How do I tell LT1 vs L99... - Chevy Impala Forums
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post #1 of (permalink) Old 04-03-2012, 01:58 PM Thread Starter
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How do I tell LT1 vs L99...

Just as the title states.. is there an easy way to distinguish the motors without removing anything? They look awfully similar.

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post #2 of (permalink) Old 04-03-2012, 04:04 PM
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SPID label is the only way I know, I think there is a casting number somewhere though that tells you as well.

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post #3 of (permalink) Old 04-03-2012, 04:31 PM
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Yeah the L99 is single exhaust LT1 is dual. IIRC that applies to all.

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post #4 of (permalink) Old 04-03-2012, 04:45 PM
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If the engine is out of the car look behind the driver's side head 5.7 is an LT1 4.3 is L99. There are other ways too but can be more confusing, will get into that later when I have more time and can maybe link some pics.

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post #5 of (permalink) Old 04-03-2012, 05:26 PM
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Dwayne, are VIN numbers cast on the blocks/heads?

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post #6 of (permalink) Old 04-05-2012, 02:55 PM
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The eighth character in the VIN number should be "P" for an LT1, and "W" for an L99.
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post #7 of (permalink) Old 04-05-2012, 05:04 PM
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See the upside down "327" above the driver's side knock sensor. Well on an L99 that would be "588". I am specific in pointing out that location because there are other places on the L99 block that say "327"

I wish I had better documented the L99 block before I scrapped it, it is so missunderstood a few pictures could really help.

Here is a pic of the heads side by side, notice the difference in the width of the gap between chambers due to the smaller L99 bore. I took that pic because a VENDOR on the big forum was claiming LT1 and L99 heads were the exact same thing.

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post #8 of (permalink) Old 04-05-2012, 05:47 PM Thread Starter
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THANK YOU guys, really. This is exactly what I was looking for.

Hopefully I have good news soon

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post #9 of (permalink) Old 04-06-2012, 07:11 AM
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Quote:
Originally Posted by 1995CapriceClassic View Post
The eighth character in the VIN number should be "P" for an LT1, and "W" for an L99.
On the Chassis of the car yes. But we are trying to identify it on the block itself.

This is still good information to have.

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