305iroc

What's the difference. They were both LB9 motor's "VIN F" Right? Which one's in my 91 Z28?

GASGZLR

Since you have the 5 speed, you have the L98 cam in it stock which makes your 305 have 230 HP. The 700R4 LB9's got 205 hp. I read somewhere that if you drive your car perfect you could run dead even with an L98 auto or maybe take it.

305iroc

That's what I thought, but wasen't sure. It's posibble that my car could hang with a L98, it did come with 3.42's from the factory, that might help. Thank's for the info.

RB83L69

That's not the difference; although the cams are different at least in some years. There's some debate as to whether the cams were still different in that year, or whether they had made them all the same by then.

The higher HP cars have the G92 RPO which gets you, among other things, dual cats. If your car is single cat, it is the lower HP version.

They are both VIN F.

305iroc

I don't think I've ever seen a 91 Z28 with a singal cat. My car has duel cat's. I think 89 would have been a year that you would see singal or duel cat's.

305iroc

Well at least on a TPI motor. Of corse a TBI motor will have a singal cat.

GASGZLR

Check your RPO codes in the center console of your car and input them into the forum decoder. I have 3.42's in my Beast and a T-5 and at 60 mph I am pullin about 1800-1900 rpm in 5th. Also if you have a 145 speedo then you have the 3.42's if it's the 110 version then you prolly have the 3.08's. If that doesn't work you could call a GM dealer and give them your VIN # and they could prolly tell you.

305iroc

Got more info.
G92-axle,rear,performance ratio
GU6-axle,rear,3.42 ratio
and N10 is the RPO for duel cat's
I do have the 145 speedo, and these RPO's are all stuff I have on my car. I think that G92 is a little more then just different gear's.
I work at a GM dealer, that's where I got the info.

Ray87Z

Supposedly the non-G92 305 TPI 5spds were rated at the same 205hp as the autos. The accepted info was that they got the crappy cam that the autos were usually stuck with. But several people here and at cz28.com have pulled the cams and spec'd them out to be the hotter cam. They would seem to be underrated pretty decently at 205hp in that case, dual cats vs single cats was previously a 10hp difference...

Now there are some thoughts that even the 91-92 TPI autos got the hotter cam too, not sure anyone has ironed that out with any certainty yet. But some of the stock 1/4 times I've heard reported for 91-92 305 TPI autos certainly make it seem quite possible...

brent4a

Just check the exhaust. Dual Cats is the higher of the 2 .

305iroc

Everything point's to it being the 230hp. That's not bad. Mustangs made 225 right? What kind of 1/4 mile times can I expect? Maybe a high 14(like 14.9) on a good run would be my guess.