[Jimbobeast]

Originally Posted by P@blo

A 322psi rate spring with a 110psi seat pressure will put you at 271psi open pressure at 0.50" which is perfect. I had a set of 670s done and used the 995 402psi spring and have 292psi open which is perfect. Not sure the focus on closed pressure but I would keep open pressure to 300psi or less.

Also, I would not trust anyone, Pontiac friendly or not, who did not verify a spring fits before installing. Not by a country mile. The issue should have been caught when checking the spring pressures before sending the heads out the door too. Two strikes right there. The third would be them willing to fix it for free. I'd run the other way with the heads you have. Scary really.

Unfortunately Yow's Machine shop closed their doors 12 years ago and Roy, Johnny and Dave Yow have long since "shuffled off this mortal coil". That's from Hamlet. It's a play. By Shakespeare. It means they're dead. In their defense they did the machine work on 5 other GTO engines for me, including a RAIV, without problems.
I do love the looks of an Orbit Orange/Black Top '70 Judge convertible, even in the garage. Always have.