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#1
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Help! Comprssion Test Results
Here are the results of a compression test on a 440 Six Pack motor. All plugs were removed and all throttle blades open. First number is Cylinder. Second number is on the first compression stroke. Second number is on the fourth stroke.
#1 100 160 #3 120 180 #5 120 160 #7 130 180 #2 120 180 #4 130 175 #6 120 155 #8 90 155 Note: Water leak on passenger (even) side, but not getting into oil. All cylinders had uneven build-up. All pressures fell somewhat quickly after fourth stroke. Motor has sat for 18 months. Cam is 292/505" Isky Hydraulic. Compression is supossedly 9.8:1 What do you think? |
#2
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I would not be surprized to see readings like this from a motor that has sat for 18 months. You need to start it, warm it up and redo. My bet is that they will be much more even.
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#3
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I agree with what cuda367 said. Gotta be close to operating temps to get
an accurate picture of things. Re-test, then post again. Performing a leakdown test would provide you with a much better indication of ring seal. Do it if you can (rent, borrow, steal, etc.) Good luck! |
#4
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I agree with those guy's...temp must be up
What's this water stuff???? |
#5
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water stuff!!!??? not good. better have it checked.
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#6
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I agree with everyone above, but even still, I am worried about #5, #6, and #8 cylinders. Overall, with 9.8:1, you should be in the 190 psi range, but moreover, the fact that you have almost 30 psi difference in those three cylinders has me worried... 5 -10 might be normal for a well-used (run) engine, but more than that is indicative of some problems... problems that would be caused by more than just 18 months of sitting.
I had a four-banger that had sat for an unknown number of years that I fired up and tested at 195 for each cylinder, with about the same compression numbers. But I made sure I changed the head gasket - first things first - before I put it in the car. But I didn't even touch the valve seals or rings. (I also lightly coated the inside of the cylinders with motor oil for the first fire up to protect the walls... She smoked like hell, but everything went smooth after that!) So, with that in mind, I might ask; how are the head gaskets? Considering you say you have a water leak, I would guess that you may need to redo the gaskets. And that might not be the only problem, but it's a place to start. A agree w/ charger_dan - a leakdown test would let you know if your rings are suspect... A poor man's way of checking this (I've never had to do this, BTW, but I have read it in service manuals) is to do a compression test, then put a small squirt of motor oil into the cylinder via the spark pug holes. Do another test. If the numbers rise, it is most likely a sign that your rings aren't sealing the way they should. Hopefully it'll just be a head gasket or two for you... Good Luck! Dave |
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