Are iron and aluminum L98 heads direct bolt ons to L05s with no fitting issues?

How much more power would "113" aluminum heads add to an otherwise mostly stock L05?

 

The Aluminum heads have a different intake bolt angle on the middle 4 bolts. The cast iron heads swap right over.

You would probably lose HP/TQ by swapping either of them on. That is without prom tuning.

Your L05 cam with 64 cc chambers stock, the corvette aluminum heads have 58cc chambers. Your L05 came from GM with flattop pistons. The L98 Corvette engines I have pulled apart had nearly 12cc dished pistons. That means that you will be up around 10.3-10.5:1 compression. That will drive you into ping city.

I am at 9.85:1 with cast iron heads and a ZZ4 camshaft and can barely run 93 octane, with a conservative timing map.

https://www.thirdgen.org/forums/tbi/...+heads+350+tbi

https://www.thirdgen.org/forums/tbi/...0-caprice.html

 

IIRC the later version of the 113 heads (1987+) have the same middle bolt angle as the iron heads. So those heads would be a bolt-on swap onto the LO5 ... but they won't flow that much better than what you have now, stock vs stock. Ditto for the 083 iron heads from the Fcar L98 (identical bolt pattern to your 193 heads, not much difference in flow). So the gains in power in using the 113 aluminum heads won't be much due to airflow, and as Fast355 said, the CR will probably be too high for a heavy car (more easily loaded engine at all speeds). So the biggest benefit in using them is the weight reduction.

IMO and in a thift sense, using 1.6 stamped rockers, keeping your L98 cam, adding duals and CAI is where you should start.... followed by DIY ECM tuning. That should yield 240+ fwhp. If you ported the heads you have and did nothing other than those mods, you'd gain another 30. That would be a combo quicker than a stock 3.08 LT1 Impala SS. HTH.

 

Wow, that's news to me. Where did you hear that? Why do my 1987-1991 L98 Corvette heads have the middle four intake bolt holes at the older angle, then?

Also keep in mind the L98 aluminum heads are missing one bolt-hole for the serpentine accessory brackets that needs to be drilled and tapped. Also, they dont have EGR passages, and there isnt a TBI intake I know of that lets you add an external EGR like the TPI does.

 

What he said, EVEN the ZZ4 heads are the older style bolt pattern.

 

Wow. That is news to me. I stand corrected.