MTFCA Forum

I need to repair a head bolt thread. I've ordered a heli coil kit, but would like to get a head start while I wait for it. Unfortunately, it's one of the ones by the fire wall, so I may have to move the engine forward. What I'd like to know, is can anyone tell me the drill bit size for the 7/16 14 heli coil repair tap. If I can get in there with a modified bit and an angle drill fine, but if I have to move the engine forward, might as well get a start on it

I think the Helicoil kit has instructions and a bit, if it is a non-standard size.

That is true, however, not the answer to my question.

29/64 drill is what you're looking for (IF IT IS TRULY A HELICOIL KIT and not some other brand)

Once you have the drill in hand, you will more than likely find that it just barely goes through the clearance hole in the head. Thus, the head is a great guide for both location and squareness when drilling. Cast iron can be wicked stuff to drill and the drill will likely want to "grab". Treating the drill the way you would for drilling brass will make the drill much more docile, while maintaining it's ability to cut.

DON'T DRILL TOO DEEP and consider purchasing a helicoil bottoming tap, too, to get the most thread engagement

Thanks Scott. That's just what I was looking for

You have the coolant drained and head off.while you are waiting, pull the engine forward so you a
and have a direct shot at the hole. SLIP A FILE ACCROSS THE HOLE TO remove any raised threads..Put some oiled rags in the cylinders to catch any debris. Take a screwdriver and loosen any junk in the hole and blow it out. Be sure to break the tang off the bottom of the new heli coil and remove it or you will stretch the threads downward when you put in the headbutt and have a real difficult mess.
It is not a hard job so do it where you can see what you are doing and look at it as a learning experience. . Good luck and see e what you have learned.

In the event the 29/64” bit for the helicoil doesn’t clean up the damage in the hole, you might try EZ-LOK from Rockler Auto, which uses a 33/64” bit. I had just such an issue last fall and the repair is holding up nicely. viewtopic.php?f=2&t=2716

Lots of good tips here. I won't discourage anyone from adding to this thread, however, by trade I'm a machinist. I've installed many different thread repairs in my career. I was just looking for the drill bit size while I wait for the kit to arrive (it's one I didn't have in the shelf) I wanted to determine if I could modify something to get at the hole under the firewall. I can't, and I'll be moving the engine forward a bit. Oh well. Of course this all started as doing some routine maintenance.

Here is a link to how Stevens Speed up tools handle the problem.
http://www.mtfca.com/discus/messages/50 ... 1425415180

That's a neat kit Dan. Does it fit under the firewall to access the rear 2 cylinder head bolts?

I think so. Was a copy of the Stevens kit. They were producing the best repair tools for Ford cars back on the day.

SteveD wrote: ↑

Mon May 30, 2022 5:36 am

Lots of good tips here. I won't discourage anyone from adding to this thread, however, by trade I'm a machinist. I've installed many different thread repairs in my career. I was just looking for the drill bit size while I wait for the kit to arrive (it's one I didn't have in the shelf) I wanted to determine if I could modify something to get at the hole under the firewall. I can't, and I'll be moving the engine forward a bit. Oh well. Of course this all started as doing some routine maintenance.

Consider whats involved removing the firewall. Depending on the year, I have found it a good option.

His car's a '24 and that may be the better of two bad options

Lesson: never pull the head for maintenance unless it is REALLY deserved!

now, to find a head gasket...

Well, since Scott brought it up..... Here's the story. Just got the car 2 months ago. Bought it as a non runner, but knew it wouldn't take much to get it running. The guy I bought it from had it running last year couldn't get it running this year, didn't really know too much about mechanics.... We made a deal. Took about 10 minutes of tuning to get it running. I've put about 700 miles on it in that time and started to hear a little rod knock. Drop the pan, sure enough a little loose. While getting a mic on the fourth crank pin I pushed the piston a little too high, and heard the click. Sigh .... Well I don't know a way to compress that top ring without pulling the head. Scott has admonished us all rightly, and many times, don't pull the head just to look and see, but what choice? Luckily I have been following this sight for 2 years prior to buying. I have been aware of the gasket shortage for a while, and have one in stock. Didn't want to use it yet but that's life. Surprised I had no coolant leak as the hole was already stripped. I've already moved the engine forward in anticipation of amazons delivery. In this whole process of just a quick tightening of the rods I found the following: safety wire in my pan. Half of the rod bolts were stripped, and lock washers were inserted to use better threads (one washer split as I took it out) luckily an old set of rods came with the car so I had some good bolts to swap in. 2 rods are in backwards, and staying that way. When I went to move the engine I found no blocks at the rear mounts and no hardware in the left mount at all Wrong hardware every where and no gasket at the ball cap. This thing is awesome!

Steve

that is a BUMMER!
hasn't happened to me but that is no guarantee it won't in the future...

Truth be told, I'm not that upset. I get it. It's a 98 test old car. I have to expect there to be problems. I'm learning, I'm improving my cars condition and finding problems that aren't too hard to remedy. It drove pretty good before, should be even better as I progress. I see wrenching on it as much a part of the hobby as driving so, I'm having fun. I will admit though, it was an absolutely perfect weekend and I would have liked to go driving, but I'll bet there will be more nice days to come.
That's my story, and I'm sticking to it!

Steve

that attitude is going to serve you well in the hobby for years to come (and I'm sure has already to this point in your life, too).

good luck and have fun

Steve,
You might consider a "Screw Length" drill bit.
It is about half the length of a "Jobber Length" bit.

So, quick update and short anecdote. Engine is back together and running sweet. When I read the manual concerning connecting rod adjustment, I scoffed at ole Henry's "tap the rod with a brass hammer" and said to myself, "self, use the modern way, use Plasti guage." So, I did. Got the job done, and just for fun, grabbed my brass hammer and gave them a tap. Well, sure enough, where I could feel shake with me hand before, a little motion was all that was detectable with the hammer. Good ole Henry! Also I noticed there is just enough room to get in the crank case with a mic, and you hands. Amazing

A number of years ago we took my head off. On the car that is. We used a drill with a wire brush and cleaned off all the carbon. Then reinstalled everything. It all works good. No leaks. You do not have to replace the head gasket every time you remove the head. They certainly did not do it in the 20's when you had to clean your head on a regular basis.

Coolant will leak where water will not, and I suspect that some or a lot of the success of reusing head gaskets in the early days was due to the fact that water was pretty much all you had and small leaks would typically just rust shut.