Head

[Gus 5]

looks like my head has either buggered a gasket or cracked after taupo..still drives fine and doesnt over heat but upon checking water there seems to be a bit of oil in it and bubbles when the engine is running.

i have a spare head so i am probably just going to get it skimmed and rebuild but use my current cam shaft.

any other suggestions as to what i should do while im there. am not planning to stay with m20 long term but will be for a while...maybe a 3 angle valve grind (done by the cylinder head shop i presume??) and i need to check if i have over sized valves in my current head.

is there any point in:

a) skimming the head more to raise compression?

polishing the combustion chambers (not just removing the carbon, which i will do anyway on the bottom end too)

c) polishing the exhaust ports?

any ideas welcomed, would prefer some with some evidence of use on the m20

cheers guys

Edited March 12, 2007 by Gus

[Silver Fox 43]

I believe 3 angle valve cut is normal now, but you can also get the valves backcut which gives improved flow.

[will 169]

looks like my head has either buggered a gasket or cracked after taupo..still drives fine and doesnt over heat but upon checking water there seems to be a bit of oil in it and bubbles when the engine is running.

easy way to check is to put a gas analyser probe in the water bottle while it is running (but above the water of course!). If you get a gas reading, it is blown.

If you can find an engine leak tester (and someone who knows how to use it properly!!)you can determine what is wrong (gasket or crack) before you strip it.

Be careful when skimming these heads, the valves are close to the piston tops standard and too much skimming can cause hitting!! If you go too high in the compression stakes you will be stuck having to use a high octane fuel, which, as Andy found during the northland meet, is not available in the wops..

Get the valves done with 3 angle cut. Opening the ports up and polishing them will show gains but is painstaking work.. need to be careful you dont break into water jacket etc when doing it. Probably best left to a pro with a flow bench imo..

Will