I believe the only way for it to break things without a broken chain is if it slipped a tooth or more on the sprocket.

You need to really look at the sprockets and see if the teeth are wave shaped. If they are they will need changing too. IN order to achiev correct mechanical compression is if the enigne is timed correctly with the cam.

Once you can verify that and verify good compression then looking at the pump makes sense.

The only reason I suggest the idea of trying it without puling the head is that nobody i have heard of here has found any piston damage from valve impacts. The valve hit the pistons squarely.

Also the cost in time and materials is very high for removing the head. It is not a side valve engine after all.

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[SIGPIC] Diesel loving autocrossing grandpa Architect. 08 Dodge 3/4 ton with Cummins & six speed; I have had about 35 benzes. I have a 39 Studebaker Coupe Express pickup in which I have had installed a 617 turbo and a five speed manual.[SIGPIC]

..I also have a 427 Cobra replica with an aluminum chassis.