[Baba O'Riley]

Hey all. The original #96 heads on my '71 Firebird Formula 400 have been throwing rockers / bending pushrods and guide plates. They've done this both before and after a long-block rebuild. This rebuilder botched things, a new mechanic I trust is now telling me that these original heads are shot, they tested horrible.

I found a "new" pair of #96's (date code four weeks after the originals) and my current engine builder says they are solid. But he'd like to have the original pushrod specs as a reference, the new valves sit a little higher and he has to make sure there's no clearance issues, etc. The old rebuilder put replacement pushrods in, I don't have any of the originals.

Pontiac, of course, is notorious for having many different pushrod lengths. Does anyone have a shop manual or something that specifies what length of pushrods this motor originally used: a 1971 YS code 400 4-barrel with AT and AC, casting code 481988, block cast 3/31/71...? The Wallace Racing site says all V8's '69-'79 were 9.171875" (9 11/64"), but this site says '55-'79 -- were all 9.146". Is it one of these? Something else? Thanks as always.