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Compression Test

2K views 11 replies 7 participants last post by  Canadian Charlie 
#1 ·
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?
 
#4 ·
Test

Canadian Charlie said:
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
 
#5 ·
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.
 
#6 ·
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
 
#9 ·
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.
 
#11 ·
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 :thumbup:
 
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