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compression checking question

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Old 04-13-09, 08:14 PM
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compression checking question

Ive searched under ''compression'' and didnt find quite what I was looking for. Just wondering how to do a compression check on an 13bt when its out of the car besides listening for puffs. I want numbers.
Old 04-13-09, 08:19 PM
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I would like to know the answer to this as well.
Old 04-13-09, 09:15 PM
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Pretty sure a special tester is usually used when compression testing an engine outside of the car. Unless you want to rig up a starter to it and make sure it has plenty of cranking amperage to keep your readings consistant, but you can see how that could become a hassle.

Picked up my engine and pulled the leading plug from each rotor and felt a strong puff of air with a buddy spinning it over and it runs well now that its in.
Old 04-13-09, 09:31 PM
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Originally Posted by SGPguy
Pretty sure a special tester is usually used when compression testing an engine outside of the car. Unless you want to rig up a starter to it and make sure it has plenty of cranking amperage to keep your readings consistant, but you can see how that could become a hassle.

Picked up my engine and pulled the leading plug from each rotor and felt a strong puff of air with a buddy spinning it over and it runs well now that its in.
You need to be getting three puffs of air from each rotor with every two turns of the engine. That is if you want to check all six apex seals.
Old 04-14-09, 09:02 AM
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Originally Posted by SGPguy
Pretty sure a special tester is usually used when compression testing an engine outside of the car. Unless you want to rig up a starter to it and make sure it has plenty of cranking amperage to keep your readings consistant, but you can see how that could become a hassle.

Picked up my engine and pulled the leading plug from each rotor and felt a strong puff of air with a buddy spinning it over and it runs well now that its in.
Yes I did forget to mention that the trans and starter is already mounted on too. I'm thinking if I had a running car on and connect the battery from the running car to the starter would that be ok? Of course we have to move the wire from the battery on and off so it doesn't keep giving the starter power constantly. Has anyone ever tried?
Old 04-14-09, 09:06 AM
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Originally Posted by bsf1980
You need to be getting three puffs of air from each rotor with every two turns of the engine. That is if you want to check all six apex seals.
I just make sure it puffs every other one.....front puff then back puff and count to 6 puffs
Old 04-14-09, 09:43 AM
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You can compression test it no problem.

If you have the tranny on the engine and starter on the bellhousing, you're almost there.

Have a 14 to 16 ga. wire, about a foot long. Connect the neg. side of the battery to a starter bolt, connect the positive to where the + from the engine harness would go. The smaller wire I mentioned goes from the pos. clamp and you touch the small male blade connector on the solenoid to start. I'd recommend a remote starter (it's just two wires with a trigger switch) if you're doing this alone.

The rest of the procedure is the same as a regular compression test as found in the sticky or archives. Note - if you have the throttle body on, you need to make sure you keep it open (when compression testing an engine in the car, you get someone to keep the throttle open). If you got all that off (TB, intake, etc.) you have one less step to worry about.
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