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Old 06-01-2005, 11:17 AM
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Compression Test

A buddy of mine was doing a compression test on a 350 Chevrolet engine and was getting between 150-180psi but on a couple of cylinders was getting nothing,

Why is this?

His car was running fine except he was losing power in 3rd gear (Automatic 400 tranny). Now his car won't start

Why is this?

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Old 06-01-2005, 11:31 AM
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cheap tools? motor in desperate need of work?
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Old 06-01-2005, 11:50 AM
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Mac Compression Gauge

Engine was running good but loosing power in the top end.

1st and 2nd gear lots of power but in drive it was sluggish
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Old 06-01-2005, 12:46 PM
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Test

Quote:
Originally Posted by Canadian Charlie
A buddy of mine was doing a compression test on a 350 Chevrolet engine and was getting between 150-180psi but on a couple of cylinders was getting nothing,

Why is this?

His car was running fine except he was losing power in 3rd gear (Automatic 400 tranny). Now his car won't start

Why is this?
Hole burnt in the piston,track burnt between cylinders, busted rockers....

Are the dead cylinders side by side????

Any more info on the engine??? Race only??? compression??? Does he spray it????

Keith
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Old 06-01-2005, 12:58 PM
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thats very strange because when you do a compression test and come up with a difference of more than 10 lbs. between cylinders you have a problem.you're saying he has a difference of 30 lbs between cylinders and still others show nothing.is he doing the test right?almost sounds like a head gasket leaking cylinder to cylinder aspecially in upper rpm's.maybe.
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Old 06-01-2005, 01:06 PM
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The rockers are ok.

We did a compression test on 5 of the 8 cylinders (headers in the way)

2 of the dead cylinders were side by side

The engine is a 350 is a 350 with 12:1 compression, low tension rings. Hasn't used the juice in a long time. Street engine.

Engine will not start when we atempt to turn it over. There is a good spark and fuel


PLEASE HELP
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Old 06-01-2005, 01:08 PM
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gasket

If the zero cylinders were side by side i say it has a torched head gasket/burnt block.... No need to even try to get it running. It needs to come out....

Keith
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Old 06-01-2005, 01:11 PM
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Would this cause it not to start?
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Old 06-01-2005, 08:10 PM
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compression test

Try running the compression test by squirting a little oil into the cylinders through the spark plug hole, and hold the throttle wide open when cranking the engine. It should not require more than 4-5 revolutions of the engine to get a good compression reading on each cylinder. See if you come up with some better readings. You should not have a variation of more than 10 psi between all the cylinders. If this is the case, and no compression in a couple holes, it sounds like time to yank some heads and see whats inside.
PS, be sure to have your ignition system completely disarmed before turning over the engine.
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Old 06-01-2005, 08:23 PM
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Side by side.....sounds like a blown head gasket to me.....It should still start, but would have a definite miss.
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Old 06-01-2005, 08:26 PM
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make sure the tool is in good working order check all the holes and record the info if still nada then pull the valve covers off make sure everything is moving right if still nadadammthing then brace yourself your going in!!

if you pull all the plugs it will spin easier if you have to drop the headers then do it to get the readings
(man i hate headers)
is there ant cross contamination??water in oil... oil in water compression in the oil or water???

sr66
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Old 06-01-2005, 09:39 PM
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Thanks every one
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