ProComp/Speedmaster aluminum heads

PRH said

Do your heads have 11/32” stem valves?
The Speedmasters do.
I didn’t measure the length of the ones I had here, but a lot of that stuff uses SBC +.100” length(nominal 5.010”).

So, if that’s what you have, they might work.
The spring installed height is taller than stock heads, so those may not work.

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Here's what I do know about my heads they were stock 596 heads with 188 intakes. I had them rebuilt with new K line valve guides and they only had to replace a couple exhaust valves I believe. I ran them for a year then took them off and had them put 202 valves in. Obviously those were new. I couldn't imagine them resizing the valve guides? So I assume whatever stock would be?