Chris Bracey Posted July 16, 2019 Report Share Posted July 16, 2019 Good evening. I have acquired a compression tester. Can i have advice on its use and what the target compression should be for a 1979 spitfire 1500. Thank you Link to comment Share on other sites More sharing options...
Pete Lewis Posted July 17, 2019 Report Share Posted July 17, 2019 Remove all spark plugs Have battery in good state Hold throttles open With gauge screwed in spark plug hole Crank to turn engine over till youmget best reading , may take 3 to 6 turns Note the result Repeat on other 3 cyls , in any order Youre looking for similar readings on all 4 There are other methods so wont confuse with that Resilts can vary but expect something between 120 to 150 psi After each test you need to release the pressure reading All 4 want to be within 10% of each other Let us know what you find Pete Link to comment Share on other sites More sharing options...
JohnD Posted July 17, 2019 Report Share Posted July 17, 2019 Chris, There is no "target compression". A compression tester is not a precision instrument, and is not calibrated. It is used to compare pressures, across the block, so that you can tell if one, or more, cylinders have leaky rings or valves. It is also very dependant on precise technique, atmospheric pressure, etc. You could test two cars/engines on the same day, same place, and know that one had better compression than the other, but that's all. Technique: I would add to Pete's list: Throughly warm the engine. Wire the throttle WIDE OPEN. Repeat the test until you get consistent results. You've never done it before, so you need to practice. The last can run down your battery! A good way to avoid this is to use jump leads from a running second car, so that keeps topping it up, while you are doing adjustments. If you do find low compression on one (or more) cylinders, then the diagnostic test is to pour a teaspoonful of engine oil into the bore. Turn it over a couple of times and then test again. This seals the rings and will increase the pressure, UNLESS the low compression is due to a valve problem, when the pressure will not rise under the 'oil test'. Good luck! John Link to comment Share on other sites More sharing options...
Pete Lewis Posted July 17, 2019 Report Share Posted July 17, 2019 Johns right but problem is to warm it up it might go terminal before its.......... hot and add to the what if's a loose cam sprocket makes a horrendous rattle . but wont explain the loss of coolant and low oil levels , sorry its still looking ............ sad Pete Link to comment Share on other sites More sharing options...
JohnD Posted July 17, 2019 Report Share Posted July 17, 2019 No mention of anything alarming in the OP, Pete. Just, "What do I do with this new tool I've bought?" Are you mixing up with another thread, or do you have a hot line to Chris Bracey?? John Link to comment Share on other sites More sharing options...
Pete Lewis Posted July 17, 2019 Report Share Posted July 17, 2019 yes john youre correct well its a wednesday and the suns out this can have senior effects . Pete Link to comment Share on other sites More sharing options...
Chris Bracey Posted July 17, 2019 Author Report Share Posted July 17, 2019 Thank you all. Will play in the next week Link to comment Share on other sites More sharing options...
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