Thread: engine problem....please help??!!

I wouldn't judge the wear by the lip to any great extent. Part of the lip will be carbon build up. Once the carbon has been removed, you can get an idea of how much the bore has worn.
Using feeler guages, measure the clearance between the piston and the bore wall. Do this front to back and side to side, at the top of the stroke and at the bottom. If the piston to bore clearance is tolerable, you may want to replace the rings only. To do this, drop the sump, undo the big ends and withdraw the conrods and pistons. Hone the bore, and fit new rings, after scraping the carbon from the ring groves. Assemble. This is assuming that it needs doing. What were the compression pressures of the other two cylinders?
You mention that the head has been off recently. Could the gasket have blown due to incorrect gasket fitting? When fitting a new gasket (any gasket in any location) always make sure that the surface is perfectly clean. I scrape both surfaces with a new Stanley knife blade until they are perfectly smooth. This means shinny metal. It does take a fair amount of time and effort to get it that way. Alternatively, you could use a brass wire wheel. Is it a copper or fibre head gasket? Did they use Hylomar? Was it re-torqued at the appropriate interval? If the two good cylinders have good compression, I would be inclined to just replace the gasket properly, and give it a run before deciding on what to do next. Head gaskets are quite cheap anyway.
Aaron.

Can't tell you what the compression on the good cylinders was because i had a ****ty compression tester that you push into the spark plug hole instead of a threaded one. The good cylinders were convincingly going past 100 psi when i couldn't hold the pressure anymore. the others were sealed and only registered 60psi.

the existing gasket is a copper one and at first glance (with the head still on) has no sealant on it. I have a replacement copper gasket to fit tomorrow.

Do people recommend using a sealant like hylomar or permatex copper gasket sealant etc on these engines?

Originally Posted by Aaron IIA

Could the gasket have blown due to incorrect gasket fitting? When fitting a new gasket (any gasket in any location) always make sure that the surface is perfectly clean. I scrape both surfaces with a new Stanley knife blade until they are perfectly smooth. This means shinny metal. It does take a fair amount of time and effort to get it that way. Alternatively, you could use a brass wire wheel. Is it a copper or fibre head gasket? Did they use Hylomar? Was it re-torqued at the appropriate interval? If the two good cylinders have good compression, I would be inclined to just replace the gasket properly, and give it a run before deciding on what to do next. Head gaskets are quite cheap anyway.
Aaron.

Just a precaution on doing this there needs to be a "surface quality" to a head and shiney aint it. while the head needs to be nearly perfectly flat the very very minor abrasions help the head gasket do its job. Once youve got all the muck off of the head/block and confirmed that both are inside of tolerances then If you can get it (for an ally head) I swear by blank newspaper if you can get it (the stuff on a roll before it goes through a press) wrap a hand full of layers around a nice soft wooden block and in small circles gently massage the block and you should come up with a dull matt grey finish after you clean it all down with metho the same applies to a cast iron part but you use a very very fine wet and dry paper. Getting the surface finish wrong can lead to the gasket letting go.

If you get one of the composite gaskets that look like expensive cardboard you usually dont need a gasketing compound but the proper one piece metal gaskets do require the goop.

Originally Posted by britchie

blown head gasket between 1 & 2, compression was way down 60 psi in these two cylinders (should be 145psi when new) I would still expect 125psi from a reasonable motor. Has anyone got an tricky way to gauge the condition of the piston rings when the head is off, without taking the pistons out??

You will most likely see vertical score/scuff marks in the bore(s) if the rings are broken.

Originally Posted by Blknight.aus

Just a precaution on doing this there needs to be a "surface quality" to a head and shiney aint it.

What you say does make sense. What the main point of my post was, make sure that all of the old gasket was removed, and that the surfaces were flat. I am usually accustomed to dealing with people who would not remove all of the old gasket. So by saying shiney, I mean that you are looking at clean metal, and not rust or old gasket. I can fully understand that a polished surface will allow the gasket to blow more easily.

If using a copper gasket, I would recommend using a sealant that is suitable for head gaskets. One that comes to mind is Hylomar. I have used it in the past, and it works quite well.
Aaron.