Technical Drill broken head bolt - advice

Hey Fellas,

Need advice to create a jig to keep my drill centered when drilling out a head bolt. Any advice/tips are appreciated. Thanks.

Chris

Photo_9113798356798490714 by MGK posted Mar 22, 2023 at 12:11 PM

Photo_8991724154714145546 by MGK posted Mar 22, 2023 at 12:11 PM

 

One thing you could do is use the head as a guide. Mount the head with several bolts. Make a bushing to fit the head bolt hole with the id at about 5/32" for the pilot drill. Any local machine shop could make one in minutes. If you were closer, I'd make one for free.

 

Chris, Peruse this search information on the topic.
how to remove a broken off head bolt in a ford flathead - Search (bing.com)

 

This can be done two ways without a jig if careful, use an "easy-out", some are spiral and some are flat/tapered, also a left hand drill bit can work, some are designed for this.
First, try get the bolt end as flat as possible even if it's broke off below the surface, as best as you can establish the center with a center punch, drill bolt full length through (if possible) about 3/4 of the bolts' minor diameter, it can be a bit of a trial and error.

 

Is it already drilled off center?

 

Yes, slightly but unfortunately.

 

Depending on the desirability/rarity of the engine, consider taking this to a machine shop.
If you want to tackle this, do not get stubborn or in a hurry.

I have seen many almost unbelievable damage from drilling a bolt out when the "driller" got stubborn.
Pretty much everything was gone but the broken bolt. The broken bolt was still there but with a ragged figure 8 shaped hole around the bolt. That's easier to do than you think when tunnel vision takes over.

 

If the start is already crooked, it may be best to stop here and find a shop that can drill it out.

 

A drill bit won't help here, I would be looking for a end mill or weld something to it at this point to remove it.

 

Thank you. I have tried both already.

1. P..B. Blaster - 5 days, twice a day
2. Parrafin wax - would not budge
3. MAPP torch - never turned bolt or block red
4. Easy Out - would grab at first then slip.
5. Fluted screw remover - same as easy out
6. Weld nut - did this 3 times, bolt twisted off all 3 times.
7. Drilled initial hole 1/4" thru bolt, then 3/16" thru bolt, made sure not to drill valley.
8. Collapse threads - no luck, would not budge.

 

I called machine shop I use and because the engine is complete they can't position it on a lathe.

 

EDM

 

Can you explain the weld method you are suggesting? Trying to visualize your suggestion. Thanks.

 

50/50 mix of atf and acetone for penetrating oil, have you tried a drift punch?

 

Peruse this information before you proceed further.
The Ford Barn - Search Results

NOW, since broken bolt has already been drilled off center, I would take a Dremel tool with and small grinding stones and carefully grind the remaining left over "OFF CENTER" bolt metal (shown on the top edge of your photo) flush with the inside diameter of the remaining internal threads so as to get concentricity. Be very patient and gentle with your grinding- a little at a time. YOUR GOAL IS TO GRIND AWAY ONLY ENOUGH METAL SO YOU ARE EVEN WITH THE CREST OF YOUR INTERNAL THREAD REMAINING IN THE BLOCK AS SHOWN HERE: (Open and scroll down.)
what is the crest of a thread - Search (bing.com)
Then take a 7/16-14 taper tap and carefully hand tap the threads to match the original 7/16-14 threads left in the block.
KEEP THE TAP AT 90 DEGREES TO THE BLOCK AND ROTATE THE TAP CLOCKWISE JUST A LITTLE BIT SO AS TO CUT NEW THREADS AND THEN COUNTERCLOCKWISE TO CLEAR THE CHIPS FROM THE TAP SO IT WON'T JAM AND BREAK. USE PLENTY OF LUBRICANT LIKE WD-40 .
If this doesn't work you can install a 7/16-14 hellicoil kit - which is what a machine shop would probably do.
Helicoil 5521-7 7/16-14 Inch Co**** Thread Repair Kit (amazon.com)

 

I would use an oxy/acetylene to heat up the broken bolt and weld a washer to it then weld a nut to it. Then I would heat it up and let it cool at least 5 times then try and turn it out.

 

I'll add my version to this.
First, under what condition did the bolt break? Did it bottom out before being attacked by some gorilla? Or was the bolt itself compromised? If it bottomed out then it will never 'un-screw'.
Because the bolt has been drilled off-center already, you can expect that it also was crooked (not parallel to bolt centerline). The only way to save the block is to strip it down and get it in a milling machine and use an end mill to take out everything out to the minor diameter.

 

I can't see your photos. What type of engine? What about if the engine was down to the bare block? For instance, a SBF bare block much easier to handle than say a flat 6.

 

Yep, I’d use a head as a jig. You will need to drill oversized, and maybe the nutsert will start with the same size as the head’s hole? Or an oversized nutsert that has a larger OD?

 

Perhaps I am misunderstanding but, didn't you mean minor diameter?

 

It's probably rust locked and will never unscrew. I'd try to thin the thickest part of it and collapse it. Don't really see a better home remedy. Good luck!

 

I'm just being honest, this is beyond you. You need to find a pro to fix this.

 

Find a friend who is SKILLED with a torch and he can blow that out without hurting the block.

 

Very good advice. Thank you.

 

Since the hole is off center, once you remove what is left of the bolt, the hole will be oversize.

You could try to re-tap, but there will not be enough thread to hold the bolt IMO.

I believe your best option is a thread insert. In order to get it in the correct location, you will need to bore the hole out. A drill will only follow the hole that is there and not cut out the remining bolt.

 

I have not tried a drift punch.

 

Excellent advice. Thank you.

 

Another good idea. I'm not sure there's enough material left to weld to. Will look though. Thanks.

 

Using a socket and ratchet to remove, it backed out about 3/16" and snapped off.

 

MGK,
Join the Ford Barn. Post your pics with the ***le "help". Be prepared for some hard news. There are some skilled guys over there or people who know skilled guys from the stock restoration world.
As far as "getting bolt out", that boat has pretty much sailed. The problem now is how to save this block.