1956 Cadillac Engine Question

[John348]

I had a telephone call from a friend of mine this afternoon asking me if I could reach out to my contacts to help him out. His had purchased for his son a 1956 Cadillac. The car was running fine but the harmonic balancer came of the crank. He wanted to know if there is a bolt that secures the balancer to the crank or is it a press fit. If it is bolted what is the size and length of bolt? He said it is a 365 engine.

Thanks a lot

[Guest]

Hey John, as you may or may not know Cadillac engine architecture goes in phases... so the first generation would be 331, 365 and 390. There is a second generation 390 in 1963 that the 429 is based on. Anyroad I'm familiar with the first generation 390 which has a vibration dampener that is bolted to the end of the crank @ 125 ft. lbs. with a 85-90 first go, then 100, and to 125 ft. lbs. I cant imagine 331's and 365's any different, although the crank timing gear is thicker ( wider ) from the 365 on. I have seen cars (390's) with that 331 gear on, but because the 331 gear is narrower, when the damper goes on and the pulley is bolted to the dampener in place the V belts don't line up as they should. Hope this helps.

[John348]

Any idea what size bolt?

[Guest]

Sorry John, might want to ask over in the Cadillac section or Technical section.

[D Yaros]

As I see no post on this in the Cad section I will comment here. My comments are generic, not 365 c.i. V8 specific:

Generally, a harmonic balancer consists of 4 parts. There is the inner ring, a rubber spacer, the outer ring and the crankshaft bolt. In a car this old what often happens is that the rubber spacer which holds the two rings together deteriorates. When that happens the outer ring slips or could, in theory, fall off.

I am not saying the hold down bolt did not break off or loosen and fall out, but that would be a rare scenario.

While I do not know the size of the hold down bolt, it is substantial. If it broke off, part of it is still in the crankshaft and will have to be removed.

Per my Master Parts List -

Group 8.0923 Screw, Balancer to Crankshaft

1949 thru 1958 Part # 146 8651 1/2" - 20 x 1 3/8"

Group 8.0924 Flat Washer, Balancer to Crankshaft

1949 thru 1958 Part # 145 1724 17/32" x 1 7/16" x 9/32"

[John348]

Once I get more information I will relay it here