Crank failure!

[big2bird]

I'm actually wondering if the imbalance of the existing crank can be duplicated and if the rods/pistons can remain in place.... if you could measure and duplicate this crank's imbalance then why mess with the pistons ? Just spin it up to 6000rpm and measure the balance.... no ?????

If your asking if a replacement crank can be matched to what he has, the answer is yes, pretty close.

that's what I was thinking... remove that crank, have the imbalance measured and duplicated to a new crank.... just work from under the engine.... not a good position but you might not have to pull the heads.....

You COULD pull the crank from an auto in the car, but not a stick. Call it my age, but I'd rather pull 8 bolts and put it on a stand for that kind of job.

 

[mrvette]

I'm actually wondering if the imbalance of the existing crank can be duplicated and if the rods/pistons can remain in place.... if you could measure and duplicate this crank's imbalance then why mess with the pistons ? Just spin it up to 6000rpm and measure the balance.... no ?????

If your asking if a replacement crank can be matched to what he has, the answer is yes, pretty close.

that's what I was thinking... remove that crank, have the imbalance measured and duplicated to a new crank.... just work from under the engine.... not a good position but you might not have to pull the heads.....

You COULD pull the crank from an auto in the car, but not a stick. Call it my age, but I'd rather pull 8 bolts and put it on a stand for that kind of job.

Still think Jims/TV's idea with the Red Locktite is good for the summer, enjoy the car, and come fall, do the crank as above come fall/winter...I don't race any more so the amount of time I see 5500-6 grand I can count on one hand in 12 years....:flash:

 

[gbak]

Maybe at 3,500 RPM, but not at 7,000 RPM. Welding cranks just doesn't work/last very long. b
Been there, done that.

What do you mean will happen if welding the balancer?
Will the crank material become weak if welding it?


What is "Red Loctite"?

Is it some kind of permanent bushing adhesive that takes up big play or what??

 

[mrvette]

Maybe at 3,500 RPM, but not at 7,000 RPM. Welding cranks just doesn't work/last very long. b
Been there, done that.

What do you mean will happen if welding the balancer?
Will the crank material become weak if welding it?


What is "Red Loctite"?

Is it some kind of permanent bushing adhesive that takes up big play or what??

Nah, Red Locktite comes in a little blue tube like super glue size, i'ts really thin like nail polish and is used as a thread locker, mainly, I don't think much as any gap filler, but it does do that to keep bolts tight, it dries fairly quickly, I used it on my crank/balancer with this engine, about 12 years ago, been there since, daily driven and every once in a while it hits higher RPM's like most vettes, but never 7 grand, maybe 6 at most....:quote:

 

[pcf_mark]

I welded a balancer on a SBC crank when it kept coming off but I did not have the $ to fix. It worked for several years of abuse. HOWEVER the balancer is junk when you are done and taking the engine apart is a pain in the balls. You can not get the balancer of so you can not get the chain or cover off so you can not get the crank out. We ended up sawing through the cover, and using bolt cutters to cut the chain. Then we machined off the balancer in a lathe. The engine machine shop then ground it to size to clean up the weld seem.

If/when you go through your bottom end I would check the balance on all your components. Something is off to cause this to happen. In my case we later discovered the flex plate was cracked causing the torque converter to "wobble" and throw off the engine balance.

 

[turtlevette]

What is "Red Loctite"?

Is it some kind of permanent bushing adhesive that takes up big play or what??

No it won't fill in gaps more than a few thousandths. That's why i originally suggested JB weld or something similar.

Definitely use locktite red on the crank bolt so it won't back out again. And don't overtorque it as someone suggested. If you strip it out, you lose your last line of defense to prevent the balancer walking off.

 

[mrvette]

What is "Red Loctite"?

Is it some kind of permanent bushing adhesive that takes up big play or what??

No it won't fill in gaps more than a few thousandths. That's why i originally suggested JB weld or something similar.

Definitely use locktite red on the crank bolt so it won't back out again. And don't overtorque it as someone suggested. If you strip it out, you lose your last line of defense to prevent the balancer walking off.

Yeh, definate PIA on a SBC, can't turn engine over by a socket on the snout, as I found out, doing the converter bolts some years ago.....other engine with REAL bolts in there have no issue, :crutches::bomb:

 

[gbak]

I welded a balancer on a SBC crank when it kept coming off but I did not have the $ to fix. It worked for several years of abuse. HOWEVER the balancer is junk when you are done and taking the engine apart is a pain in the balls. You can not get the balancer of so you can not get the chain or cover off so you can not get the crank out. We ended up sawing through the cover, and using bolt cutters to cut the chain. Then we machined off the balancer in a lathe. The engine machine shop then ground it to size to clean up the weld seem.

If/when you go through your bottom end I would check the balance on all your components. Something is off to cause this to happen. In my case we later discovered the flex plate was cracked causing the torque converter to "wobble" and throw off the engine balance.

You have convinced me not to go for the permanent welding.


