Engine Tear-Down has Begun
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Pro
Joined: Oct 2000
Posts: 629
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Engine Tear-Down has Begun, Compression Ratio Question
OK, the engine (402) on my stand has had its tear-down started.
I was told this engine was a virgin and as always ya never really know until you get right into it.
To date these are the numbers that I have collected.
Block Casting Number 3969854
Head Casting Number 3993820
Camshaft Number 3963545
When I removed the heads this evening I was greeted by cylinder walls without any sign of ridge at all. Now for me this was a pleasant surprise but I'm still going to send it out and have it checked over.
My big question is with regards to compression. The numbers indicate that this engine is a 1971 402 so what was the compression back then with this engine. This project I hope ends up with about 425-450 horsepower so if anyone has any kewl budget wise tips I'm all ears here.
The reason I'm stressing budget, my significant other thinks the old engine works fine so why do this all over again.
Sometimes, they just don't get it. Do they?
Thanks as always
Indynut
I was told this engine was a virgin and as always ya never really know until you get right into it.
To date these are the numbers that I have collected.
Block Casting Number 3969854
Head Casting Number 3993820
Camshaft Number 3963545
When I removed the heads this evening I was greeted by cylinder walls without any sign of ridge at all. Now for me this was a pleasant surprise but I'm still going to send it out and have it checked over.
My big question is with regards to compression. The numbers indicate that this engine is a 1971 402 so what was the compression back then with this engine. This project I hope ends up with about 425-450 horsepower so if anyone has any kewl budget wise tips I'm all ears here.
The reason I'm stressing budget, my significant other thinks the old engine works fine so why do this all over again.
Sometimes, they just don't get it. Do they?
Thanks as always
Indynut
Last edited by Indynut; Sep 27, 2004 at 07:25 PM.
Drifting
Joined: Nov 2002
Posts: 1,665
Likes: 1
From: Ontario
Melting Slicks
Joined: Dec 2000
Posts: 2,198
Likes: 2
From: Eastern Connecticut
LS3 402-300hp in '71. 71 was the first year of net horsepower. They also lowered compression for emissions that year. The heads are 113cc chambers, are the pistons flat of dished? Here's a compression ratio calculator, I can't remember the bore and stoke numbers for a 402. http://www.csgnetwork.com/compcalc.html
Also, try www.chevelles.com and www.mortec.com for further info.
Joe
Also, try www.chevelles.com and www.mortec.com for further info.
Joe
Pro
Joined: Jan 2004
Posts: 653
Likes: 56
From: TX
1971 402 - 300hp@4800 and 400ft/lbs@3200. That was gross NOT net (Net started in 1972). CR was 8.5:1.
For relevance the base L48 of '71 put out 270hp.
I don't know how realistic that HP goal is - at least on a budget. My impression was this engine was a great torque engine but that kind of HP would likely require a lot more RPMs...? For me, torque is where it's at anyway.
Post some pics - I'd like to see the orig pistons but I suspect they had a small dish to them in addition to valve reliefs??? (-12ccs?)
For relevance the base L48 of '71 put out 270hp.
I don't know how realistic that HP goal is - at least on a budget. My impression was this engine was a great torque engine but that kind of HP would likely require a lot more RPMs...? For me, torque is where it's at anyway.
Post some pics - I'd like to see the orig pistons but I suspect they had a small dish to them in addition to valve reliefs??? (-12ccs?)
