DSKRALL

Is the '85-'86 cam a good match with the 113 casting heads? Will the combination produce more torque than the original set up? I know the timing specs of the flat tappet L98 cam and the L98 roller are similar, but that the flat tappet cam may open and close the valves more slowly. I don't know if that would negate the benefits of the 113 heads.

Also, are 1.5 ratio roller rockers a good addition to the combination of '85-'86 cam and 113 heads? Will 1.5 roller rockers fit under the stock valve covers? If not, can the LT4 covers be used?

MtlSphere

It's definitely not a bad match.

Be aware that the combustion chamber size of the 113's is like 58cc's. So your compression ratio is going to be significantly increased. You'll feel it in the SOTP!!

I haven't found a pair of 113's that I like the price of yet... The iron heads on my 85 (from 87 crate motor) have 64cc combustion chambers and will NOT run on regular gas without knocking the guts out of it! Premium works great and the knock counts are few. I don't hear or feel them but the scan tool picks them up.

If you have a set of them use them!

MrNuke

Actually the '85 heads use 72cc chambers, with 9:1 to 9.5:1 compression stock. Going to 58cc chambers, will raise you to at least 10.2:1 or higher.

You will also NOT be able to retain your stock EGR setup. (Dports dont' have the middle EGR passage open). This means you have to get a new later model lower intake manifold, external EGR tube and later model exhaust manifold to connect to the EGR plumbing (Or weld it to the old exhaust manifold).. Or you could just forget all about the Emissions stuff i fyour state doesn't care.

On a positive note, IF you get past these issues, you will be about 40lbs lighter, and about 20-40hp better off just because of the CRAPPY POS smog heads the '85's have.

ps.. your stock gm rockers are 'around' 1.5 ratio... I wouldn't waste my time upgradeing to aftermarket 1.5, unless they are roller rockers. (I'm using a set of 1.52rr's myself).

CFI-EFI

Actually the '85 heads use 76cc chambers. The '85, L98, long block is the same as my '84, L83, with the exception of the camshaft. *I* assumed the 64cc iron heads, MtlSphere said he was using on his '85, were other than the stock heads.

RACE ON!!!

JAKE

I'm not sure which way you meant this. Do you have the cam and are considering swapping heads OR do you have the heads and are considering swapping cams?

Do you already have the 113s or a line on a pair?

Yes, they'd be a good match, but depending on the cost of thr 113s, they may not be your best option. It depends on what you have to pay for them Vs the cost of a pair of aftermarket heads - that flow better - but would cost about the same as the 113s.

If you are already running the heads and are considering swapping out the roller cam, I'd say you'd be taking a step backwards if yours is a roller cam engine. There are some other unknowns, too, like is yours a roller or non-roller block; is this a fresh re-build, what parts do you already have, etc.

To use roller rockers under the stock covers, most likely you'll have to grind off (notice I didn't say "break-off) the oil drip tabs. Breaking them off can leave you with nice little holes in you valve covers. Ask me how I know.

Jake

DSKRALL

Thank you for the good replies. To clarify, I was thinking about adding the 113 heads to an '85 or '86 with the stock flat-tappet cam. Although using 113 heads seems to be a good idea, the change is more involved than I thought (OF COURSE). By the way, I thought that the aluminum heads would only raise the compression from 9.0 to 9.5:1, which is all that I would want.

Another question: Will the '85 and early '86 computer handle the half point increase in compression?

CFI-EFI

Generally, computers don't know about compression. An increase would have no effect. IF the higher compression were to cause excessive pinging (unlikely) the ESC woud handle it.

RACE ON!!!