New to me 525

[Ed Courter]

My new, 1990 e34 M20 manual, 200k, good (not perfect) idle, no oil use, no coolant use, feels strong on road.

Max compression dry and wet. butterfly open, engine cold. From front...

145 180
150 170
145 165
140 190
110 150
110 150

The 110s being 5&6... bad gasket?

I have to go in for a timing belt this winter and wonder if I should pull the head for a new gasket, or would these wet numbers mean the rings are worn badly, so just yank the whole thing? What are the chances I only need to pull the pistons, add rings, clean up the cylinders and roll? The M20 is my favorite e34 engine.

I am also willing to drive it the way it is and see what happens. (new belt of course), Thanks in advance, Ed Courter

[ross1]

I think a HG. Identical low #s between adjacent cylinders is almost always a failed fire ring between those cylinders. Using coolant yet?

If you start seeing steam on start up you run the risk of hydro-locking a cylinder. Over heating is the other obvious issue.
It's better to address this now, you have a long cylinder head that likes to twist when over heated. Combustion gasses going between those cylinders wont do the sealing surfaces any favors either.
Your #s will probably even out a bit when warm and are not bad as is, I'd leave the bottom end alone.

I'm an M20 fan too, not so much in a 3600# car but still a good engine.

[Ed Courter]

Thanks, for the help, Are you including rings in the bottom end to be left alone? Any thing else that should be done to the head when its off? cam ,springs, seats? Ed

[ross1]

Thanks, for the help, Are you including rings in the bottom end to be left alone? Any thing else that should be done to the head when its off? cam ,springs, seats? Ed
It needs to be examined, especially for straightness and evaluated. From what you've posted I suspect the HG is your only issue.
You have a 25 yr old, 200k car worth $1.5k or so. Only you can decide how much you want to invest. Me? I'd fix what needs fixing and be grateful for any remaining service it provides.

[5mall5nail5]

Do a leak down test, you'll know with more certainty

[Binjammin]

Do a leak down test, you'll know with more certainty

Or, for the cost of a leakdown kit, just buy another m50. :dunno

[5mall5nail5]

Its an M20 in OP so, yeah or that

[imae30driver]

My new, 1990 e34 M20 manual, 200k, good (not perfect) idle, no oil use, no coolant use, feels strong on road.

Max compression dry and wet. butterfly open, engine cold. From front...

145 180
150 170
145 165
140 190
110 150
110 150

The 110s being 5&6... bad gasket?

I have to go in for a timing belt this winter and wonder if I should pull the head for a new gasket, or would these wet numbers mean the rings are worn badly, so just yank the whole thing? What are the chances I only need to pull the pistons, add rings, clean up the cylinders and roll? The M20 is my favorite e34 engine.

I am also willing to drive it the way it is and see what happens. (new belt of course), Thanks in advance, Ed Courter


I think the m20 e34 is cool. (Rare!)

If you love it, rebuild it.. Pull it out, replace all gaskets, rings and seals.. (Bearing's if its a lifetime car even) and enjoy another 200k

goodluck

[Binjammin]

Its an M20 in OP so, yeah or that

Meh, missed that, but really doesnt invalidate the point. Why fix a borked m20 when you can has m50?

Hell, a head gasket set plus pressure testing and decking at a machine shop will cost as much as some of the e34s I've bought... buy a whole parts car at that point.

[Ed Courter]

Looking at the head gasket I see very little material between the cylinders. Also the coolant passages are located where I might only have a compression leak (5,6), I'm going in, gasket kit/studs at hand, Thanks for the help, I'll let you know what I find, Edward