This question is not to start an argument, but an honest question.
Can/should you use Loctite to hold stainless header bolts in an aluminum head?
The reason I ask, I searched the forums, and on the C5 board, it is mentioned that repacement factory header bolts come with Loctite. It was also said that the shop manual specifies Loctite.

My C4 manual, 1987 specifies neither Loctite or antiseize.

Loctite would work best for me, as the bolts would not back off. So what is the downside of this? A fear of the aluminum seizing to the stainless bolt and stripping the threads out of the head.

Why not use antiseize? Because the bolts are inaccessible for retightening in my application. This is being used on a header adapter, sandwiched between the header flange and aluminum head. I would have to take the header off to tighten these, then reinstall the header. :sad:

Would like to hear from those that have used blue Loctite (#242), and whether they encountered stripped threads. If they did, was it from overtorquing upon installation, or dry threads just seizing the aluminum upon remoing the bolt? Someone that has used Loctite for a period of time, and then had to remove the bolts please respond.

Also what has been your experience with Loctite(#242) on intake manifold bolts going into an aluminum head?

Please, no "I use Loctite" or "I use antiseize" responses that load up this thread. This is not a poll, but a search for real information.

Thanks for being patient and understanding. I posted this on the C4 forum, but this is probably more appropriate here, as it is my understanding that the C5 manual calls for Loctite, from reading a C5 post from last November.

:cheers:

 

My vote is NO LOCTITE.. I use anti-seize quite successfully. My experience has been that over time, with header removal and re-installation for misc reasons, the heads will accumulate that loctite and it becomes harder and harder to get the bolts started and properly torqued. If you use nothing, expect to have some bolts that are tough to get out and could cause stress to the delicate threads in the aluminum. I use copper based anti-seize, made for disc brake calipers, with great success.. No loosening, no need to retorque, and easy to remove when you need to..

Just my $0.02.. I'm sure other replies will flame this answer but it works for me in the dozens I've done on C5's....

 

I hope they don't. Your reasoning is SOUND! And, you know your shiate :D :cheers:

 

I used blue loctite on my old 2000 SS 2 years ago. They came out like nothing last year. I ended up switching to studs anyway, just for peace of mind. Let me tell ya, getting that header on with studs in place is light years easier than trying to line up bolts, possibly stripping out the first few threads, etc. Just throw it on the studs, tighten down the nuts, the end!

Dope

 

Gene,

If I recall correctly (I'm not at work, so do not have the specs in front of me) Loctite threadlocking compound is actually a thermoplastic liquid. As such, high heat conditions will soften or liquify it, reducing any "locking" properties it had initially.

In addition, you should know that the proper compressive force required to provide adequate sealiing of gaskets and o-rings is used to calculate bolt torque. There is a K-factor in the equation that varies, based upon:

a) the bolt and mating material and
b) whether any lubricants are used

Loctite Threadlocker is considered a lubricant. Therefore, if conditions (low heat) allow that this be used, the dry torque must be reduced. The same (obviously) holds true for the use of an antiseize.

Now the quandry: Should you use Loctite 242 which would probably not provide much back-out resistance if it sees high temps, or use antiseize and hope that the bolt never loosens?

Let me ask you this: Is there any room to add a split-lock or bellville washer?
Ideally, having both a n antiseize and a hardware locking component can be used in combination.

And Finally, let me say that "galling" or "seizing" normally can occur if both the bolt and mating material/nut are of the same material. If, for instance, a steel bolt is threaded into aluminum threads, simply warming up the aluminum should relax the threads (open them a bit) aaaaand allow the steel bolt to be withdrawn. However, dirt and grime could complicate matters and cause withdrawal difficulty. This is why I like to use antiseize + a hardware lock with reduced installation torque.

If you'd like to know approximately how much less torque to use, let me know and I'll look it up tomorrow.

Dave

 

:iagree:

 

I had another car and the header bolts always backed out, it was a real PITA so I always use loctite, just remember when you remove the bolts to always use hand tools only (no air tools) and if you get a stubborn bolt that you may have to work it back and forth on the way out.
I've never had a problem yet but now that I've read this thread, the next time I take my headers off I'll probably snap every bolt off :p:

 

When I installed my headers I used an anti-sieze to protect from gauling. I used a Stage 8 bolt and keeper system to eliminate the possibility of bolts backing out.

 

The guy who installed my headers said no hi temp Loctite. He was afraid of aluminum threads coming out if header bolts are removed. So far no problems with header bolts loosening after 5000 miles.