1st off Hey Doug good to see ya and hope ya up for a good racing season.
There are many more on here much more qualified to answer your question than me on the best route to go...
but what i would like to say is that a close friend of mine 3 years ago had almost the same identical problem with a 555 he purchased from the same company.
He ended up having to get a new set of pistons and had Gene Fulton work the block etc......
so this problem from this company seems to be pretty common from what i gather.
Brian
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Bjuice..
"I'M YOUR HUCKLEBERRY ! "