The builder who built my engine said that he has had many, many, many problems with the MSD gear on the 351's but never on the 428. I was the first.
He says there was a bad heat-treat process that was the cause from MSD. Better check it out.
His name is Joe and he works at Danbury Competition.
He is a good guy, doesn't talk much on the phone unless you keep the conversation going. Give him a try...
203 748-7356.
Good Luck.
My engine is back in his shop getting torn down.
