busted head bolt in a flat head v8

Hi all, was wondering if I could get some right minded flat head v8 guys to help me with a vex I'm having....I have a 59 A-B flatty...1946-1948 100 hp motor and I'm dieing to rebuild it but I have a problem....it has 2 broken head bolts on top rear right cylinder and middle rear right cylinder....is it worth it to try and carefully drill them out or find a new block...are these block's plentiful or should i can the whole mess and start with another engine....I received the engine as payment for labor on another vehicle and it is complete....all accessories included...so I'm out around $150 ...it doesn't spin but looks good and clean in the bore's...valve's look messy (lil corrosion around the seats) any suggestion or opinions are greatly appreciated...again thanks in advance

 

hi, i had the same problem on one of my flatheads, took it to a local machine shop, they welded a nut on the stud, the heat from welding loosened it up and they backed it right out.
mine was broke off flush with the block. good luck, good flathead blocks are getting harder to come by.
bill

 

If they are broke off flush weld a washer to the stud, then weld a nut to the washer. may take a couple attempts but that almost always worked for me.

 

Before you get too far into it, have the block magnafluxed to be sure it's not shot. If it checks out, then you can worry about busted bolts. The place that mags it might have an EDM and can burn them out.

 

I would tear it apart to start with and check the rest of the block out. if it checks out OK as in no none repairable cracks then I would fish the busted head bolts out. if the block is busted beyond repair or reasonable repair I would look for another block and then you will not have wasted your time fishing the head bolts out of a block that cannot be repaired.

 

Build up the broken bolt with a weld, then weld a nut to that. Wait for it to cool, give it and hour or so, then back it out carefully. Don't worry about welding to the block, it won't stick.

 

Absolutely right. The washer is the first step, it gives something to weld the nut to and protects the block.

Even if the broken bolt is recessed down into the threads you can start a SMAW rod arc on the top of the broken bolt and fill the hole with weld before you weld the washer on.

You can do this because the flux flows to the outside and fills and protects the threads.

Then you weld on the nut.

The reason it takes a couple of attempts is because of the way the heat affects the broken stud or bolt.

It's called "Upset". The heat causes the bolt or stud to shrink in diameter and grow slightly in length as it cools.

This is what loosens it in the threads and allows it to come out.

I have made it work even when the rust in the threads is extreme.

 

If nothing comes of this, Ive got some flatty blocks....

 

I'm in South Central Mi. My welding guy I go to when it's beyond my capacity has taken out many a broken head bolt with the weld a nut on method. This little shop has been going for more than sixty years his dad made my first bike a used girls into a boys bike by welding in a bar nearly 60 years ago. Another thing I've seen him do is weld a piece of steel with a 90 degree bend on it then just grab the off set with a crescent wrench.

 

The washer then the nut thing almost always works…. But heat the surrounding block first.
When and if it doesn’t I drill progressively larger and the last one usually ends with the thing unscrewing when the bit grabs.