Piston Domes

I've seen a number of pictures of different engines being rebuilt, and it brings a question to mind. The tops of new stock pistons are sometimes very rough, but sometimes I see pictures where the tops look to be very smooth or polished. Should piston domes be polished when rebuilding, or doesn't it really matter one way or the other? Ed

Id say the surface finish is directly related to amount of machine work done to pistons.

650ed wrote: I've seen a number of pictures of different engines being rebuilt, and it brings a question to mind. The tops of new stock pistons are sometimes very rough, but sometimes I see pictures where the tops look to be very smooth or polished. Should piston domes be polished when rebuilding, or doesn't it really matter one way or the other? Ed

I polished the tops of my pistons when I did my rebuild using progressively finer sandpaper grits. The theory was that if it was smoother, heavy carbom would not be as likely to accumulate as much..... I should point out, the finest grit I used was about 180. I don't think mirror finishing is a good thing, I was just trying to level the major craters.

wireman wrote: Id say the surface finish is directly related to amount of machine work done to pistons.

The tops appear to have no machining, they look like cast parts and only the critical sizing dimensions are machined. The rest are just cast rough finish.

my mtcs had a smooth top.

:ohmy: cast vs forged :woohoo: .......forged pistons have smooth machined tops and valve reliefs.....a cast piston usually has valve reliefs built in along with the front pointing installation arrow ...... :huh: all forged pistons like mtc's,JE's have a smooth finish machined top :dry:
:pinch: BTW.forged pistons are stronger than cast

Borrowed this picture off APEs site,this is an aftermarket forged piston.
They get extra machine work done at factory to make the domes and valve notches just right,that and the forging process leaves a denser/smoother surface compared to a casting to start with.

www.google.com/url?sa=t&rct=j&q=piston%2...vm=bv.45175338,d.b2I :)

Cool video! Thanks!

Ideally the piston top is coated with an insulating layer, either ceramic or hard carbon build up. This keeps the heat (heat is power) in the combustion chamber where it can push the piston down harder.
It's not about pretty...it's about HP.