Help--Exhaust Manifold bolts won't stay tight

I mentioned Lock-Tite in my original post, and anti-seize has also been mentioned. Does anti-seize have "locking" properties, or strictly "anti-seize" properties?

You should MOST DEFINATELY be using anti-sieze on the threads. It doesn't make your spark plugs back out so it won't make your fasteners back out. (you are using it on your plugs right?) Anti-sieze is way cheaper than having to pull your heads and have them tapped for helicoils and replacing the head gaskets. Use it any time you use a steel fastener on an aluminum part.

Split type lock washers should stop the loosening. Studs are awesome because they go from course thread to fine thread which has better torque retention and vibration resistence. If you want the ultimate in torque retention you could always get bolts drilled for safety wire like the NASCAR and other racing guys do. If you do it right, the bolts CAN NOT MOVE. If your scared of lockwire then you can try Stage 8's locking bolts. They're pricey but they can't back out unless you disassemble them.

You have options. I like the mechanically locking hardware around high heat. Metal won't melt, plastic and chemicals will.

Try some new Grade 8 bolts and split lock washers first. That shouldn't cost more than $10.

Thanks for the advise. Yes, I am using anti-seize on the spark plugs.

I just spent good money buying the correct factory-style fastener kit for the hi-po manifolds. As I mentioned, it is a combination of sleeve-bolts, studs w/nuts, and bolts. I'm thinking of giving the anti-seize a try first, and if that doesn't work, anti-seize and lock-washers. I was using lock washers previously, and still had problems.

The guy that mentioned different expansion rates nailed it. A lot of guys helicoil all the threaded holes right from the get go. You could try selling that original kit and get those Stage 8's. They have a e-clip groove cut into the wrench flats and locking tangs that slip over the bolt heads. The locking tangs have a 12 point hole so they can be positioned properly on the bolt head. Then you lock it in place with the e-clip. If the bolt loosens the tang will hit the manifold and stop the bolt from turning. So it can't loosen more than 1/12 turn. Pretty darned fail safe.

http://www.stage8.com/products_lhb.html

Safety wire works too.

Hey 318 .. using anti-seize on these will make the problem WORSE.

I still say use a high-temp RTV and let it cure WELL before using.

If you have studs and nuts,try double nutting to keep them tight.

I use studs in my aluminum heads except for 1 or 2 that wont fit with headers.I use antisieze on them.2 years of street driving and they never come loose.I use the larger thick flat washers on mine also.Rocky

How did you get them to fit? you must have done a ton of grinding to the heads.
I have a pair of Edelbrock closed chambers (04 vintage I think) and wanted to install my H/P manifolds, but no go unless I did a whole bunch of grinding.
Went with TTIs that slipped in easier then iron.
Never a leak or losen up.