stripped Threads coolant fitting Model A
 

I have a 1930 Model A Fordor with "original" engine setup. One of the bolts that fastens the coolant tube to the engine block is stripped. It holds all the way in and when I'm turning what I feel should be the last 1/4 turn the bolt pops loose.


Any suggestions? I'm thinking helicoil but I've never done one so don't know anything about size needed etc..

Re: stripped Threads coolant fitting Model A
 

I would try to tap to next size up or use some JB Weld epoxy snung it up and let it set for 24 hrs.

Re: stripped Threads coolant fitting Model A
 

Hili coil it Mc Masters Carr sales kits.

Re: stripped Threads coolant fitting Model A
 

I'd install a hilli coil insert

Re: stripped Threads coolant fitting Model A
 

Not hard. This one almost the perfect Heli-coil repair.

They give you the drill and tap, and (commonly) an "insertion" tool. You drill centered on the existing threads with the drill, then tap the hole with the tap. Then - using the tool (I've done it with needle nose pliers) you screw the insert into the tapped hole you created. Using needle nose I end a bit short and grind off the heli-coil "spring" (what it is really.) Using their tool you turn it in until the tang breaks off - sort of mindless.

Since I was ending short I used Loctite. Full depth you don't need to.

Heli-coil actually makes the threads "stronger" than the original. Cast iron racing motors are commonly "heli-coil'ed" on head studs of high compression/high performance engines for this reason. And - just so you'll feel some measure of assurance - Heli-coil system is APPROVED for nuclear application.

Some might think this a downside - but Nuclear is but another demanding client who normally can afford the best - and is willing to pay for it.

Some like the larger diameter "plugs" - these work too and for the same reasons.

Joe K

Re: stripped Threads coolant fitting Model A
 

Thanks guys.

Re: stripped Threads coolant fitting Model A
 

Helicoils are available everywhere. NAPA has them and Cat and about any parts house or farm equipment store.

Re: stripped Threads coolant fitting Model A
 

Go with the Helicoil. Just be mindful to drill it straight and not go deeper than what the hole already is. Measure the depth of the hole and mark your bit with a wrap of tape around it to make sure you don't go too deep.

Re: stripped Threads coolant fitting Model A
 

get a long bolt with threads all the way,run a nut up to the head, or threaded rod, run it into the threads at the bottom of the hole, tighten nut, cut off excess

Re: stripped Threads coolant fitting Model A
 

The problem you will have with drilling out the hole for the Helicoil is that the drill will try to dive into the hole, cocking the drill to one side and opening up the top of the hole. It is very hard to hold the drill 90 degrees to the block also. You might make up a 1 1/2 in. hardwood block and drill two holes in it on a drill press so they are vertical. Use one hole to fasten the wood to the block and the other to insert the drill correctly.

Buy two new drills in sizes that lead up to the Helicoil drill size. I don't remember the size of these bolts but one drill would be about 0.003 smaller and the second drill 0.006 smaller than the Helicoil drill. This way you are increasing the size of the hole in the block in increments and just skimming the hole larger until you finish up with the Helicoil drill. It is easier to hold the hand drill when you are removing less material. Good luck with your repair. Ed

Re: stripped Threads coolant fitting Model A
 

I would try a new or good used bolt first. the bolt threads wear the most .

Re: stripped Threads coolant fitting Model A
 

Good advise on making a drill guide to ensure 90 degree alignment. This technique is often used to drill and tap rocker studs. Recommend an aluminum block for more precision. A second guide should be used for the tap.

Re: stripped Threads coolant fitting Model A
 

So what was your choice you decided on?

Re: stripped Threads coolant fitting Model A
 

Simple things first. Buy a tap for the correct size and thread, run it into the hole a couple times, then use a new bolt. Often times you can increase the length of the new bolt a bit. Check thread depth first of course.

Re: stripped Threads coolant fitting Model A
 

You should try a bottom tap and a new bolt and Locktite. JMHO

Re: stripped Threads coolant fitting Model A
 

Thank you all for the advice. I have a few blocks of mahogany that I can make a jig out of to hold the drill straight. I like the idea of taping the drill bit as well so I don't go too deep. All great ideas. I'll let you all know how I make out. I did try a new bolt and it was only marginally better than the old one but still made that little chink sound as it popped out on the last quarter turn.

Re: stripped Threads coolant fitting Model A
 

Thank you everyone that made suggestions and to all that were there in spirit. I finally tackled installing the helicoil for the coolant fitting in my A.
I have to tell you I was nervous and kept putting it off as I couldn't help but think I might mess up a 90 year old engine block because of my lack of experience. It went flawlessly because of some of the suggestions I received and I wanted you all to know how much I appreciated your help.

Re: stripped Threads coolant fitting Model A
 

Waaay to go!
Glad you tackled it and won.
I've often stepped back from a job that I was unfamiliar with or nervous about doing.
Sometimes one just needs time to think it over.

Re: stripped Threads coolant fitting Model A
 

Well done Dave.