88TPI406GTA

Guess what? In the August 02 issue of Car Craft, they take their HT383 and make 450 HP with it using a more wild cam (but not extreme) and lots of torque.

The key here is that they tested the engine with 1 3/4" headers and then with 1 5/8" headers and the 1 5/8" headers not only made more power, but made the higher HP #'s up to 6000 rpm.

This is not the only dyno test that I have seen that show that 1 5/8" headers make good power up to 450 HP anyway.

All of you who say that a 350 MUST have 1 3/4" headers, especially you SLP fans, please explain this to me.

87 B4Z

i had good results with the 1 3/4 headers on my 305 with stock heads and peanut cam.

88TPI406GTA

Do you mean the SLP 1 3/4" headers with a y-pipe that restricts to 2.25" just before the cat?

Or some other variation?

The dyno test BTW had 1 5/8" headers each going to a 2.5" exhaust pipe and a Dynomax Muffler.

87 B4Z

yes they are SLP header and no its not reduced to 2.5 at the cat.

five7kid

iTrader: (14)

I don't know why we keep going 'round & 'round about this.

I have yet to see a magazine article do dyno tests with shorties - it's always long-tubes. Ever wonder why? It's because, at least in the GM performance world, our 3rd gens are the bastards. Most everything else uses long tubes.

Comparing primary size performance between short- and long-tube headers is like comparing performance mod equipment between 3rd gens & Accords. Interesting exercise, perhaps, but real-world useless.

88TPI406GTA

The problem is that there are still a lot of people who claim 1 3/4" headers are a necessity (especially the SLP crowd) for a stock 350. This simply isn't the case. This issue is similar to the stock TB issue in that some people simply refuse to believe that smaller can make power, either TB or headers. Why? Because of what they see in general, from the average hot-rodder public or very generic magazine articles about power show the big engine combos that use some parts that are overmatched for the average engine combo.

I understand buying parts for the future, but that isn't the issue here. Buying long tube headers for a 13 second ride or even 1 3/4" headers for the same ride isn't the best decision.

People need to understand that a lot of the time, the restrictions in their engines rest in the heads and cam, not the exhaust.

If you do a search on this, I have been trying to help people understand this fact as there are always threads asking this question.

And frankly, there have been tests between intermediate length headers (what some people call Shorty for our cars) and the long tubes. These tests have shown that the long tubes make a bit more torque and a small amount of HP more, but we aren't talking 50 HP or anything close to that.

The point is that with our body, people understand that ground clearance is sacrificed with long tube headers but they don't understand that bigger isn't always better. Just like a 750 CFM carb on a stock 350, but you see that all the time too.

See my point?

iroc4ever

You make some interesting points... Well you've made up my mind,it's Hooker Super Comp 1 5/8 headers for my 305 and future 350... i WAS thinking about going with SLP 1 3/4,but i dont really think its worth it...

89BlueTA

Was this test with shorty style headers or long tubes?

nick

I guess this test does not mean much to me, since it was not done on headers installed in an f-body, that is already fighting a choked exhaust system y-pipe back.

Anyways thanks for the info.

88TPI406GTA

Iroc4ever: I agree, but it depends on when what your final HP goal is as part of the system.

89BlueTA: I think that the header issue is seperate from the y-pipe issue and single exhaust with our cars. I think that almost all of the aftermarket y-pipes are restrictive and the same with a cat (sorry you emissions types). I would recommend buying headers seperately and having a y-pipe setup made seperately by a local exhaust shop to hook to your cat. (or with no cat if you can find the right guy like I did) The exhaust system is only as good as its bottleneck, which isn't necessarily the headers. That is my point.

This test should mean something to you though as you CAN duplicate it with 1 5/8" headers to 2.5" mufflers dumping to before the rear wheels if you feel the need to. I agree that chassis dynos tell the better story than engine dynos, but a lot of people with automatic trans still ignore a quality torque convertor too. That doesn't mean you ignore the test done out of the car just because it isn't at the dragstrip. At least that is my opinion.

HTH somebody else too,

Marc 85Z28

iTrader: (3)

Hey 88TPI406GTA:

I just finished my SLP 1 3/4" install. SOTP difference without a doubt. I will have times too. I'll bet another 1-2 MPH easy.

I bought them for 5 reasons:
1. Stainless steel
2. Price - only $200 with the Y-pipe.
3. No AIR tubes.
4. Near future heads/cam install.
5. Most importantly - quality. These are the nicest shorty headers you can buy for an F-body plain and simple. Just compare some.

