Hello ford guru's-i have an old PAW long block. With a history of a leaky main seal and a vibration .it's never been a smooth happy motor.put it together in the late eighty's early ninety's. It has a 50 oz. Flex plate and dampner. I am thinking maybe its a early crank with the28 oz balance. Any way to tell what the balance should be? Any way to Id the crank? Any ideas? Thanks for any help!
I believe they changed in 82 to 50 oz. except the 351W. There's a lot of info if you google 28 oz vs. 50 oz. Minot an expert ,just what I found on a quick read.
Look at the harmonic balancer and get the part number from that then get the right flex plate. I just went thru this ****.
The 28 oz cranks had 'full' counterweights at each throw, the 50 oz were smaller/partially cut away. Much lighter crank....
If it is post 80 it should be a 28 oz imbalance. Since you say it has never been a smooth runner that sort of makes me believe you put the wrong flexplate and balancer on it to start. My 331 is a 50 oz, but that is the way **** designed the stroker kit. Don
If you have the oil pan off look at the casting number (if it's a stock Ford crank). The 50 oz cranks have a 2MAE casting number, the 28 oz cranks have a 2M or 2MA casting number.
I am going to say look at the torque converter running and make sure it is not viabrating....flex plate on backwards or wrong flex plate....wrong balancer.....or a mud dobbers nest in balancer.....my super mechanic had that happen once...cleaned out the nest....smooth after that.
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