Stipped head bolt thread in block.

[TriPolar]

Went to do the 180degree tighten, then this happens. All the rest are fin and tight. What options do i have..? Its the middle long bolt.

[Blknight.aus]

If it's a middle bolt why did you do the rest up?

It can be helicoiled if you are lucky and if not your up for a new block.

You want a special helicoil thats a 4d specification.. you won't get it off the shelf.

Via the modern day equivalent to smoke signals fromsome place other than the cave where my hat hangs.

[TriPolar]

The rest are done to make sure it would not happen to any others. Which it did not. No point in fixing one if a few more are going to do it.

[TriPolar]

So after riding round the coast today, no bolt shops are open. So itll have to wait. But i was thinking, since its a 7/16 bolt, cold i possible retap it to take a m12 or still the helicoil way.

[Bigbjorn]

What diameter is the bolt-hole in the head? Will it take the next size up bolt or can be accurately machined to do so? If so, then you can drill and re-tap the block to take the larger bolt.

[TriPolar]

There is some play with the bolt in the head. 7/16 = 11.1125mm. Because i didnt bother buying a m12 bolt i cant test to see, but i think itll take it.
Highly doubt anyone would sell a 15/32 (11.9063mm) bol.

[Bigbjorn]

There is some play with the bolt in the head. 7/16 = 11.1125mm. Because i didnt bother buying a m12 bolt i cant test to see, but i think itll take it.
Highly doubt anyone would sell a 15/32 (11.9063mm) bol.

Easy to make a 15/32" bolt from a larger one, say a 1/2" with sufficient length of unthreaded shank. I can supply 15/32" x 32 taps ex USA for about AU$15 and a 15/32" x 32 x 1 1/2" die for about $35. This includes air-mail and at exchange rate of 0.87. These are high speed tools of machine shop quality.

If capable, you can save the die and screw cut the bolt.

[101RRS]

I had one like that in my block - I took the block to an engine builder who put the appropriate helicoil in - all up was about $50. A threaded insert is an alternative.

Also I would ditch the head bolts and us ARB head studs - much easier on the alloy threads in the block.

Garry

[bee utey]

Helicoil or "Recoil" thread repair would be best, you can just stack two inserts in the hole. Recoil brand kits aren't that dear and should be perfectly adequate, I've used them for years. I agree though that ARP studs are much better than TTY bolts.

[PLR]

G`day ,

i`ve used a Recoil kit .

Part# 33070 , has the tap the coils and the tool to fit the coils .

Size i used is UNC 7/16 - 14 , you may want a different length but for the same job .


You`ll need a bit 11.5 or 29/64 for the hole .

As you`ll be working on a slating face you`ll need to get the angle right but that`s the hardest part and be sure you have enough depth .