rallysport

i just want to get about 300 hp out of my 88 L98. Will 1 1/2 " headers support 300. Thanks

Tas

too small.

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-Tas
'89 Formula WS-6

305, TBI, auto, 14x3 chrome flat based open element with K&N, Milodon 160* thermo, functional Formula hood, cross-flow Flowmaster, '99z28 rear pipes and tips....

To be installed eventually far far far into the future: Yours if the price is right and I don't have to ship :
Hooker 1-5/8" 50 state legal headers, Dynomax 3" I pipe (PN 44063 and 43248), Catco 3" cat, and injector spacer.

Super GRK_Taz World
F-Body Dual Exaust
EFI & Intake Options
AOL IM: superGRtaz

Sitting Bull

I'd say it is borderline but you'd only get a few more hp by going to 1 5/8.

breathment

if u have a 350 then should u go with 1 3/4?

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88' GTA 350 MODS---> air foil, K&N, Shift Kit, 180* therm, TB bypass, Gutted CAT

Sitting Bull

No, 1 3/4 inch headers will kill your low end torque on anything small block. That size of pipe only helps if you are revving to 6000 rpm a lot. I doubt you are, if it is a street car.

Up to around 300hp the 1 1/2 headers are really good.

Kevin91Z

iTrader: (1)

Kill my low end torque?? Riiiiiight! Thats a myth. I put SLP 1 3/4" headers over SLP 1 5/8" on my car and gained 37 peak TQ at the rear wheels! A 350 or larger engine needs to breathe!

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1991 Camaro Z28
5.7L 5-Speed (originally 305)
317 RWHP, 418 RWTQ
13.23 @ 107.62 MPH
Southern California
Member: SoCal 3rd Gen F-Bodies
Member: SoCal F-Bodies
-=ICON Motorsports=-

five7kid

iTrader: (14)

SLP recommends 1-5/8" for 305's, 1-3/4" for 350's.

1-1/2" are good on 350 torque motors - like the '71 GMC 3/4 ton Camper Special that I put a set on. Helped it greatly over the stock manifolds, but RPMs stayed under 4500. Probably a 225 horse engine at most.

So, 1-5/8" at a minimum, 1-3/4" if you go with SLP's.

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82 Berlinetta, orig V-6 car, now w/86 LG4/TH700R4. 2.93 limited slip. Cat-back from '91 GTA, ZZ3 intake, Accel HEI SuperCoil. AMSOIL syn lubes bumper-to-bumper. Daily driver, work-in-progress (LG4 w/'87 LB9 block, ZZ3 cam, ported World 305 heads, Hooker headers & y-pipe, 3" Catco cat & 3" cat-back, Spohn SFCs).
57 Bel Air, my 1st car. '66 396, 9.7 CR forged TRWs, Weiand Action+, Edelbrock 1901 Q-Jet (Holley 3310 on the way), GK 270 cam, Magnum rockers, Jacobs Omnipack, 1-3/4" Hedders & 3" Warlocks, TH400 w/TCI Sat Night Special conv & Trans-Scat shift kit, MegaShifter, 3.08 8.2" 10-bolt w/Powertrax, AMSOIL syn lubes bumper-to-bumper. Idles smooth @ 600 RPM in D. Best 15.02/95.06 @ 5800' Bandimere (corrected 13.93/102.4 @ sea level).

Sitting Bull

Kevin,

Tell your argument to Steven, one of the other moderators. I'd guess you might have something else exotic in your engine that is being allowed to breathe by using the 1 3/4 headers.

My argument still stands :P

Ed Maher

Does steven's car run severely traction limited low 13s, even after 'losing his torque' to 1 3/4 headers?
And steven who, whats he moderate, one of the regional boards? If you're giving him technical credibilty just cuz he's a mod, well we have ways of fixing that, lol.

Have you ever run the same car w/ different sized header primaries and measured both at the track and at the dyno comparisons. How can you spout theory blindly when you are looking at hard numbers. Why do you think kevin is hiding something, what reason would he have for lying?

Here's a 3 minute physics lesson for you.
-Torque is a function of cylinder pressure on the power stroke.
-Cylinder pressure is a function of volume of air/fuel in the cylinder and other variables of compbustion, but this isn't really as relevant as the VOLUME part.
-Simplified, a 350 that makes 400 lbft of torque is effectively moving 1/3 more air than a 350 making 300lbft.
-Now exactly how does RPM range figure into this, it doesn't. RPM range is a function of heads/cam/bore/stroke/etc, and is the operation point that the engine can move that much air to make that much torque, but torque is always an INSTANTANEOUS quantity dependent on cylinder pressure (as well as bore/stroke/rod length/friction - all constants). That's the important part.

