1980 242 with 1993 B-230 block under original 1980 K-jet head. Runs quite well with good power. I put 180 miles on it this week and returned about 22mpg.

It is an M46 with 3.91 gears and pretty much lives at 3k on the drive to and from labor.

Unfortunately, the engine vibration is a bit excessive. Much worse than any other 240 that I have owned or worked on.

I would have had to use a B21/B23 flywheel at the time, since the B230 donor car was auto. So, before I dig too deep, was the B21 flywheel OK on the late B230?

Yes, I am using the B230 harmonic damper.

I know it could be a number of other things, but I was really curious about the choice of flywheel before I start looking any further.

Hi,

Disclaimer! I’m not going to very good at helping you here!

The word vibrations is very nondescript or loose of a direction of when and how much, where?

Are you idling or driving? What speed, if so?

Are you thinking engine balance, in more, than a drive train issue?
All flywheels should be balanced as it is a weight in motion.

I have no experience in an automatics flywheel and torque converter combination to what goes on there either!
How flywheels are designed in relation to the counter weights of a crankshaft, I cannot answer.

I don’t really understand a harmonic balancing theory in how it controls “the flexing” of the crankshaft @ certain speeds to break up harmonics either.
Apparently, to me, it’s more of a compensation device for the accessories of pumps or compressors and alternator loads.
It has a rubber membrane that does, sort of, disconnect a direct connection to the crankshaft.

I’m more surprised that you were able to put a B-21 head on a B-230 block.
Maybe you have a B-23 head instead with the k-jet system.
In any case I would have thought the breathing was tuned differently over the years.
My 1984 seem to have a different torque band than my 1986 and the in nineties they got smoother too!
More upgrading with the fuel management systems than anything else!

I do not know when the B-23 block came out but I know that a 1978 GT clutch is different with the splines off the transmission so you must have the later transmission for the B-23.

The B-230 of 1993 has a different flywheel and clutch systems than the B-23 or possibly the earlier B-230s of 1985 on. Flywheels change to make room for clutch assemblies.
Changes were made due throughout the eighties due to the turbo pushes and the early nineties getting clutches that required less pressure plate feed back to the driver. Some wanted V-8 power and others wanting luxury of American and Japanese competition.
You see this in a big weight hung on the cable end of the throw out lever with a rubber blob to lessen or dampen “vibrations” up the cable to the pedal.
The last part about the weight, is just a guess on my part, of why it even appeared!

Is this where you are feeling vibrations?
If you are looking at the engine and leaning on the fenders to feel vibrations?
Is the engine being held correctly, on the “mounts,” in a 1980 car?
You need that one inch space above the crossmember and away from the firewall.

The drive train can be affected, to some extent and deserve some conservative thoughts for the area of actual driving and vibrations.

You see … I’m not much help but others might be able to shed light light into the areas of our darknesses!

Phil

I've driven a 240 with a collapsed motor mount, and one with a bad transmission mount. The motor mount collapse caused a lot of vibration, but the car was still driveable. As Phil suggested, if it's engine-related vibration the mounts are very important.