Cross threaded manifold bolt

[hairy dog]

I have a clacking noise which is getting worse on my Chim which appears to be coming from the manifold connection to the head, it looks as if the bottom bolt 2nd from the front on the drivers side has been inserted on a slight angle. Does anyone know if this can be drilled and re-tapped without removing the head?

[2Munkys]

Well, your manifold is gonna have to come off so that you can clean up the mating faces and change the gaskets (I'd recommend Clever Trevor's metal backed items). You can assess the damage when that's off.

I guess you could drill out and retap oversize without removing the head but you'd be best off having a thread insert of some description fitted. Whether the head needs to be removed will be determined by available access for the tooling particular to the chosen insert. It may not come to that though, you may be lucky.

[mb450]

I found when a bunch of bolts sheared off during my cam change that it would have been almost impossible to get access to the holes with any of the gear to fix the thread (though it might work with a 90 degree air drill if you can line it up correctly which might be tricky).

The cam change meant the heads were coming off anyway but I ended up cleaning and measuring the threads, if they were worn or suspect I drilled and helicoiled all but the front 2 on each side needed doing. I found all sorts or crap inside the threads including what appeared to be the remains of some ptfe tape and evidence of thread locking compounds - clearly someone had tried to fix it in the past. I bought an arp bolt kit an apart from an initial nip up after a tank of fuel they haven't needed any attention since (I do check them ever now and then just to make sure)

[GreenV8S]

hairy dog said:

I have a clacking noise which is getting worse on my Chim which appears to be coming from the manifold connection to the head

That's probably a blown manifold gasket, but could be a cracked manifold. They tend to crack close to the 4:1 collector.

hairy dog said:

it looks as if the bottom bolt 2nd from the front on the drivers side has been inserted on a slight angle. Does anyone know if this can be drilled and re-tapped without removing the head?

That seems rather unlikely since a cross-threaded bolt wouldn't go in far enough to clamp the manifold. Slacken that bolt to confirm whether there is actually a problem before you start planning engineering work on the heads.

[hairy dog]

Thanks for the advise chaps. GreenV8 the gasket were new on when I brought the car I guess this is how the cross threading of the bolt may have happened. You say to slacken off the bolt, what indication of a problem would that give me? except more tractor like noise.

There is another symptom, at approx 4k rpm it goes flat and misfires which has only occurred in the last couple of weeks, I have put this down to the manifold leak which is affecting the mixture.

[griffter]

I suspect if the bolt is visibly in at an angle, it's already been drilled and tapped at a clumsy angle. As V8S says, merely cross threading the bolt wouldn't let it wind in enough.

If this is the case, and it won't tighten the manifold sufficiently, then removal of the head, drilling (at the correct angle - probably oversize) and tapping or helicoiling sounds like the most likely option.

[Meatball]

I had a similar problem not long ago and i was recommended trying a longer bolt..it worked a treat ive had no problems since.

[hairy dog]

I did read that on one of the threads on here, what length bolt did you use?