Yes, there is more to it than thsi, but this was the short version. Velocity in the header primary is a nice variable to look at b/c the effects of scavenging boost torque by reducing pumping losses while the next cylinder is on it's power stroke. However, velocity is a function of exhaust gas volume and energy. Since we know a healthier engine moves more air, it naturally will maintain the same velocity in a bigger primary.

As to the lost low end argument as a function of velocity. Well, true, at lets say 1500 rpms, a 350 is gonna be making well under it's peak torque number, and thus be moving much less air, and thus velocity will be low in the primaries and it is even possible that the exhaust waves will run into each other thus negating scavenging effects. So you won't reap the 'boost' in effective torque that perhaps a smaller primary might give. However, running a smaller primary is a pyhric victory, yeah you will get a boost at low cylinder pressure/torque, hoever you have now compromised your exhaust and now once you get over 2k rpms and your healthy engein is now pushing over 300lbft and those small primaries are working against you, and wll continue to do so for the rest of your rpm range until you fall off well past peak power.
That is where kevin's numbers come in. His dyno and track proof show that the small (might even be negligible as the effects of scavenging at low rpms is diminished b/c the high pressure pulses move too fast for the low pressure wave to effectively dwell on the exhaust port long enough to provide any help.) amount of extra exhaust velocity that smaller header provide is nothing in comparison to the amount of compromise on power that you give up to get that.

Basically, for the newbies/lurkers who may be reading this post and looking for answers, who are you gonna believe, the man with dyno sheets and timeslips and a fast car, or some guy who is spouting something he can't back up with anything.

If anybody cares to refute this, please come back w/ science. Or at least some real hard numbers and some sign of original thought as to why your numbers prove your point.

Sitting Bull

Ed,

For the life of me I just can't find Stephen's (not Steven, actually, my mistake) post on the subject! It was just a few days ago but may have been on another forum like CamaroZ28.com.

In any event, my information comes from a very good racer, Stephen Iroc 87, who as you probably know is one of this sites moderators, as well. This is his signature:

------------------
Follow my racing progress on Stephen's racing page
and check out the race car

87 IROC-Z SuperPro ET Bracket Race Car
461 naturally aspirated Big Block

Best ET on a time slip: 11.242 altitude corrected to 10.89
Best MPH on a time slip: 121.52 altitude corrected to 125.89
Altitude corrected rear wheel HP: 497.9
Best 60 foot: 1.546

Racing at 3500 feet elevation but most race days it's over 5000 feet density altitude!
Member of the Calgary Drag Racing Association

87 IROC bracket car, 91 454SS daily driver, 95 Homebuilt Harley

Thus your argument is not with me, "some guy who is spouting something he can't back up with anything," as you describe me but with a man whose car's ETs humble yours quite significantly, if your own boastings proclaimed:

"Does steven's car run severely traction limited low 13s, even after 'losing his torque' to 1 3/4 headers?
And steven who, whats he moderate, one of the regional boards? If you're giving him technical credibilty just cuz he's a mod, well we have ways of fixing that, lol."

So, be my guest, go and "fix" him good.

Disappointingly, your arrogance is quite unpleasant to behold and suggests a lack of maturity in the extreme or a need to display your supposed superiority in this field. Since your measure of credibility is, by your own words, a low ET, Stephen's credibility is the accurate measure in this case.

Sorry you are so upset.


------------------
1986 Camaro Sports Coupe
T-tops, variable wiper, power hatch, rear defrost, third brake light
LG4 305 V8, Hooker Shorty headers, 3" pipe into Walker Quiet Flow dual exhaust
Edelbrock Performer intake, "Damonized" Q-Jet 4bbl, K&N filter, Crane ignition kit
TH700R4 transmission and Derale cooler
Air conditioning, power windows, power door locks, power brakes, power steering, tilt wheel
Kenwood cassette, Pioneer 6x4 component front speakers
Rockford Fosgate 6x9 Punch rear speakers
Z-28 front and rear sway bars
Aluminum slots and Goodyear 225x60R15 Eagle HP tires
243 horsepower and 326 foot pounds of torque at the flywheel
_ _ _ _ _ __ _ _ _ _ _
Yea verily, and he smote the smog heathens from his small block Chevy, even from the air pump to the converter ...
Todd 1:1

Sitting Bull

Ed,

This thread discusses the issue in some detail:

https://www.thirdgen.org/messgboard/...ML/000594.html

IROCZTWENTYGR8

iTrader: (1)

BTTT.