Rather than compare generic 1 5/8" primaries to 1 3/4" primaries, try comparing a set of F-body headers. They are quite different.

kevinc

Well hey, that's good enough for me!! The magazine tests extensively and reports dyno data, but on the other hand you've "had good results" so wow let me run out and ditch my 355 for a 305 peanut cam and 1-3/4" headers. Woo hoo.

bigman

A couple of years back CC did a comparison issue of cheap parts. Mufflers under $30, headers under $100, etc. The header comparison included a pair of dyno-max 3/4 length headers with 1 5/8 tubes. The shorties made slightly more power, but the difference between them all was only a couple of hp tops. I think (well just guessing really) that the engine was in the 400hp range. So take it for what it's worth. I'd be curious to hear from anyone on this board who went from one brand of shorties to another with no other changes and noticed any difference.

Dan

88TPI406GTA

Hey Marc85Z28, I can appreciate some of your points, but last I checked those headers were like $450. Good score on a used set. And if you plan to hit 450 HP or over, then good luck, but you have a ways to go.

Hey Kevin C...thank you. I knew I wasn't the only one thinking that...

Bigman...I saw those tests, in Car Craft I think. That is why I don't really think that F-Body headers are THAT much different than G body headers for flow (same primary size). If someone has hard data indicating differently, please post it.

AJ_92RS

I still have that article (somewhere. I'm in the middle of moving to a new house. ). IIRC, the Dynomax were only 1 1/2" primaries, as well as the Flowtechs. The larger 1 5/8" headers did make more peak HP and TQ, but when they averaged out the #s, the Dynomax shorties were the clear winner.

Averages may not be impressive when you're chewing the rag at the local cruise night, but they matter when talking about VE, and MPG, and certainly ET's. An engine spends more time at 'average' power than it does peak HP. Think about it. If you're engine make Peak HP at 5800 RPM, how much time does it spend there? About a 1/2 second? But average HP lasts the hole time you're running through the gears, right?

Now that was ONE engine, on ONE dyno, with ONE certain head, etc. And, there was no exhaust system hooked up to any of the headers. That in itself will make a difference also.

My point is that (as said before) "bigger isn't always better". Which reminds me of another article I read recently. CHP made 500HP with a 406. They used 1 3/4" headers to do it. But they lost ~10 ft/lb of torque after taking off the 1 5/8" headers. They even said for street use, and 1/4 mile runs, they'd stick with the 1 5/8" headers. Again, "Dyno" versus "real world".

AJ

87 B4Z

**** you *******

IROC57TPI

SLP sends some mixed messages....

First off, they make the 3rd gen Firehawks with their 1 5/8's headers on a 350 with a t-ram manifold and custom cam profile and make 300HP IIRC.

Next, they market their headers and recommend 1 3/4's for 350's. So does this tell us something? I think it tells us that they made too many 1 3/4's headers and need to sell them! You have to think like marketing people....

88TPI406GTA

Marketing is the key there. That is a bit why I am suspect of SLP in general...that and they tend to have their products overpriced. They can be comparable to TPIS that way, but I am pretty sure that SLP does make a lot of their own products, instead of buying other products and re-boxing them...

88IROCs

Unless we get a totally different version of Car Craft up here, there is no HT383 buildup in the August 2002 issue. There is a story about the 383 in their '71 Nova though. However, with a single-plane manifold, AFR heads and 1 7/8" headers, no-one is going to mistake that 540(!)hp brute for a HT383.

The August 2002 issue of CHP does have a continuing build-up of a HT383, and yes they switched from 1 3/4 to 1 5/8 headers and made more torque and hp. What they don't say is what specific tuning(if any) they did for each combination. With their combination, the 1 3/4 headers would scavenge the cylinders much more effectively than the smaller tubes. That means more air gets into the cylinders and more fuel is required. If the headers are too efficient for the combo, airflow into the cylinders will go past the point where the carb can supply enough fuel. That lean condition will contribute to lower torque and hp. Rejet the carb for the larger headers, and you'll likely see a very different result than what they got. It ain't the first time a magazine test has made that mistake, and it probably won't be the last. Or you could just use smaller headers, leave more exhaust in the cylinder - which requires less fuel. The richer mixture makes more power and you fool yourself into thinking you've optimized the combination.

