Join Date: Jan 2015
Location: Injun Territory, 'Merica!
Mentioned: 0 Post(s)
Tagged: 1 Thread(s)
Quoted: 121 Post(s)
Mike, the following are "5 bolt" engine mtg bracket 400 blocks, first introduced lfor the '70 model. earlier 400 blocks had their own casting number AND only had provisions for two bolt engine mounts.
#979914 '70 model 400, both 2 bolt and 4bolt main caps (4 bolt is typically RAIII,mthough a few '70 WT 400's have surfaced w factory 4 bolt caps
#979915 or 97991(5) '70 RAIV, but a few '70 WS RAIII also used his casting
*the last digit, 4, was wiped and the proper font large 5 was stamped.
#481988. First cast for '71 400 usage but continued on into early '75 model production. The complete application of the 481888 block is exactly as I mentioned above. Throughmy specialty core business I provided select 400 shortblock cores along with 6X-4 head cores for many years to a major national Pontiac engine builder. I seriously doubt anyone on his forum has had as many 400 Pontiac cores go through his hands.
#500557 Partial '75 usage, then into '76 model.
During the'76 model year, the 5 bolt mtg boss arrangement on side of the block stopped and the late style 3 mounting boss block began. Crank register size (for the flywheel) changed from 2.75" to 2.5" as well.
Checked my engine code/ build database, the following is the earliast 481988 casting 400 have run across. Note block cast July 1st, 1970.
(004541......YS........G010.......08D.....276571A1 00529....400 Grand Prix (Paul's farmer yard)
The above pertinent info is from an extremely early '71 build from the Lakewood GA plant.
The VINs of T-37's, LeMans, GTO's, as well GrandPrixs all were intermixed at the plant as far as the sequential last 6 digits go, the preceding and following VIN could be another GP or a Pontiac A-body.