The critical speed thing makes sense to me. The main part of the shaft after all is 40 years old - so between age and the magic frequency it let go.
I will tell you the engine sounded so sweet just before it came undone.
Engine specs:
stock short block - rebuilt with a ring/bearing kit. I bought it for $400 in 2005 as a take out from a stolen 2000 Trans Am that had hit the road bed and broke the pan open. It was starting to spin a rod bearing. I put a $160 crank kit in it and was good to go.
I bought a "stage III" SLP head/cam and 36# injector kit. It is a LS6 intake (non ported) and stock throttle body.
I put a set of non-emission Pace Setter headers on it and had to make some small changes to get them around the rack on the drive side - passenger side slipped right in.
Trans is a 4L60E out of a truck with a stock rebuild on the clutch/seals and a trans go shift kit. It is a TCI 2,800 stall converter with lock up.
All that is tied to a Ford 9" with a 3.5 gear.
For what it is...the whole combo was a major budget build. Nervous system is a Painless Harness on a 98 Camaro PCM.
I made some calls this afternoon. Hope to have a PSTD shaft soon and will most likely get a set of PYPES mandrel bent 2.5" exhaust and Race Pro mufflers.
The big issue is the floor. I'll post pics later when I can get them off the camera.
Here is what the bottom use to look like...and the motor. No bling under the hood.
