Quote:
Originally Posted by Frank Reiner
The questions are somewhat irrelevant; five of the bolt locations of the aluminum block heads do not match the corresponding locations of the iron block heads.
But no, the port sizes are smaller than those of the 5.6 heads.
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From what I understand realigning the bolt holes in the head is a simple machining job. The pre 86 5.0 and all 4.2 have a bigger exhaust valve(and same as a 5.6) than the iron block engines. The 5.6 exhaust ports is way bigger than a 3.5/4.5.. intake valves are larger in the 5.6 and 86^ 5.0. the combustion chamber from the 4.2 would suit my 4.5 better with the same bore, plus the chamber looks smaller in the pics I see on eBay, so less compression loss than a 5.6 head. Unfortunately none of the 4.2 heads are private sales and stores with thousands of items aren't going to go put a digital caliper in the ports for me. I'd love to run an alloy block 5.6 or 5.0 but I just doubt it will take the abuse I give my car, plus it doesn't bolt up to the manual trans. 3.5 heads are one option to just raise compression for power. But the set I have need a full going through. I'd love to know the.4.2 chamber volume since I want to port and redo whatever set Im going to use. Kinda stupid to start with a smaller port head and work it if the 4.2 is similar and has bigger valves and ports. And before anyone says anything about low end losses it in a manual trans drift car. It doesn't do anything below 3500 rpm.