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post #1 of (permalink) Old 05-26-2002, 07:02 PM Thread Starter
 
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Did compression test, what do these numbers mean?

I have bad blowby, and was instructed to do a compression test.
Here are the numbers
This is a 86 4.3L chevy engine
These round things will be my headlights, and I will line up the pistions in order from them

Driver Passenger
side Side

O O
____________
165 150
140 165
155 150

Any help is appreciated!
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post #2 of (permalink) Old 05-26-2002, 08:28 PM
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Re: Did compression test, what do these numbers mean?

While the one cyl. is down some, 140 isn't that bad. I'd be looking for a problem elsewhere. Thats too high to have a bunch of blow-by. Make sure that you PCV stuff is set up right and in working order. Are you sure it's blow-by, and not excess crancase pressure?
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post #3 of (permalink) Old 05-26-2002, 09:40 PM Thread Starter
 
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Re: Did compression test, what do these numbers mean?

I have no idea.
I checked my pcv, and it rattles and pulls vacuum.
I'll buy another one just for the heck of it, they are cheap.
I heard that it could have come from the valve seals and is comiung up through the intake??
I tried the bottle,and it didn't seem to help anything.
Thanks dirt
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post #4 of (permalink) Old 05-26-2002, 10:25 PM
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Re: Did compression test, what do these numbers mean?

I'm not sure what "the bottle" in your post means, but if you squirt a little motor oil into the low (140) cylinders spark plug hole and re check it, your readings will either rise = bad rings/cyl or remain the same = bad valve/guides .
post #5 of (permalink) Old 05-26-2002, 11:14 PM Thread Starter
 
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Re: Did compression test, what do these numbers mean?

how much oil?

The bottle i attached in place of my air cleaner to collect oil
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post #6 of (permalink) Old 05-26-2002, 11:34 PM
 
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Re: Did compression test, what do these numbers mean?

Seems kind of loose-loose situation..

If it goes up, bad rings and cyl, stays the same it's bad valves or guides..

if it lowers is it good?
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post #7 of (permalink) Old 05-26-2002, 11:39 PM Thread Starter
 
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Re: Did compression test, what do these numbers mean?

Maybe I put too much oil in?
I got a 180 after I put the oil in though.
My engine doesn't like this dry cranking [img]images/icons/smile.gif[/img]
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post #8 of (permalink) Old 05-27-2002, 01:50 AM
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Re: Did compression test, what do these numbers mean?

well, sorry if i made it sound bad or "lose/lose", 140 isnt really bad. I dont have a manual for that motor, but most say that cylinders can vary as much as 15 and still be within limits of normal wear. and those numbers seem pretty good for an 86 motor.
post #9 of (permalink) Old 05-27-2002, 01:54 AM Thread Starter
 
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Re: Did compression test, what do these numbers mean?

cool [img]images/icons/smile.gif[/img]
so all i need to do is change that one valve seal?
is it very hard?
I was seriously considering buying a new motor soon.
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post #10 of (permalink) Old 05-27-2002, 07:17 AM
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Re: Did compression test, what do these numbers mean?

Since compression went up with oil squirted into cylinder[about 3 squirts] that means worn rings.You could look in a manual[the engine specs page] and find out what range compression is suppose to be.That will help determine source of problem.A 4.0L or 4.2L is 120 to 150, a 2.5L is 155 to 185.Those are the only engines I have info on.
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