knowledgable engine guys!

[moper]

In this 318s case, the factory head is a smaller chamber open design. The last set I had was IIRC 58cc. I milled the crap out of them. I dont think milling is the best way, because you have a ton into cutting them, then you still need to get pushrods by the time you're done. That being said, I've raised static ratios about 1.5pts doing it on ultra low budget builds. The sad part is, by the time you have the heads milled, and the intake milled to fit, you have 2/3 the $$ of the pistons anyway. If you have the money, the right way to make it all work is the right pistons and good block machining to get the parts together well.

 

[66dartgt]

For what its worth - I did something very similar with the engine in my 66. I used a 68 block, and the existing pistons from a previous overhaul. I dont remember what the pin height was on the pistons, since they were good I just used them. I cc'd the cylinder volume at tdc with a buret. I used a set of these later model closed chamber "302" heads, and cc'd the heads with a buret. I used the mopar thin gaskets and calculated the CR as being right at 9:1. If your pin height happens to be taller than mine you should end up at very close to 9.5:1 or 10:1.

I'd do some theoretical calculations (before buying anything) based on the pin height of the pistons you intend to use and the combustion chamber volume of around 59 CC. Don't forget the gasket volumes as well. Fel pro blue head gaskets are thick and contribute around 8 or 9 cc to the chamber volume if I remember right. The thin mopar gaskets are around 5 or 6 cc ? (not sure on that one).

The other thing to remember is that with a closed chamber head, for each .001 you take off the actual change in volume will be less (since the combustion chamber is closed). The figures that mopar uses for milling is for open chambers.

 

[rbdart]

Great responses, so many recipe's and combo's, have ran 302s on 318s[mods were 1.88-1.60 valves lite milling[ .o20] mild port work[chambers are tall and skinny unlike 360 head but they are pretty efficent for their size so choice of intakes and their runner size needs to be considered, when cleaning up ports dont get nutty on hogging them out width wise. 302s can be a very decent head with their tulip or heart shaped comb. chamber and on average raise comp. .5--.8 of a point of comp. [some call them swirl port-somewhat true] and used on smaller cu. inch motor respond well.....but since u mentioned 360 that would be my choice,more cubes,more torque more choices more hp and 360s already have 1.88/1.60 valve much more potential, I think that if ur gonna mill heads, change valves,and change cams etc. why not get the most bang for ur buck? And if ur rebuilding motor, which i'm assumong ur, have 360 crank balanced so u can run behind 4spd without all the weight/balance issues of flywheel, or the ultimate[ imop] take 400, stroke it......well whole new deal.......back to 318s, good little motor lots of ways to go, best advice is to get books, info,and study other moparites combo's and decide what exactly u want to do ,what ur compromises and trade-off's are[and how much money ur willing to spend] but bottom line is to have fun and drive the crap out of it---a 318 is just a baby 340...and they are legends, just have a real well thought out game plan and make it happen...the more knowledge and info u can aquire means better decision you'll make...good luck