Hi-Po Heads exhaust threads

Brian Magee

Supporter
Can one of you experts tell me if it is normal with Hi-Po heads for the exhaust threads to go through into the water galleries? I have just refilled my engine with water after having the engine out and there was a drip from the rear exhaust bolt on No. 8 cylinder. I have just changed from cap head bolts to ARP 12 point polts. I removed the bolt and it was like removing a drain plug! It has been replaced with some PTFE liquid sealer on it but I have not run the engine yet. The car goes for an MOT tomorrow morning so I will find out if it has sealed it.

Brian
 
Possibly a case where there has been a damaged/repaired thread in a previous life like old stud/bolt drilled out, have seen core shift that lets this happen plus one drag race motor that cracked the head from freeze plug around to exh port in that area after a detonation issue.
 
No, they don't protrude into the water galleries, at least not on the 289 HP block I have. Which year block do you have, has it had any work done on it, and is the head gasket intact?
John
 
I seem to remember that my set of hipo heads had to have sealer on some of the exhaust studs because they intruded on the water jacket. They were extensively modified - that may or may not be relevant. It's 25 years since that engine was together!
 

Brian Magee

Supporter
I think Jac Mac got it in one. At some stage before I aquired the heads the corner in question had been stitched to repair a crack from the head bolt post round to the freeze plug on the end of the head, it must have been drilled out during that repair. I had suspected the repair was leaking again but now I beleive it was the same problem, leaking from the bolt hole.
Anyway the PTFE liquid seems to have sold the problem. Next time I remove the exaust system I will investigate the rest of the holes.

Brian.
 
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