TPITuned Port Injection discussion and questions. LB9 and L98 tech, porting, tuning, and bolt-on aftermarket products.
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not quite true - I found some flow data for both that suggests that the 081 heads flow 20cfm better on the intake side.
Also - I have empirical data from somebody who dyno'ed with the 187 heads and the smaller 305 cam and made 197hp, then switched to the 081 heads and larger cam and retested - pulled 232hp, so it was worth 35hp. Also the power curve died after 3500rpm with the smaller cam / heads and had a good 1000-1500 more useable RPM with the bigger cam / 081 heads. Hard to say how much was heads vs. the cam, but I am not taking any chances and will just go with the 081 heads to be sure. The port design is also a bit different and optimized for TPI, so that should work better as a system.
Yeah they're pretty much the same except the change from perimeter bolt valve covers to center bolt valve covers.
That's not specific to LB9/LG4. I had an 87 LG4 with the centerbolt valve covers.
Quote:
Originally Posted by c4racers
Also - I have empirical data from somebody who dyno'ed with the 187 heads and the smaller 305 cam and made 197hp, then switched to the 081 heads and larger cam and retested - pulled 232hp, so it was worth 35hp.
IIRC, the 187's were the TBI swirl-port heads, which is yet another different head from the two previously mentioned.
LB9's and LG4's should have the same head. The only difference should be the valve covers/manifold bolts, which changed from 86->87, not from LG4<->LB9
I have taken apart stock LG4s from 1987-1988 Caprices that had 187s heads. I have also seen 1987-1988 Monte Carlos with 081s on the L69 and 187s on the LG4.
It is a spec class with stock motors in NASA called CMC - Camaro Mustang Challenge. Road racing. We get about 15-20 cars per event in CA, so there are plenty of people to race!! Very popular series with great driving and competition.
You're probably correct, but since this is a thirdgen website, so what came on Caprices and Monte Carlo's isnt relevant. I would agree GM used up whatever stock they had left, using the good stuff on better cars and the rest on other cars.
The Camaro-Mustang Challenge is a lot of fun! I've been out to their races several times helping my friend Nick Steel. They're limited to 230 RWHP and 300 RWTQ, but there's no limit on area under the curve. I still wouldnt know which heads are better, but the new-tech guy in me would say to use the newer heads.
You're probably correct, but since this is a thirdgen website, so what came on Caprices and Monte Carlo's isnt relevant. I would agree GM used up whatever stock they had left, using the good stuff on better cars and the rest on other cars.
The Camaro-Mustang Challenge is a lot of fun! I've been out to their races several times helping my friend Nick Steel. They're limited to 230 RWHP and 300 RWTQ, but there's no limit on area under the curve. I still wouldnt know which heads are better, but the new-tech guy in me would say to use the newer heads.
Yes it is a Camaro/Firebird website, BUT I feel the fact that LG4s came with 187s is VERY RELEVANT. It has been 20 years since the general built the last of the LG4s and MANY of the engines have been rebuilt and swapped around. Unless it is a documented stock car, it very well could have 187s on it. I've even seen 193 and 083 350 heads on rebuilt 305 engines.
