# Decoding this block



## Bredfan (Feb 20, 2017)

Hi - 

I'm trying to figure out what block I have.... On the ledge, passenger side behind the last cylinder (under right side of distributor as sitting in drivers seat) I found the number 9790071. On the front of the block, I found stamped YC.

So after a ton of reading, I did a lookup here: Pontiac Hunters - Pontiac V8 Engine Codes

Best I can tell, it's a 400 block out of a 68 or 69 B-body. (See attached screen grab)

So what I'm left wondering, and what I hope someone here can chime in on:

- Do you agree with my assessment that it's a 68 or 69 B-Body based on the numbers and stamp I found?

- If it is indeed a 68 or 69 B-Body 400, is there any way to tell what car it came from?

Any input would be great - there's a TON of info out there, some conflicting and I'd love to figure out the history of this block. 

Thanks!


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## Pinion head (Jan 3, 2015)

Welcome to the Forum. To narrow down what year, you're going to need to look back by the distrib hole & look at the alphanumeric date code. "071" 400 blocks wre indeed cast for both '68 & '69 model years of common 400 Pontiac blocks. The YC coded 400 was very common in '68 & '69 models, as it was the base 400 2bbl code for 400/auto Catalinas. YC or YE coded 400 2bl were also used in '69 Executives. Nearly all Catalina's & '69 Executives, had the 400 2bbl & matching T400 auto. Very very few of these entry level B series slipped out of the factory in '68 with the base 3spd manual 400 2bbl engine. The base engine for a '68 Bonneville is the 340 horse 400 4bbl with small valve ('68 model) 15 heads. The base engine for the '69 Bonneville was the YH coded 428. 

Below is a link to Wallace Racings engine code list, it's 99% complete & correct. I surfed the Pontiac Hunters link you put up & noticed quite a few errors. The Pontiac Hunters list also does not list the cyl head(s) originally used on said engines by cyl head code. Hope this helps.

Wallace Racing - Engine Code Charts


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## Bredfan (Feb 20, 2017)

Great info - thank you!

So, here's what I have now...

- Number on drivers side of distributor is K157 - I have this as November 15, 1967

- Block number is 9790071, YC - that would be 1968 or 69

- Cylinder head is 15 - the "1" and "5" are separate, not positioned together

- Cylinder head has date stamp K217 - I have this as November 21, 1967

Since the date code on the block is late in 67 (Nov) and the date stamp on the head is also November, can I safely assume that the block and head have been together since birth and that they were originally in a 1968 full size?

Looks like a 290HP 2bbl from 1968... See attached from Wallace...

Thanks again!!


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## PontiacJim (Dec 29, 2012)

Yep, you got it. Big car 400.


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## Bredfan (Feb 20, 2017)

Thank you so much for pointing me in the right direction. It's a new ride for me and I have a list of about 10 things I need to post....  At least now I know what the block and head is. Now, for the rest of the million things.....

Thanks again -


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