Cylinder Head Cracks

[RALPHARAMA]

I vaguely remember someone talking 'bout cracks in Big Zed heads ... saying that it is a common feature but nothing to worry 'bout.

I've just bought a head from flea bay to recondition and after removing the valves I have noticed that on the inner two cylinder there are cracks between the valves and from the valves to the plug holes. The valve seats aren't affected. I wouldn't have thought welding was practical as I would have thought that the localised heat would warp the head into a right off situation.

Any info on this would be much appreciated.

[zed1015]

Cracks like yours are very common on these heads and most don't extend more than a couple of mm below the surface. I've never heard of any major problems because of these so i would carry on with the refurb. You should be able to see how deep the crack goes up the threads in the plug hole to confirm this. If still not satisfied you could always have some wurth type inserts put in the plug holes and any competent tig pilot should be able to 'spot' the crack between the valve seats without creating anywhere near the heat required to warp the head.

[AndyZ1R]

Seconded, i had what i thought were large cracks in mine but was told that was very common and nothing to worry about.

[ROZZER]

You could always try getting head pressure tested to be sure that cracks don't extend to the outside world/into ports. I would test before spending dosh on refurb.

[RALPHARAMA]

Thanks for the swift replies.

I'm an OK amateur TIG pilot but sadly can't afford a an AC/DC TIG needed to glue ally, but I know a TIG ace fighter pilot who has access to an AC/DC plant.

How does one pressure test a head ? Can this be done without the rest of the engine?

[zed1015]

You could have the head crack tested which involves treating the head with a dye that shows up all the nooks and crannys when x'rayed or similar. I know a bloke that uses this process at the firm he works for testing samples from british steel (corus) but i really do think you would be wasting your money as i have never had any crack related problems on a zed and one of the heads i am using now with 12-1 yoshi pistons has cracks in EVERY combustion chamber with no prob's at all.