Motor ID question

Hi new to the forum, i just picked up a 79 trans am and when checking the block casting numbers it says its 455 from 1971 HO motor. Can anyone advise if this is the 325 or 335 horse motor and does it have a 4 bolt main. Date code is A131 and casting number is 485428 any ideas. Thanks as always

I would be more interested in the two-letter code stamped on the passenger's side front of the block. 455s of that era were all the same castings (except the SD), so that's not much help. The date code does indicate a '71 (Jan 13, '71).

Does it have a "197" on one of the exhaust ports? If so, those are the '71 HO heads. If not, what are the numbers cast into the center exhaust ports?

For the best info available, get Jim Hand's book "How to Build Max-performance Pontiac V8s", published by SA Designs. This is the most current study of the old Injun, and sheds a lot of light on many questions.

FWIW, if it IS a 455HO, you have a solid basis for a MONSTER street motor...

Jim

Jim, thanks for the info i see on the side of the block the letters YC and all i see so far on the heads is J141. I will take another look at the heads and block and post what i find. Thanks Kenny

According to wallaceracing.com's database, the YC ('71) is a 325 HP 455, with "66" heads and a single 4-bbl. NOT an "HO". The date code for the heads is Dec 14, '71, making the heads '72 models.

Jim

I looked on the heads today and stamped into the center by the ports looks like its cast 745. Does anyone know what it would be from. Is that the only place for the casting number. date code is J141. Thanks

The numbers are CAST into the center ports, not stamped. They're probably "7J2s" if original. Maybe "7K3". No "745" casting for the Pontiac. Other numbers are 6X, 5C, 11, 12, 13 , 16, 48, 62, 96, and so on...

Jim