Hi Perf. Pass?

[seho]

Kinda directing this to Infomaniac but feel free to chime in, anybody. I picked up a 454 dirt cheap with the trans still attached thinking I might build it up for a project to be named later. Upon disassembling this engine (spun rod bearing) and searching for casting numbers under a 1/2 inch of old grease and oil, I keep coming across the words 'HI PERF PASS' on the block and heads. Understanding this to mean Hi Performance Passenger (car) does it really have any significance or did they mold this into every car engine block during any certain dates? I still haven't found any casting numbers to speak of and will continue to clean as time permits but was curious about this. Rect. port heads btw and the guy I got it from seems to think it came out of a pick-up altho his memory is hazy.
Diamond in the rough or junk yard special?

[cdog]

The casting #'s will be on the back of the block next to the oil plug. The actual Car/truck #'s will be on the front of the engine on the deck of the block in small stamped #'s and letters. If their not their, the block may have been decked and the #'s have been removed.

[Liberator TJ1984]

Look by the oil filter mount , the better hi-perf. blocks have plugs in the housing right above where the filter monts for a remote oil filter / cooler lines, I think one is a 3/8 NPT and the other is 1/2" NPT thread ?
look above the filter in this pic....you can see one of the ports being utilized for the oil pressure gauge hose but plug wires are in the way of other one :notam:
http://www.***boat.com/image_center/data/509/913new_motor_with_zoomies.JPG

[BrendellaJet]

The "High Perf Pass" is pretty common and doesn't necessarily mean that the block is worth more than any other...

[SmokinLowriderSS]

My 454 is a Hi Perf Pass, but seems not uncomon. It is a 2-bolt main so it is no guarantee of a 4-bolt-er. Look on the "shelf" behind the heads where the bellhousing mates up for the casting numbers (right where all the greasy crud settles a half-inch deep). :D
According to 1 site I just looked at, all Mk IV big blocks had either Hi-Perf Pass or "Truck" cast in them. Now, it's NOT a GM site, so I cannot guarantee the accuracy of this. They also said the 4-bolters had larger cooler line plugs in them than the 2-bolters did, perhaps others hewre can verify. I'd bet the tall blocks had TRUCK cast into them, and maybe the peanut port heads did not get Hi-Perf. My large oval heads are just cast "Pass". Maybe the peanuts are Truck and the rectangles might be Hi-Perf.