8.1L 496 vortec big block chevy, what is it? - Page 2 - Hot Rod Forum : Hotrodders Bulletin Board
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Old 05-02-2013, 03:32 AM
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So I found a 2002 Chevy vortec 8.1L with trans and I want to throw it in my 57 Bel aire. I want to completely rework the engine and make some serious power with it. Think it's a good idea? I want fuel injection and I'll probably supercharge or turbo the thing as well. Any clue on where to buy performance parts for these things? Any way to get rid of the auto trans and put a beefed up 6 speed behind it? Any help would be much appreciated.

Pat

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  #17 (permalink)  
Old 05-02-2013, 05:34 AM
BOBCRMAN@aol.com's Avatar
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See other post.

Back in 004 I had my first 8.1L and was going to make a street motor out of it. I found no reasonably priced stuff for the engine. Mostly marine stuff. So I sold it.

Since then I have had several customers with the same ideas and experiences. Too costly for parts.. Even the stock stuff is $$$$$$
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Old 05-02-2013, 09:22 PM
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The crankshaft and rods can be used in the earlier big blocks and is somewhat common as the cranks are nodular iron, not much else for performance tho.
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Old 11-02-2014, 09:58 AM
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You or someone might know this, is the 8.1L balanced the same as the 7.4 or does it have it's own balance. The reason I'm asking is I'm going to install one were a 7.4L was and the 8.1L had an auto. behind it and the 7.4L has a manual. Another thing is the exhaust the same or is it different
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Old 11-03-2014, 09:49 AM
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The 2001+ 8.1 is a GEN 7 BBC, it is Coil Near Plug CNP. Rated at 340hp and 450lb/ft torque. The GEN 6 Vortec 454 7.4 rpo L29 it replaced was rated at 290hp/410lb/ft torque.
the GEN 7 L18 8.1 uses the different firing order of 1-8-7-2-6-5-4-3, just like the GEN 3 SBC like LS1's and such.

The 8.1 is comaptible with and transmission just like any other Chev engine. The 8.1 came stock with teh 4l80e/85e and the 6 speed manual as well as teh Allison transmissions.

IIRC the exhaust manifolds are compatible.

Back in 2003 GM was using the 8.1 in a marine application for APBA racing. The engine was a truck L18 with ported stock iron heads. It was rated at 525hp and 560 lb/ft torque. It was a standard truck engine with factorry iron ported heads, higher pressure FPR, HP3 specced camshaft by Crane cams, and heavier valvesprings.
The HP3 engine was listed as COMING soon in the GMPP Performance PArst calatogue back in 2003, but the engine was cancelled after much testing as Mercury was choked that GM had a "truck" engine that was beating its high dollar race engines. Mercury was GM's largest BBC buyer so GM dropped teh HP3 program.

HP3 8.1


And the boat it is in


peace
Hog
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Old 11-03-2014, 12:11 PM
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Correction, I had a buddy take a pic for me.

Here is a GEN 7 L18 8.1l exhaust manifold. You will have to drill out the 8.1 manifolds to fit the correct diameter GEN 6 bolt size.



And his quote to go along with the pic
"Both manifolds have one cylinder that the holes are the correct size for the retention bolts. since 8mm bolts hold the manifold on. So if you wanted to use them on an older bbc you would have to fix the hole size on both manifolds on one cylinder. You then could use factory exhaust off of a newer truck."

EDIT AND another


peace
Hog

Last edited by Hogg; 11-03-2014 at 12:20 PM.
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