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89 RS

STILL Looking For:
An 87 IROC-Z28 350 TPI

Kevin91Z

iTrader: (1)

Regarding Stephen's 87 IROC Race Car, also notice in his sig he is racing at 3500 feet above sea level. The air is much less up there, as a result he isnt moving as much air thru his engine as us at sea level.

Think about it this way: Most high performance aftermarket heads have 2.02" intake valves and 1.60" exhaust valves. Stock exhaust valves are 1.50". Header tubes are measured as outside diameter, the actual inside size is slightly smaller. If you've got exhaust pushing thru a 1.60" exhaust valve, and knowing that hot exhaust gas likes to expand, wouldnt you want to give it the biggest chamber to expand into you can get? (up to a point of diminishing returns, of course) Why choke your exhaust by pushing it thru a smaller header? Unless you're building a torque engine like for a truck, you'll need larger headers, 1.625" (1 5/8") minimum, with 1 3/4" (1.75") preferred.

Lets try it another way: We all know that TPI engines produce a tremendous amount of torque. One look at my engine dyno and any similar engine will tell you that. Since we can agree that smaller headers produce more torque, I know that my engine can produce torque no matter what headers I put on it. So I want to build for horsepower. Hence, I put larger tube headers on it, SLP 1 3/4". While I may be giving up some low end torque, as Ed described, TPI engines more than make up for it due to the design of the system.

I was holding back some information. I didnt just swap from 1 5/8" headers to 1 3/4" headers and gain 37 TQ. I also swapped to a larger cam (which would give more horsepower and less torque) and a TPIS intake and large tube runners combo. I wasnt expecting to gain that much, but I did. You decide what was the biggest contributor to the torque gain.

91'firebrd

Even though 1 1/2" primaries would be considered too small for a 350 in most circles, they still must be an improvement compared to the stock exhaust manifold.

On one side of the story, TPI's don't generate very high rpm's so they can make do with a smaller primary. But since there is so much intake on a tpi bigger primaries don't hurt much of the low end torque.

Edelbrock TES headers have 1 1/2" primaries for 4 cylinders and 1 5/8" for the other 4.
And if you look in Summit, SLP with their 1 3/4" primary header makes xx more torque and xx more horsepower compared to Edelbrock TES headers on a 383 ci engine. Kind of funny that SLP did not compare their headers to TES headers on a 350. My guess is because the numbers were not impressive enough.
And 1 1/2" primaries on a 383 is clearly too small.

Sitting Bull

What I find most regrettable, as this thread degenerated into chest-thumping and "newbie listen to me" -isms, is the fact that the original question had nothing to do with a race-car but was simply a guy with his street car wanting to know if 1 1/2 inch headers would work OK with his 350 making about 300hp.

Quote:

I just want to get about 300 hp out of my 88 L98. Will 1 1/2 " headers support 300. Thanks

Sure it will

BadSS

Bull,, 1.75" headers will not kill the bottom end on a 300 horse small block,, especially if you're running a full exhaust system. Those of us that have worked on a number of cars,, and have run a number of headers ourselves,, know this to be a fact. I did some R&D work a number of years ago with a 12.4 car. The car ran just as fast with 1.75" headers through the exhaust as a 1.625" uncapped (with torque tubes). Granted that was more than 300 horse,, but I got the same business that you're shouting way back then (12 years ago),, that the 1.75" headers would kill the bottom end - and it's just not true. I had to run the old 305's 1.5" headers before buying the 1.75" they replaced,,, and the car picked up from go to whoa. I know that you haven't run different sized headers,, or you would know this also.

I don't care what the guy runs. 1.5" will be better than the stock manifolds, and that's about all I can say for a 1.5" header. 1.625" would probably be the best bet on a 300 horse engine,,, but it's a lot better to "oversize" by one size than "undersize". Plus,,, you buy the 1.75" headers,, and you're done - until you push 600 horses or more,, and need 1 7/8" headers.

