Im working with a 1984 305 with dish pistons and 2 of the pistons are fried! I have a 1988 305 with dish 4 valve relief pistons! Can I use 2 of them to replace the fried dish pistons? I really didnt know if it would make a difference in compression or not. They are same in every thing else except for the top of the pistons. Here is the spec on the 2 types i have --the dish wo/valve relief http://shop.advanceautoparts.com/web...R%7CGRPENGPAMS_____ and the one w/valve relief http://shop.advanceautoparts.com/web...R%7CGRPENGPAMS_____ I know I can just buy a couple, but i would rather not if I dont have to, Thanks

 

I wouldn't. The LG4 pistons (84-down) were "deep dish" and yielded an 8.5:1 compression ratio. The later 1 piece rear main seal 305s had a smaller, shallower dish that yielded 9.2:1 compression. Heads were 58cc in both cases, so the difference was basically due to the pistons.

Any reason you don't want to swap all 8 while you're at it?

 

Well I thought about using all the 88' piston, but didnt want to clean them all :/ But now seeing the compression is better with the 88's over the 84's, I guess I will give it a try! Thanks for the info,