MTFCA Forum

I had to take my head off to check for a blown gasket. After cleaning it up and putting it on, all of the bolts torque to 45 ft lbs (Z head) except for the bolt that held the horn on. I even tried leaving off the horn and the bolt tightens down past finger tight, but beyond that it keeps spinning and never fully tightens up. What can I do?

Maybe your threads are stripped. You don't want the head bolt to bottom out but you may be able to use a slightly longer bolt that can engage the threads that remain. If you have a bottoming tap it's a good idea to run it down the threads and clean out the bolt hole. Worst case scenario you might have to install a helicoil or similar.

Head off and helicoil the bolt hole.

Anyone know what size helicoil?

JBog wrote: ↑

Sun Aug 14, 2022 6:44 pm

Anyone know what size helicoil?

Same size as thhe head bolt, 7/16-14.

First thing to do is to clean out the bolt hole. Use a screwdriver and loosen any rust or crud that may be causing your bolt to bottom out. Then use a tap and to see if you can run it down a little more. You can strip out head bolts if the holes have packed in crud.
Over tightening has stripped more than a few bolt holes and bolts also.
You may have to use a heli coil if that’s happened. Good luck

So, I have to ask: "Was the gasket actually blown?" A compression check is a lot less aggravating than chasing down a headgasket these days, simply to find out after installation that a bolt hole is now stripped...

Compression checks are so easy, so instructive, and so rarely done, one wonders why that is...

If it is any consolation, stripping a hole in a T block is so common it is one of the main reasons I will do ANYTHING else possible to solve a problem before removing a sealed head and inviting that problem to rear its head. It is so common, that when I am forced to remove one, each hole is carefully evaluated and pre-emptively restored if excessive wear is evident...and in all of those land-mine locations, one or more usually are worn.

You might clean the hole out very clean, use a bottom hole tap to cut the threads as deep as possible, clean the hole again then use an all thread—7/16 -14 bottomed out in the hole with a nut. With the horn in place I don’t think it would be very noticeable If cut flush with the nut.

Jason, Did you lube the bolt threads and bolt shoulder when you installed the head. Doing so can over tension the bolt and then the heat expansion of the aluminum head adds even more bolt tension.

I suspect a helicoil or equivalent will be needed, but try other ideas first.

Art Mirtes

While you are at it, chase the threads of all the bolt holes and blow out with compressed air. Before doing this, using duct tape, tape over all water jacket holes and cylinder holes to prevent metal shards from going into the holes. Tape over the threaded holes not being cleaned out for the same reason. When installing the head, stagger the tightening of the bolts and be sure to torque no more than 50 lbs. Hopefully, you were able to salvage your head gasket. Be sure to use copper head gasket sealant on both sides of the gasket. Jim Patrick