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Discussion Starter #1
I'm looking at a 5.3 that a friend of mine has. He did a dry compression test on it, and the numbers have me scratching my head.

Passenger Driver
8 - 150 7 - 230
6 - 220 5 - 150
4 - 240 3 - 150
2 - 150 1 - 210

Now I know a 15% deviation is generally a bad thing, but I'm wondering if maybe I'm missing something. It just looks too uniform, if that makes any sense. Going by the firing order, it is high-low, high-low, high-low and high-low. I don't have any specifics about the engine, other than it is a LM7 with 706 heads. He doesn't know the miles or what it came out of. It is complete from the pan to the intake and is just missing the coils, starter, alternator, and ps pump. It has been setting on an engine stand dry for the past year. I haven't asked him to go back and do a wet test yet. Is it possible the varying numbers would be a false read because of something simple, like the lifters being dry and held up from sitting, or am I definitely looking at either rings or worn head valves???

Any insight you guys could give as to what is going on with it, would be appreciated. Thanks!
 

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Discussion Starter #3
I wasn't around when he did it. I'm just getting info through texts, so far. To the best of my understanding though, those numbers were with the engine on the stand, dry and right where it's set for quite a while, and hand cranked. It's not been fired since he's had it, and that's been more than a year.
 

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I'm guessing he turned it over a few times by hand, since it is just sitting on the stand and he said there was no starter. He's a big dude, but I would think that doing it that way would still be too slow to get an accurate reading. I'm definitely no mechanic though, so I don't know much. This guy has a ton of F-bodies and has built several pretty stout ones, so I hate to question his abilities. I guess too, it's possible he hooked a starter up to it to get it to crank. If it was just turned over by hand though, I guess that be why every other cylinder in the firing order was low.
 

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I agree. I don't think I'm going to hold much value in the numbers. He wants so little for the engine, I think I'm going to pick it up and hope for the best. If it needs new piston rings or head valves or something, I'd still be in it cheap after replacing them.
 

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Yes, I have an idea.

Discount the hand turned engine compression check and do a leakdown test! :)
 

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I have a fresh non-fired , 440. I am wondering, how much cranking compression i will have. Also yes, I hope the engine is a Zero-Leak down engine. It is funny how I think about this compression thing. When you have a little, you want more. I have only ran my engine one time. Back when we ran the engine on what I will call Dyno-Day one. The engines mechanical was set in the Low range. My engine is now in the Medium Mechanical Compression range, 14 to 1. How I would like to switch to Methanol and try out running the Mechanical up into the high range. To me that would be 20 to 1, or more.

Ok, I think I have typed enough jabber. Do you guys have any Thoughts?

Good By Chris [email protected] 925-497-1059
 
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