96 F150- it’s pretty much smooth in the hole where the harmonic balancer screw goes. I need to tap it but never drilled and tapped before. This is what I’ve come up with. Please tell me if I’m wrong. 15/16 bolt. (24x1.5 drill size 22.5). Should I drill and tap for the next size up which would be 26x 1.5, drill size 24.5?
My logic is since the original bolt is 24 do I need to only drill out .5mm and tap for the 24.5? Or to simplify what the hell do I do?

 

If you are talking about the bolt that holds the harmonic balancer to the crankshaft then I think you need to consult a local speed shop for advice. The crankshaft is hardened steel and I would think that you probably need a professional machinist. Just the drill will cost alot (maybe $80) tap will cost alot (mabe $100) Drill will likely require 3/4" chuck. This is big stuff and even a pro will have to be careful to get it right. Is the crankshaft out of the truck? If it is out of the truck then a machine shop needs to be consulted. Report back as you progress.
You might search and see if there is an expoxy material like JB Weld available. JB Weld has about five or six different formulations and you would need to choose the right one for the job which would not likely to be the one at Walmart.

 

Are the threads wiped all the way to the bottom of the bore?

To drill and tap you will need to find the suitable size replacement bolt and matching drill (based on the tap), and the tap. The tap package or a quick internet search will help you identify the correct drill.


The important thing is getting it drilled and tapped perfectly straight into the end of the crank with threads formed to the correct depth. This could be hard to do with the engine in the vehicle.

Since you are new to this I would advise getting someone with experience to help. The necessary techniques, tools, and knowledge needed to sucessfully complete a job like this is very involved.

 

JB Weld for the balancer bolt, I don't think so. I am still scratching my head how these threads could have gotten screwed up?

 

Most likely someone used the threads to install the damper with the bolt instead of using an installer
I just had to have a 454 crank of mine drilled and re tapped
Yes, the machine shop did mine with the crank on his machine
I advise you do the same and remove the crank
That said I would be looking at doing it myself if the engine is in the truck and runs good
Correct, the drill and tap will be expensive
Talk to the machine shop about numbers (bolt sizes) yours are wrong
The 15/16 headed bolt in your crank is a 5/8-18 thread
You will be going up to 3/4-18 thread, so you find a drill that will work for that thread and a tap
Good luck
I have had to fix a few Mitsibitchys by the drill and tap method with the engine still in the truck
It can be done
You should be able to find the drill and tap as a set for 50 bucks or less on google

 

I really appreciate your help and the others that responded. I’ve been asking for two weeks, parts stores garages…and it seemed no one wanted to answer me and some contradicted others. I will do as you say and report back. Again, thanks so much. You motor heads are awesome.

 

By the way, your crank is cast iron and drills easily
Use a high speed steel drill bit

 

This is the first time I was in one of these sites. Maybe I’ve been beat down in the outside world. It’s so cool you guys share your knowledge with us challenged people just for the sake of helping someone and everybody is so friendly. It’s weird. Next time I need proof that there’s still hope for society I’ll make up a problem for my truck and visit.