[Mark Simiele]

The current engine block in my 67 Bonneville is a 1968 and was curious to see if its even a 428 but it was hard to get the numbers. I did manage to find a YH code with the last 6 of the former cars vin 177647 and on the heads I saw what appeared to be DN and the casting number on the intake was 9786286. I also saw KO76 on the intake.

Any ideas what all this is? I never had a problem id'ing 69 and 70 GTO underhood stuff but this one has me confused. The plan is to eventually find a date coded 67 block or better yet a correct SR block but I would like to know what is sitting under there now.

[b-man]

The YH engine code was used during all 3 years of 428 production. Block casting number 9786135 was used in 1967, 9792968 was used in '68 & '69.

All '67 -'68 428s had 4-bolt mains, some of the '69 428s were 2-bolt main and included with those were the '69 YH 428 blocks.

If the date code cast into the block indicates the '68 model year (late '67 thru mid-'68)and the casting number 9792968 is on the block at the top rear (behind one of the cylinder heads or by the distributor) you definitely have a '68 428.

9786286 intake casting number indicates a 1967 Quadreajet intake, casting date KO76 indicates it was cast on Oct. 7, 1966. Pretty sure the letter 'I' was skipped in the month sequence.

DN only indicates whether the heads were cast during the day or night. Look for 2 or 3 digits cast into the top of the center two exhaust ports to ID the heads.