fixing threads in a cylinder head

February 27, 2021, 05:16 PM

One of the bolt holes in the cylinder head of my CJ7 with the inline 6 has damaged threads.

I am converting from the plastic valve cover to an aluminum one to help stop serious oil leaks.

Do you think if I put some JB Weld in the hole and then thread in a bolt sprayed with lubricant to act as a release agent will work?

I have read about this method but I wanted to consult the all knowing membership of this forum prior to trying this venture.

February 27, 2021, 05:19 PM

egregore

If there is sufficient metal surrounding the hole to work with, a Heli-Coil is your best bet. I don't think much of the epoxy idea.

February 27, 2021, 05:24 PM

Greymann

Keen-serts are the easiest.
You drill then tap for the keen-sert.
Screw in the insert and tap in the lock pins. Available in just every screw size and metric.

https://www.clarendonsf.com/pr...rts/keensert-inserts

https://www.mscdirect.com/brow...06001&rdrct=Keensert

February 27, 2021, 05:26 PM

powermad

Plenty of meat for a helicoil on that head.

February 27, 2021, 09:28 PM

cas

While I do know someone who used Marine-Tex to make a repair on a head and it lasted for years (I believe he filled it, then drilled and tapped it), a Heli-Coil would be my choice.

Were I to use a "chemical fix", I'd glue a stud in and put a nut on it.

February 27, 2021, 10:48 PM

Balzé Halzé

A Heli-Coil for chrissakes. It's why they exist.

February 28, 2021, 12:35 AM

slosig

quote:
Originally posted by Balzé Halzé:
A Heli-Coil for chrissakes. It's why they exist.

A little kurt, but full of truth.

I read the title and before even opening the thread Heli-coil sprang to mind as the answer.

February 28, 2021, 01:49 AM

Jelly

Time-sert or Helicoil would be best for that issue.
Keensert also works well but I think you will have to remove more material, off the top of my head. Not sure were my charts are since I retired.

Another option is... if I remember right some or many of those Jeep 6 bangers used 1/4" and 5/16" bolts in some places on the valve cover. If it is in a spot that used a 1/4 bolt you could just drill and tap it for the 5/16 bolt as they were already a bit of a clusterfuck from the factory on many.

JB Weld has its places but for threads it wouldn't be my choice.

February 28, 2021, 03:29 AM

sns3guppy

Do not put epoxy in the hole. Do it properly. Drill helicoil it.

Running JB weld or other epoxy in there is on the same shade-tree level of half-baked, as putting teflon tape on a bolt to keep in in place, instead of fixing the hole.

Fix the hole.

February 28, 2021, 04:01 AM

egregore

I haven't used them myself but have seen the Time-Sert used. This is pretty slick, but is a needless expense for just one hole that you'll probably never have the bolt out of again. Heli-Coils are readily available in any auto parts store. Your valve cover hole, I am 99% certain, is ¼-20. Hopefully the bad hole isn't back by the firewall where you have less room to work, especially the hole drilling part. If it is, you may need an angle drill and possibly a shorter drill bit called "screw machine" length. To turn the tap and the insert installer you need a small 8-point (square) socket.

I have not-so-fond memories of having to put 24 Heli-Coils in the camshaft housing holes of the POS GM "Quad-4" engine.

February 28, 2021, 09:05 AM

Balzé Halzé

quote:
Originally posted by slosig:
quote:
Originally posted by Balzé Halzé:
A Heli-Coil for chrissakes. It's why they exist.

A little kurt, but full of truth.

You're right. That wasn't necessary. Sorry to the OP.

February 28, 2021, 10:33 AM

rburg

Look, this isn't a high stress situation. Most folks just glue the cover down with more silicon. They're not the only leaky place on a CJ. Its how you find your way back out of where you got yourself, just follow your own oil trail. Both diffs will still drip. We used to refer to the oil trail as "bread crumbs". You can't tighten the stupid screws down enough to stop the leaks, and they added the stress spreader under those things to try to keep them from leaking. Maybe yours got lost?

Have you tried a good cork gasket? Its what they designed the mess to make it cheaper, not more effective. The classic fix was to find an old 360 and swap it in. They used a shorter 4 cyl long valve cover screwed down with actual bolts. Those didn't leak...much.

The bottom line is that you're trying to fix something that can't be fixed permanently. Try running it without oil, that'll end the leak problem.

February 28, 2021, 11:04 AM

jimmy123x

Helicoil is the right way to fix it, but you might get lucky, are there enough threads to use a longer bolt?

February 28, 2021, 11:26 AM

Some Shot

quote:
are there enough threads to use a longer bolt?

After carefully measuring that the longer bolt doesn't bottom out.

February 28, 2021, 11:41 AM

powermad

quote:
Originally posted by rburg:
Look, this isn't a high stress situation. Most folks just glue the cover down with more silicon. They're not the only leaky place on a CJ. Its how you find your way back out of where you got yourself, just follow your own oil trail. Both diffs will still drip. We used to refer to the oil trail as "bread crumbs". You can't tighten the stupid screws down enough to stop the leaks, and they added the stress spreader under those things to try to keep them from leaking. Maybe yours got lost?

Have you tried a good cork gasket? Its what they designed the mess to make it cheaper, not more effective. The classic fix was to find an old 360 and swap it in. They used a shorter 4 cyl long valve cover screwed down with actual bolts. Those didn't leak...much.

The bottom line is that you're trying to fix something that can't be fixed permanently. Try running it without oil, that'll end the leak problem.

I've had good results using a gasket with inserts for Small Block and Big Block Chevy engines.
PERMADRYPLUS
https://www.felpro.com/parts/l...ver-gasket-sets.html

Solid valve covers with spreaders and that type of gasket works well.

February 28, 2021, 11:45 AM

HRK

Who on Roadkill were you talking to this about...Freiburger? Finnegan?

Absolutely not a good idea, if you are taking the time to fix it, do it correctly. the weak threads are probably part of the leak problem.

TimeSert, HeliCoil any of those solutions are a good fix and you'll be able to get proper clamp/torque on the cover....

February 28, 2021, 07:23 PM

Apphunter

The biggest problem is originally from the factory the Jeep had a plastic valve cover that was only secured with bolts at the front and the back.

The aftermarket aluminum valve cover utilizes 5 bolts in addition to the ones in the front and the rear.

The holes for these bolts have very few if any threads. The holes in the cylinder head were only meant for plastic studs that protrude from the bottom of the valve cover that just indexed the valve cover.

I have ordered key inserts to help fix the wallowed out threads. Hopefully I will at least slow the oil leak.

February 28, 2021, 08:54 PM

sns3guppy

If your tab-slots are through-holes with space beyond, you may simply be able to put a nut on the other side, backed with a washer against the engine material, and also against the valve cover.

February 28, 2021, 09:16 PM

Apphunter

quote:
Originally posted by sns3guppy:
If your tab-slots are through-holes with space beyond, you may simply be able to put a nut on the other side, backed with a washer against the engine material, and also against the valve cover.

No such luck. They caution drilling/tapping too deep or you will get into the water jackets in the head.