Fresh Head For an Old Bottom End ?

[jeffnhiscars]

Now that I'm about to put a rebuilt head on my M20 barnfind, my thoughts are drifting to the M10. I bought it 14 yrs ago with 157k and it has about 215k now and the internals have never been touched. Externally, it has an 8lb JB Racing fw, BavAuto headers and a full Ansa Sport cat delete (header to tail).

Conventional wisdom is that if you freshen the head on an old engine you put unwelcome stress on the bottom and and threaten your bearings. Does this apply to an otherwise well running M10 or is it much ado about nothing ?

TIA for the input.

[Hey_You]

It applies to all engines. It puts more stress on your piston rings (as the compression has been restored) which in turn puts a little more stress on the bearings. If I were you, I would leave the top end alone unless you were going to add some more goodies to it. If it aint broke, don't fix it :)

[E30_Pare]

But it ain't broke. So upgrade. Lol.

Ive Also thought about this, but I'm afraid to pull my head & find my block cracked at the headbolts.

[jeffnhiscars]

It applies to all engines. It puts more stress on your piston rings (as the compression has been restored) which in turn puts a little more stress on the bearings. If I were you, I would leave the top end alone unless you were going to add some more goodies to it. If it aint broke, don't fix it :)

That begs the next question which has been discussed ad nauseum so I wont talk about engine "goodies". I believe my compression is low but I dont trust my gauge since it's older than most of you and I have had my oil pressure light stay on longer than it used to on cold start so Im just thinking the old girl is getting long in the tooth (and yes I should just probably service the oil pressure relief valve or find the check valve that probably doesnt exist).

May be time to do some long range planning and find a 2.0 block. After all, now that I've torn into my 1st BMW engine, it's a whole new world :)

[TobyB]

Meh, it doesn't matter. If the head's worn out, freshening it will help some.

But then you'll realize half your oil was coming out of the bottom end.

Bearings in M10's are super- durable- if you keep clean oil in 'em,
they go forever. Rings lose their spring no matter what, pistons wear out
no matter what...

t

[Hey_You]

If I were you, just source a 2.0L block to start. Freshen it up while it's out of the car, and then freshen the head up, and put it on your shortblock. That's how I did mine, and I'm glad I did. 2.0L actually adds a little bit of torque down low so I didn't have to downshift as much up hills