OK i found this tidbit of information online;

LB9 V8 9.3:1 5.0 (305) 195@4000 295@2800 TPI

LB9 V8 9.3:1 5.0 (305) 220@4400 290@3200 TPI


so.. how does one determin which LB9 they have?

 

What year are those specs from, they seem odd. One may be the dual cat version or the 5 speed one.

 

those specs are supposed to be for '88. I believe dual cats were only for 350's?

 

No LB9's came with 290 hp PERIOD. I think around 250 Hp. being modest

 

LB9 V8 9.3:1 5.0 (305) 195@4000 HP 295@2800 TQ TPI

LB9 V8 9.3:1 5.0 (305) 220@4400 HP 290@3200 TQ TPI

 

Thank you very much LOL
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I would assume that the difference between these two would either be the dual cat option and 5 speed. Or you are off base witht the years and possibly the difference is MAF And Speed Density

 

195 HP @ 4000 RPM / 295 FT/LB @ 2800 RPM (MXO Transmission)
220 HP @ 4400 RPM / 285 FT/LB @ 3200 RPM (MM5 Transmission)

My understanding is for 88 the N10 dual cat was not available as an option.
I believe that the automatic version got the smaller camshaft. The 5-speed version LB9 got the L98 camshaft.

 

smith is right

The power gain come from the more aggressive cam.

pat

 

hum, are you positive about that? I've owned three '88 IROCs, all TPI LB9 T-5's. Two seemed kinda wimpy wimpy, while the most recent one I sold seemed to have alot better torque, pickup, and power. **Although I did not verify if that car did or did not have the stock cam and internals.

 

I think there is some info about this in the history/Restoration board...I think it confirms the different cam is the reason....I'll see if I can find it.

 

Correct
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Yes

 

That's what the documentation shows.
Your "wimpy" cars may have possessed a higher rear gear ratio which would limit off line acceleration. The model year, weight of car, "tune" of engine, etc. could have also played a part.

 

What was the first year for the dual cat option?

 

yeah different cam for the auto . The Manual cars got the L-98 ( B2L) camshaft.

 

Also the one with more horespower has the G92 option which gave it bigger exhaust manifolds and from 90 - 92 G92 gave it dual cats.

 

Actually ...lets use the 1988 for example . It had 190 hp ( auto) 220 hp ( manual) then 230 hp ( for manual dual cat ).... the 220 hp is a single cat 5 speed.

 

Difference in Cams, manifolds, and number of cats.
85 TPI auto had 215hp, iirc, and the next year it dropped to 195hp (smaller cam).

My 88 305TPI Auto was rated at 195hp and with some bolt ons it dynos 195hp at the wheels.

 

See my reply........

 

Brisk, the reason you may have noticed a difference in performance is because these TPI cars were notorious for being "inconsistent" in performance. TPIS pointed this fact out years ago in their "Insider Hints" booklet where they stated a few could be extremely fast, a few extremely slow and the rest "moderate" in performance.

TPIS suggested that one of primary reasons for the difference was fuel pressure. But, I think it has more to do with "how well" the tune in the eprom matched the subtle differences that occur in any mass produced engine. The most common reason I believe is the "noises" in the enigne and who it interacts with the Knock Sensor (which results in timing being pulled).

I know for a fact that I have a particular bin that was optimized for my L98 (before I started to modify it). It was much quicker and got better mileage all from tuning my eprom.

I met a few guys who wanted to try my bin. I found most of them could not run the bin that ran on my car due to detonation. I had disabled the knock sensor in WOT and had it set to the "max" where just a fraction more of spark would result in knock. Everyone who tried the bin encountered knock and I had to retard the max spark in all of them. Some only need 1 degree and a couple need as much as 4 degrees.

That few extra degrees makes a BIG DIFFERENCE in the performance you obtain from your engine.

I would say that if you had those cars again, and could optimize the "tune" in the eprom that you would find that there performance would greatly increase and you may even find them more comparable. But, there will always be one that is just a "little quicker" than the other, and one that is just a "little slower" than the others. You will probably find the reason is the "quicker car" can run just a little more spark without detonating when compared to the "slower car".