Originally Posted by retiredfireguy
I have a '55 Pontiac with a BBC under the hood. When I bought it, I was told that it had a 427, but now I'm not so sure. I believe the head casting numbers (3933148) indicate that they came off a tall deck 427 truck engine. Cannot see the engine casting number, but the serial number is T0621TRW. I believe this tells me that it is a Tonawanda engine, built on June 21st, and the TRW means that it is a 454 truck motor. Any additional info would be appreciated. Thanks!
Looks like a 1974 454 block, RPO LS4, originally 245 hp, bolted to a TH400.
So, it's original bore was 4.250" and original stroke was 4.000", with an original block deck height of 9.800". Someone could have replaced the 454 crank with a 396 or 427 crank to make a 427 out of it. (4.250" x 3.760"). The heads are very unusual, originally for a 396 standard deck motor or 366T tall deck or 427T tall deck. They have large oval ports (225cc intake runners) and a semi-open chamber (~112cc). No way to know the valve sizes without disassembly and measurement.
If it's a 427 with the short crank, pistons with a 26cc dome would yield a static compression ratio of 10.3:1.
Same build with 17cc dome would yield 9.50:1.
Same build with 7cc dome would yield 8.75:1.