Which 400 should I use? - Pontiac GTO Forum
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post #1 of 2 (permalink) Old 07-03-2014, 05:40 PM Thread Starter
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Which 400 should I use?

Alright so I bought a 79 T/A project to rebuild and restore back in April. The 400 block in it isn't the original but is a YX code block. It runs but it still needs some tuning.

When I bought the car the man gave me an extra 400 engine block with 6x heads for free. I did some research on it and if I'm not mistaken it came out of a 1970 GTO Ram Air III car.
Here's the numbers I found...
Engine Code 0613314 YZ
Block Cast # 9799914
Block Date Code E280
Block Vin 20L110143
The heads have a date code H297 so they aren't original to the block.

So the question I'm getting to is; if I'm not concerned with having original parts anyways, which motor would give me better performance if I were to drop it in my T/A? Thanks
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post #2 of 2 (permalink) Old 10-13-2014, 01:06 AM
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Either block will work but you could sell the RAIII block and partly finance the other block build. The 6X heads need more ID or be CC'd to know if they would be worth working on. If you want to build an engine that makes power and you can drive shoot for around 9 to 1 compression.

1964 400 4 speed Roller cammed RoadRacer
1969 400 T400 auto 2nd owner
2004 LS1 6 speed modded for roadracing
1966 GTO Altered wheelbase former 1970s show car
1973 Challenger 360/727
1931 Ford Model A
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