121 ti head gasket

[Mikesmalaga72]

Can anyone tell me which type of cyl head gasket to use with 9.5 cr pistons, and 121 ti cyl head? The workshop manual says the regular e12 headgaskets are not interchangeable. IE reinforced, or serrated ring. Also where to get an upper gasket set for the 121 ti. Thanks all!

[jerry]

i JUST did a gasket refresh on an engine i had lying around. this particular engine has a 121T (not 121ti) head with a casting date of 1979. the compression test on it prior to removal was 180 psi across all cylinders. i would characterize this as a high compression engine.

anyway, the head gasket that i removed was NO different than a standard head gasket i bought from the usual sources.

and yes, i was very pleased to see a set of very nice original, clean 02ti spec bathtub pistons in those bores. can't wait to install this engine.

[Mikesmalaga72]

Thanks!!

[Guest Anonymous]

This is a little off point, perhaps deserving of its own new thread.

As most know, the Tii head gasket is "more robust" in that it involves a cutting ring that makes an impression into the head. I have been led to believe that once this type of head gasket is used, head resurfacing is a must.

I have gambled with not using the "cutting head gasket" on high compression applications because all my heads have been resurfaced to the maximum. In one case I was forced to slot the timing gear to adjust for the resurfacing. I have also tried a thicker head gasket, but my luck - after 6 months gasket blew between chambers two and three. I am told another possibility is to o-ring the block, which I am considering.

Now, to my point. Anyone out there with a Tii or high compression set up use the standard off-the-shelf head gasket? There must be some of you out there. How do you deal with the situation meaning am I missing something obvious?

TIA

[jerry]

Anyone out there with a Tii or high compression set up use the standard off-the-shelf head gasket? There must be some of you out there. How do you deal with the situation meaning am I missing something obvious?

TIA

uh, i thought i answered this in my previous post.

the engine i recently cleaned up was found with the STANDARD-issue, plain-jane head gasket with no evidence of blowby or other issues. in fact, were it not for the fact that the head gasket broke at the junction between the timing cover cases i would have left it alone. it was not a 'cutting ring' gasket nor a special tii-spec gasket.

i did spray both sides of the new head gasket with hi-temp copper spray prior to installation and made sure the head bolt holes were absolutely clean, and retorqued in stages per the Haynes manual.

the compression was measured at 180psi which i would consider a high-compression engine.

[2761876]

did, do you, use new head bolts?

[jerry]

did, do you, use new head bolts?

the head bolts on the M10 engine are NOT stretched during the torqueing procedure. i cleaned and inspected them and decided to reuse as-is.

it's my understanding that some engines rely head bolts that will stretch during proper torque and these bolts should not be reused.

[PatAllen]

well, i am running 14psi of boost on a standard head gasket, with head bolts used at least 3 times by me...no problem so far.

That makes a hell of a presure into the cylinders believe me, and i did experience some preignition in the past as well, so it holds up very good.

What i NEVER miss when i build an engine is i make both the block and the head a slight resurface, which makes the gasket "stick" into the rough surface.

My understanding of the whole thing is that if the surfaces are straight, bolts properly torqued***, and there is no "high level" pre ignition, the gasket should not blow even with 12:1 pistons.

***means that the bolt threads are super clean, with some anti seaze so all the bolts can be bolted down by hand without any tension, that leads to a super even torqueing.

[02fanatic]

I was under the impression that a cutting ring style gasket was a "good thing" to use! I had a friend with a fresh tii engine rebuild blow his head gasket while following me down to Mid-Atlantik '02 Fest in Virginia years ago and it was NOT a pretty sight! When he repaired the blow-out he used a cutting ring gasket and no more issues.

I am going to rebuild my 121tii engine with stock bathtub pistons someday, so I am interested in this issue.

[Guest Anonymous]

Jerry: beg your pardon, I was free associating. I did read your post about using the "standard" headgasket. I suppose I was looking for additional nonexistent feedback.

Some folks assume BMW's engineers must always be right and that must include the use of the cutting ring gasket for Tii's. The designer's track record is pretty good but not infallible. Obviously, time and scientific advancement marches on as do better adhesives, composites, fasteners, etc.

Nevertheless, BMW still sells the cutting ring gaskets. I wondered if someone with actual experience could opine at what point the cutting gasket really became necessary. What is the limiting factor, heat, pressure a combination of both. Only when turbo charging? The 11:1 big block aluminum head Chevy gasket s do not use a cutting ring, does that translate to our itty bitty four banger? It is interesting to note that the "higher compression" 6 cyl version of the tii found in the 3.0 models did not , to the best of my knowledge use a cutting ring gasket.

Respecting the reuse of head bolts. It has been addressed many times. In my case I keep a new one handy. If any of the other bolts are longer than the new bolt, i.e., stretched - they dont get reused.

[TobyB]

I don't use the cutting ring on the race car, either-

broken lots of things, never had the gasket go!

Yes, you're supposed to take a cut every time you use a cutting ring- if you've ever seen a head that's had one on it, you'd see why. If the new ring was slightly mis- aligned, it's a guaranteed leak...

Toby