Thread: Helicoil

Tweet

Anybody install a Helicoil for a main bearing cap bolt? I am going to attempt to do it tomorrow unless someone warns me otherwise. I am worried about affecting the alignment of the cap.

I had an aluminum block repaired at a main saddle and they used a fastener insert called Time Sert. I'm not 100% positive about the spelling. It's much larger and stronger than a helicoil , and won't come out. I'm sure your local machine shop will know about them. Just my 2 cents...

I'll talk to the machine shop who prepped my block. I would like to do this myself, but if if I don't drill the hole straight I am screwed. I might be able to use the cap as a guide, but the drill bit will likely be too large for the hole. The drill required for a 7/16ths 14 tpi helicoil is 29/64ths which is only .0156" larger than the bolt which is slightly smaller than the hole in the cap. I have my fingers crossed that I can use it as a guide, I will measure tommorow.

Ok, I couldn't wait. I measured the hole in the main cap and it was .470". The drill required is .453". That means I can use the hole as a guide and if I line it with some .005" shim stock, that will leave me with .002" of slop for the drill and that is more accurate than most drill presses so I should be ok. I'll still call my machine shop and my grandpa to see what they say.

Originally posted by blwn31
I had an aluminum block repaired at a main saddle and they used a fastener insert called Time Sert. I'm not 100% positive about the spelling. It's much larger and stronger than a helicoil , and won't come out. I'm sure your local machine shop will know about them. Just my 2 cents...

Thread serts is what I am familliar with and I recommend the ones with the four pins on the side they will not work out and still can be removed have used them many times and they are great. Mc Master Carr and many machine shop supply houses have them Graingers also. good luck Ed

PICTURES,PICTURES,PICTURES.!!!


~ Vegas ~

I don't believe I would use a block with a helicoil insert. Hopefully it is at least a 4 bolt main block so there are 3 other bolts holding it in place, and hopefully it is one of the outer bolts???? I wouldn't risk all the good parts on a cap that could pull and gernade the motor. JMO

It is a 4 bolt block, but the damaged bolt hole is on the rear cap which is a 2 bolt. I'm not worried about the helicoil pulling out, they are actually stronger than a bolt through just the cast iron of the block. I was just worried about affecting the alignment of the cap.

Something's wrong here. I haven't kept up, but I assume you're talking about a SBC. The main cap bolts are 7/16" diameter, I can't remember whether they're 14 or 20 TPI, but they're 7/16" diameter (0.4375"). The drill to use for threaded inserts for a finished 7/16" thread is 37/64" (0.578125"), so you will not be able to use the main cap as a guide.

If I were doing this in a home garage and didn't want to haul the block to the machine shop, I might proceed thusly:

1. Use a bottoming tap to clean up the threads in the hole and make sure I had maximum thread length in the hole.
2. Get myself a used rear main cap and mount it on the drill press to drill out the bolt hole with the 37/64" drill bit.
3. Mount the used cap on the block, using the bolt on the other side of the cap to secure it.
4. Drill the hole.
5. Remove the main cap, mount it on the drill press again and drill the hole out to 0.625", the diameter of the tap you will use.
6. Secure the cap to the block again and use it for a guide to keep the tap lined up. If the tap is too short to start in the hole through the guide hole, grab your Sawzall and slice off a slab of material from the cap, making it thinner.
7. Install the insert with loctite after cleaning all lube from the hole.
8. Get yourself a set of main cap studs from Milodon or other premium supplier and stud all the caps.

Well, I'm down to my last 30 dollars and 10 days to get this engine back together so Milodon caps and studs are out of the question. I do have a spare rear cap from my old block that I could drill for use as a guide and may do that. I kind of figured 29/64ths was too small, but that is what I found listed on the internet.

Ok, it's helicoiled. Turns out 29/64ths is the correct drill size, but the drill ended up not being necessary as the hole was already the right size for the tap being the threads were ripped out and all. The guys at the parts store also suggested a time sert but couldn't find anybody in the area who sold them.