theedge

Just want to be sure here. Today I bought a Dremel style tool with some felt polishing bits. I also got some Mothers Mag and Aluminum Polish paste.

It just takes a few minutes and the surface is perfectly smooth and shiny. If I went all out, I could get a mirror finish.

So, TOO smooth?

Jfrahm

smooth schmoooth. What you want is flat. And yeah I would suppose some surface texture is good to key into the gasket.

-Joel.

AznDrgn

hmm I use a wire wheel to clean off the surfaces and lightly scratch it to seat the new gasket.

hacker-pschorr

My thought would be you don't want a polished surface - I use elbow greese and some green scotch bright pads.

mwc951

I used 2000 grit sand paper

awilson40

you want flat and clean...but not an ultra smooth surface.
I would degloss it with scotch brite.
I'm an Mfg engineer and on one of our processes, an alum gear housing for Cummins,
we produced a part with a mirror surface using diamond inserts and high SFM.
The part wouldnt seal, gaskets would just squeeze right out.
Cummins ended up putting a target zone for the surface finish.
It was the first time we had a customer tell us our part was too good

inactiveuser92616

I heard a rumor that ferrari used to polish their cylinder head mating surfaces to the point that no gasket was needed, as on contact the perfectly smooth surfaces made a light bond. Anyone know the truth of this?

theedge

Good to know, thanks. Ill go at it all with some 1000 grit to be safe.

Jfrahm

I'd use 400 or 320, and glue it to a glass tabletop with rubber cement Then rub the head on it in a square pattern (not circular, which will sand some areas more than others.) Use four sheets. Works well. Some water and dish soap will make the sandpaper last longer (like more than eight seconds.)

Good luck,
-Joel.

theedge

The studs are in though. And that sounds way too gritty to me...?

apierce918

you can paint a car after using 400 or 320, i think it would be fine for a head

Peckster

What is it about some guys and polishing?

Oooooohhh, shiny!

The last thing you want to do with a flat mating surface is take a dremel to it.

Make sure you clean all those metal particles you can't see out of the head.

nine-44

At the dealer we used a planed sanding block(steele block, perfectly true) and 180 grit paper. Also we sprayed them down with brake cleaner to keep the paper from loading up. Sanding was flat, long strokes with a crosshatch pattern. IE, don't dig into it with the corner of the block. Also we used the same metod on the block when possible(studs suck to work around). This is called RA, roughness average if I'm not mistaken. When expanding or contracting due to heat, you want the mating surfaces to grab the gasket equally in all ways to keep from slipping or pulling the gasket unevenly and loosing the seal. I've used this method many times, all with good results on my own cars and customer cars. I would suggest checking the head and block with a very good straight edge, length and diagonally for trueness. Good luck