I have an 83 TA with the carburated 5.0L/305. In 1984 I replaced the crankshaft with a reground unit from a machine shop, and since then I have become more and more aware of a vibration. My paranoia, or simply, my question is this: Are the 350 and 305 cranks different? Logic tells me that the lighter pistons in a 305 would require a crank with lighter bob weights. Yet when I order a crank the shops all try to sell me a 350 crank. I read the part # on the crank out of a truck 350 in my garage which is 3932442, the same # on the reman shops part. ( I will be pulling the engine to inspect the crank that is in it currently, but I bet its the same #) Is my engine vibrating due to the wrong crank or is there an issue with the flywheel or torsional damper?


I realize that the years have crept by but I really didn't want to mess with it back then and heck I hardly drive it anyway. Now I want to got it out again and possibly even sell it, but I want the vibe to go away!!

 

They are the same casting #, but are balanced differently.

You'll either need to get a properly balanced crank, or have yours balanced.

 

What if the damper/balancer ring has slipped? It would then be out of phase and cause a vibe?
Supposedly the reciprocating assy was balanced at the machine shop

 

The ring isn't "phased", i.e., doesn't have to be in a particular place on the hub. But, a bad damper could cause vibration.

If the rotating assembly was supposed to have been balanced, then I'd go talk to the shop. Can we assume it has always vibrated, and isn't getting worse?

 

yup I`d go back to your shop, if you know with out a doubt that the harmonic bal. is ok, and i wonder if mabey the flywheel was put on goofy, crooked, ur sumpin, they say to make sure to replaced it exactly as it was removed,but with a new crank how can u? I never had issues with flywheel placment, but mabey you are?

 

Going back to the shop is probably out of the question as he stated it was done in 1984.

 

I assumed that was a typo . . .

 

Not a type error, I don't get it out much anymore as I have been racing motocross since 1992. It has sat a year partially disassembled waiting for me to get to the botom of this problem!

The shop will remain nameless simply out of respect as I cant say they were at fault in any way. It was however in Moline and I am now in Charleston.

I can pull it all apart and inspect it, but as with a lot of guys, I don't want to spend money where it isn't necessary. I have bought a reman crank and a new balancer for it. I felt the crank (from the machine shop in '84) was out of a 350 and was not correct for the ap. but with five7's response I decided to slow down and look hard at whats going on here. The balancer is 'umteen years old with plenty of drag races under its belt and without doubt at least questionable. I have repositioned the flywheel several times as I believe the balancer and flywheel were balanced and marked as such from the shop, but the markings have disappeared in the twenty-two years of service.
We can believe it has always vibrated and it seems to me (hey I'm fourty-lucky to notice my shoe laces these days!) that a few years ago I noticed it worse...a swinging motion at low speeds, ie. 1000 rpm. An annoying vibe at higher rpm.

In all this long winded schpeel I will try the new balancer with out using the new crank. I feel that may be the problem. I also may need to look hard at the flywheel. There is no pin or locating I.D., but perhaps with some consideration I can locate a machine shop mark. I feel a trip to the local shop is probably in order to get all the spinning parts lined up again.