I recently bought a 1991 Formula ws6
With a LB9 engine.

I am looking for any information on the factory heads that came on this car.

Flow rates,
valve sizes,
Chambers CC

Pros and cons of this style head.

 

The stock LB9 heads flow 195@.500 on the intake, I dont know the exhuast. The stock valve size is 1.84 and 1.5. and have 58cc combustion chambers. These heads are good for a lightly modded 305 and can be made even better with bigger valves and minor porting. A few guys on here have made them flow as well as vortecs with minor work. I am using a set just like them with bigger valves and some bowl work and I like them very much.

 

Was there to different LB9 engines in 1991?

I searched and saw specs on a 205 hp and a 235hp

I think.
How do I tell which one I have.
I am assuming Vin Must tell me.

Thanks

 

The 230hp 305 had a 5sp and dual exhaust. The auto was 205hp and was not dual exhaust. These were found only on Z28's and the special service cars (B4C, 1LE models). RS models and plain Firebirds (even if they have a 5sp) did not get the LB9 engine.

The VIN will tell you:

8=L98 350 TPI 245 hp automatic only, no 5sp from factory
F=LB9 305 TPI 205/230 hp auto/5sp (see above)
E=LO3 305 TBI 170 hp auto or 5sp.
T=LHO v6 140 hp

 

I guess I should explain that the center digit on the vin will tell you what you have.

Also check out the tech data page of Thirdgen. It has a ton of info for ya.