deemed "optimal" or actually is optimal in regard to average power.
I highlighted part of your quote because it demonstrates the best approach to cam selection in as far as power production is concerned. I wouldn't stray too far from that. Why alter the optimal cam spec to suit some compromise? It's been demonstrated time and again that getting the LSA right will produce not only the most horsepower and torque but also the greatest area under the curve.
But I don't want to get too far off topic because as mentioned, this isn't a best cam question.
And to follow up.
Originally Posted by Ja85z28
... with 10.5:1 compression
You'll need to pay attention to that value should you move towards a smaller cam. 10.5:1 SCR with a 272 adv cam (as an example) is likely to produce much too high of a dynamic compression ratio value. Once in touch with Vizard, perhaps through his COS Cam program via Terry Walters Engines, you'll be able to dial that in.
... and compromises that must be met and that typically involves a wider spread than deemed "optimal" ...
Perhaps this particular build idea does represent a compromise and the wider LSA may be useful in getting idle quality and engine vacuum up to what the OP is looking for.
Last edited by skinny z; 04-15-2018 at 12:25 PM.
Reason: Added a "compromise" factor.
Based on that I offered up overlap specs similar to the XR276HR mentioned, with an LSA better suited to the larger cubes. The 276 has 59°. With a 106 LSA and about the same overlap gets you 272° of adv duration.
Is that going to produce the most power? I would certainly think not. Will it idle well, (or well enough) and produce 15" of idle vacuum? I would think so.
Originally Posted by skinny z
I wouldn't build a 406 to use a 272/272-106.
Originally Posted by skinny z
Perhaps this particular build idea does represent a compromise and the wider LSA may be useful in getting idle quality and engine vacuum up to what the OP is looking for.
Thanks for clarifying that you were not suggesting that the 272/272-106 would be “better” than the cam he said he was looking at.
Lsa is simply the result of valve opening and closing events. Nothing magical. You get them right for the application. Thats it.
That being said the compromise with a big inch driver is going to a slightly wider lsa to reduce overlap at idle. The big inches make torque so not much worry about losing any with a wider lsa. If the motor has good heads and intake, wider lsa will not hurt. Ls motors are very efficient and work best with wider lsa for a reason. Medium long runner length and good heads, makes for efficient induction. Dont need alot of duration or overlap for that matter
04-12-2018, 09:14 AM
