Change Headbolts/studs from 3/8 to 1/2" on a -39 212 splasher engine

[Deleted User]

Hello!
The studs in my engine block for the head keeps breaking at low torque, one of them broke in the block aswell, so it need drilling.
I was thinking about changing them to 1/2" studs instead if that is a doable conversion? The block should have enough thinkness what it seems like, but will the thickness in the top hold up for 1/2" holes instead of the holes for 3/8" studs?
Otherwise the operation seems to be quite simple.

[Deleted User]

How tight are you are you torqueing them ? The spec is only 45lf/ft and the original studs should be able to handle that amount.

[Deleted User]

sorry that should read 45lb/ft.

Geoff

I would definitely not recommend drilling out to half inch. These old blocks don't have much intestinal fortitude, and by drilling the head, and putting 1/2" studs you are going to weaken it even further, and will not be able to hold head gaskets. Fit a new set of 3/8" studs, and keep the torque to 40 lbs, and you should not have any trouble.

[Deleted User]

You may even have a bad torque wrench . If its the clicker type in particular.
Roger

[Deleted User]

I have tested with two dofferent wrenches, good quality. They snap at around 35-40, but then i will startt with changing all bolts and nuts that might need re-tightening to a higher grade and see if it holds up better.

Marconi

It may be overkill but I'd make sure to use grade 8 studs and use hardened flat washers under the nuts.