65 327/300hp harmonic balancer fell off!!!

[fredd65]

started the car up last night to wash it and get ready for a car show this morning, had a strange noise under the hood...holy crap, the balancer and pulley were off...i figured i lost a center bolt out of the crank, but upon inspection no broken bolt or evidence of threads, so i assumed it's just pressed on....used a socket to pound it back on and it wanted to come right back off when revving the engine...since i wanted to go to this show today, i took it back apart, cleaned everything up, used a small chisel to burr up the inside of the balancer a little, then pounded it back on with some red loctite 271...i drove it 10 miles and it stayed on fine...
first off, no scolding me for using the chisel...now what i'd like to do is use an angle drill and put a hole in the end of the crank and tap it...has anyone ever done this or is the crank too hard too drill?...if so, what size bolt would you use?...or do you think i'll be fine with the loctite?...might i be compromising the strength of the crank?...or am i just thinking too much?....i'm amazed there was no center bolt and just pressed on....thanks for any help...
ps the show went great, i got second place out of over 40 vettes

 

[Mike McKown]

You're my kinda' guy

I applaud you for your ingenuity with the chisel and loctite. Yes, you can drill the crank for a bolt. I think the factory bolt is a fine thread 5/8ths. You can look it up.

Since you upset the balancer and used loc-tite, you may not have to do anything further to keep it on.

 

[Rowdy1]

Interesting..........

I'm going to watch this thread to see what the "Pro's" say.

 

[bradfordsvettes]

i would get a new balancer you could try tapping the crank the newer cranks are tapped . i would inspect the crank for wear just because the balancer had to be wobbling at some point. i have seen this before on the older cars . the new balancer may give a tighter fit . you would not want this to come off at a 5000 rpm shift or on the highway real bad things will happen and i do mean BAD :nono :eyerole STEVE

 

[studiog]

I thought only the early 283 cranks were not tapped for a balancer bolt. I had a 283 crank drilled & tapped once but it was out of the car. I don't know how you would be able to get it tapped straight when it is still in the car. You may wind up ruining an otherwise perfectly good crank. :confused
If it is a press on crank maybe you could find a press on balancer for it if pullies line up.

 

[fredd65]

I applaud you for your ingenuity with the chisel and loctite. Yes, you can drill the crank for a bolt. I think the factory bolt is a fine thread 5/8ths. You can look it up.

Since you upset the balancer and used loc-tite, you may not have to do anything further to keep it on.

well, trust me, i didn't like knicking up the inside of the balancer...if i didn't really want to get to that show, i probably wouldn't have done it...i'm thinking the loctite will hold, but it still makes me a little nervous...how deep would you tap into the crank with those 5/8 inch threads?....hard to believe my wife says i think too much, isn't it?

 

[studiog]

One more thing. I would want a proper fix. If the balancer winds up going through the radiator it will only compound your problem

 

[bradfordsvettes]

not sure how deep but you can get a bolt and washer from the general and measure it steve

 

[ro.co2]

Fred 65, I know just how you feel I had the same thing happen to me awhile back. If you do a search (harmonic balancer again) for the heading ,you should find my old thread on this subject. I drilled threaded and bolted the balancer on with sleve retainer inside the balancer and locktite red on the bolt threads if it comes off now the cranks coming with it. Check out that thread and let me know if you have any questions.

 

[Mike McKown]

well, trust me, i didn't like knicking up the inside of the balancer...if i didn't really want to get to that show, i probably wouldn't have done it...i'm thinking the loctite will hold, but it still makes me a little nervous...how deep would you tap into the crank with those 5/8 inch threads?....hard to believe my wife says i think too much, isn't it?

Don't feel guilty about knicking the balancer. If you didn't do it, it wasn't any good anyway. If your crank nose happened to be a little undersize, even a new balancer may not fit tight. Put the bolt in it as described above and it should be fine.

One other thing to check. Look at the keyway on the crank and in the balancer and make sure it is not hogged out. If it is, you may want to change direction here.

I don't know if the bolt/washers assembly can be purchased from Chevrolet now but you can get the grade 8 bolt in a hardware store along with the star washer. The big thick flat washer is a specialty item. They can be found in Corvette vendor's catalogues.

If you can't find the correct drill depth anywhere, e-mail me and I will measure a crank and a bolt when I get back to the garage.

All solid lifter 327's and the L-79 engine had drilled cranks. All the hydraulic lifter engines (yours included) were not drilled.



What would "the pros" do in this case? Well, I've seen them INSIST that you replace not only the balancer but the crankshaft as well. 'Nuff said on that.

 

[Tom Bryant]

First off. I don't know how you could possibly drill the hole straight and centered with the crank in the engine. Sounds like a recipe for disaster. I'd not trust it until a proper repair is done.

First I'd pull it back off and look for damage like a wear pattern from wobbling. Then I'd mic the crank snout to make sure it is not worn undersize. If it's in specs I'd install a new balancer. With the snout in specs a new balancer pressed on properly should not give you a problem. There is a reason it come off after all these years. I would guess that the elasomer is shot and it is out of balance and the weight is moving on the hub. A sure cure for a radiator that is not leaking,

If the snout is worn there is only one thing to do. That's pull the engine and take the crank to a quality crankshaft shop to have the snout welded and re-machined to specs....or get a new crank. Of course, at this time, you can have it drilled and tapped for a balancer bolt.

