[steve25]

If in the car you may have to jam the flywheel with something when you tap it.

[Gach]

Personally looking at those threads in crank, they are totally trashed . No insert is going to help you. Not when your talking torquing to 150 lbs. bite the bullet, and pull the motor and replace the crank. Especially if that’s a cast crank.

[JSchmitz]

You should not hand drill and tap your balancer bolt. It needs to be done on a machine to be perfectly straight. If it's not straight, it will likely not stay tight. It could also cause a failure of the bolt and/or balancer. My opinion.

[Gach]

I’ve seen this done with an insert and end results was not good. Guy spent allot of money and the results was a disaster.

[chiphead]

I agree with Mgarblik. If you heli-coil it correctly with a deep insert, it'll live. If you then stud it, it'll outlive us.

I've done this on a 235 chevy 6 that uses a press fit balancer. Those were awful for walking off the front of the crank. I tapped the snout and used a 5/8 bolt to hold it on. It's been fine for years.

If you swap the crank, you'll have to balance the new crank and swap it in. You'll have to re-check all the bearings at a minimum. You should totally disassemble the engine to properly replace the crank. You could push all the pistons to the top of the cyls during the swap, but that's a shadetree way to do it.

[BILL BOWMAN1]

Hand tools, in the car, on such a critical part. No thanks!!

[NeighborsComplaint]

Have you considered tapping it for an M16 or M18 bolt? The minor diameter (bottom) of the threads is slightly larger than the major diameter (outer) of your 5/8" threads. They come in multiple thread pitches also. You would have to ream the balancer hub, but that might be the easiest fix.

[Stan Weiss]

Originally Posted by NeighborsComplaint

Have you considered tapping it for an M16 or M18 bolt? The minor diameter (bottom) of the threads is slightly larger than the major diameter (outer) of your 5/8" threads. They come in multiple thread pitches also. You would have to ream the balancer hub, but that might be the easiest fix.

Years ago I did something similar. Only it was a forged SBC crank and the engine was not in the car. But it worked out great.

Stan

[Mr Twister]

Originally Posted by NeighborsComplaint

Have you considered tapping it for an M16 or M18 bolt? The minor diameter (bottom) of the threads is slightly larger than the major diameter (outer) of your 5/8" threads. They come in multiple thread pitches also. You would have to ream the balancer hub, but that might be the easiest fix.

This!

[70pontiaction]

But here they are on EBay.

https://www.ebay.com/itm/295704120907

Good luck!

[Schurkey]

Installing fine-thread Heli-Coils requires a special installation tool; the fine-thread kits cost more because of that. Properly installed, it will not be "as good as new", it'll be stronger than the original threads (which isn't a big challenge, since the original threads are cast-iron.)

Yes, the big deal is making sure the drill bit goes in straight, whether drilling for a Heli-Coil or an oversized bolt. Someone with access to a lathe could take a proper-size drill bit, and carve the first half-inch to make a pilot diameter. But then you'd maybe need a second drill bit to get to the bottom of the hole.

[hurryinhoosier62]

Originally Posted by chiphead

A properly installed threaded insert will be just as strong as the original threads. My first thought would be to install a heli-coil yourself. The professional machinists here can comment if a heli-coil would hold 160 ft/lbs. The next option is the time-cert, which I'm sure will hold the torque. Again you can install yourself or have a shop do it.

If this was me, I'd see if a mag-drill could be used to drill the hole accurately without removing engine from car. Then you could tap the crank snout for the threaded insert of your choice.

160 ft/lbs would negate using a HeliCoil. A TimeCert would be a far better choice.

[sdbob]

Should the time cert or helicoil be red loctite in place so as to remove balancer in the future? Curious.

[Gach]

Originally Posted by hurryinhoosier62

160 ft/lbs would negate using a HeliCoil. A TimeCert would be a far better choice.

Agree !

[mgarblik]

Originally Posted by Schurkey

Installing fine-thread Heli-Coils requires a special installation tool; the fine-thread kits cost more because of that. Properly installed, it will not be "as good as new", it'll be stronger than the original threads (which isn't a big challenge, since the original threads are cast-iron.)

Yes, the big deal is making sure the drill bit goes in straight, whether drilling for a Heli-Coil or an oversized bolt. Someone with access to a lathe could take a proper-size drill bit, and carve the first half-inch to make a pilot diameter. But then you'd maybe need a second drill bit to get to the bottom of the hole.

Thank you Shurkey. Finally, the most important point has been addressed. That crank nose with a heli- coil will be a stronger joint than a bolt installed into a direct tap cast iron part. It seemed to me the OP just had a problem and hoped for a solution that would do the job with the least amount of hassle and expense. Sure he can take the engine out remove the crank, put in in a lathe repair it correctly with a time cert, perfect heli-coil, drill/tap oversize, even weld the hole up and start over with the stock size. Or put a forged crank in it and build a new engine. But to just put the car back in service in an hour or less, be cruising around the neighborhood, I stand by putting a heli-coil in and be done with it.

