74Sebring
Well-Known Member
Ok, I'm probably going to sound stupid here but, I'm tired of guessing. I'm hoping that someone here can lead me to my personal come to Mopar moment. I've got a 1974 Satellite Sebring Plus, 360LA BBL, 727 Torqueflite. I've rebuilt both the engine and transmission. I have a lot of vibration in the engine now. I am using the factory crankshaft and rods. I swapped out the stock pistons, the ones with the ashtray tops, for a set of speedpro hypereuctic, flatops w/ 5cc valve relief. I also replaced the harmonic balancer with a badger performance unit. The factory flexplate has been shelved in favor of a b&m flexplate for externally balanced 360LA engine. I reused the torque converter that was in the car when i bought it. All main and rod bearings are new. I swapped out the new badger balancer for the old factory balancer and it seems to have smoothed out a bit. I'm considering swapping the flexplate out with a more standard design to see if that improves things any more. My questions are, 1. does the piston swap make enough weight difference to require a machine shop rebalance? 2. Can I make changes to the rotating assembly via the balancer/flexplate and possibly torque converter to correct the vibration and 3. is there any way to identify if the previous owner swapped the crankshaft to an internally balanced type from the factory externally balanced type? Bonus question for extra credit, am I nuts? Any assistance will be GREATLY appreciated!! I'm dying to dive my car!