Interesting thread covering slightly higher compresson height 5.0 pistons in the high deck, mid 70's 302's, to overcome the lower compression. Maybe some have already done it. But made me consider a motor I can get cheap I would have passed on earlier. http://www.network54.com/Forum/119417/thread/1137148196/289+questions
Well, I didn't find a cheap answer there. One guy used 289 rods and milled the pistons. I thought of that, but the 1/8 stroke difference was larger than the .023 block difference, so I don't know how much cheaper it would be. They never produced any evidence of the piston differences in the 5.0 and the 302. if anyone has a set, its worth checking out. I'll see if my cousin still has his stock 5.0 pistons. Personally, I plan on having the deck milled to get my height back to stock.
I had to look at the same thing when I used a 74 block to build my 347. I ended up just getting the block decked. Decking and magnaflux cost around $160.
Dang it. I was trying to be lazy on two different threads but you guys made me go look up what I was thinking about. I knew I saw some different compression distance pistons when I was looking to select for the 289. Most 289/302 listed stuff is 1.605 compression distance. Which puts the piston ideally .016 down in the hole(if I remember correctly) This part number is 1.619 compression distance, TRW L2488, listed for 5.0/302, which would give about zero deck on a non shaved, non high deck height block, which is just too iffy for piston and valve clearance for what I wanted to do, and any shaving and there's no way. But, this should make a good quench distance in a high deck block. No? Ideally this piston would be (.016 + .023) - (1.619 - 1.605) = .025 in the hole on a non shaved high deck. .023 being the difference in deck height between the normal and high deck blocks. So a little shaving just to make it flat, a thin gasket, and quench should be good and high deck blocks are no longer a problem. Unless I've just confused myself.
Depends what thickness head gasket your looking at using. You can get copper .021" but you have to o-ring the block or heads. Cometic sells a .027" head gasket but that would add up to .052" quench which is outside the optimum .035-.045 quench distance. 'Course you could just run real rich and build up about .010" of carbon on your pistons.
or leak oil through the intake gasket, same difference. I thought about just going with domed pistons, and I'm sure when the time comes I'll look into that more thoroughly, but right now I'm assuming I'll have the money to have the block milled to standard run of the mill 302 specs. Its just less complicated. It has to help with the intake fitment.
ok. High deck really isn't a problem anyway, just shave it off. Didn't think about the intake fit. Might even be easier to set compression ratio with my small chamber '66 heads. Just shave to fit the exact desired number. I'll go through compression ratio on those pistons anyway, like I said, shaved flat will take the quench down a little anyway, no oil or carbon needed. Not thinking real high performance on this one, just cheap, so quench a little high wouldn't bother me.
