I recently put together a stroker 3.7L parts in a 3.2L block and twice in 1,000 miles driven ive broken one and sheared the keyway off the other cam sproket on the 4,5,6 side of head. Any ideas?

 

You gotz some serious resistance somewhere--you didn't use the longer pushrods, did you?

 

No, pulled it apart and camshaft siezed in head cyl.1-3 so used donor head and did both head gaskets and put all back together as ive done ten times and now car wont start when turning over,checked timing ,coil packs,compression and dont have any codes on code reader, any idea what to check next,thank you.