340 J Head Combustion Chamber

[Demon_Jeff_71]

I am looking to try and find the combustion chamber size for 188 160 valve 340 J heads. Trying to find the right pistons to go with the heads I am going to go with.

THanks

JEff

 

['64 Cuda]

When I cc'd a set of J heads they were at about 72cc's.

 

[lead69]

If your looking for accuracy I would cc the heads after they have a valve job,otherwise its just guessing,especially if the history is unkown.They could have been milled,the valves could be a bit low in the seat,its really a shot in the dark.You can get a cc kit or just pay a shop to do it but its money well spent,Ive seen j heads from 68-72 range without milling depending on the valvejob and size/type of valves.

 

[fishy68]

I cc'd a set and they were 71.6 cc's

 

[rumblefish360]

What compresion ratio are you looking for?

An example of a zero deck piston in a 360 and .039 (Fel-Pro gaskets) thick yeilds a ratio of 9.8-1.

 

[Demon_Jeff_71]

I am going to go around 10:1 or 10.5:1 when I am finished with a 318 and the J heads. I am looking at some Keith Black pistons with this cam.


http://www.hughesengines.com/Index/...ZW5naW5lcw==&level1=Q2Ftc2hhZnQ=&partid=21854

 

[rumblefish360]

Keith Black has zero deck pisons as well as small domed units for the 318. At there site, they also have a compresion ratio calc.

 

[moper]

If they are untouched Js, I'd use 74ccs. They are never smaller than the max spec from the factory. The only way to know for sure is to have them CC'd.