Think my studs are pulling?

Neilk · 01:24 PM

Hello,

Well it looks like it is engine rebuild time for me. I was driving a couple of weeks ago and as the car reached operating temperature of about 180, I started hearing some farting sounds from the back and the car felt like it was running on 5 cylinders. I pulled the valve covers off and the top cylinder head nuts for 2 where loose and 3 were barely tight. When I went to tighten them, the allen wrench bottomed out on the stud.

I pulled the engine and below is some photographic evidence.

Threads are showing on the #2 studs and the #3 stud closest to #2

Exhaust coming between the head and the cylinder. I hope it didn't cause too much damage

So it goes without saying, you will be see a lot of me around here for quite a while.

Engine is a 2.4S. Lastly, what is the secret to getting a good picture of your intake valves?

Talk to you soon,
Neil

Flat6pac · 05-29-2010, 02:01 PM

When you do the rebuild you need to remove some metal from the cylinder dividers. It will better cool the cylinders.
I dont remember much problem with the 2.4 pulling studs
Bruce

kenikh · 05-29-2010, 10:05 PM

Quote:

Originally Posted by Flat6pac

When you do the rebuild you need to remove some metal from the cylinder dividers. It will better cool the cylinders.
I dont remember much problem with the 2.4 pulling studs
Bruce

Or use a set of the Supertec 906 style tins.

The only way to get gert valve shots is with a camera w/ "Supermacro"

Walt Fricke · 06-01-2010, 08:21 PM

I'd be inclined to temporize on this.

If your head studs are actually pulling (and you don't hear about this happening on the 2.4s, as Bruce says), you will have to have the case head stud holes inserted. This is basically a machine shop job (though not a particularly tough one).

What I'd do is remove the head nuts which won't torque up. You may have to be ingenious with the one which has bottomed.

Then I'd try to screw the studs back down. How, you ask? Well, take one of those cylindrical head stud barrel nuts and drill a hole through it crosswise below the level of the allen socket. Put a piece of short round steel rod (a nail, for instance, though something stronger might be better)through the holes and cut off sort of flush. Remove the big thick washer. Screw your new stud twister tool onto the end of the stud. Crank on it to try to move the stud back down some.

Don't move it too far, or you won't have enough threads when you put a nut back on. Measure the depth of some good studs so you will have a reference other than looking at threads in the case. The studs are supposed to protrude from the case for 135mm, but that would be hard to measure in situ.

If they turn back in some, you can then see if they will retorque.

Alternatively, I like to use nuts with a 15mm wrench size, and with a wider base (called "flange nuts"). Almost as if it has a permanently attached washer base. I bought a bunch of these from Maryland Metric or some other usual suspect a while back. The advantage of these is that your tool won't bottom, because you use an ordinary 15mm socket. (they also present less of an obstacle to cooling air, and are the bee's knees for twin plugging, not a help for you). You could see if things will torque up. If the threads are pulling out of the magnesium alloy case, one would suppose the studs won't torque.

There is a sealing ring which fits in a groove in the cylinder up where it mates with the heads. It is possible this has been damaged by the leakage you show, but it is also possible it has not.

Though maybe you are ready for a tear down anyway?

I can't find my copy of Wayne's book, but Anderson has a diagram showing how to alter the cylinder tin. Just a quick tin snips job.

Walt

Neilk · 06-02-2010, 02:11 PM

Quote:

Originally Posted by Walt Fricke

I'd be inclined to temporize on this.

If your head studs are actually pulling (and you don't hear about this happening on the 2.4s, as Bruce says), you will have to have the case head stud holes inserted. This is basically a machine shop job (though not a particularly tough one).

Walt

Hi Walt,

The guy who restored my car was surprised and had me contact Walt at C.E. I asked him the same question because I thought 2.4s were safe, but he wrote back the following

"It's true that 20 years ago, 2.4s often had no work performed to the cylinder studs. The thought was that the "Stud Pulling" issue was peculiar to the 2.7. But now we even install (Case Savers) in 2.0ltr cases. We are seeing the cylinder studs pull out of all of the Magnesium cases. All of the 2.7s pull studs. 3/4 of the 2.4s. And probably 1/3 of the 2.2s."

I have another thing going against me, I haveone of those '73S WITHOUT an oil cooler (damn Porsche) and the car has spent the last 17 years in Miami or Dallas, not exactly ideal places not to have an oil cooler. I bought a trombone oil cooler for my car that I will install, but that will require removing the left heat exchanger which I will replace with a new set of SSIs. Might as well go all out.

At this point, I think I am ready to tackle a rebuild as trying your repair at this point seems futile. Although I wish I had tried it the first time I had tightened my head nuts.

Neilk · 06-11-2010, 08:14 PM

Engine is pulled and on engine stand.

I am wondering if my studs are really pulling or were poorly installed. I took off the heat exchangers tonight. On a lark, I put a wrench on nut and twisted and the stud and nut came out. On one side 5 of 6 studs came unscrewed with the nut and on the other 3 out of 6 studs unscrewed. I am thinking whoever rebuilt the engine last didn't know what locktite was. All the studs came out cleanly.

It would be tempting to take out the studs and reinstall them with locktite, but that isn't a good long term solution.

Picture of intake and exhaust valve to come.

Walt Fricke · 06-12-2010, 07:10 PM

Er, exhaust studs came out? 6 of those per side, but 12 head studs.

Loctite should not be necessary to keep studs in place. The tension torquing produces ought to produce enough thread friction so that nothing works loose. Ordinarily.

There is good authority for using a thread locker on the head studs into the case, though I think originally the factory did not say to do that in the workshop manual. But that is to keep them from loosening and being a bother when you are disassembling things, not to keep them in place and holding their needed tension.

I kind of like not using thread locker, so I can remove the head studs more easily on a rebuild. But I only work on my own engines.

Walt