re threading exhaust manifold

[marc69]

I recently bought a 1.3 exhaust manifold but when fitting it the thread nearest the engine and driver for the exhaust were threaded, so I tightened as much as seemed best and use gun gum. It has held for a few weeks but is now farting.

I have tapped and dyed alloy before but not cast iron. Is it just the same method or is cast iron more likely to crack?

Thanks

[Will F]

Best bet would be to drill and fit a helicoil mate

[marc69]

I went out just now and put new bolts in ( the old ones had flattened threads), cleaned up the surfaces. the new bolts seem to tighten (I didn't try to over tighten) but the leak is still from the same place. I was thinking of putting in two gaskets to see if that would help it seal? The existing gasket is the thin metal strip. Waste of time or worth a try?

Also is it worth putting thread lock on the bolts or will that just create more hassle on changing the exhaust in the future?

[millworm]

Assume this is down pipe to manifold? Helicoil is my best suggestion from what you've said. Wouldn't threadlock really as the heat will probably render it useless anyway. Some proper lock nuts would suffice if that's a worry (obviously not nylocks). Drilling cast is fine
Just make sure it's straight lol and not really close to an edge

[marc69]

Yes, downpipe to manifold. Well what I did today was to use the studs that are used for the manifold to block as they are longer and the nut will turn when the stud runs out of thread in the manifold. It seems to have worked, I got the studs very tight (Haynes torque settings)and no farting, fingers crossed that will be it. Typically I won't get a chance to use it for a long drive as a test until next month. Thanks for the advice and yes if this hasn't worked then it will need helicoiling.