Compression Test etc..
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Compression Test etc.. Hope this is in the right section. When I go to purchase my ls1, I assume its a good idea to run a compression check on the engine? According to the search, psi should be 160-180 on a "normal" motor and 180-210 on a more "aggressive" motor. Is this the case? Should I run this test before I purchase it no matter what or will I know when Im driving that something might be wrong? Also, should I run a leakdown test? I couldnt find much on this test, what is it and how do I do it? Is it even worth doing on a car before I buy it? Finally, what other things should I look out for? Ive posted this before, but I want any specifics. Obviously I know about the clutch, tire wear, any noises in the rear end etc. Am I missing anything? Thanks guys.
Both tests I would not think you would want to do before you bought a car since they require time with the car and I don't think someone will let you take it home to do these (since you will be fiddling around in the engine compartment), unless maybe to a mechanic to get it checked out.
I would just listen for the tell tale signs that you mentioned above.
Anyway....since you asked
To do the comp test. you need a comp guage and spark plug fitting of coarse.
You warm the engine up to operating temperature then shut down.
Then open the hood, disconnect both coil pack connectors and fuel pump relay.
Take a spark plug out, install fitting, hose and guage and crank over the engine 5-7 times. Record reading. reinstall plug and repeat on all 8 cylinders. Lowest reading should not be below 10% of highest reading. Last time I did mine, all cylinders were around 200-205
Leakdown is much more complicated and usually is only done if strange results arise from the compression test. It requires another different instrument (dual guage leakdown tester) and access to an air compressor.
Never did one, but if memeory serve you would have to make sure both valves are closed either by making sure you are on the compression stroke by turning the engine by hand or by taking the rockers off to close all the valves. The purpose is to fill the cylinders with air from the compressor and read the guages and listen for air escaping from the intake, exhaust, head gasket, or piston rings. A certain percentage is acceptable as read by the guages. Anymore than that, you have air leaking through one of the 4 places I mentioned in the above sentence, and repair is needed.
I would just listen for the tell tale signs that you mentioned above.
Anyway....since you asked
To do the comp test. you need a comp guage and spark plug fitting of coarse.
You warm the engine up to operating temperature then shut down.
Then open the hood, disconnect both coil pack connectors and fuel pump relay.
Take a spark plug out, install fitting, hose and guage and crank over the engine 5-7 times. Record reading. reinstall plug and repeat on all 8 cylinders. Lowest reading should not be below 10% of highest reading. Last time I did mine, all cylinders were around 200-205
Leakdown is much more complicated and usually is only done if strange results arise from the compression test. It requires another different instrument (dual guage leakdown tester) and access to an air compressor.
Never did one, but if memeory serve you would have to make sure both valves are closed either by making sure you are on the compression stroke by turning the engine by hand or by taking the rockers off to close all the valves. The purpose is to fill the cylinders with air from the compressor and read the guages and listen for air escaping from the intake, exhaust, head gasket, or piston rings. A certain percentage is acceptable as read by the guages. Anymore than that, you have air leaking through one of the 4 places I mentioned in the above sentence, and repair is needed.
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Thanks for the help. I've heard of people doing these tests on their cars if something might be wrong. Ive also heard of people doing it before they bought a car, but I wasn't sure. So I should be good to go with a car if everything checks out? Anything else I'm missing? Would it be smart to have a mechanic check it out for me, or would(should) the dealer do that?
