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#80012 07/14/2007 3:46 PM | Joined: Jun 2007 Posts: 110 Wrench Fetcher | | Wrench Fetcher Joined: Jun 2007 Posts: 110 | whats a good way to run a compression check on my 235? someone said to remove all the spark plugs and use a comp. gauge on each cylinder on down the line and see what the numbers show...this true? also what should a low psi 235 compression with 20,000 miles show? | | |
#80013 07/14/2007 4:00 PM | Joined: Jan 2002 Posts: 2,839 'Bolter | | 'Bolter Joined: Jan 2002 Posts: 2,839 | You can remove or loosen all plugs enough to allow air to pass. Hold the throttle fully open, disconnect coil wire and start testing.
Craig My '50 Chevy 3100 5 window, '62-235cu, 3:55 rear My truck ....... Respect The Rust If I'm not working on my truck, '65 m00stang or VW camper, I'm fishing with the wife or smoking Salmon.
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#80014 07/14/2007 4:54 PM | Joined: Mar 2004 Posts: 3,068 'Bolter | | 'Bolter Joined: Mar 2004 Posts: 3,068 | Pretty much as Cmayna said. I would pull all of the plugs, this is to give you the most cranking speed. Block the throttle open, this is to give you as much air for the engine draw in as possible. I like to clamp off the fuel line before the pump to so it doesn't flood or wash any of the cylinders and giving you a false reading. Ground the coil wire so it does'nt bite you too. If you do find something out of spec, diagnose it first, don't assume it's a bad engine.
Good luck,
Scott | | |
#80015 07/16/2007 4:53 PM | Joined: Jul 2006 Posts: 707 Shop Shark | | Shop Shark Joined: Jul 2006 Posts: 707 | The most accurate readings come from the testers that thread into the spark plug hole. Do everything everyone here has said, then thread the tester into #1 cylinder (snug, but not tight) and crank it like nine cycles until the reading has stopped rising. That's your dry number for #1. Repeat 5 more times in the other holes, write down your results then take an oil squirt can and squirt about 3 squirts into each cylinder through the plug holes. Let it settle for a bit, then turn the engine about 20 turns to spread the oil on the cylinder walls, and do a new course of compression tests as before. What the oil does is seal up the rings so you can read the valve seals. That is your wet test. It doesn't matter what the numbers are; If they are close and even, there's no problem. If both tests show a low reading on one cylinder, a valve adjustment is probably in order. Any anomalous readings need an explanation, but don't go manufacturing trouble. If it sounds and feels good, it is probably good.
1951 3800 Be the change you want to see. -hotshoe
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#80016 07/17/2007 2:37 AM | Joined: Jun 2007 Posts: 137 'Bolter | | 'Bolter Joined: Jun 2007 Posts: 137 | How much should the psi be in a 1934 206 cylinder? I have the hand crank to turn the motor but you can only go so fast. I got a reading of 25 psi in one and 0 in another.
I will get one of the starters to work to continue on. I did use the screw in type too. | | |
#80017 07/23/2007 1:58 AM | Joined: Feb 2006 Posts: 395 Shop Shark | | Shop Shark Joined: Feb 2006 Posts: 395 | remove all plugs,,open throttle and prop open donot open with each cyl check ,,,,turn over 4 comp strokes for each reading,,,,comp some where around 120lbs...doc | | |
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