Manifold bolts won't stay tight

[SilverXJ]

my engine is running well, however some of the manifold bolts don't want to stay tight. They keep loosening up enough to cause a small exhaust leak. I used high strength locktite (red stuff) when assembling the manifolds, however I don't know if maybe the threads were dirty of if I didn't use enough, etc. I am considering removing the offending bolts one at a time and slipping on a lock washer. However, I don't know if I should use the split type of lock washer or the tooth type of lock washer. One other thing is that Thorley calls for 40 ft lbs of torque to tighten the manifolds, so I don't know if that will have some bearing on a lock washer or not. Suggestions?

[ajmorell]

I had issues with my manifold bolts not staying tight for a while either. It eventually led to the destruction of a manifold gasket. When I replaced it I bought new manifold bolts and coated them with anti-seize and haven't had an issue since.

[SilverXJ]

You think the antiseize helped? The bolts I used were only used for a few thousand miles at most, so they are pretty much new.

[5-90]

Never-seez /may/ help, but I'm not sure just how it would.

I typically use LocTite #272 on manifold screws - it's the only grade of LocTite that will last, since it's actually formulated for dealing with exhaust heat. Any other grade will break down (yes, even the high-strength stuff. Why? Because you use heat to break it...)

It takes a little looking to find - I got my bottle at an MRO house, of all places - but it's out there.

[Exos]

Torquing with anti-seize may help because it will lubricate the threads and the clamping force will actually be higher than a dry torque. Aircraft engines maintenance manuals state that their general torque values are to be attained with the use of "castor oil" as a lubricant. Clean threads (cleaned with a tap and die set) will also help getting the right torque value.

[ajmorell]

You think the antiseize helped? The bolts I used were only used for a few thousand miles at most, so they are pretty much new.

I really can't say with any certainty, I just know that I didn't have a problem after I replaced the gasket.

[John]

Clean the threads as mentioned earlier and don't use traditional gaskets, use for the exhaust manifold Ultra Copper RTV Silicone Gasket Maker and permatex anerobic gasket maker (permatex 515) for the intake manifold. Use a torque wrench on the bolts to spec and I find everything stays put.
John

[ajmorell]

Clean the threads as mentioned earlier and don't use traditional gaskets, use for the exhaust manifold Ultra Copper RTV Silicone Gasket Maker and permatex anerobic gasket maker (permatex 515) for the intake manifold. Use a torque wrench on the bolts to spec and I find everything stays put.
John

I should also add that I sprayed my gasket down with ultra copper too, don't know if that had any effect on it but I just remembered that.

http://permatex.carshopinc.com/product_ ... 2287/80697

[SilverXJ]

Clean the threads as mentioned earlier and don't use traditional gaskets, use for the exhaust manifold Ultra Copper RTV Silicone Gasket Maker and permatex anerobic gasket maker (permatex 515) for the intake manifold. Use a torque wrench on the bolts to spec and I find everything stays put.
John

I've heard of that, but I'm not comfortable with it. Especially since anerobic sealant is hard as nails to remove once hardened.

Originally what I did was put copper RTV on the intake manifold and exhaust manifold, then spray the side of the gasket contacting the head with the copper spray. So it went together like this: head -> copper spray -> gasket -> copper RTV -> manifolds.

I think I am going to stop using the copper spray because both times I used it leaks have developed. Just copper RTV on both sides of the gasket has worked in the past for me. I also have not had a problem with the bolts coming lose except these two times. And its always two or 3 of the bottom bolts.

So if I need to replace a gasket I am thinking of going with a Felpro or try a Remflex gasket. Any better gasket options?

Then run a tap through the holes, RTV on both sides of the gasket and locktite 272 on the bolts.

Now, besides using the loctite I have been considering using some other type of lock, like a Nordlock washer or safety wire. Opinions on that?

[RAPTORFAN85]

Make sure the loctite is high temp. The regular stuff breaks down at high temps as stated before. Safety wire is more for keeping you from loosing bolts, like in a rear end or something. They can still loosen up some even when wired.

[Muad'Dib]

I made my own stainless steel studs from threaded rod, and used stainless steel bolts everywhere else. Loctite #272 keeps the bolts tight. Use it or use nothing on them. Everything else will just cause problems because they cant deal with the heat.

Copper RTV around the exhaust and intake ports only .. not on the whole gasket.

Also when torquing .. i have found it to be best to (of course follow torque sequence) torque just slightly more than what the book calls for.


Doing all those things has given me great results. I think the biggest is using either loctite 272 or nothing on the bolts / studs.

[SilverXJ]

I made my own stainless steel studs from threaded rod, and used stainless steel bolts everywhere else. Loctite #272 keeps the bolts tight. Use it or use nothing on them. Everything else will just cause problems because they cant deal with the heat.

I have heard some good things about the Nordlock washers.

Copper RTV around the exhaust and intake ports only .. not on the whole gasket.

Yeah, I know that.

Also when torquing .. i have found it to be best to (of course follow torque sequence) torque just slightly more than what the book calls for.

Thats another thing. Doug Throley calls for 40 ft.lbs on their header.. why so high?

Doing all those things has given me great results. I think the biggest is using either loctite 272 or nothing on the bolts / studs.

Yeah, I definitely used the wrong loctite., but I have a bottle of 272 on the way. Local Fastenal wanted close to $50 for a 50ml bottle (what is it, crack!??!). Found it much cheaper elsewhere.