I'm not entirely convinced that the jets were even able to supply enough fuel for the smaller headers. I would think that with the RPM "Air Gap" manifold and the CompCams XE282, this motor should have had a much peakier torque curve. Yet between 3500 and 4500 rpm, the torque never varies by more than 5 lbs/ft(481 - 486 lbs/ft). While it is not as flat as the combo with the larger headers, there appears to be a limitation(could be airflow limited because of the Vortec heads too).

I've never read where anyone on this board said "a 350 MUST have 1 3/4" headers", but it's been proven many times over that with the short tubes that will fit into a thirdgen, the 1 3/4" headers make more hp AND torque. It's not the optimum choice, but it is the best compromise. Until someone makes full-length(30" primaries and 12" collectors!!!) 1 5/8" headers that will fit our cars without decreasing ground clearance to 1/2"(don't hold your breath), the larger tubes make up for the lack of length.

IROC57TPI

Someone does make them. Performance Fabrication & Engineering in Chesterfield, MI makes custom headers for 3rd gens on a made to order basis. You can get them steel, coated, or stainless. I will be sporting a set here this winter. I will post pics when they are done.

If anyone wants to give PF&E a call their number is 586-949-3400. They will build you a set to your specs and you will still have ground clearance.

bluemeanney

as i recall they started out with the 1 3/4 headders and swapped on the 1 5/8. wich you would assume that the combo was setup for the 1 3/4 set, not the smaller ones.

88TPI406GTA

It is CHEVY HIGH PERFORMANCE...with reading so many per month, sometimes I get the magazine confused.

The whole reason that I started this thread is because the general opinion of this board WAS that to make any serious power, you needed to have 1 3/4" headers. Well, you don't. That is my point.

You make an interesting point about the headers being TOO efficient for the rest of the combo. That is my point exactly. If you are building a 350 HP engine, then the 1 3/4" headers are TOO efficient for that combo. Glad that you see the whole "systems" approach like I do.

Also, when dealing with fitment, the slightly smaller headers work well too. Anyway, the key is to have some discussion based on facts...and that is now accomplished

88IROCs

That's just the thing,... no mention is made of any specific tuning that was done, to make sure that adequate fuel delivery and best spark timing were being used by any of the combinations.

They started-out this month with a combo that delivered 416 hp and 466 lbs/ft with a 1 3/4 headers, the "RPM Air Gap" manifold, 1.6 rocker arms, HEI ignition, Holley 0-4779 750 CFM carb and HOT cam. Yet no mention is made of tuning to ensure optimal fuel and spark. They then switched to a BG Speed Demon 750 cfm carb, electric water pump, and the CompCams XE282HR cam and recorded 473 lbs/ft and 446 hp. The torque curve hits a plateau between 3400 - 4700 rpm(max. variance of 6 lbs ft) and the peak(if you can call it that) occurring at 4400 - which is 800 rpm higher than the previous combo. The torque gain could be entirely attributable to the electric pump, with the bigger cam unable to add anything due to inadequate fuel flow. The horsepower curve similiarly plateaus between 5100 - 5700 rpm(max variance 9 hp) with the peak occurring at 5400 rpm(which is 200 rpm below the previous combo) and again, no mention of combo-specific tuning. Looking at both curves, it appears in the second combo that the motor is starved for fuel at the torque peak and starved for air at the hp peak. Just for comparison's sake, GMPP recommends a 750 cfm carb for a stock HT383 and it would seem larger jets on a larger carb would be advisable on a substantially modified HT383.

For the third combo they switch to 1 5/8" headers. The torque climbs to 486 lbs/ft @ 4200 rpm and the horsepower nudges to 449 hp @ 5400 rpm. Both curves still show a plateau(though not as drastic as with the previous combo), but if the 1 5/8" headers are doing a poor job of scavenging the cylinders it could mean that the carb is more likely to supply a richer mixture which will increase the torque all along the curve. At the top end, it still appears to be starved for air. Larger valves in the Vortec's may help to some degree, but I'd bet an 850 cfm carb(properly jetted for the combo's) would help more. Last I checked, this was 2002. Why do some folks still seem to be afraid of O2 and knock sensors? I know if I was paying for the dyno time($100/hr, min 8 hrs: in my area), I'd want to use evry tool to make sure I was optimizing the combo.

