[Guy Hiltz]

I got my new Speed Pro pistons for my re build next year,they have a smallish dome for open chamber BBC heads.The top of the dome is smooth and shiny,the rest of the top of the piston is rough and grey.I sat down for an hour or so with a peice of medium emery paper,a peice of green scotch brite pad and some aluminum polish.A little bit of elbow grease sure made a big difference,now I got the rest of the piston almost as shiny and smooth as the dome,plus I smoothed off the sharp edges.Before I continue on with this I was wondering if doing this is a waste of time or not ??

 

[ap72]

not a waste of time- reduces carbon deposits and detonation

 

[Rick WI]

I smoothed off the sharp edges.

That is not a total waste of time, but if your not on the ragged edge not going to make a whole lot of difference. We certainly will dress the edges round the valve cutouts on top of a piston on a really high performance street engine or race engine. Does it help, who knows? Does it make you feel like your doing a better job, I guess.

Who's to say on the rough part of the piston the mixture and flame front might not like the rough surface better? Who knows? I don't.

 

[texastomeh]

Guy -

I did essentially the exact same thing that you described on the SBC 405 that I have been building. What really happened was that I decided to "dress-up and smooth-out" some of the rough edges/spots on the cast Speed Pro pistons and they began to look so pretty that I couldn't seem to find a place to stop!!!!

Will it make any difference? I think that Rick hit it right on the head! :thumbup:

Did I "enjoy" it and feel that I was make a MAJOR contribution to the performance capability of my "custom built" engine? - Of course!! Everyone knows that chrome and shiney works better, goes faster and lasts longer!! And even if it doesn't - it sure is pretty!!! :thumbup: :thumbup:

texastomeh

 

[61bone]

Kinda off the thread, but in the sixties, Rolls Bought a few Gm Autos for testing. They disassembled them and rebuilt them to Rolls spec for fit and finish. In other words, they polished all rough surfaces and smoothed edges, When done the trans wouldnt work. Piston seals wouldn't seal. Just saying that all that's polished maybe shouldn't be.
Piston tops? Who knows. I would be inclined to think the rough surface would enable flame propagation through turbulance. Kinda like a smooth Golfball won't travel as far or fast as a dimpled one. .02