aluminum head leaks

[Rick Kirchner]

The Pinto aluminum head has the bottom exhaust manifold bolt holes go all the way to the head studs. So oil comes out through the threads.

Ive used permatex anaerobic sealant with some success, just wondering if others have a method that works - teflon tape? Some other goo?

I might give Quicksilver a call if nobody has an answer.

[BeerBudgetRacing]

Or call Doug Learned - he designed them.

[Rick Kirchner]

Or call Doug Learned - he designed them.

I have. doug designed them but never was a user. Another difficult area is access to four of the lash adjusters.

[DaveW]

The Pinto aluminum head has the bottom exhaust manifold bolt holes go all the way to the head studs. So oil comes out through the threads.

Ive used permatex anaerobic sealant with some success, just wondering if others have a method that works - teflon tape? Some other goo?

I might give Quicksilver a call if nobody has an answer.

May be dumb questions/suggestions, but how deep are the exhaust manifold holes in question? If they're deep enough, you could clean the manifold holes and then insert aluminum threaded plugs (with screwdriver slots to screw them in) with sealant in the holes in front of them and run them in until they just contact the head bolts or bottom out in the holes. Or you could use sealant on the head bolts when you install them. That way you'd avoid having to seal the manifold bolts each time they're R&R'd.

[Rick Kirchner]

May be dumb questions/suggestions, but how deep are the exhaust manifold holes in question? If they're deep enough, you could clean the manifold holes and then insert aluminum threaded plugs (with screwdriver slots to screw them in) with sealant and run them in until they just contact the head bolts. Or you could use sealant on the head bolts when you install them. That way you'd avoid having to seal the manifold bolts each time they're R&R'd.

I looked into that a couple years back and didn't go through with it, for reasons I can no longer remember....I should have another look.

[DaveW]

I added a few words in bold red in my previous post.

[Rick Kirchner]

Holes are 16mm deep, bolts are a 1mm pitch. So theoretically, I could put one in that has 4-6 threads and still get a decent grab on the header bolts.

So basically, trying to figure out how to cut down a M8x1 setscrew. Maybe gluing it onto a piece of hex stock, spinning it in the lathe, and using an abrasive tool to gently grind it down and not goober up the threads.

[CARSHouston]

Not knowing how your header is designed, would it be possible to use studs with nuts instead of bolts. That way you wouldn't have to worry what type of sealant you used, as you wouldn't be removing the studs to take the header off.

[Rick Kirchner]

Not knowing how your header is designed, would it be possible to use studs with nuts instead of bolts. That way you wouldn't have to worry what type of sealant you used, as you wouldn't be removing the studs to take the header off.

Maybe - but there's very little room to maneuver the pipes in. Might be able to do it with studs on the bottom and bolts on the top, but studs on both - I have my doubts.

[DaveW]

Holes are 16mm deep, bolts are a 1mm pitch. So theoretically, I could put one in that has 4-6 threads and still get a decent grab on the header bolts.

So basically, trying to figure out how to cut down a M8x1 setscrew. Maybe gluing it onto a piece of hex stock, spinning it in the lathe, and using an abrasive tool to gently grind it down and not goober up the threads.

I'd worry that a steel plug might eventually loosen/leak with repeated heat cycles due to the difference in thermal expansion coefficients. That's why i said to use aluminum plugs.

[tlracer]

I'd worry that a steel plug might eventually loosen/leak with repeated heat cycles due to the difference in thermal expansion coefficients. That's why i said to use aluminum plugs.

This...plus, have the aluminum plugs threaded slightly oversize, then heat the head/freeze the plugs before fitting.

[DaveW]

This...plus, have the aluminum plugs threaded slightly oversize, then heat the head/freeze the plugs before fitting.

Especially in this case - a relatively long path to screw in - I'd worry that the small cooled interference-fit screw-in aluminum plug would rapidly warm up and jam in place halfway in. IMO, sealant is a much more practical solution.

[tlracer]

Especially in this case - a relatively long path to screw in - I'd worry that the small cooled interference-fit screw-in aluminum plug would rapidly warm up and jam in place halfway in. IMO, sealant is a much more practical solution.

I did consider that, Dave, though I was trying to find an alternative to sealant. Getting the latter to the right location might be tricky...and avoiding it spreading/degrading over time. My thought - though I may be incorrect - was that the mass of the head casting would mean it retained heat (and thus expansion) for long enough to insert the plug without galling, especially if the plugs were machined to only minimal interference.

[DaveW]

I did consider that, Dave, though I was trying to find an alternative to sealant. Getting the latter to the right location might be tricky...and avoiding it spreading/degrading over time. My thought - though I may be incorrect - was that the mass of the head casting would mean it retained heat (and thus expansion) for long enough to insert the plug without galling, especially if the plugs were machined to only minimal interference.

The head would retain heat just fine - the issue would be the plug which would only weigh a gram or 2 and warm almost instantly.

[tlracer]

The head would retain heat just fine - the issue would be the plug which would only weigh a gram or 2 and warm almost instantly.

Exactly, meaning the holes would remain expanded and allow insertion of a suitably machined plug as it would take longer for the head to shrink than the plug to warm up. Or am I missing something?

[jrh3]

You could also put a thin wall sleeve in the head bolt holes. Only deep enough.

[DaveW]

The head would retain heat just fine - the issue would be the plug which would only weigh a gram or 2 and warm almost instantly.

Exactly, meaning the holes would remain expanded and allow insertion of a suitably machined plug as it would take longer for the head to shrink than the plug to warm up. Or am I missing something?

I think you may, indeed, be missing my point - I don't think you'd be able to fully insert the plug before it warmed up and expanded to the degree that it bound up before it was all the way in. That, of course, is only my opinion, but I wouldn't want to take that chance if I was doing it.

That goes along with one of my personal rules: Don't assume anything, because assumptions too often come back to bite you in the butt.

And, adding to that, is the issue of hermetically sealing a non-tapered thread interface. That almost never works, requiring some type of sealant, crush washer, etc. Tapered NPT threads can seal w/o sealant, but sealant is recommended for those, also.

Case in point - I had an issue with an oil leak at the rear of my Zetec engine that turned out to be coming from the flywheel interface with the crankshaft. QS had been using only enough Loctite to assure the FW bolts would not loosen, and that was not enough to seal the path past the threads. A more generous amount of Loctite solved the issue.

[tlracer]

Agreed absolutely about 'assumptions', empirical data is far better! Goes along with 'if you want something doing properly, do it yourself'

Indeed, the only thing worse than an assumption is '...it said on the internet that...'!