HRM did a similiar HT383 test in their Mar 02 issue(the CHP article mentions it in a sidebar). In that test they started with a 625 cfm carb, despite the fact that GMPP recommends a 750 cfm unit. They tested first with 1 3/4" headers and then switched to Hedman Tork-Step headers. These headers, if you are unfamiliar with them, start out with 1 1/2"(!) primaries and then step-up to 1 5/8" tubes. Now on a mild 350, these will probably offer better low-torque, at the expense of top-end breathing. However, HRM's stated goal with this build-up was to make 500 hp, and one should question why they would place an obvious restriction in the exhaust system. Not surpisingly, considering the smallish carb they wer using, the motor picked-up a small amount of torque over the what the 1 3/4" headers produced. Later on in the article, using the dyno's sensors, they discovered the jets on the 625 cfm carb were maxed-out even with the tiny headers they were using. They switched to a 750 cfm carb and produced a big gain in torque and hp. Then they rejetted the carb and found additional power, while still using the small headers. The obvious next step, to me at least, would have been to switch back to the larger headers, check the jets ability to supply fuel and, if need be rejet or, (gasp!!!) maybe even try a larger carb. They didn't do that, and if you read the article you might know why. This article was less concerned with providing helpful editorial content than it was with providing free ad copy for a valued customer. They tried to leave the impression that the small headers were the best choice for the project, but their own testing showed there was a clear bias against competing products. Both HRM and CHP belong to the same media group, and when CHP tries to make the case for using a smaller set of headers, those headers are again made by Hedman. Make of that what you want, but I think both HRM's and CHP's objectivity and journalistic integrity should be questioned, rather than using their tests as a shining example to prove a point.

88IROCs

If we were talking about a 350 hp 350 cid motor, I would argue that the full-length 1 3/4" headers would not be efficient at all. Their size would significantly decrease the velocity of the exiting exhaust plug, which would decrease cylinder evacuation and create a weak scavenging pulse when the plug entered the collector. But on a motor that didn't(or couldn't) use full-length headers, 1 3/4" headers will make up for the lost tube volume. The larger tube would lose velocity due to the larger cross-section, but make up for that by reducing restriction and being able to contain more exiting exhaust plugs than a tube of smaller diameter.

titeride85

I am working towards a 400HP/460TQ 406 sbc. I have been debating which will be best for my set-up. What do you guys think? When I had the engine combo run through Engine Analyzer, I ran the 1-5/8 and the 1-3/4. The 1-3/4 had 3 hp more and 3 lb-ft more torque.

Is this about right? I am getting a great deal on SLP headers if I want them. But I am not sure if it will help me or not.

OPINIONS? BTW, I am still considering a dual stage 150hp(total) hit of "squeeze." I am unsure of that though.

aziroc

i have SLP's headers on my 406. they are the 1 5/8"jey hot coeated kind (very sweet headers). i always get asked why 1 5/8 and not 1 3/4's. my answer is simple. i wanted more low end torque. thats what the difference really was. either lower end toque or high end torque. im happy with my #'s i got on my engine. to bad i need some 30# SVO's/new prom and more time on a dyno to tune it. but i see an easy 40 rwph and 50 rwtq coming from the injectors alone *thats how bad its running lean* hopefully ill get 10-15 more hp and tq just from the new prom.

:lala: :lala: :lala:

aziroc

titeride85

just a friendly reminder.. make sure u get a forged bottom end and some low compression pistons. i had the same idea in mind when building my 406. i wanted to run 150-200 shot or a 12psi blower with liek 8.5:1 comp. well that was before i put in my 10.4:1 custom made ROSS forged pistons. so now instead of running 200 shot confortably ill be only running 125 and 150 *if $$ is on the line* or only 8-9 psi, with intercooler, ati procharger *and the blower is more likely to happen*

88TPI406GTA

AZIROC, thanks for again corroborating my point with smaller headers...I would say that 400 rwhp is a good sign that the smaller headers make good power

Just out of curiousity, what injectors are you using now (at what PSI)? And what are you switching to?

Thanks,

aziroc

right now i am currently using ACCEL 26# injectors at 60 PSI. i will be getting the 30# SVO red injectors and im sure ill be runing it between 42-47 psi. the only real problem i will have with the SVO's is ill be dumping full like crazy at idle.. but anythign about 1000 rps and ill be right where i need to be with the a/f ratio. i get 18-20 mpg now, but after the svo's ill prob be around 16-19 mpg.

titeride85

I have kicked around the idea of fuel injection. What set-up are you using to get those #s and that kind of mileage? If I could do that somewhat affordably, I would rather do it that way. Could you shoot me some ideas of the equipment and the cost?

