Time for an overhaul

[wahlstrom1]

Elevation has a lot to do with it.....I could run 11-1 compression on 89 in red deer, but be adding octane boost to 93 in vancouver. I wouldn't worry about it if I were you.

-andrew

 

[CopyKat]

I know a 422 cam would help with this. The other thing is I'm going to be running some boost through this engine and I'm worried the 10:1 compression is going to be fighting me left and right.

 

[wahlstrom1]

Yup, usually you try lower compression to run boost...I'd build the engine as your planning, then use the 95 block and build a strong bottom end with low compression pistons and swap that in when you boost it.

-andrew

 

[CopyKat]

Nope this one I'm building is going to get boosted. I'm thinking the stock heads may be better suited for this. If the bottom end of the 95 block was any good I'd likely put the 91 heads on it, with the concave pistons. I wouldn't have to worry about running low compression pistons.

 

[rickcdewitt]

the early block is supposedly better than 95+. i'm not sure about the 1991 3.55 driven gear color i'll see if i still have a spare.

 

[CopyKat]

I don't need one I have a yellow one, black one, pink one and a white. I may have a red one also.

The block itself yes is better for a 91 but I don't know if the heads/gaskets/bolts can support a 10:1 compression AND 5 psi boost at the same time.

Fawk I'm thinking of sticking with the 91 heads I have on right now if they are not cracked.

 

[CopyKat]

OK this pretty much explains which way I'm going.

Copycat - installing the 95+heads on a pre-95 shortblock will result in a copression ratio of around 10:1, normally necessitating the need to run premium fuel, depending on conditions. 99.99% of the time - no ping results and in those few that do, it usually the result of other factors combined.

DO NOT expect to be able to run boost with that compression with the ODB1 PCM unless you can find a tuner that really knows how to crack into the PCM and tune it properly (key word is 'properly').

Bird

The 91 heads are going to stay, but they will get ported on the exhaust side.