Exhaust stud thread sealant?

[amarino]

Anyone know of a good exhaust stud thread sealant? Not anti-seize or threadlocker but something to seal it so oil doesn't seep through onto the exhaust manifold. The hole goes all the way though when I shine a flashlight from the outside. I already have new hardware. Just want to make sure I don't have to do this job again one day if possible.

exhaust-1.jpg exhaust-2.jpg

exhaust-3.jpg

[mjweimer]

I used Curil T on the very end of the studs where they are exposed to the inside of the head and loctite 243 towards the outside to lock them in place. You could use any non-hardening sealer that can handle oil exposure in place of the Curil, like Aviation form-a-gasket 2, Honda-bond, Yama-bond, etc.

It was a bit tricky but doable....clean the threaded holes and run the stud in dry so the back is flush with the hole at the inside of the head. Check that the remaining exposed thread has enough length to accommodate the exhaust manifold and a fully threaded nut. Mark the outside of the stud where it meets the head with a Sharpie, etc. In my case the studs were long enough that they could be screwed in flush to the inside of the head and allow for the manifold/nuts with some room to spare.

I then partially removed the stud, applied a bit of the loctite just behind the Sharpie mark and then threaded it back in past flush on the inside ~5mm. At this point I applied the Curil-T to the full diameter of inner threads and backed the studs out until they were again flush to the inside. Give everything 24 hours to set-up. If you place the loctite correctly, it will be located at the outer portion of the head and the Curil will be able to seal the inside threads. The Curil will stay flexible and the loctite will cure so the studs will not move when you install the nuts.

Hopefully I explained this reasonably. So far no leaks from the area but admittedly there are only a couple thousand miles on the rebuild.


MJ

[okieflats]

are you using these type of studs with a "shoulder" on them? You screw them in till they bottom out. I would use teflon plumbers tape. I think it could withstand the heat

[amarino]

Thanks for the detailed info MJ. I'll look at some of those products.

okie, I have these: https://www.iemotorsport.com/product...s-m10-m20-m30/

Teflon tape and some of the sealants MJ suggested above all seem to max out around the 200-250C range. Not sure if that is heat resistant enough to be right on the exhaust manifold.

[okieflats]

I wouldn't use those type of studs.

these other type are readily available on ebay and elsewhere. screw them in till they bottom out, with some teflon tape which will get "pinched" in there, where the "shoulder" contacts the head.

[okieflats]

Where's Randy?

[320iAman]

Right Here

Randy

[320iAman]

Permatex 59235 High Temperature Thread Sealant, 50 ml Tube Contains PTFE.

Temperature range from -65 degrees fahrenheit to 400 degrees fahrenheit

What I have done is use stainless steel nuts and remember to tightened up the exhaust nuts every 6 months or so I used Liqui Moly LM 508 Anti-seize( Good to 2000 F(1093 C) or so), no leaks,,the above Permatex 59235 has high reviews and worth a try so is the Germany made LM 508.


Randy

[amarino]

Mark the outside of the stud where it meets the head with a Sharpie, etc. In my case the studs were long enough that they could be screwed in flush to the inside of the head and allow for the manifold/nuts with some room to spare.

I then partially removed the stud, applied a bit of the loctite just behind the Sharpie mark and then threaded it back in past flush on the inside ~5mm. At this point I applied the Curil-T to the full diameter of inner threads and backed the studs out until they were again flush to the inside. Give everything 24 hours to set-up. If you place the loctite correctly, it will be located at the outer portion of the head and the Curil will be able to seal the inside threads. The Curil will stay flexible and the loctite will cure so the studs will not move when you install the nuts.

Sorry a bit confused rereading this again before I put it together. Just to simplify the steps:
1. Thread in stud by hand and mark where it meets the head with a Sharpie.
2. Unscrew the stud a bit and apply some Locktite just behind the Sharpie mark then screw it back in.
3. Unscrew the stud all the way and apply Curil-T (or whatever thread sealant) to everything behind the Locktite?
4. Put the stud back in by hand and then assemble everything else.
5. Let it sit for 24 hours and recheck the torque on the nuts.


Sorry okie but I'm gonna give the hardware I have a shot. Hopefully cleaning everything and using the sealant will keep away any leaks. But if this IE hardware does/doesn't work out then I can leave an honest review.

I'm just waiting for AutoZone to get my new 02 sensor to reassemble everything. I took the time and chased everything with a tap and die set to make assembly easier. The 02 sensor used to be a pain to screw in as it would only go 1-2 turns and then I had to force it the rest of the way. Now after chasing the threads I am able to screw the old 02 sensor in all the way flush to the manifold by hand.

