Originally Posted by Horsepoweraddiction
I have 3 sets of big block heads 1. 3856206. 2. 4081045 3. 346236 so I take it all of them are peanut ports? And 550 sounds great but I cant, definitely in the future ! But if those heads aren't the oval ports I need imight can try and find a set of the 049 or 781s. But if I can't get any I'll take vinnies advice and get the bigger valves and port a set of them.
The 236 are PP. I think the 045 are too.
The 206 heads (below) are closed chamber oval port heads. They will bring the compression up, but they don't flow as well as open chamber heads. The open chamber heads require a domed piston to bring up the compression.
There's an "in between" head called a semi-open chamber, like the casting number 215 and 063 heads. They are about 100-103cc. Open chamber heads are around 118cc.
Semi-open chamber on left, open chamber PP heads, right