Cross threaded fuel pump bolt, now what?!

autonomousbronco · Apr 21, 2024

Hey all, I pulled a boneheaded mistake and cross-threaded one of the bolts for the fuel pump on the block…I know, I was in a rush and it was a roadside repair (had to push the car off the highway to when the engine sputtered out). The replacement fuel pump still works but I’m dreading the day I’ll have to replace it. Just wanted to ask if I should do one of 3 options:

1) Fix it with a heli-coil (if so, any installation tips/tricks are greatly welcomed).

2) Replace it with a blank out plate and fit with an electric fuel pump and carburetor w/ a deadhead pressure regulator as I unfortunately got rid of the return line for the old evap system (CA car)

3) Go full EFI with a Holley Sniper 2 system and replace the missing return line to the gas tank.

Thanks in advance,
-Hank

Bentworker · Apr 21, 2024

I’d do a thread insert or helicoil. DO NOT have the first time you install one be on your own engine. Practice on some scrap steel first if you are dead set on doing it yourself.

Preferably find a machinist or mechanic familiar with them.

Lots of ways to screw them up, but done right they are great.

My tips…
Purchase whatever inset kit you desire of the correct diameter, thread pitch and length…. but get a quality one. Helicoil has kind of a bad rep, but they are fine as long as you insert them at least one thread past flush.

Use the drill bit size directed by the kit, Use a quality sharp bit. McMaster-Carr is a good retailer of quality tooling. Research the correct speed and feed for that size drill. Before drilling practice positioning the drill so that you drill perfectly in line with the existing hole.

Use quality lube for drilling and tapping. The gnarliest stuff I know of is Castrol Moly Dee.

When tapping be positive you are in line with the hole. Go a few turns clockwise, then remove the tap, clear the chips, re-lubricate and tap further. If you are crooked you are screwed.

Once tapped flush out the hole with solvent and compressed air. If you are using a helicoil load one on the insert tool, and install it by carefully rotating the insert tool clockwise. Stop and make sure you are not cross threading. Continue until the insert is below flush about one thread. Once at desired depth use a pin punch and a hammer to snap off the drive “dogleg” on the insert. Fish out the broken drive so that bit of helicoil isn’t floating around at the bottom of the hole.

Test fit a fresh quality fastener and you should be good to go.

This is a task that requires finesse and experience. I cannot stress enough how important is is to practice using thread inserts on something other than your engine.

c9zx · Apr 22, 2024

Any hope of using a thread chaser to repair the threads? Loctite/Henkel make a thread repair kit. Reviews indicate a 50/50 chance of success. In the worst case use this. https://www.timesert.com/ Good luck. Chuck

MikeGriese · Apr 22, 2024

I prefer timeserts to helicoils as they are stronger and easier to install, but if there isn't much metal around the hole, a helicoil may be the best option.

rcadd1ct · Apr 22, 2024

If it is the top bolt. Thread chaser, red loctite and a stud might get you there.

Spike Morelli · Apr 22, 2024

I'm kinda intrigued by people who want to go with an EFI system, when , for the most part, it appears those same people have difficulty to overhaul or troubleshoot their carburetor. Carburetors are simple, reliable fuel delivery units, and perfect for the type of engines used in our Mustangs. I'm not against EFI at all, however I haven't seen enough honest, accurate evidence off of comparative engine analysis that show enough of a difference to make the cost and effort of the change-over so eminently worthwhile.. I would think over-complicating our cars is the opposite of what separates them from new cars, which will be worth nothing to enthusiasts in the future. I certainly wouldn't be thinking about such a large and complicated investment just because of a fastener issue.