For future reference:
Holes in the cylinder head for the exhaust studs: M8x1.25
The 3 studs on the exhaust manifold to the downpipe: M10x1.5
02 sensor hole: M18x1.5 (I used this "Lisle 12230 Oxygen Sensor Thread Chaser" https://www.amazon.com/gp/product/B000XETMW0/ )

Thanks again everyone for the info!

[mikey710]

I’ve dealt with this on 3-4 different e21’s, every time it was “all thread” studs leaking and I replaced them all with “shouldered” studs, bottomed out snug. No sealant. Worked for me, but a proper sealant is a good idea. Good luck

[mikey710]

When you use shouldered studs you screw them in hand tight. Then screw 2 nuts on the exposed threads. Tighten the nuts to each other tight. Then with your wrench only on the outer nut tighten the stud to the head. Then the studs don’t move when you put your manifold on. And don’t leak.

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Use stainless nuts and locking washers. I think I’m done now

[amarino]

I’ve dealt with this on 3-4 different e21’s, every time it was “all thread” studs leaking and I replaced them all with “shouldered” studs, bottomed out snug. No sealant. Worked for me, but a proper sealant is a good idea. Good luck

When you use shouldered studs you screw them in hand tight. Then screw 2 nuts on the exposed threads. Tighten the nuts to each other tight. Then with your wrench only on the outer nut tighten the stud to the head. Then the studs don’t move when you put your manifold on. And don’t leak.

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Use stainless nuts and locking washers. I think I’m done now

Ugh now you're really making me doubt myself. So it's the shoulder that does the sealing against the head then? Like okie said above?

Also dumb question since I've never really used these that I can remember, the longer length goes into the head and the short side is for the manifold and nut to go on? For example on this: https://www.belmetric.com/m8x125-coa...ck-p-9875.html

Any why the stainless vs copper nut? Just trying to learn.

Thanks!

[okieflats]

Sounds like mikey710 knows what he is talking about. And IE is selling stuff without putting a lot of thought into it.

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by the way, my name is Mikey too. many times I've heard give it to Mikey, Mikey likes it.

[mikey710]

I like it. And I always used studs equal length to the stock ones with 3/16ish shoulder right in the middle. From what I remember....

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And I used stainless because they didn’t have copper at the hardware store, and they work nicely more than once.

[mikey710]

I looked at the stud in the pic. You need minimum 24mm to go through the manifold washer and nut. This length includes the shoulder. That stud is 24mm, 8mm, 8mm. You want 16,8,16. More stud in the head is good, but not too much. And I think there are clearance issues if they stick out too far.

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I’m not sure how to reply to specific people sorry!!!

[mjweimer]

Sorry a bit confused rereading this again before I put it together. Just to simplify the steps:

1. Thread in stud by hand and mark where it meets the head with a Sharpie.
Yes

2. Unscrew the stud a bit and apply some Locktite just behind the Sharpie mark then screw it back in.
Yes

3. Unscrew the stud all the way and apply Curil-T (or whatever thread sealant) to everything behind the Locktite?
Don't unscrew the stud at this step, screw the stud further into the head exposing the stud on the inside of the head (near the rockers). With the inner area exposed, apply the sealant to the threads and then unnscrew until flush with the inner head/proper depth.

4. Put the stud back in by hand and then assemble everything else.
With the studs back in from the prior step, test fit the manifold to make sure you have enough thread engagement. I used plain M8 washers and nuts during this step and did not fully tighten/torque to avoid turning the studs (the locking copper nuts will apply too much torque). Once all is confirmed good you can leave the manifold in place with the temp. hardware.

5. Let it sit for 24 hours and recheck the torque on the nuts.

After I completed the above steps, I let the Loctite and sealant cure for 24 hours and then installed the copper locking nuts on exhaust manifold.


Sorry okie but I'm gonna give the hardware I have a shot. Hopefully cleaning everything and using the sealant will keep away any leaks. But if this IE hardware does/doesn't work out then I can leave an honest review.

I'm just waiting for AutoZone to get my new 02 sensor to reassemble everything. I took the time and chased everything with a tap and die set to make assembly easier. The 02 sensor used to be a pain to screw in as it would only go 1-2 turns and then I had to force it the rest of the way. Now after chasing the threads I am able to screw the old 02 sensor in all the way flush to the manifold by hand.

For future reference:
Holes in the cylinder head for the exhaust studs: M8x1.25
The 3 studs on the exhaust manifold to the downpipe: M10x1.5
02 sensor hole: M18x1.5 (I used this "Lisle 12230 Oxygen Sensor Thread Chaser" https://www.amazon.com/gp/product/B000XETMW0/ )

Thanks again everyone for the info!