88IROCs

In a perfect world, 1 5/8" tubes would be the largest size you would need for the primaries on a 350. In that perfect world, you would have all the room you need for the length of tube required. On your typical 'street' 350 which makes peak torque around 3500 - 4000 rpm, the resonant tuning for this rpm would require a primary tube length of about 30 - 36" for 1 5/8" tube. The collector would be about 12" long to maximize the effect of the scavenging pulse.

Now open the hood of your thirdgen and then look under the motor too. If you can see a way to fit a header with 36" primaries and 12" collectors, do tell. IT'S NOT A PERFECT WORLD!

So to achieve the same resonant tuning as a small pipe with more length, we use a larger pipe with less length. Yes, the larger pipe will have diminished some of the scvenging pulse, but it's compensated by the exiting plug encountering less friction from the tube.

All of this has been discussed(ad nauseum) before. In a perfect world we could press a button that would punt the naysayers into the archives until they came up with a fresh argument.

As to the original question, sure you could make 300 hp with 1 1/2" headers. Hell, it's been proven you can make over 350 hp with the original exhaust manifolds(and about 8 lbs of boost). But if you recall the air pump analogy, any restriction downstream will require more pressure upstream to move the same volume. So while you could spend thousands on intake and valvetrain to achieve 300 hp with undersized headers, you could spend a lot less to make sure the exhaust doesn't restrict the rest of the motor(1 1/2" & 1 5/8" headers cost the same amount, 1 3/4" headers only cost a little bit more). You'd probably spend as much(or more) trying to achieve 300 hp with 1 1/2", as you would achieving 320 with 1 3/4" headers. If it was me, I'd much rather have the 320 hp.

[This message has been edited by 88IROCs (edited September 02, 2001).]

Mista

Well in July 1999 Car Craft they did a test with CHEAP headers, call the $99 Header Shootout. They were tested on a 400+ hp 355 and were designed to fit 67-69 F Bodys. Tested were the Dynomax 3/4 length with 1.5" primary and 2.5" collectors, along with Flowtech, Hedman, PAW, and Summit which all had 1.625" primarys and 3" collectors. The test was done with the headers "open".
Peak hp/Trq
Dynomax 85118 412.3/390.3
Flowtech 11108 412.7/386.5
Hedman 68720 411.2/396.1
PAW 7102 398.3/391.7
Summit G9001 410.9/364.0

"Not only did the Dynomax headers fit well, but they produced the best overall horsepower and torque averages, plus they were a near tie for best peak power."

Now if you wanna get into exhaust tuning, you'll find that 1.625" will give little or no gains over 1.5" given proper primary length on engines 400 hp or less.

But like stated above, do the room issues in a 3rd gen, You use larger tubes to make up for the shorter pipe length.

I guess I save too many old issues of car mags.



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86 T/A 5.0 A4 & 2.77 gear
15.62 @ 86 mph
93 Civic 1.6L
13.5 @ 100 mph

88IROCs

Without seeing the actual issue of CC(I don't keep magazines for more than about 2 years) I couldn't really comment to accurately on the results. The engine combination plays a big part in picking the right header(If peak torque occurs at 4500 rpm, I'd want a different primary length than on an engine making peak torque at 3000 rpm). The length of the primaries and collectors does play a big part in the effectiveness of cylinder scavenging, as does equal-length primaries(a rarity on most headers).

The title you mentioned, "$99 Header Shootout" seems to imply the emphasis was on cheap(probably shorty headers) instead of each manufacturer's best product.

The fact there was significant differences in the peak torque, says the type of header can make a difference. The near identical result at the hp peak seems to indicate some part of the engine was choking-off the peak potential. Meaning that no one header, unless it was grossly undersized or oversized, would make much of a difference.

[This message has been edited by 88IROCs (edited September 03, 2001).]

AJ_92RS

I was gonna post those same results due to the surprise it was to me after reading it.

I have that same issue. I keep old magazines. It's nice to go back and look at what has been tested and proven. Lord knows I can't remember everything about every issue.

Unfortunately They don't give the RPM levels at which the peaks are reached. I can tell you that this is not a low RPM torque engine. The peak HP #s range from 398.3-412.7 and the peak torque #s range from 386.5-396.1. That itself would suggest that the torque probably doesn't reach peak until around 4K-4500RPM.

