#1 Exhaust head bolt missing, need opinion - Pic included Options

[Trevorg7]

So I put the car back up on stands this morning and went through them to ensure the HE were snug. Oddly enough the #3 was fairly loose. All were snugged up and I ran the car again. It was better but I am not sure if it was perfect.

Do the copper gaskets between the head and HE take time to seat? Is there something I am missing?

Let me know.

Thanks

T

[HAM Inc]

Trevor there is a good chance that the ex. sealing surface in the head is no longer flat. I remachine that surface on every T4 head I do and I would say that well over 50% are no longer flat. The fact that you lost a stud and the HE was still torqued on one side makes it likely that the HE dug into the torqued side. You would think that the copper gasket would take the abuse, but the reality is that it passes it to the head. There really isn't much you can do about it without major work. Another bit of advise, if you can live with the leak that you have (if it isn't to bad) don't fool with the connection any more than you have to. Those old studs are brittle, I don't care how good they look! They will break if you overtorque them, and overtorque for an old heat fatiqued stud is well below the book torque spec.

In my experience ex. studs problems are quite often an indicator of aging heads that are ready for a complete overhaul. I have had MANY heads come to me for ex. stud problems and when I tore them down to do the work I found more serious problems that could very easliy have lead to catastrophic failure.
BTW you did a good job with the stud replacement. I know it's tough on the car. The stud closest to the rocker chamber (as your's was) is tight and hard to access. You would be amazed at some of the DIY repair job nightmares I've seen over the years!

[jk76.914]

Same thing happened on my '76. I put in the 9mm/8mm stud, and about 1000 miles later it was gone. Pulled out. If you pull an 8mm stud, you leave an 8mm hole, best case. It's actually worse than that because the hole is ragged. Anyway, when you tap to 9mm, you don't have full depth threads and it can (or almost certainly will!) pull out again

So, either go with a 10mm/8mm step stud, or a timecert with a 9mm/8mm stud. There are pros and cons of timecert vs helicoil, but I think the concensus is timecert in this application. It's harder to find and more expensive than helicoil, though.

My favorite metric fastener place is Bel-Metric- www.belmetric.com . They have the timecert kit AND the 10mm/8mm stud AND 9mm/8mm studs, as well as copper plated locking nuts.

There's an article I think at Ratwell.com on how to ensure the exhaust HE sealing surfaces are flat, and another on on how to anneal (soften) the copper gaskets so they'll seal more reliably...

Finally, install the heat exchanger, and then carefully check the alignment with the hanger in back. If you have to bend the HE to align the screw holes, you'll be leaving residual stress in the system at the mounting studs. I had to remove the hanger and drag the mounting holes (where it mounts to the transmission studs) to get a perfect alignment and not stress the head studs.

Piece of cake. Really, not bad. The aluminum head cuts threads for the timesert like butter, and the install was probably about 15 minutes (car was already up and HE off).

Good luck!
Jim

Jim

[euro911]

Posting here as well Trevor ...

My recent (and first) experience with the T-4 exhaust system:

One stud unscrewed from the head when I unscrewed the nut. I proceeded to remove the remaining nuts with no problems. I removed the exhaust system, cut the H/E tin off (cause I'm running an electric heater in the passenger compartment), wire brushed the whole thing and painted it w/ VHT.

Back to the head ... the one stud that came out was worn and had a helicoil in the hole. I screwed a NEW stud in and made sure it fully seated (using 2 exhaust standard nuts (locked together) ... then unlocked and removed both nuts.

Also, I had to pry the old head seals out. They appear to flatten and expand when torqued into place.

New head seals:

After I got the old seals out, I cleaned the recesses with a small flat-blade screwdriver. The seals need to seat well it into these recesses, as the nuts only torque down to 23 ft lbs. Most of them stayed in place OK, but a couple wanted to fall back down when I started fitting the system back up. It took me a few times to get it right. I balanced the exhaust system on my chest and lifted the back with my legs to fit it back up.

It was a real exercise for me ... I had a washboard stomach when I was done ... even though its still covered with a layer of fat (IMG:style_emoticons/default/laugh.gif)

[Trevorg7]

Great advice guys, thank you. I've put it up on stands for a third time. Removed all the heating connections and went thourgh all the nuts again. They are as tight as I dare get them and the car runs well now, not perfect, but pretty close.

BTW you did a good job with the stud replacement.

Thanks, it wasn't easy...slow is good while working in there.

I would say that well over 50% are no longer flat.

I suspect this is the problem.

I put in the 9mm/8mm stud, and about 1000 miles later it was gone

Sorry to hear that, hope I don't follow suit. (IMG:style_emoticons/default/biggrin.gif)

Thanks again guys.

T