Well I'm in the middle of a head gasket job and was wondering what you guys do to prep the mating surfaces. I've been using gasket remover to loosen the heavy stuff then scraping with a razor. This has got everything pretty clean, but there are still stains/imprints of the old gasket.

So do the surfaces need lightly sanded or polished or something along those lines? I ran a .002" feelers under a straight edge and they are both perfectly flat. I know these MLS gaskets can be picky when it comes to the finish, so I want to make sure I do it right!

 

Forgot to say I didn't use a razor on the head. Gasket removed and scrubbing with paper towel got it clean.

 

Anyone? I'm about to just slap it on there as is.

 

bring it to a good machine shop and have them surface it. its usually $50-$75 and they will leave a better surface than anything you can do.

 

if it already has been set up with a good RA, do NOT sand it at all.. and if you did take it to a shop, make sure they are familiar with the proper finishes for MLS head gaskets.. it has to be extremely smooth not like the old school head gaskets. (oh yea, and especially if you have oversize valves, if they are extremely close to the head surface, they will have to come out to do it right.)

Most can be cleaned with towel and brake parts cleaner...

some stuff that won't come off you can remove with the plastic razor blades if you can find them, if not be careful to not dig into the surface.

Good rule of thumb here is.. the "thumbnail" test.. drag your thumbnail accross the surface and if anything "catches" or you can feel imperfections in the surface, they will probably be a problem (I'm talking about old gasket material or residue... if there was something else that made it that way you have bigger problems than buying a new gasket)

 

The head was machined about 5,000 miles ago. I don't want to take anymore material off the head since it has been done already.

I haven't sanded the head or even taken a razor to it.

I may take it to get machined...

 

You can use sandpaper beneath either a machinist's block or a pane of plate glass, topped with evenly distributed weight to lightly surface the head. Do this procedure deck surface facing up, using long smooth motions. It's a delicate procedure, but It's been done before. I wouldn't recommend you use this method to straighten out a warped head, because you'll be there for a month, but if you just want a good surface, this can work out beautifully, but if you doubt for a second that you can do it, take your head to a machine shop. It's not worth the gamble.

 

 

The more you mess with it by hand, the less flat it will be. Using a sheet of glass and sandpaper will never give you a flat deck. The only way to hand finish a head and get it flat is lapping it with paste on a granite table.

 

Like I said the head is flat. It was checked with a .002" feeler and a straight edge that was machined to within .0005"

My goal here was to basically "polish" the surface, but I think I'm going to leave it as is.

 

glad to hear you're not going to use a 2x4, belt sander, sanding block, block and tackle and whatever else was mentioned