I understand the concern with drilling and holding the drill straight. So how about this simple solution. The hole right now is .625" and stripped. To install a heli-coil, it needs to go to .6406". That's only .015" larger than the stripped hole major diameter. If you use a cordless drill and a short 5/8" drill bit, it will follow the existing hole and take the rest of the remaining threads out of the nose. Unless, you are just terrible operating a cordless drill you should get a straight hole as it follows it's way in. Then just direct tap the hole with the heli-coil tap. Your only talking .007" on each side extra material to remove. In cast iron, that's easy. Start the tap and turn it in 1 turn. Use a 6 or 12 inch square to make sure the tap starts straight. Adjust as necessary. Check it every turn for the first several turns to keep the tap straight. Once in 3 or 4 threads, it will follow the hole. Tap till it bottoms, remove clean and tap again. Then install the coil. The heli-coil will easily handle 160 ft. lbs. Make sure the coil is in the nose 2 threads in case it tries to pull. If your really worried about it, put red locktite on the assembly. Be warned, if you use red locktite, heat will be mandatory to remove the bolt in the future or you will ruin the bolt, heli-coil and possibly crank. Need about 400 degrees to remove easily. Good luck with whatever method you end up using.

I agree a Time Cert would be even a better repair but would be very difficult IMO to install with the engine in the car. You have much longer tools to deal with and certainly the radiator would have to come out. cutting the counterbore for the Time Cert would be a challenge in the car. Also the kit would be over $200.00 for a single repair. If the crank was out of the car and I had the kit, a Time Cert would be my first choice. I would install it in a lathe.

[RAIIIJudge]

morning, fellas,

you guys have given me so much to chew on .. I really appreciate this discussion and everyone's thoughtfulness, thank you all.

- it seems the big thing if I were to try a motor-in-car repair is drilling and tapping straight as no repair will live long, especially at the end of a crank shaft, if work isnt straight. components will wallow and eventually fail. as with even this thread there's differing opinions across web as what'd be stronger heli-coils or serts. one thing I don't get is if a coil or insert is an option why just tapping and going w/ next larger bolt (M?) isnt the clear first choice? (I think a few of you (NeighborsComplaint?) were getting at this, above). I understand what mgarblik and Shurkey are getting at that new threads will be stronger than original but even w/ stronger new threads you've now introduced <more> componants therefore tolorances to the assembly no? And why if I were to go w/ a coil couldn't only the outside of coil get the red Loctite? (thereby allowing bolt removal if needed).

- as far as pulling the motor goes, I'm already hemorrhaging money pulling this long stalled body-off-frame restoration together. it's been going really well and ive been having a ball but there's no "shop" here only a kinda' crappy little garage w/ a good roof where car <barely> fits. up until this new mess, I'd "drive" car (ha zero interior still) into driveway to work on it. btw .. nose, passenger fender and hood are off car (radiator, cowl, fan, alt and PS pump too) so that's all a positive if I were to yank motor. but again i dont yet understand how far a tear down is needed and what kind of cost I'd be looking at. new crank shaft, balancing, main bearings and rod bearings + labor? feels like it could turn into an onion <fast>.
keep in mind motor has easily less than 5 hours on a rebuild and except for crank snout it runs excellent w/ good oil pressure, no smoke and sounds like a beast.

I do want to be able to really get on car and don't want to lose sleep over whether or not any repair is going to go south. motor is the original WS from car w/ a 041 cam, M20 and 3.73s (12 bolt .. lost track of original rear in 82' doh!)

GACH is down the road in RI so we can't be too far from one another. he's graciously agreed to a phone call. hopefully I'll learn a few things and maybe there's a shop in the vicinity who's comfortable w/ Pontiacs (and isn't backed up 5 years).

Hope this doesn't come off as unnecessary whining or hand wringing. really, I'm just on steeper side of learning curve and trying to get my head around stuff.
I appreciate the patience!

thanks again fellas, I'll be back : )

mike
MA

[JSchmitz]

If you're very careful, the crank can be pulled without full disassembly. I'd put the engine on a stand and pull the crank. Take it to a good machine shop. Get it drilled/reamed and tapped dead straight. Put it back together and sleep well at night. Shouldn't cost much if you do most of the work. Oversize or metric bolt would be my first choice. Followed by thread insert. I HATE Heli-coils!!! Absolute last resort for me.

[Formulas]

I recently and 100% sucessufully installed a helicoil in the outer hole of a 4bolt main SBC block
Of course i was worried about angluarity i bolted down a drill bar from the oil pan bolt hole to help keep it straight and when i drilled it was almost like the drill bit was sucked down in the hole straight it was almost like it was over before it started mainly because not much material is being removed

as stated in my first post i would examine hole size in relation to just taping for metric fewer steps and in good place at the end

you can make a fixture out of hard wood "oak" why? wood its easy to work with and you only need it once , you have a wide flat surface above the crank snout glue two pieces of wood together to get over the seal step on the cover drill a perpendicular hole in the wood thats the size of the OD of the new tap use the wood fixture to get the tap started well and once its 3 or 4 turns started then you dont need the wood so much just dont side load the tap as much as possible..

its called controlled tooling, used in the military aircraft production, prototype world

[RAIIIJudge]

JSchmitz and Formulas ..
you're both advocating tapping to next size up but differ whether it's a good idea to attempt w/ motor in car, yes?

[mrennie]

I'm with the others about preferring a fix in the car.

The cost of new seals and gaskets, the time involved, the likelihood of nicking the crank if trying to remove it with the rods/pistons in place is all unnecessary risk.

Helicoils get a bad rap at times but this does seem like the easiest fix and if you mess it up you can still use a timesert as it will want a larger tapped hole anyway. Going straight to the timesert now leaves little chance of a "second" repair if you mess that up.

The stainless wire of the helicoil is going to be stronger than the cast iron threads so I don't see any reason why it can't handle 160 ft lbs of torque. The helicoil doesn't know what the application is...if there was a restriction on how much torque could be placed on it, the packaging would say so.