375HP OR 425HP ?

[GREEK 1967]

HAVE A 396 WITH BLOCK #3955272  DATE I-17-68 HEADS ARE 3904391 BOTH ARE DATE I-20-68 4 BOLT BLOCK  6223 CRANK . HOW DO YOU TELL IF 375HP OR 425HP EVERY 375HP I HAVE EVER SEEN HAD 840 HEADS MOTOR WAS IN 69 CAMARO ITS ALL FRESH WITH ROLLER CAM AND 42CC PISTONS   HAD 750 CARB ON DYNO MADE 600HP .

[Ed Bertrand]

HAVE A 396 WITH BLOCK #3955272  DATE I-17-68 HEADS ARE 3904391 BOTH ARE DATE I-20-68 4 BOLT BLOCK  6223 CRANK . HOW DO YOU TELL IF 375HP OR 425HP EVERY 375HP I HAVE EVER SEEN HAD 840 HEADS MOTOR WAS IN 69 CAMARO ITS ALL FRESH WITH ROLLER CAM AND 42CC PISTONS   HAD 750 CARB ON DYNO MADE 600HP.

3955272 is a 1969 396 block that was used in applications ranging from 265HP to 375HP. Since yours is a 4 bolt main, it was originally a 375HP configuration. (There were no 425HP 396 engines built in 1969.)

The 3904391 heads are 1967 only, and were used on the Chevelle and Camaro 396/375 engine and the Corvette 427/435 engine. You have a 1969 block and 1967 heads. However, since both your heads are dated I-20-68, it appears they may be service replacements. Can you post a picture of the head dates?

Ed

[Ed Bertrand]

Got the picture John (see below), thanks. I cropped it and rotated it a bit so it could be posted.

The date code is actually I-20-6, so that would be September 20th, 1966, which is correct for the 3904391 heads.

By the way, can you check to see if there's a partial VIN stamped on the block? There should also be a suffix code.

Ed

[rsr]

The 272 block would be a 69 block but it appears you have a 67 model  block that was cast in 1966 if those numbers came from your 4 bolt block with the roller cam making 600 hp??

[Ed Bertrand]

rsr, you may be getting confused on the casting numbers and date codes.

His block is a 3955272, date coded I-17-68 (September 17th, 1968). His heads are 3904391, date coded I-20-6 (September 20th, 1966). The picture I posted is the one he sent me showing the date code of his heads.

Ed