Yeah I am already looking at the CR. If I do use juice, it will only be like I said, a 150 dual stage shot.

aziroc

well then engine alone cost me $10k *well the engine, fuelsystem, ignition system * if u want PM me and ill shoot u a list of stuff i have on the engine.

titeride85

you have mail

92BLKL98

If you read Lingenfelter's book on building SBC's he also makes this statement about building an engine for the rpm you expect it to spend most of it's time in. Plus the fact that with stock heads with 1.50 exhaust valves the 1 3/4 headers are bearly a large tube header. With 1.60 exhaust valves for large tube headers you would have to start with a primary tube size of 1.92 since no one makes a header that size you go to a 2" tube. Try fitting that into your F-body. Small tube headers are 95-105% of valve size and large tube is 120-140% of valve size. So if you have a set of heads with 1.60 valves even the mighty SLP 1 3/4 headers are considered small. According to the Desktop Dyno going from small to large tube headers is still in the single digits so why is the SLP 1 3/4 header really needed. As was said in an earlier post "marketing".

Black Knight

Lemons make headers in a variety of sizes and they fit in the frame.

Black Knight

Here is a picture under the car

Black Knight

Here's another shot of ground clearance

92BLKL98

Black Knight those looked pretty nice. How about with a complete exhaust system how is the clearance going under the trans x-member? Do they have a website?

Black Knight

92BLKL98

There website is www.lemonsheaders.com
I do not think they make a complete exhaust system, but I have never asked. Give them a call on Monday and see.

Kevin91Z

iTrader: (1)

What you guys all fail to realize is these dyno tests were all done on CARB engines, not EFI, and certainly not TPI. Carb engines respond very differently to the same setups than TPI engines. While its true 1 5/8" headers might make more torque, the TPI engine already makes more than enough torque, so I will gladly give some of that up to make more upper RPM breathing. If you've got a stock long runner intake, you cant take advantage of it, so 1 5/8" are fine for you. But for those of us with better intakes, we need more upper RPM power, which larger headers can provide. Keep in mind exhaust gas is hot, and it wants to expand. If you give it a large tube to expand into, it will scavenge the cylinder better providing more room for fresh cold air to come in. Also, you want the header tube bigger than the exhaust port, or the header tube will create a wall where the head meets the flange. That causes reversion and is very bad for flow.

Lastly, the 91-92 Firehawks have 1 5/8" headers because they provide more engine room to change spark plugs, wires, etc. Remember these cars were race cars disguised as street cars. The smaller headers make them easier to work on.

I fully the support the idea of 1 3/4" headers on any wild 350 engine or larger. A mild 350 or smaller engine probably wont benefit from larger headers, and will more than likely lose power.

88TPI406GTA

Kevin...I agree with you to a certain extent. But the fact is that whether they are carb or TPI, the flow and limits therein are the issue. This analagous to the stock TB debate...when GM uses it on the Ramjet 502 and can make 500 HP, then it must be a limitation on our engines, right? Because the L98 and the Ramjet are different engines altogether....but the flow is still the key.

If by a wild 350, you mean over 450 HP, then I agree with you...If you want to limit wheelspin and a bit of low-end torque...just retard your timing (PROM burning).

Believe me, with my 406, I understand the torque issues you speak of, especially since I initially had a stock TPI setup on it. But the reality of it is that control of the engine can be had with the throttle, right?

Believe it or not, the gas expansion/contraction issue is a big deal with the import crowd (I own a 95 Talon TSI Turbo AWD as a daily driver) and having an exhaust setup in line with the rest of your engine (ie, the system approach) is the way to go.

Lastly, I will say this...whether carbed or fuel injected, the process is the same, and if we were talking about induction components I would tend to agree with you. But a well tuned carb or FI engine will be efficient and the exhaust gas evacuation principles are still the same.

If you have specific dyno proof, I would really like to see it...after all, that is what I am basing my opinions on...and I may be wrong, so educate me

Perry93TransAm

let me tell you my experience, This is on my 4th gen (93 T/A) and not my 86 T/A, but they both have crappy factory y-pipe exhausts. My set-up is an LT1 355 6 inch rod block and at the time I had the CC305 cam w/1.6 rockers and stock cating but ported LT1 heads. Auto 3000 stall and 3.73 rear gears . At the time I had the JBA 1 5/8s headers, no cat and a Hooker cat-back. At the track I ran a very best of 12.54 @ 108 mph In the nice nov weather (it was like 65 degrees outside. The following year I changed to Hooker 1 3/4 longtubes with a Mufflex Y-pipe, Same cat-back same engine combo to a T. In 90 degree weather with a headwind I ran a 12.31@112 mph, same car, same kinda gas, same elevation etc. This was enough to convince me that with my set-up (3800 # car too) the 1 3/4 were the way to go. Now with the Shorty 1 3/4s I cant see the kind of gain happening that I had but I do beleive that all things constant the 1 3/4s would do better on a mildly to wildly built 350+ cube motor.
Perry

