here is my dilema..
I just built some 336781 heads dated H10 76/ O25 74 with new stainless valves, new compcams 924-16 springs,741-16 retainers and new 10 degree locks #612-16 to go with a comp cams H284 which has .574 intake and .578 exh.

I have since bought a date correct CTW 70 396 350hp engine. These heads are #3964290 dated C18 70/ D16 70

Now my question is..... do I spend the $ and swap my valves,springs,etc to the 3964290 heads or just run the later model 336781 heads?? and why?

thanks in advance, Jim

Well, I dont know if the engine you bought is built as original, but assuming it is, the 781 heads (open chamber) will have much bigger chambers than the 290 heads (closed chamber), and you will lose a bunch of compression. And of course, some power with it. The 290's are around the 100cc range, the 781's are more like 118 to 120. I would use the 290's for sure. What are you using the car for? You can swap the springs, retainers, locks, etc. and leave the stock valves in the 290's and save some money. Or get the bigger valves intalled and be done with it. I personally would not use the 781's on that engine unless you're going to do a piston change to keep your c/r up. That cam is going to require a decent c/r to run good. Do you know what pistons are in it now? Then we could figure out where you would be with either head.