Cylinder Head Surface Preparation

[curryinahurry 39]

Hello,

I'm currently in the process of cleaning up the mating surface on my M20B25 aluminium cylinder head and was wondering how clean does it need to be?

I've carefully gone over it with a razor blade and scraped off all the old gasket material that I could. However, there are still black areas around the coolant channels which I'm having trouble cleaning up completely. At the moment it feels smooth to touch.

Would it be necessary to get the head surface completely spotless? If so, how would you recommend doing so? (Without skimming the head - mine is straight, and I would prefer to keep the factory compression ratio)

Thanks in advance!

Cheers,

Andrew

[Etwenty1 45]

Hello,

I'm currently in the process of cleaning up the mating surface on my M20B25 aluminium cylinder head and was wondering how clean does it need to be?

I've carefully gone over it with a razor blade and scraped off all the old gasket material that I could. However, there are still black areas around the coolant channels which I'm having trouble cleaning up completely. At the moment it feels smooth to touch.

Would it be necessary to get the head surface completely spotless? If so, how would you recommend doing so? (Without skimming the head - mine is straight, and I would prefer to keep the factory compression ratio)

Thanks in advance!

Cheers,

Andrew

Some of that ingrained looking oil staining stays there, even after a skim. I'm waiting for parts to do mine ), paid $120 for a light skim at the engine reconditioners and $60 to replace the valve stem seals that i supplied.

I find that carefully using a good quality scraper blade with some engine oil on the surface gets rid of any old gasket stuff then a scrub with a plastic scourer pad and some de-greaser works well on both the block and the head (plastic only not a metal pad). Take care with solvents as some may damage your value guide seals. Then clean it another 2-3 times with degreaser and paper towels till its clean and dry with no residue. Make sure your bolt holes in the block are clean and dry too - rolled up paper towels works then compressed air.

Hope you have a helper to position the head. Mine has blown as a result of PO damaging the fire ring on the back cylinder, most likely from dropping the head on it.