Limiting factors on 915 heads?

[Dustin The PcP]

If I were to use these heads on my 318, that has 1.77X1.5 heads on it. What would be benefits, and what would be drawbacks? The engine sees 6,500+ rpm pretty heavily. Would I still be able to spin the engine that high, or higher?

 

[EL5DEMON340]

You talking about the 71/72 915 heads? they had 2.02 in 71 and 1.88 in 72. They are more CC's so your CR will drop over the 318 head but if you spin it at 6,500 and keep it in the upper rpm range most of the time the 915's should be much better than the 318 heads.

 

[1wild&crazyguy]

they flow more than the 318 heads but like mentioned have larger chmber volume than 318 heads--70-72cc vs 68cc[318]

so you will have to mill them down and I would do a bowl blend.

I would mill them down around 4cc smaller than the 318 heads 68cc, like 64cc wuld really help with this combo

 

[66fs]

they flow more than the 318 heads but like mentioned have larger chmber volume than 318 heads--70-72cc vs 68cc[318] so you will have to mill them down and I would do a bowl blend.
I would mill them down around 4cc smaller than the 318 heads 68cc, like 64cc wuld really help with this combo

I agree with the above. "J" heads can have 1.88 or 2.02 intake valves. Both are much better than 318 heads. If you mill .040 off the block side you should end up with about 65cc chambers. Mill the intake side of the heads .038 so your intake will bolt on correctly. Exhaust seats are not hardened. Use a 340 or 360 intake to take full advantage of the larger intake ports. Same with the exhaust manifolds.

 

[Dustin The PcP]

Thank you for the info.