[newdad1]

Hello once again fellow gearheads. I am helping my brother finish putting his chevy 350 together. It has been completly rebuilt, will only be used for street use for the most part. He has a mild cam, quadrajet, etc. He is using the stock crank. Speaking of which, when he was disassembling the engine, taking the old harmonic balancer off, he stripped the threads where the harmonic balancer bolt goes inside the crankshaft. The machinist that did the machine work on the motor re-tapped it. Well, everything is put together on the motor, just went to put the pulley/harmonic balancer on, can't get 60 ft lbs on the bolt which is the spec. The harmonic balancer bolt is a 7/16"-20.
Can I retap the hole to 1/2-20 and try to get it to proper torque?

[dawg]

are you positive that is the correct bolt?
seems awful small to me?
I dont think you can redrill and tap the hole because the crank is hardened and getting the hole straight is key.
cant be done properly with a hand drill

[454C10]

I don see why not. should be easy to do. the existing will keep the drill running straight. Don't get metal in the pan. Made sure to use a high quality tap!!!!!! use a tap made from high speed tool steel, not a high carbon pos.

[Jmark]

What is keeping you from getting past 60 pounds? Is it stripped again? Or is the engine turning over?

Mark

[streetrodderbn]

Remember, the early Chevy small blocks had NO bolt holding the damper on, they were pressed on at the factory! I don't know if I would get real upset if you can't achieve 60 ft/lbs on a street (non-supercharged) engine. as long as you can get 40-45 ft/lbs. and use a blue-removable locktite product to keep the bolt from loosening so the damper cant back off! I know I'll probably get beat up for this comment from the "manual mechanics", but I have had an early 283 in a work truck for over 20 years with the early crank that has no tapped hole to even install a bolt in, and it has'nt come loose yet.

[454C10]

You could also try threading in a stud into the end of the crank with some thread locker then use a nut to get the torque you need. I have done it this way in the past with some fine thread 7/16" all-thread. I would spin the engine past 7000 rpm and did it for years with out any problems.

[richard stewart 3rd]

Hi,
I'm asking the same question as J Mark.

Rich

[dirtinla]

Thread Size: 7/16X20R
Underhead Length: 2.25"
Washer Included: Yes
Lock Washer Included: Yes
Material: Steel
Finish: Gold Iridite
Head Style: High Hex

[454C10]

I think we should assume the engine isn't turning. Especially after he mentioned the threads got messed up.

I hope we can assume that.

[DrBee8457]

I JUST had the same problem. Make sure you use a grade 8 bolt. I was using the one supplied by an after market part. As soon as I switched to the grade 8 bolt, I got 60#.

Tried to redrill a crank once, which turned into a disaster. If it is not exact, the vibration will go berserk.

Good luck.

[Jmark]

Originally Posted by newdad1

The machinist that did the machine work on the motor re-tapped it. Well, everything is put together on the motor, just went to put the pulley/harmonic balancer on, can't get 60 ft lbs on the bolt which is the spec. The harmonic balancer bolt is a 7/16"-20.
Can I retap the hole to 1/2-20 and try to get it to proper torque?

Kinda confusing at this point. If the crank was "re-tapped" IE: cleaned up the bad threads and hoped for the best" type of fix, it may have let go again.

Lets hope the guy actually drilled it out and did a proper helicoil fix.

The redneck fix would be to get the balancer on and then tack weld it to the crank snout! LOL Then put it on eBay!!!

[406 bug]

Stud it with a grade 8 . clean hole/ stud with laq. thinner; coat the hole/ thread with JB weld, insert the stud and let it cure and clamp your balancer on with a grade 8 nut. (or you could do it the correct way).

before you get too crazy, make sure you are not bottoming out your existing bolt.

[Jmark]

Originally Posted by 406 bug

Stud it with a grade 8 . clean hole/ stud with laq. thinner; coat the hole/ thread with JB weld, insert the stud and let it cure and clamp your balancer on with a grade 8 nut. (or you could do it the correct way).

before you get too crazy, make sure you are not bottoming out your existing bolt.

Years ago, some guy came to our shop and showed us some new kind of thread maker. He cleaned the buggered up hole with some kind of solvent. Then sprayed a new bolt with some kind of release agent. He then mixed up some kind of two part epoxy or something similar and put it in the hole. He then kinda sorta threaded the bolt into the goo filled hole and let it dry. He then unscrewed the bolt and called it good! He then put a couple of washers on the bolt and torqued it to the bolts suggested torque and it held.

Is this stuff still around? And does it work?

Mark