Head stud to block

31 Woody

31 Woody

Senior Member
What is the thread size for the head stud into the block? I just test fired my rebuilt engine and warmed it up, then on retorquing the head, the front left stud at the water neck pulled loose from the block. I am hoping I can just pull the head and helicoil it. What size is the thread size at the block? Thanks!

On the plus side, it ran great!
 
The Helicoil will work just fine. It will provide more pull out strength than the original threaded hole. Only one thing to watch out for and that is the accuracy of drilling the hole for the tap for the Helicoil. This is best done with the head placed on the engine and using the bolt hole as a guide. Put the head down over the remaining studs but no need to fasten it down. If you are concerned about enlarging the bolt hole in the head, use an old scrap head. But the hole can be enlarged slightly without hurting anything.
 
One last point to be concerned with here
Be careful to not drill too deeply
The stud boss is fairly thin in the bottom and you do not want to penetrate into the water jacket
 
Good tips—thank you! I will measure the hole depth and then use a collar on the drill bit to prevent going too deep.
 
nkaminar said:
The Helicoil will work just fine. It will provide more pull out strength than the original threaded hole. Only one thing to watch out for and that is the accuracy of drilling the hole for the tap for the Helicoil. This is best done with the head placed on the engine and using the bolt hole as a guide. Put the head down over the remaining studs but no need to fasten it down. If you are concerned about enlarging the bolt hole in the head, use an old scrap head. But the hole can be enlarged slightly without hurting anything.
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Ditto to NK. Be very careful that you drill the hole centered and vertical. I'd suggest that you install the head with a couple of the other studs and snug them slightly to keep the head from shifting. Since this is one of the front (long) studs then the head should be an adequate drill guide. Keeping the tap vertical may be another challenge. As NK suggests, perhaps finding an old head and drilling out that opening to the tap OD would be in order.
 
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A friend and I drilled and installed a helicoil for a head stud free hand today. We had 3 sets of eyes on the bit and tap as well as using a small square. We were concerned about being off but felt better when the head gasket slid right on and really relieved when the head slid on without any effort...:)
TOB
 
I have one head stud that a previous owner installed a Helicoil slightly catawampus. When I install the gasket and head I have to remove several studs, install the gasket and head, then reinstall the studs using two jam nuts on the studs after the head and gasket are in place. All because I can’t get things to line up due to that off-kilter stud. Kind of a pain.
 
JayJay said:
I have one head stud that a previous owner installed a Helicoil slightly catawampus. When I install the gasket and head I have to remove several studs, install the gasket and head, then reinstall the studs using two jam nuts on the studs after the head and gasket are in place. All because I can’t get things to line up due to that off-kilter stud. Kind of a pain.
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To straighten it out and use a thicker wall insert like this would be pretty tough unless the bare block was on a mill.

I used that insert on my motor and as mentioned above, used the head as a drill guide and checked the tap for squareness every quarter turn. It came out well.
 
I still have a big assortment of those inserts from working on equipment.All the taps,and drill bits are kept in the assortment and not allowed out in the rest of the world.Mine are called Keenserts.
 
TerryO said:
A friend and I drilled and installed a helicoil for a head stud free hand today. We had 3 sets of eyes on the bit and tap as well as using a small square. We were concerned about being off but felt better when the head gasket slid right on and really relieved when the head slid on without any effort...:)
TOB
Click to expand...

Having several sets of eyes watching from different angles to keep it square works well.
 
Bruce of MN said:
To straighten it out and use a thicker wall insert like this would be pretty tough unless the bare block was on a mill.

I used that insert on my motor and as mentioned above, used the head as a drill guide and checked the tap for squareness every quarter turn. It came out well.
Click to expand...
It can be done well. It also can be, and more often is, done not well. The latter is what happened to my block. Fortunately taking the head on and off is not a frequent operation.
 
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