I've typed some clarifications in red above. As others have stated there are other methods and hardware to get this done and I'm sure they work well. I have had some success with shouldered studs and loctite on a prior build but I still had some weeping from the rear-most upper stud. This is just my attempt at a "better" way from experience...it is more of a pain then the shouldered stud method but it has performed well so far.

Cheers,

MJ

[amarino]

Sounds like mikey710 knows what he is talking about. And IE is selling stuff without putting a lot of thought into it.

Eh I wouldn't blame IE too much. The original stud isn't shouldered and it's the same for M20 and M30 engines so they're just selling a stock replacement. Also from what I've seen not all M10 heads are though-hole, I have another head as a spare and it doesn't go all the way through.

3. Unscrew the stud all the way and apply Curil-T (or whatever thread sealant) to everything behind the Locktite?
Don't unscrew the stud at this step, screw the stud further into the head exposing the stud on the inside of the head (near the rockers). With the inner area exposed, apply the sealant to the threads and then unscrew until flush with the inner head/proper depth.

My issue with that is when dry fitting the new stud it bottoms out before I see it exposed on the inside of the head. And I didn't want to try and force it in there too much. However with the tapered tap I do see the thinner tip poke out inside the head. I was thinking of using a straw or something like a syringe to inject from inside the head.

I looked at the stud in the pic. You need minimum 24mm to go through the manifold washer and nut. This length includes the shoulder. That stud is 24mm, 8mm, 8mm. You want 16,8,16. More stud in the head is good, but not too much. And I think there are clearance issues if they stick out too far.

I took some measurements this morning and just hand tighten the stud into the head it goes in 17mm with 23mm sticking out. The exhaust manifold is 13mm and nut is 8.5mm. So rounding up would be around 24mm like you said. This might work as it has 16mm inside the head and then 25mm outside: https://www.belmetric.com/m8x125-coa...s-p-10205.html


Thanks for all the tips and insight everyone. I haven't decided what I'm going to do yet. I might place a order with Belmetric just to see how that fits with the shoulder. Who knew such a little thing could be such a big topic.

[amarino]

Sorry for the suspense and delay everyone. Been waiting on AutoZone still for a new 02 sensor. At first it was "should be here tomorrow" to "maybe one more day" to me just giving up and ordering it on Amazon.

But this waiting did give me time to order some shouldered studs from Belmetric and test them out. I ended up going with these because the dimensions lined up the most with the 16mm end going into the head and the 25mm shoulder and other end sticking out for the manifold: https://www.belmetric.com/m8x125-coa...s-p-10205.html

They are almost a perfect fit but as you can see they don't all go in the same depth:
overview.jpg


With double nutting them and tightening the stud just barely with a socket they don't all go in the same depth where the shoulder is resting against the head. And with the shoulder not sitting flush against the head it wont seal up the hole as best as it can. I'm not sure if I should use the tap to cut the threaded hole a bit deeper for the ones that aren't flush.

cyl-4.jpgcyl-3.jpgcyl-2.jpgcyl-1.jpg


I'm trying to hopefully never have to touch this again and seal these studs for good.

[320iAman]

What sealant did you use on the threads ?

Randy

[okieflats]

Cut some off the stud, from the end that goes into the head, for those that don't go in all the way. So that the shoulder part will seat tight.

Anywhere from about 12mm to 16mm going into the head should be good enough

I use some small channellock pliers to put them in, easier than double-nut method. Use the pliers on the unthreaded portion

[amarino]

Randy, I used none, that was just a dry fit test.

okie thanks for the tip!

[mikey710]

I assume you made sure the holes were clean with some poking and blowing. You could carefully tap it out a little more, or if you have a bench grinder put a nut on the stud down to the shoulder then grind a couple mm’s off and remove the nut to fix the thread. Or get some shorter studs. I don’t remember having to dealing with this sorry!!!

[autox320]

Studs with shoulders here as well. After making sure they seat, I back out a few threads and put a dab of ultra black rtv just for good measure then bottom out on the shoulder. Use steel top lock nuts and never lose a nut or stud. My head is a 79 so has the through holes for the top row; oil can leak onto the header if no attention to detail.

Never use stainless hardware on steel ex: stainless nut on steel stud. Stainless has rolled threads and will always bind/freeze better than locktite feels like cross threading. Some think its a good idea to keep from rust but it makes it worse for removal in the future.

[mikey710]

I can only only speak from my experience and have never had a problem using stainless. I agree a dab of sealant is a good idea. I’m not sure why you would tighten the nut against the manifold without some kind of washer.

[OLD MAN]

Building small block chevys and others I have just always used good old anti seize. Use it on my BMW engines also.