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post #1 of 4 (permalink) Old 11-28-2016, 09:50 AM Thread Starter
 
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Engine Mystery

Need your help with my engine, not sure exactly what I have. I bought this 71 GTO convertible last year, I finally have got around to working on it and in the process if tearing into the engine. so this is what I have found. the block is a 1970 400ci engine with the #9799914 on the rear of the block. #'s around the distributer are 70, and L109. the heads are 7H1. Engine has Hooker headers. The carb is and Edelbrock 600, and sits on an Eldenbrock performer intake. It's been converted to the serpentine belt out front and electric fan. I know nothing about what all this is together. Here are my questions. Why would someone put 350 heads on this engine? Is this a Ram Air iii block? Is this engine something that would need to run hi octane fuel. I bought this car for a driver, so not to concerned about non matching numbers. Thanks for your feedback.
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post #2 of 4 (permalink) Old 11-28-2016, 01:35 PM
 
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Many times original engines are pulled, & a combination of parts end up back between the fenders. have you by chance sent off for PHS docs on the '71 convert to see what the original engine was?

To ID original use of your L109 dated 9799914 block, going to have to look on the block face on the passenger side & see what the two letter ID code is that is stamped right below the 7 digit assembly number. The most common two letter 400 ID codes for '70 Pontiacs are: YD (400 2 bbl auto Catalina) & XH (400 auto GrandPrix). The 9799914 block would have only been from a RAIII GTO or F-body, IF as an original '70 usage block, & the original two letter engine ID code is YZ or WS. On the heads, it's any ones guess why the 7H1's were used... my guess, they were handy. Have, myself, a pair on very low mile '72 350 engine, not sure why I keep that engine around. might need it one day to move a roller, I guess..

Love to hear more about the '71 convert!
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post #3 of 4 (permalink) Old 11-28-2016, 09:26 PM Thread Starter
 
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Pinion Head, I found the 2 letters on the front of the block, they were YS. I found the PHS papers, don't see anything special about the engine. Notable on the PHS. Front disc brakes, air conditioning, safe-t-track, deck lid, tach, turbo/hyd, power locks and windows.
Thanks for your feedback
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post #4 of 4 (permalink) Old 11-29-2016, 04:41 PM
 
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Those 9799914 blocks were used in everything from 2-barrel engines to some RA4 engines, according to the Wallace site. So, you will definitely need the 2-letter code to ID it. In 1970 a YS code was a 350hp 400 with an auto trans.

Wallace Racing's Pontiac Engine Search


"... Is this engine something that would need to run hi octane fuel..."

Might be a good idea. Several sites show those heads to have 80cc chambers. IF that is the case, you should have a little over 9:1 CR. That could possibly be why the 350 heads were used. The '70 #13 heads would produce closer to 10:1 CR.

http://www.wallaceracing.com/cr_test2.php

Last edited by bigD; 11-29-2016 at 05:08 PM.
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  Pontiac GTO Forum > The 1964-1974 Pontiac Tempest, Lemans & GTO > 1964-1974 Tempest, LeMans & GTO Engine Tuning and High Performance

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