JSM Posted May 15, 2012 Share Posted May 15, 2012 I picked up a used motor from the JY for my Lexus. Of course mileage is unknown and no starter or trans came with the car because I had to pay for it if I kept it! Anyway, I'd like to do a compression check. I was curious if I were to spin the motor with an impact wrench on the crank pulley if that would be a bad idea? Anyone else try something like this? Thoughts? Any other method to check compression? Talk about loads of fun! Quote Link to comment Share on other sites More sharing options...
Six_Shooter Posted May 15, 2012 Share Posted May 15, 2012 Impact gun on the crank pulley won't turn it fast enough, if it will turn it at all. All I see happening is tightening the crank bolt too much and possibly stripping the threads. Need a starter or motor that will turn it at least 300 RPM. Quote Link to comment Share on other sites More sharing options...
getoffmyinternet Posted May 15, 2012 Share Posted May 15, 2012 You'd need Thor's impact got get it to spin at anything more than a crawl.... Just do a differential pressure test. Quote Link to comment Share on other sites More sharing options...
JSM Posted May 15, 2012 Author Share Posted May 15, 2012 Thanks guys. Quote Link to comment Share on other sites More sharing options...
Leon Posted May 15, 2012 Share Posted May 15, 2012 (edited) You could easily perform a leakdown test, but you'd need a source of compressed air. Edited May 15, 2012 by Leon Quote Link to comment Share on other sites More sharing options...
getoffmyinternet Posted May 15, 2012 Share Posted May 15, 2012 I hate to steal your title Leon, but if he has an impact he probably has a source of compressed air. Quote Link to comment Share on other sites More sharing options...
JSM Posted May 16, 2012 Author Share Posted May 16, 2012 I hate to steal your title Leon, but if he has an impact he probably has a source of compressed air. That made me laugh, thank you. No bad feelings Leon, just found it funny. Quote Link to comment Share on other sites More sharing options...
Leon Posted May 16, 2012 Share Posted May 16, 2012 I hate to steal your title Leon, but if he has an impact he probably has a source of compressed air. Good call. Quote Link to comment Share on other sites More sharing options...
GOTHALOSISM Posted May 17, 2012 Share Posted May 17, 2012 It could be an electric impact, but who really uses those. Quote Link to comment Share on other sites More sharing options...
beermanpete Posted May 17, 2012 Share Posted May 17, 2012 It could be an electric impact, but who really uses those. The guy without an air compressor, of course. Quote Link to comment Share on other sites More sharing options...
duragg Posted July 10, 2012 Share Posted July 10, 2012 Electric impact rocks! Oh, and we do thumb compressions on aircraft engines all the time. If its hot and difficult to contain its a keeper. Quote Link to comment Share on other sites More sharing options...
getoffmyinternet Posted July 11, 2012 Share Posted July 11, 2012 Well that's scary. Quote Link to comment Share on other sites More sharing options...
suparman Posted July 12, 2012 Share Posted July 12, 2012 Well that's scary. +1 on that Quote Link to comment Share on other sites More sharing options...
HowlerMonkey Posted July 16, 2012 Share Posted July 16, 2012 I just got done checking a mitsu. 3000gt VR4 compression as it sat on the engine stand before I spent more time assembling it. Other than piston ring issues, most of what lowers compression usually removes all compression from a cranking speed standpoint. I wanted to see if I had to go further into this engine so I simply removed all the spark plugs and hand cranked it. It had between 15 and 20 psi hand cranking on an engine that sat for 5 years. Quote Link to comment Share on other sites More sharing options...
JSM Posted July 17, 2012 Author Share Posted July 17, 2012 I just got done checking a mitsu. 3000gt VR4 compression as it sat on the engine stand before I spent more time assembling it. Other than piston ring issues, most of what lowers compression usually removes all compression from a cranking speed standpoint. I wanted to see if I had to go further into this engine so I simply removed all the spark plugs and hand cranked it. It had between 15 and 20 psi hand cranking on an engine that sat for 5 years. I was able to get close to 50 PSI doing the same thing. At least gave me a little more confidence. Quote Link to comment Share on other sites More sharing options...
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