10-09-2021, 09:40 AM
Hi Captain Mike
I suspect many touring engines are running round happily with one or two hairline cracks from that centre stud, it's quite common. The liners stop them propagating any further. In themselves they don't necessarily cause gasket leakage/failure as long as you can still torque the centre head nut adequately.
The "water past the stud thread" effect is exacerbated by the use of helicoils. Austins used fairly tight fitting studs, possibly with some sort of assembly sealant ? but who knows. The aftermarket studs I have encountered have sometimes had ragged threads and don't seem to have been made to tight tolerances, so this doesn't help. I have had success sealing threads with a PTFE loaded paste compound made by loctite. If you use normal threadlocker it may cause problems with the helicoil if you ever have to remove it. Again, this leakage isn't necessarily going to upset the gasket, it is not under any appreciable pressure.
In your case I think the gasket trouble is more likely to be related to the pitting/scoring or a low point where someone has been a bit too vigorous with the emery/scraper/chisel in the past. A light skim of the block (and maybe the head as well) may be the best way forward. Unfortunately this means removing all the studs and is an engine out job. If you have an HC head, watch out for insufficient piston to head clearance at TDC after block skimming, and if necessary put a shim plate or thicker base gasket between crankcase and block.
For a quick fix, maybe metal loaded epoxy like JB weld applied to a localised area and then carefully ground flat would work.
I suspect many touring engines are running round happily with one or two hairline cracks from that centre stud, it's quite common. The liners stop them propagating any further. In themselves they don't necessarily cause gasket leakage/failure as long as you can still torque the centre head nut adequately.
The "water past the stud thread" effect is exacerbated by the use of helicoils. Austins used fairly tight fitting studs, possibly with some sort of assembly sealant ? but who knows. The aftermarket studs I have encountered have sometimes had ragged threads and don't seem to have been made to tight tolerances, so this doesn't help. I have had success sealing threads with a PTFE loaded paste compound made by loctite. If you use normal threadlocker it may cause problems with the helicoil if you ever have to remove it. Again, this leakage isn't necessarily going to upset the gasket, it is not under any appreciable pressure.
In your case I think the gasket trouble is more likely to be related to the pitting/scoring or a low point where someone has been a bit too vigorous with the emery/scraper/chisel in the past. A light skim of the block (and maybe the head as well) may be the best way forward. Unfortunately this means removing all the studs and is an engine out job. If you have an HC head, watch out for insufficient piston to head clearance at TDC after block skimming, and if necessary put a shim plate or thicker base gasket between crankcase and block.
For a quick fix, maybe metal loaded epoxy like JB weld applied to a localised area and then carefully ground flat would work.