MTFCA Forum

Well I finally got to installing my new copper head gasket and my new (to me) head...and of course one of the head bolts stripped in the block.

I had cleaned out all the holes and ran a tap through them to clean up the threads beforehand. I also checked that the new bolts were not too long for the holes. Many of the holes had already been helicoiled by the previous owner, with the exception of 4 that looked ok.

The bolt stripped at 20 ft lbs. It's the very last bolt on the back right of the head...not easy to get even the torque wrench in there.

Any tips on how I would helicoil that hole? There's no way to get a drill in there. If I could turn the drill bit by hand it might be accessible. I really hope I don't have to pull the whole block.

MB

I doubt there are any nice easy answers. You could probably get away with removing the radiator, and disconnect enough to pull the engine forward in the frame. Pretty much the same as pulling it completely but at least it's still resting in the frame while you work rather than messing with a cherry picker and engine stand.

If a brass car, pulling the firewall might provide the needed access…?

You might be able to drill it by using a right angle drive attachment and a short bit on a hand held drill.

Kevin Pharis wrote: ↑

Wed Oct 15, 2025 8:30 pm

If a brass car, pulling the firewall might provide the needed access…?

15 as listed in your profile?
Pull the hood former/firewall. Short drill bit & drill. Drill angle drive maybe.

A good point to remember you don’t have to really pull down on the head bolts. Sometime we forget to get them good and tight and that’s enough. The key to getting the head to get a good seal is to stick with starting in the middle first and going out evenly from there. You don’t need a cheater bar to tighten them up.

I'm concerned that anything short of moving engine forward would make it difficult to get a perpendicular hole drilled and tapped..Don't rely on the existing hole to align things. I've seen more than one block helicoiled without using an alignment block where the headblolts won't pass thru the head into misaligned helicoils.
It's worth the extra time.

Very important to get this right the first time, because if it is crooked it could ruin the block. Slide the engine forward and or remove the firewall. You need to get the hole straight and centered. Also deep enough to get the bolt down but not into the water jacket which could cause the bolt to rust in place. A good way to do this would be to place the head on the block without a gasket and use it as a guide to drill the hole. You will need a drill bit long enough to go through the head and into the block. Then tap the new hole to place the helicoil. All the bolts should be he length which will go all the way down with the head in place without the gasket. Then they will be able to compress the gasket. If the bolts bottom out before the gasket is compressed, you will have water and compression leaks This can either get water in the cylinders or leak out. So do it right the first time because you might not have a second chance.
Norm

You'd need an accurate drill guide, no matter how you do it.

Here is a link to a Stevens tool I reproduced years ago for this job. Works great.
But now I use the Lock n Stitch Full torque insert system. It has a line up jig that works great and the inserts hold to +90 ftlbs.
https://www.mtfca.com/discus/messages/5 ... 1425415180
I only made a few of the Stevens tools. Dan

TXGOAT2 wrote: ↑

Thu Oct 16, 2025 10:59 am

You'd need an accurate drill guide, no matter how you do it.

Used the cyl head as guide as the drill size fits the bolt hole. Just measure very closely to be sure the long drill won’t cut into the water jackets.

Drill straight carefully with depth indicator on the drill bit. In this fix, measured depth of block hole to compare to conical tip of the drill bit to have assurance.

The HeliCoil made for me a very good fix to the old poor threads in the block.

Thanks to everyone for all the tips, I really appreciate it.

I'll try and remove the hood former and firewall and see how much room I have to work.
MB

Hi Murry,
Using a drill extension may get you up high enough to clear the firewall. I keep old junk heads just for this. if the insert drill is larger that the
hole in the head then drill it out & use it for a guide to drill the block. use plenty of bolts the hold the head secure & aligned. Cut the center
of the drill so it will not go deeper than the factory hole. Drill the old head to the O. D. of the tap & reinstall the head using it for a tap guide
remove the drill & tap regularly & blow out the chips. Use a bottom tap to cut the threads full depth. Remove the head & install the insert &
make sure it is not proud in the head, if it is very carefully grind it flush. In a earlier post I showed using fast food drink cup lids installed upside
down to keep dirt & chips out of the cylinders.