Motor home cast crank damper

[Bobby Sixkiller]

So my challenger has a motor home 440 with a cast crank. The balancer is new unknown brand but looks like a steel crank balancer. The issue is some vibration at idle. I thought it was a misfire but now I’m thinking not. Goes away at around 1200 to 1400 rpm but it feels like solid mounted engine at idle. I have a couple motor home 440s and was thinking of just swapping on a balancer from one of them. Any thoughts.

 

[Chryco Psycho]

true, if you have a cast crank & the thin 1" balancer it will vibrate , the cast damper is closer to 2" thick

 

[Cud@]

I have a balancer from a 73 440 that was in a motor home, the balancer is 15/16 thick and the crankshaft is a cast crank.

 

[Bobby Sixkiller]

There’s so many different balancers on these things. My 73 dated 440 cast is thin too but reads 440 cast crank only. The later ones I have are two inches thick. I think I’m gonna just swap on one of the thick balancers. And try it. I might pull the dust cover and make sure it has the weights on the converter. I really don’t think it’s a misfire at idle because it’s so responsive and runs great. Just vibrates at idle. It really feels like solid mounts. I’m swapping in a new radiator in a few days. Probably do it then to see.

 

[Cud@]

Hope you figure out what the problem is, Good Luck!

 

[Bobby Sixkiller]

Swapped on a factory cast crank balancer this evening. Smooth as silk. That was the problem.

 

[Chryco Psycho]

great news !

 

[Cud@]

So was the factory cast crank balancer you swapped to close to 2 inches thick?

 

[Bobby Sixkiller]

Yea about two inches thick. Kinda tapered on the outside. It was from another motor home 440 I have

 

[Cud@]

Huh, the 440 I used was from a 73 motor home and rebuilt before I got it. I'm sure the crankshaft was a cast crankshaft and it had a thin (15/16) balancer. Maybe it ran poorly at low RPM? i don't know because I never ran it with that balancer.
Thanks for the information, glad you have your issue resolved!

 

[Bobby Sixkiller]

I’ve seen two types for cast crank. One is just a tad thicker than a steel crank. The other is almost twice as thick with a bit of taper to it. Only one type for steel. The one that was on my engine I found to be aftermarket neutral balanced. It’s really easy to mix and match them and get the wrong combination. I had never had one vibrate like this though. Cast cranks have the weights on the converter too.

 

[Bobby Sixkiller]

I’ll add that the 73 cast crank non rv engine in my roadrunner has the thinner cast crank balancer. I’m betting that later engines swapped to the tapered thick one. My New Yorker is 77 and not tapered. All my motor home engines are 78 79. Really late in production. Most everything 71 down is steel and will have the thin neutral balancer.