Crank pulley bolt...Lost again!!

jrvariel48

jrvariel48

Well-known member
So this is the second time my crank pulley bolt came loose and disappeared onto the road. The first time it happened, I just figured I didn't tighten it enough. I installed a new bolt, torqued it to 50lbs. with red lock-tite and it came off this morning. This is a blower motor so the crank bolt and pulley are not stock, but I'm not sure if that has anything to do with it.
Looking for an explanation.
Thanks Joe
 
Joe could you drill the shank and use a castle nut, You got me curious.

Get one of those remote cameras and possibly video that area by the pulley and see what is going on while driving, good luck and let us know how you make out.
 
Are you torquing bolt to specs? Are the threads worn? Is there any type of lock washer or "spring washer" you could use with the bolt.

Here's a very good link to washers that might solve your problem. Lots of great information.
https://www.google.com/search?q=spe.....69i57j33.13703j0j4&sourceid=chrome&ie=UTF-8

Read this:
https://vention.io/blogs/best-anti-vibration-product-for-fasteners-178

Read about "Smart Bolts".
http://www.smartbolts.com/insights/...le washers, are,in order to prevent loosening.

First thing I would do is try a brand new Grade 8 bolt.
What engine is in your car?
 
Last edited:
19Fordy said:
Are you torquing bolt to specs? Are the threads worn? Is there any type of lock washer or "spring washer" you could use with the bolt.

Here's a very good link to washers that might solve your problem. Lots of great information.
https://www.google.com/search?q=spe.....69i57j33.13703j0j4&sourceid=chrome&ie=UTF-8

Read this:
https://vention.io/blogs/best-anti-vibration-product-for-fasteners-178

Read about "Smart Bolts".
http://www.smartbolts.com/insights/...le washers, are,in order to prevent loosening.

First thing I would do is try a brand new Grade 8 bolt.
What engine is in your car?
Click to expand...

Lotsa great reading Fordy! The crank is new as was the bolt. I'm looking into the Nord-lock washer system. They seem to hold up to just about any situation.
I was using grade 8 bolts, but no lock washer, just some red lock-tite.
Engine is a blown 1950 8BA.
Thanks Joe
 
39portlander said:
Joe could you drill the shank and use a castle nut, You got me curious.

Get one of those remote cameras and possibly video that area by the pulley and see what is going on while driving, good luck and let us know how you make out.
Click to expand...

Not sure if I could drill the shank, but the camera's a great idea. I use three of them on board to record A/F reading, fuel pressure, vacuum and rpm when tuning.
Thanks!
Joe
 
I would speak with Loctite on their 800 number and get it from the people that know. The red is basically bomb proof.



R
 
Just a thought, how tight is the hub and pulley onto the crank? with the added load of the blower and if it's not a tight enough fit it might cause some wobbling and loosening of the bolt that holds it in place.
 
I was thinking the same as earlyride, and perhaps the 2 surfaces (crank side and bolt side) of the pulley are not exactly 90 degrees from the centerline which would permit a wobble.
Also, did you clean the internal threads of the crank with Brakecleen or lacquer thinner and blow it out before using the locktite?
 
Joe in the past when I have experienced the exact same issue as yours even with the blower belt helping the dampening. The problem was due to a balance issue which turned out to be the flywheel area. Even red locktite would not help. I would suggest try green locktite its a lot stronger than red if the bolt still comes loose after going to green then checking the bolt regularly to be sure its tight would at least keep the bolt in place and not on the road someplace.
Ronnieroadster
 
Hi Joe, appears to be not enough torque on the bolt, this will cause your problem. If it doesn't get enough torque it will eventually work its way out!

What happens is having the correct "tension" on the bolt keeps it in place!

To add to the problem, the OEM dampers are NOT a press fit to begin with, this makes the torque number even more important.

Thanks, Gary in N.Y.

P.S. It's a bit ironic but Pontiac builds share the same characteristics, the OEM damper has always been a "slip-fit", getting the damper bolt up to torque does take a bit of doing! I don't have the OEM torque handy for the Flathead but the Pontiacs must get a minimum of 150# (160# preferred) to do the job! Same size bolt/washer as the Flatheads, being 5/8-18 x 1.750" I believe?
 

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The torque specifications on a grade 8 5/8-18 bolt is 240 ft-lbs dry and 180 ft-lbs lubed. So 50 is not even close. 50 ft-lbs is in the range of a 3/8 inch bolt.
 

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It sounds like the torque you are using is too low. If the bolt is a 5/8"-18 and a grade 8 capscrew, the torque should be in the 235 lb-ft range, reference Craftsman generic torque table.

There is a lot of torsional vibration going through that joint to the crank pulleys. Increasing the grip length of the bolt will get more stretch in the bolt and resistance to loosening. You can increase the length by adding a thick wall spacer.

I do not recommend using a lock washer, it is just another spring in the system.
 
earlyride said:
Just a thought, how tight is the hub and pulley onto the crank? with the added load of the blower and if it's not a tight enough fit it might cause some wobbling and loosening of the bolt that holds it in place.
Click to expand...

It's a pretty snug fit as I remember it. I can pull the belts and check to see if my memory serves me right!
 
A steel bolt in a steel nut of suitable grade of steel will achieve the numbers quoted above, but as it is being screwed into a cast iron crank snout would a lower value be more appropriate? I am thinking 50 lbs sounds a bit low, though.

Mart.
 
deuce_roadster said:
I was thinking the same as earlyride, and perhaps the 2 surfaces (crank side and bolt side) of the pulley are not exactly 90 degrees from the centerline which would permit a wobble.
Also, did you clean the internal threads of the crank with Brakecleen or lacquer thinner and blow it out before using the locktite?
Click to expand...

I did clean everything with brake clean and a bore brush. Also used bore style Qtips until there was no dirt. Thanks deuce
 
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