A quote by David Vizard.
"I've heard engine builders and racers make a big deal about their engines having headers with the primaries uniform to within .05-inch.....Building a set of headers to such precision is a waste of time for a race engine and totally ludicrous for a street engine. Under ideal contitions, it's entirely practical for an exhaust system to scavenge the cylinder at near maximum intensity over a 4,000 RPM band width......A good street motor can have a working RPM range as high as 6000 RPM. One way to spread that 4000 RPM band is to use differing primary lengths...Since a typical street header can have pipes ranging in length from 24 to 36 inches, we safely can conclude that each pipe comes into its own somewhere in the used RPM range, thus helping to spread the powerband."

True. However, why spend the money if you don't have to? The Dynomax are the only 1 1/2" primaries. The Flowtechs are also shortie headers, but they have (as well as all the other headers) 1 5/8" primaries. ALL the other headers are full length headers with 3" collectors!!!

True, but isn't every engine somehow being choked off from it's peak potential? And we aren't discussing the engine itself. We are discussing primary sizing.

Mista failed to show the AVERAGE HP and Torque #s. (No flame intended Mista I'm actually backing up what you are showing.)

The list is as follows. (From 2,500-6,000 RPM)

Dynomax--85118---321.3/369.6
Flowtech-11108----320.8/368.9
Hedman---68720---314.4/363.0
PAW------7102----312.1/361.2
Summit---G9001---314.7/364.0

Now as you can see, the Dynomax headers gave the best averages in both HP and TQ. For a street/strip car, that is what you want. Part of it is surely due to the fact that they are shorties. But then how do you explain the better averages and peak torque over the Flowtechs? The Flowtechs are 1 5/8" primaries and 3" collectors. According to about 85% of people on hear say that bigger primaries help low end torque. HUH? Strange, isn't it?

Sometimes the "peak" #s aren't as important as the averages, especially for a street driven car. The goal is a flat power band for overall drivability.

Rallysport,

Go with the 1 1/2" primaries. For the money, you can't beat 'em. Plus they will be so much easier to work around as far as spark plug changing, spark plug boot clearance, and they'll be easier to install/re-torque due to the larger clearance between the primaries and header bolts. A lot easier to get that socket on those bolts.

AJ

[This message has been edited by AJ_92RS (edited September 03, 2001).]

BadSS

LOL - I'm glad I didn't read that magazine article before swapping from 1.5" to 1.75" headers. If I had,, I might not have been near as fast as I was.

Kevin91Z

iTrader: (1)

Keep in mind those header tests were on carb engines, which exhibit completely different characteristics than TPI engines. What works on a carb engine may or may not be the same on a TPI engine. I say TPI engines make their own torque, so you dont lose as much or anything with larger headers than you would think.

BadSS, nice reply.

AJ_92RS

Another victim of 1/4 mile times. (Not that it's bad, it's just typical.)

I never said that the smaller headers would increase peak power, nor 1/4 mile E.T.s, nor overall speed. I said Ever heard of practicality? Practicality is why we don't put 550HP engines in our cars which we drive every day that'll pass everything but a gas station. It's so we don't design an engine that doesn't make over 150 lb.ft. of TQ until 3500RPM so we can't beat a car off a stop light unless we launch at 4K RPM. It's also why we don't run open headers on the street, then drive past the nursing home at Midnight (at least I don't).

Streetable is the key word here. Designing an engine for bracket racing, or one for street use (and occasional drag strip runs) are two totally different things. That's what that article was all about. And doing it while still being able to buy food & beer while your installing them.

Sounds like a lot of you guys are the "bottom of the page" people. Rallysport is only looking for 300HP!!!! He obviously knows what practicality is. Sorry, but 1 1/2" primary headers are what sound like they would be the best use for him.

AJ

Jim85IROC

iTrader: (2)

I agree. I read a magazine article a while ago (I can not for the life of me remember what magazine it was in) where they swapped from 1 5/8" to 1 3/4" headers on a TPI thirdgen. The car was mostly stock. They were surprised to find a gain at ALL RPMS with the 1 3/4". They went through the usual spheal about the larger primaries hurting low end torque and concluded that they had done this many times on TPI cars, always with the same result of added power at all rpms. They came right out and said they didn't know why but said that it was a consistant gain every time.

I figure that the scavenging effect gained by exhaust pulses is not in rythm with the intake pulse effect found on TPI cars. By going with the larger primaries and reducing the scavenging effect on the exhaust, I think it may allow the harmonic pulse effect of the TPI system to have a greater presence. Then again, maybe I'm just talking trash.


