Headers for a 92 TBI 350
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5.0 and 5.7 Discussion, Headers for a 92 TBI 350 in Cadillac Engine Technical Discussion; In the near future, I may be swapping engines on my roadmaster because I have one good TBI 350, and ...
  1. #1
    pimpin88's Avatar
    pimpin88 is offline Cadillac Owners Connoisseur
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    Headers for a 92 TBI 350

    In the near future, I may be swapping engines on my roadmaster because I have one good TBI 350, and the one in the roadmaster I just bought has blown headgaskets, so while I have the engine out, I figured it would be easier to do some mods to it.

    Are there any headers for a TBI 350, and what is the price/quality?

    Thanks.

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  3. #2
    90Brougham350's Avatar
    90Brougham350 is offline Cadillac Owners Connoisseur
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    Re: Headers for a 92 TBI 350

    There are header options available. I'm not sure if Impala SS headers will work but Jegs and Summit each sell a few different brands. I'd love to find some Tri-Y's for my '90 but $$$ is always the issue. Just call Summit and they'll tell you exactly fits.

  4. #3
    xxcaddytech is offline Cadillac Owners Member
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    Re: Headers for a 92 TBI 350

    the engine-trans-rear are out of a 1/2ton chevy truck shorty headers for it should work fine. impala ss headers should work also just more $$ raodmaster-deville-impala were all built on the same frame

  5. #4
    90Brougham350's Avatar
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    Re: Headers for a 92 TBI 350

    Shorties will work, but with the peak power at 2000 rpm from the L05, long-tubes or tri-y's are the better header to work with the powerband.

  6. #5
    xxcaddytech is offline Cadillac Owners Member
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    Re: Headers for a 92 TBI 350

    true... but with the lo5 being such a weak motor with pathetic intake ports. (fairly useless above 3500rpm) i would not waste my money on any mods till i got a better set of heads at least and a better cam. remember those things are luxury boats. not racecars.. if you want more power do the swap the tbi is no tpi for sure.

  7. #6
    kdrolt is offline Cadillac Owners Member
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    Re: Headers for a 92 TBI 350

    Quote Originally Posted by xxcaddytech View Post
    true... but with the lo5 being such a weak motor with pathetic intake ports. (fairly useless above 3500rpm) i would not waste my money on any mods till i got a better set of heads at least and a better cam. remember those things are luxury boats. not racecars.. if you want more power do the swap the tbi is no tpi for sure.
    TPI isn't much better. It makes MUCH better torque from approx 2500-3500 rpm from the enhanced-cylinder-filling of acoustic resonance, but it makes less torque elsewhere as compared to TBI when using the same cam & exhaust (dyno test proven by Fast355 on TGO). And TPI suffers from the well-known breathing problem at high rpms due to the losses in the runners, which can only be corrected by fairly expensive aftermarket replacements to the runners and lower manifold.

    As for the weak LO5 motor: with the 179/185 deg roller cam in the non-police LO5s and the built-for-quiet exhaust, it's no surprise that they were only 180 fwhp @ 4000 rpm and 300 ftlbs. With the copcar cam (same as L98, "773" stamping, 202/207 deg) and the bigger (but still restrictive) copcar Ypipe, the power went to 205 fwhp. Using an aftermarket exhaust and a decent cold air intake/filter bumps the power to 225+ fwhp. That's still not great by LT1 and LS1 standards but it's also equal to the iron-head L98 TPI engine's rating.

    Thirdgen Fcar owners that have used LO5 (replacement) engines have run mid 13s @ 101+ mph in the quarter, by using a cam & exhaust swap, and a carb to sidestep the needed ECM (re)tuning. That means the fw torque and fwhp is on-par with the Fcar LT1 1993-1997 (because they run in that range), and that's when using stock LO5 heads. If the intake port was that much of a problem, then the car would not have run that quickly nor have that trap speed. That fact has been driven home by many other people.

    So the problem isn't the heads on the LO5; the fastburn character makes up for their lack of good stock flow. Stock unported LO3 heads have been dyno'd against a set of ported 416s --- on the exact same engine -- and the ported 416s didn't outpower the stock LO3 heads until after 4200 rpm. That's stock L03 heads (which flow in the 165/140 cfm range intake/exhaust) vs ported 416s (220/160 cfm typically). The headflow numbers say the ported 416s should kill the stock L03 heads -- and yet they don't until 4200+ rpm. What hasn't been done (yet) is porting the LO3 heads and comparing them to the ported 416s.

    So the better combustion chambers (fast burn) and need for less ignition advance (28 degs vs 36) on the stock L03 heads makes up for the lack of airflow as compared to the 416s. And LO3 heads are esentially the same as those on the L05; the only difference is the intake valve is 1.84" diameter (LO3) vs 1.94" (LO5).

    The problem on the LO3, LO5, and other GM engines of the 1980s and early 1990s is the very restrictive exhaust and the puny cams. So that comment applies to the owner of a 92 TBI 350 Cadillac.

    There are now many threads discussing ALL of the above items, on the TBI forum at TBI - Third Gen .org : F-Body : Chevrolet Camaro, IROC, Z28, Pontiac Firebird, Trans Am and on the Fullsize Chevy Engine Performance forum at FULLSIZEforums - Chevy Truck so it's not just hearsay.

    I agree on the boat comment, but the 94-96 Caprice/Impala was also a boat and they move quite well with 260 fwhp and 330 fw ftlbs, from a 350 with very good heads, a 191/196 deg cam, and decent factory dual exhaust. A TBI LO5 won't flow like the LT1 heads will (unless you port them) but it is reasonable to get 230+ fwhp and 320+ fwhp if you alter the exhaust, use the copcar/L98 cam or equivalent, copcar injectors, and a decent cold air intake. I'd also use the 91-93 EPROM chip from a 9C1 copcar because it will still run well with those mods, but the factory Caddy EPROM won't because it's expecting a 180 fwhp engine using smaller fuel injectors. TBI 9C1 owners that have modified the exhaust and added a decent DIY CAI, have run mid 15s @ 86-88 mph. It's not as good as an LT1, but it's pretty good considering how little modified the engine is. HTH.

  8. #7
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    Re: Headers for a 92 TBI 350

    Exhuast is often noted as the first upgrade one should apply to an engine, because it allows all mods after it to work much more efficiently. Heads and a cam are excellent upgrades, but will work much better with headers. Plus, headers are a good place to start because they do not require a re-programming of the computer, whereas heads or a cam do. If you've already got headers and you upgrade heads or a cam, you can account for that as well with the re-programming.

  9. #8
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    Re: Headers for a 92 TBI 350

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  10. #9
    Kriegar is offline Cadillac Owners Member
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    Re: Headers for a 92 TBI 350

    What about swapping to a stock dual exhaust off a later model LT1 car?

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