Is there a way to test compression while the motor is out of the car?

[xikyle]

so i bought a motor to drop in the car because my old m20b25 is shot.
the new motor is also a m20b25, supposedly in better condition. I want to check the compression before i go to the trouble to pull the old 1 and drop the new 1 in.

Is there a way to test compression while the motor is out of the car?

[Farbin Kaiber]

Rotate the crank with a long breaker bar on the engine stand. If it sat, you may want to squirt some Marvel Mystery Oil in the cylinders, and give it a good number of rotations to free up the rings.

[xikyle]

were do i get some mysetery oil?

[Farbin Kaiber]

Likely a small autoparts store. Where in CA are you?

or,

http://www.marvelmysteryoil.com/index.php/site/wheretobuy/

[slammin.e28]

I'll hook up a starter and jump a battery to it to get 'er turning good 'n fast. Just don't have any open containers of gasoline around....we know what happens then....

[Farbin Kaiber]

Keep in mind, my suggestion was what is called a Wet Compression Test. It is best for checking the top end, when you are using an engine that has sat unused, you might get incorrect readings as rings will seize to the pistons, this will help free them up, while also lubricating the engine while not turning it at over 750 RPM's, which could cause damage unless you properly run the oiling system before running it as the guy above stated.

How long has it sat?

[slammin.e28]

Keep in mind, my suggestion was what is called a Wet Compression Test. It is best for checking the top end, when you are using an engine that has sat unused, you might get incorrect readings as rings will seize to the pistons, this will help free them up, while also lubricating the engine while not turning it at over 750 RPM's, which could cause damage unless you properly run the oiling system before running it as the guy above stated.

How long has it sat?

This.

I was thinking along the lines of fresh pull out of a runner. Not thinking along the lines of an engine that has set.

[scottinAZ]

wont be that easy to hook up a starter, unless you have a spare bellhousing around. the starter mounts to the trans, not the engine. if you can rig it up, this would be the best scenario to test the compression

[jlevie]

Testing compression without having a transmission (or at least the bell housing) on the engine is going to be a problem. But a better test would be a leak down test, and that is easy enough to do with the engine out.

[euro2fast4u]

why not run a leak down test. you would get more data from this then a hand spun wet compression test.

[MaksV]

why not run a leak down test. you would get more data from this then a hand spun wet compression test.

+1 but you need two valves a guage and a air compressor.

[euro2fast4u]

+1 but you need two valves a guage and a air compressor.

cheaper then cutting up a bellhousing


$34.99 plus shipping



how much is a bell housing?

[Farbin Kaiber]

I scanned and posted these years ago, might be of some help.

http://www.hondatuningmagazine.com/tech/htup_0812_diy_leak_down_testing/index.html

[slammin.e28]

cheaper then cutting up a bellhousing

Unless you have a trans that's locked up and garbage anyways.

I've gotten so used to my ways, I don't realize they may not work for those without 3 parts cars and a whole barn of parts and shit.

[euro2fast4u]

Unless you have a trans that's locked up and garbage anyways.

I've gotten so used to my ways, I don't realize they may not work for those without 3 parts cars and a whole barn of parts and shit.

bahaha i went on a purging expedition 1 shell and a dually full of parts. 4,000 lbs later and my buddy and i went drinking on the town. i now have a roomy place for the e30. and was hungover the next day