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the roc

AJ, you’re the reason the internet will never be a viable resource for new performance enthusiast. In this thread there are people that obviously have real world experiences with changes in primary header sizes. I don’t understand why you would beg to differ with them when you obviously have no actual experiences regarding primary size changes. It’s a shame that you think by reading David Vizard and playing on your desktop dyno, that those give you enough insight to critic a dyno result of uncapped headers from a magazine, validate it’s findings, and make a recommendation for a street car that will run an exhaust system. Sad thing about it,, I think you really think you’re trying to help.

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People who think they know it all,,, are especially annoying to those of us who do.

AJ_92RS

YOU have no idea what you are talking about!!!!! It's pretty obvious that David Vizard knows what he's talking about!!!! And you say that I have no experiences changing primary sizes, you are SO wrong. You don't know anything about what I have and haven't done!!!

As far as my DD2000 goes, I never even used it for this situation!!!!! You need to quit ASSUMING, and quit critsizing others, including me. I don't critsize others. I critisize myself enough, so I don't need your help. Thanks anyway though.

I've read and heard from many engine builders, as well as used their advice multiple times with a lot of success!!!!

I guess I'm just older and have had all the "young, dumb, and full of ***" experiences that I need, so I finally decided to listen to the experts. Like using a 650 cfm carb over a 750 just because it's more streetable and gives better throttle response.

Look at the new 502 Ram Jet available from GM. They could have easily made it produce much more HP, but they chose the more streetable route. It's just more practical. Maybe you should call them and tell them it's obvious they have no experience building engines. They should stop playing with their computers and go ***** out with that engine so that it rips through a pair of tires once a week.

Rallysport isn't looking to build a 12 sec. car (not yet anyway ). Same with my selection of the engine I am building for my car. I've had my share of 12 sec. cars, but I want to be able to drive to Mich. to visit my brother, or southern IL, to visit my buddy, AND be able to get there on less than 10 tanks of fuel.

Again I never said that the smaller headers would give more peak power!!!! I NEVER SAID THAT, DID I? Again I speak of practical, streetable, and more maintenance friendly.

And last but not least, I'm the reason? Huh? Glad you can blame only one guy. Hope you feel better. I don't know it all, but I will die trying, and as open eyed as I can. I am just trying to help rallysport make the best decision for HIS application. All the rest of you are talking about engines 100+ HP more than his. He doesn't "need" huge headers. Maybe, if he's gonna eventually move up in HP, then yea he could benefit from larger primary headers. But did he ask that? NO!! Did he say that later on he wants to go with 400+HP? NO!!!! So yea, I am helping!!!

Spend the money on what you know you need instead of what you think you need. That way you'll have all the money to buy what you DO need.

Do you have a fixed income to live on? If you do then you know what I'm talking about. I have about $50 a month to spend on my car, whether it's to keep it running, or make it run better, that's all I get. Can you build a 12 sec. car in 2 yrs on that amount of money? I can and I have. It's called homework and junkyards!!

AJ

BadSS

[QUOTE]Originally posted by AJ_92RS:
Another victim of 1/4 mile times. (Not that it's bad, it's just typical.)

There is nothing typical about me or the cars I’ve built. In over 21 years I’ve built engines for and tuned hundreds of street and race cars ranging from LG4s to 9 second (no nitrous) somewhat streeteable small block Chevys. So look at yourself before you say anything to the roc about assuming. The car that I switched from 1.5” to 1.75”headers was a very “practical” mid 13 second car. The car increased in power from off idle through the shift point which increased a couple hundred RPM, as well as the flash point on the stall. Yes the quarter mile times were better, but so was part throttle and fuel economy. So who is a victim?

Now as you can see, the Dynomax headers gave the best averages in both HP and TQ. For a street/strip car, that is what you want. Part of it is surely due to the fact that they are shorties. But then how do you explain the better averages and peak torque over the Flowtechs? The Flowtechs are 1 5/8" primaries and 3" collectors. According to about 85% of people on hear say that bigger primaries help low end torque. HUH? Strange, isn't it?

So why do you think it’s strange? That this test showed the 1.5” headers put out more average power than the 1.625” headers and the people responding on this board are saying that 1.75” primaries does not give a loss as opposed to 1.5” headers? Real simple. That magazine testing was done uncapped,, correct? It does not surprise me at all that a small primary header run uncapped could generate better average power – depending on the camshaft. Throw an exhaust in the equation and that test is trash my friend.

Go with the 1 1/2" primaries. For the money, you can't beat 'em.

