Ok, i just thought it was interesting that John Lenginfelter (sp?) suggesting using a 1 5/8" headers until ur running 400+HP, then he suggest 1 3/4" headers, i was in barns and noble and was reading his chevy hi perf. book. pretty interesting, wish i wash rich so i could buy all those books. anyways, i just thought i would share that since i know there has been alot of arguing, but then again, i would still guess it depends on the type of power ur wanting to make, especialy since SLP recomends 1 3/4" headers for all 350's. oh well..

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- David
88' GTA 5.7L TPI MODS---> air foil, K&N, Shift Kit, 180* therm, TB bypass, Gutted CAT, Flowmaster 80 Series

 

well that guy knows what he's talking about, so there's no reason not to trust what he's saying.

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'86 IROC 5-speed
305 LG4
edelbrock performer rpm intake
edelbrock 600 cfm carb
msd pro billet hei distributer
'95 3.23 rearend
hotchkis rear suspension
PST front polygraphite suspension
"speed kills. buy a f@&d, live forever."

 

Well, maybe he can afford to buy headers more than once. I know mine are gonna kill the 305, but no matter what else I throw in the car, I'll never have to buy another set of headers...

 

Most likely, Mr. Lenginfelter (sp?) was basing his recommendations on testing with long-tube, equal-length type headers dumped to the atmosphere, on high horsepower, high rpm engines. Since our typical shorties are neither long-tube (not optimum for pulse tuning) nor equal-length (not optimum for cylinder-to-cylinder performance), and are on cars with full emissions-legal exhaust that typical stay below 6000 rpm, there is good reason to believe SLP also knows what they are talking about as well.

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82 Berlinetta, orig V-6 car, now w/86 LG4/TH700R4. 2.93 limited slip. 2-1/2" cat-back, ZZ3 intake, Accel HEI SuperCoil. AMSOIL syn lubes bumper-to-bumper. Daily driver, work-in-progress (LG4 CC system w/'87 LB9 block, ZZ3 cam, ported World 305 heads, Hooker 2055 headers, 3" Catco cat & 3" catback, restalled TC, Spohn SFCs).
57 Bel Air, my 1st car. '66 396, 9.7 CR forged TRWs, Weiand Action+, Holley 750VS w/4150 conversion, 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).

 

Also dont forget that 99% of all engine dyno testing is done with carburetors, which exhibit different characteristics than TPI engines.

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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=-

 

i thought that maybe it was a Fuel injection book, but i also think it might be just a small block book, but it think its a combination of both, but yes that is a good point.

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- David
88' GTA 5.7L TPI MODS---> air foil, K&N, Shift Kit, 180* therm, TB bypass, Gutted CAT, Flowmaster 80 Series

 

I've actually got his book. Most of it reads like a catalog for LPE. It's interesting to note that while he says you don't need 1 3/4" tubes under 380 hp, he doesn't supply any proof that they will help or hurt output(I'm still waiting for someone who can prove using 1 3/4" tubes on a L98, will do something besides increase output at all rpm's). He claims that pipe diameter is more important than pipe length, but also says "Typical exhaust headers for the small-block Chevy are the four-into-one design with lengths between 32 and 36 inches". Take a look on the cover of the book(the motor on the left) to see what he's talking about, and ask yourself how you would fit those headers into any Chevy chassis built in the last 20 years. The relevance of his claim is lost on me.

So lacking the room to fit "full-length" headers into my thirdgens, I'll make up the difference by using a larger pipe diameter.

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[This message has been edited by 88IROCs (edited September 14, 2001).]