DTL504

iTrader: (1)

Now that im changing my engine to a 406, what would be a good choice for me. Im will be using AFR 195 heads 74cc. i already have a set of Holley 2460-1 coated headers that new or should I try to sell them and get 1 3/4. In my opinion I dont think that it would make a very big difference on a street performance vehicle. All I want to do is eat my friend Mustang Cobra A$$ with this 406.

johnyIROC

I just bought the Hedman 1 5/8", I will be installing them this weekend.

88TPI406GTA

CHP just did the next installment on their HT383 buildup and this time made 490 HP with the 1 5/8" headers...

So...we know that they will support even more...although CHP does admit this evidence is fairly contrary to most educated opinions out there...

There may have been some questioning about 450 HP, but 490???? Any skeptics still?

Perry93TransAm

I just read the same article this weekend as well, I did notice that the headers they listed of the part#s the 1 3/4s are tehy the torque step or not? If it is they are not a true 1 3/4 inch header and they also have very small collectors. Is this right?
Perry

88TPI406GTA

I don't have the article with me at work...but I will look when I get home and try to post something on it tomorrow...unless somebody beats me to it.....

Kevin91Z

iTrader: (1)

Again, its a carb engine, and they used full length long tube headers. We're talking about EFI (TPI specifically?), and shorty street headers.
You cannot compare apples to oranges.

Perry93TransAm

That may be so but we are debating this particular engines results, not everyone runs EFI and Shorties. Also a short runnered EFI system would have simular curves to the carbed engine.
Perry

88TPI406GTA

And also the point is whether 1 5/8" primaries are the restriction or not...if they are/were a restriction to flow, then it wouldn't matter if the headers were shorty or long tubes as the flow would be restricted by the small primary size.

The fact is that there may be slight variation between Carb and EFI engines, but it still comes down to flow. If the 1 5/8" are a restriction to flow on the higher end, it would be apparent. That is the point of this thread...a specific set of dyno results with a regard to the higher RPM HP #'s...which I equate to an issue of flow on the top end.

Is flow limited to EFI or carb? Example...If the Victor Jr. Intake flows 275 cfm (guess) and the Miniram flows 280 (also guess), which is the theoretical restriction? In this case too, there are dyno results that contradict popular opinion.

I appreciate your viewpoint Kevin91Z as I think you are generally very correct both on Thirdgen and the F-body mailing list...and if you have specific dyno results and a specific EFI combo to post...please do so...I am just going on what I see here with this combo.

My guess is that if they kept the same combo and slapped on a miniram and SD EFI system, that the results would be similar...with a broader torque curve at lower RPM's due to the EFI advantage...

David 91RS/Z28

It really depends on the setup, IMO. I recently did a swap from 1-5/8" Tri-y headers to Hooker 1-3/4" long tube headers on my 91. The results were amazing. So far the car has picked up 4 tenths and 3 mph and there is still more in it. Before the header swap my car dynoed 335hp and 388tq to the rear. I was disappointed in the power so I started looking at what might be the cause. I figured the long tube headers would maybe help out just a little but not this much. I haven't dynoed after the new exhaust but I'm figuring around 350-360hp and 410tq or more to the rear based on the 1/4 and mph of my best ET. A quick rundown on the setup: AFR 190 heads, SuperRam, and exteme 224/230 camshaft. I've still got some more tuning to do, but I have been very happy with the results. As I said earlier, it all depends on the setup. On a 305 or stock 350 TPI a shorty 1-5/8" would be the best. On a modified 350+ci TPI a 1-3/4" shorty or long tube(my preference) would be the best.

88TPI406GTA

Hey David...

I will bet that you didn't just change the headers though...(I cheated and checked out your site. Nice pics though)...In fact, you have 3" y-pipes going to a single 3.5" catback as well...

I can appreciate your input, but in this case, your exhaust will most likely support 500 HP...not just from the header swap.

I really do like your idea though and when the time comes to upgrade my setup, I think I will use your setup as my template...Sweet car all the way around.