Sure you can,, 1.625” headers are no more expensive and they will yield better results through an exhaust than 1.5” headers on anything close to 300 horses.

Sounds like a lot of you guys are the "bottom of the page" people.

If I’m bottom of the page,, you better hope you get there some day.


And you say that I have no experiences changing primary sizes, you are SO wrong. You don't know anything about what I have and haven't done!!!

This was directed toward the roc,, but I had you pegged wrong also, I would have sworn you never ran a set of headers before. So,, do you care to share your experiences,, I’m curious - surely you had similar results as the rest of us.

I guess I'm just older and have had all the "young, dumb, and full of ***" experiences that I need, so I finally decided to listen to the experts. Like using a 650 cfm carb over a 750 just because it's more streetable and gives better throttle response.

LOL – What size engine and rpm band are you talking about? Is it possible you may have been talking to “experts” that think you are not capable of tuning a carb?

I am just trying to help rallysport make the best decision for HIS application. All the rest of you are talking about engines 100+ HP more than his. He doesn't "need" huge headers. Maybe, if he's gonna eventually move up in HP, then yea he could benefit from larger primary headers. But did he ask that?

I agree for the most part. If he already has the 1.5” primaries no need to buy anything else as long as he content with 300 horses. If he’s buying a set,, 1.625” primaries are no more costly and will perform better in front of a full exhaust.

jnjspdshop

I would say a mild to stronger 350 go with the 1 3/4" you might, might lose a little bottom end torque but you will make up for it at the top end, and the L98 engines already have enough torque stock to roast the tires to molten rubber.



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[b]Jason "TrickFlow" Zajac/b]

JnJSpdShop@aol.com

88IROCs

Personally, I don't see why we bother to argue with AJ. He's read David Vizard and at least one Car Craft article and that should be all the reason we need to consider him an exhaust expert. Practical experience should play no part here(every exhaust upgrade I've done to my IROC's has boosted low end-torque, to the point where I'd now gladly trade 50 lbs/ft below 2000 rpm for 20 hp above 4500), and for him it obviously doesn't. And gawd help us if we dare to consider a source other than those he certifies as valid.

AJ,

I know you'll continue reading this as justification for arguing a point that no-one agrees on with you. However, when you are old enough to obtain a library card, may I suggest you look up an author by the name of Hubert Smith(you might be surprised to find out how little David Vizard knows about exhaust systems, - or at least how little info he's passed on to you). For now I'll ignore you, confident that when you referred to both of us as idiots, you were at least 1/2 right.

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"The reasonable man adapts himself to the world.
The unreasonable one persists in trying to adapt the world to himself.
Therefore all progress depends on the unreasonable man"
--George Bernard Shaw.

[This message has been edited by 88IROCs (edited September 06, 2001).]

AJ_92RS

OK 88IROCs. Why do you have to make personal comments? You have no idea what I have done, read, seen, listened to, or even how old I am. As a matter of fact, why do any of you have to make personal comments? Is that how you release your frustration of a bad day or something? Try beer. It works for me. And also, as I said before, the idiot thing was a joke, that's why I included myself. Have a sense of humor every once in a while.

This is what I call a debate, difference of opinion, a personal preference, whatever you want to call it. I have seen, read, and heard exactly what I am saying numerous times, oh, and I've also experienced it.

Again I am just trying to help rallysport. And I just commented on someone else's response about that Car Craft article. And I only used David Vizard's findings because I figured it was a name that some of you may recognize.

You have probably never heard of Bruce Albers. He's the local engine designer/builder in my area. He has said similar things to me over the years that David Vizard has said in his newest book. And just for the assumptions that I have a feeling you are going to make that Bruce must have read "Mr. Vizard" (is that better roc? ). He had never even heard of David Vizard before ~1 yr. ago. That's when I bought the book and asked Bruce if he'd heard of "Mr. Vizard". He said "No."

Sorry for the lack of personal comments. I guess I need a library card so I can go learn how to belittle others as much as needed to make me feel good about myself. I'm glad all of you hate me now. LØRD knows that's what I wanted. To **** all of you off.

And just for the record, I never said any of you were wrong, did I?

Good Night, and GØD Bless,
AJ

[This message has been edited by AJ_92RS (edited September 07, 2001).]

BadSS

No hate here AJ - I take things a little too personal on a very unpersonal media. If we were at the local hangout BSing I'm sure we'd get along fine.