Color by WEASEL

I've been looking at new pistons for my 289. I have slap in one and I just want it perfect. So, new pistons and rings may be in my near future. Not being a real wrench, what if any is the benefit or negative of "flat top" -vs- "stock replacement" pistons? The bores are good and no other issues with the slap. No gouges, heat nothing...just want new to rebuild.

monkeydude3

well what kind are in there now? arey they dished or do they have valve reliefs?

If you are going from dished to flat top you may get a slight bump in compression but I'm not sure. Also, is that 289 an interference motor?

Color by WEASEL

They have the valve reliefs as do the flat tops I am looking at. I do not think they are dished. I do not remember, but I think not. I am not familiar with the term "interference". It is a 1966 "C" code standard 2bbl 289, stock, totally. Well, with OS pistons. 040 over. And I do know that is the max. Like I said before, no other issues and no block worries. Basic rebuild. But, if I can get some benefit from flat tops, I may get them. I have a lead on a set of new flat tops with moly rings for 125 bucks. Thanks in advance!

monkeydude3

hmmm then it sounds like they will be almost the same as what you have? I'm not too familiar with engine building but I have rebuilt them before... for a simple rebuild those should work fine. You gonna put in new crank bearings and cam bearings? usually a good idea while you are in there

Color by WEASEL

After looking again, they are dished with valve reliefs. The crank and rod bearings were just done. I done my make over prior to starting after sitting by replacing the bottom end stuff. Cam and lifters were not. I hear people almost brag about their engines being .030 over. Mine is .040 over and if I add flat tops, what does that mean performance wise? Is there any HP gain?

monkeydude3

i'm not sure if the HP gain will there but you may get more torque. Just upping that size usually gets a lil more torque than the stock dimensions. The flat tops might get a little more power... but I'm not really sure how much the compression ratio will change