I will fix a new balancer, key and bolt and hook it up and with a little luck I might have the correct diam somewhere on that snout. If not, I can at least use the parts when renovating/changing the crank next winter.

If I'm lucky the crank/balancer will last this summer.

I recall that it was very easy to install the balancer on the crank each time. But it was nothing I was worried about by that time.
The balancer could have been out of tolerance from beginning, or maby the crank?

 

[DeeVeeEight]

If I'm lucky the crank/balancer will last this summer.

I recall that it was very easy to install the balancer on the crank each time. But it was nothing I was worried about by that time.
The balancer could have been out of tolerance from beginning, or maby the crank?[/QUOTE]

It sounds like the crank snout was compromised a long time back. I would be inclined to try and sleeve the snout to take the wobble out of the balancer, sort of like shimming it to keep it centered.

 

[MYBAD79]

Just so you're not depending on the bolt I'd add a weld, you don't have to weld all the way around, just two sections that you can grind off when time comes to disassemble....

 

[Twin_Turbo]

I would try locktite quick metal (I think it's #660) first. That stuff is pretty damn tough.

 

[BRUTAL64]

Maybe at 3,500 RPM, but not at 7,000 RPM. Welding cranks just doesn't work/last very long. b
Been there, done that.

What do you mean will happen if welding the balancer?
Will the crank material become weak if welding it?


What is "Red Loctite"?

Is it some kind of permanent bushing adhesive that takes up big play or what??

Nah, Red Locktite comes in a little blue tube like super glue size, i'ts really thin like nail polish and is used as a thread locker, mainly, I don't think much as any gap filler, but it does do that to keep bolts tight, it dries fairly quickly, I used it on my crank/balancer with this engine, about 12 years ago, been there since, daily driven and every once in a while it hits higher RPM's like most vettes, but never 7 grand, maybe 6 at most....:quote:

Actually "Red LockTite" is used for bearings and such. Can be used for bolts but you need to heat up the bolt with a torch to get the bolt off.:smash:

 

[BRUTAL64]

Just so you're not depending on the bolt I'd add a weld, you don't have to weld all the way around, just two sections that you can grind off when time comes to disassemble....

Yep, that was what I was thinking. This is something that will induce a safety net for him.:bounce:

 

[DeeVeeEight]

Just so you're not depending on the bolt I'd add a weld, you don't have to weld all the way around, just two sections that you can grind off when time comes to disassemble....

Gee, I was gonna say sumthin' jus' like that! Easier to grind off a couple of spot welds when it is time.

 

[gbak]

I would try locktite quick metal (I think it's #660) first. That stuff is pretty damn tough.

Do you mean that I should use Loctite 660 to glue the balancer and crank together?
Or try to rebuild the crank's surface?

 

[damoroso]

Can you measure the snout and a balancer to understand how much space you have to fill? Then decide the best way to fill the gap, JB weld, loctite whatever, to take up the slop between the balancer and the crank snout and then tap the snout for a slightly larger bolt?? If I'm following this right, there aren't enough threads left to hold the balancer on regardless of the fix. Either way, I don't think I'd use the welding option...too much PITA when you get to the correct fix.

 

[Twin_Turbo]

I would try locktite quick metal (I think it's #660) first. That stuff is pretty damn tough.

Do you mean that I should use Loctite 660 to glue the balancer and crank together?
Or try to rebuild the crank's surface?

Yes, that's what I meant. if you pull down the balancer tight against the lower gear it should sit flush, that will allow the loctite to cure with the balancer on straight.

 

[mrvette]

I would try locktite quick metal (I think it's #660) first. That stuff is pretty damn tough.

Do you mean that I should use Loctite 660 to glue the balancer and crank together?
Or try to rebuild the crank's surface?

Yes, that's what I meant. if you pull down the balancer tight against the lower gear it should sit flush, that will allow the loctite to cure with the balancer on straight.

:smash: Exactly, but if 3/4 inch off the end is wiped out, that leaves 1.5+ left over toward the gear, so I would make sure the threads are worth a damn, then shove it to it....

even if you have to drill/tap for next step larger, like I did long time ago...

 

[gbak]

I would not consider a bubba repair like this but these parts are junk already and the summer in Sweden isn't very long.... 3 months maybe ????

A short update!

In my last posts I was worried about how to get the damper in place, here is what I did:
I bought a new chinese (cheap & crappy) damper, key and bolt, torqued the bolt to it's maximum and locked it with medium Loctite thread lock.
The damper is still in place after one month of driving and everything is working fine!

 

[mrvette]

I would not consider a bubba repair like this but these parts are junk already and the summer in Sweden isn't very long.... 3 months maybe ????

A short update!

In my last posts I was worried about how to get the damper in place, here is what I did:
I bought a new chinese (cheap & crappy) damper, key and bolt, torqued the bolt to it's maximum and locked it with medium Loctite thread lock.
The damper is still in place after one month of driving and everything is working fine!

Well, good news it's running for summer, keep a eye on it, obviously...