Here is what you want to use.

GM Balancer bolt part number 3815933.

GM balancer washer 14001829.

It will cost you about $5. for both.

Tom

 

[JohnZ]

As noted on the bag, the SB balancer bolt is a 7/16"-20 thread. As an interim fix, Loctite "Bearing Mount" should do the job; it won't be easy to pull off, but if it's out of the car at that point it doesn't make much difference.

 

[fredd65]

First off. I don't know how you could possibly drill the hole straight and centered with the crank in the engine. Sounds like a recipe for disaster. I'd not trust it until a proper repair is done.

First I'd pull it back off and look for damage like a wear pattern from wobbling. Then I'd mic the crank snout to make sure it is not worn undersize. If it's in specs I'd install a new balancer. With the snout in specs a new balancer pressed on properly should not give you a problem. There is a reason it come off after all these years. I would guess that the elasomer is shot and it is out of balance and the weight is moving on the hub. A sure cure for a radiator that is not leaking,

If the snout is worn there is only one thing to do. That's pull the engine and take the crank to a quality crankshaft shop to have the snout welded and re-machined to specs....or get a new crank. Of course, at this time, you can have it drilled and tapped for a balancer bolt.

Here is what you want to use.

GM Balancer bolt part number 3815933.

GM balancer washer 14001829.

It will cost you about $5. for both.

Tom

it's held fine for 10 miles with mild driving the way i have it, but i'm still not comfortable with it....i'm going to order the bolt and washer and try drilling it in the car with an angle drill....anyone know how deep i should go?...or should i just wait until i get the bolt and washer and measure...that crank is probably going to be mighty hard to drill...
ok, another thought...since it is a press fitting and the bolt and washer are for non-press fits, could i go with a smaller diameter bolt?...this is making me nuts...i sure don't want to pull the engine if i don't have to...thanks
ps will any gm dealer have the bolt and washer?

 

[Tom Bryant]

They are all press fit. The bolt is just insurance. Any GM dealer can order it or they may have it in stock.

 

[coves4me]

Fredd65,

I share your concerns...I have a 59 that has a press fit harmonic dampner and I too am concerned how to keep it on. I do know that Summit Racing sells the bolt and washer kit on their website. I have thought of making a jig that slides on two bolts threaded into the dampner to assist in keeping my right-angle air drill perpendicular to the crank snout. It can be done, but you are going to need to keep pressure on the drill for the bit to bite into the steel. I too have thought of going with a smaller diameter thread, but I'm somewhat wary of doing that. I've even considered using J-B Weld on the crank snout, but I'm apprehensive for it to be that permanent. The dampner would probably never come off!!!! I think the only real solution is to use a helluva lot of patience, go real s-l-o-w, have several drill bits handy, and pray a lot. A cold six-pack to celebrate at the end would also be handy if we're successful. Good luck!!

 

[ctjackster]

these threads come up almost as often as "my midyear runs hot".

Me, if I had a non-SHP C2 (I happen to own an L76 SHP, it has the balancer bolt) I would be looking at drilling it (the crank) for one, especially if my HB had just wobbled off on me. There are guys on here and the other forums who have successfully drilled their crank snout for such a thing, I think they then use an SHP "with bolt hole" balancer (that may cause other issues with the timing mark tab plate that need to also be addressed though). I also think that those who have done an "in car" drill job might have pulled thier rad out, no big thing really in the grand scheme of things (I have that job down to a 10 minute drill). I also seem to recall hearing that the crank snout has a center punch depression - makes sense to me - that can be used as a guide. I once posted a pic of JEG's bolt and washer part for the 327, a few months back. maybe it was on the "other" forum.

 

[allcoupedup]

Jack,
You are correct, a non SHP crank (undrilled) has a what appears to be a small hole in the snout. In fact, when I pulled my engine, I had to look twice to make sure there weren't threads. This hole/depression is what I used to center the crank puller.

Drop me a line if you need the GM bolt/washer. I have a few sets.
brian

 

[fredd65]

Jack,
You are correct, a non SHP crank (undrilled) has a what appears to be a small hole in the snout. In fact, when I pulled my engine, I had to look twice to make sure there weren't threads. This hole/depression is what I used to center the crank puller.

Drop me a line if you need the GM bolt/washer. I have a few sets.
brian

i just got back from the local chevy dealer and ordered the bolt and washer...their older stuff mechanic said to drill and tap for sure...he said the loctite and knicking up the balancer might work, but be safe with the bolt...one more thing, the bottom pulley wasn't in line with the water pump pulley before (it was in more) so i shimmed it out a little more than a sixteenth..this could have been trying pull the balancer off, who knows...i sure hope i can drill and tap it in the car..anyone know what size hole the 7/16-20 bolt will need before tapping?...thanks

 

[JohnZ]

The standard tap drill for 7/16"-20 threads is a 25/64".

 

[fredd65]

hi...mission accomplished!...it didn't drill out too bad, was easy to tap then...i did get the correct gm bolt and washer...thanks everyone for the valuable advice