Some people dont understand balance weights on flywheels

[mountainexplorer]

I just picked up a whole truck on a trade from a previous deal last summer. It's a '76 K20 with a 350/TH350/203. Originally it had a SB400 according to the grille emblem. When I drove it home yesterday it felt like it had a vibration in the motor.

I figured it needed a major tune up. Then I thought, well, someone swapped in the 350... I wonder if they knew enough to put a 350 flexplate on it and not the original 400 externally balanced one. I look under, and sure enough, a 400 balance weighted flexplate.

This makes several rigs Ive gotten that had improper flywheels on them. The last one was a Crew Cab that had a 454 flywheel on a 350.

Hopefully the bearings havent been hurt too badly in this motor.

 

[3 on the tree]

Some people shouldn't even be allowed to own a crescent wrench.I have in the past, just used an angle grinder to remove the weights. It ain't perfect balance, but a large improvement.I KNOW you just LOVE pulling drivetrains, so when is the correct flywheel being installed?

 

[mountainexplorer]

The reason I wanted this truck was to transplant all the drivetrain into an '80 K20 that has a better body. But first I have to finish paying a friend for the '80, then I'll probably put it together using the parts out of the '76 and then sell it to get my money back out of what I'm into both of them.

 

[sled_dog]

hope it wasn't like that long, lot of stress on main bearings.

 

[mountainexplorer]

Yeah, thats what I'm worried about. Once I found that today, I decided not to run it again till I pull it out, change the flexplate and drop it into the '80. Who knows how longs it's already been run that way, but theres no noises from the motor and oil pressure is good.

The 350 in the crew cab that had a 454 flywheel is still running good since I changed that one.

But I had a 400SB that was out of balance once, I put the right flywheel on and it lasted only a few months and started knocking and the bearings were wiped out.

 

[gravdigr]

i have a question that may be related to this thread. Currently my dd (86 K5) has a tired 305 with 130k miles on it. I want to swap in a 350 I have. I originally got the 350 from jaspers for my 71 chevelle with the powerglide auto tranny. The 86 I'm swapping it into has the sm465 manual. I know around that time there was a changeover in the motors from 1 piece rear main seal to a 2 piece. Do I need a different flywheel for the 350? Can I use my current clutch and pressure plate?

TY in advance.