Compression testers

[mattyguk1]

Hi all, I’m looking to buy a compression tester. Can anybody recommend an affordable one that works? I understand it’s preferable to get one with a schrader valve in the end that screws into the head?

[philthehill]

The Gunson compression tester a most suitable and affordable item and that is what I use.

https://www.ebay.co.uk/itm/Gunsons-Hi-G ... Swgy1ekIIJ

or pre owned

https://www.ebay.co.uk/itm/Gunson-s-Hi- ... Sw5j9elK2j

[mattyguk1]

Thanks Phil, I’ve ordered one

[mattyguk1]

The new Gunson compression tester has arrived, seems to be a solid bit of kit. I’m going to check compression tomorrow, the box says to just remove one plug at a time and test but I’m sure I’ve read to remove all of them before you start ? How many times do I need to crank? What’s the best system and what would be classed as good and bad results?

[philthehill]

You can remove all the plugs if you like.

Make sure that you wedge the throttle fully open (brick on the accelerator pedal).

Try each cylinder dry - then squirt a small amount of oil down each plug hole and try again.

If there is a considerable difference between non oil and oil that indicates worn rings.

I would be looking for at least 175 lb on the gauge.. Hopefully it will be more not less.

The face of the gauge has an indication sector (green) of good bad and indifferent pressures.

Write down the readings for each cylinder without oil and with oil so that you can compare the pressures/differences.

Good luck.

Phil

[mattyguk1]

Cheers Phil I’ll let you know how I get on.

[mattyguk1]

Do I keep spinning engine until reading settles or for a certain amount ?

[GavinL]

Phil, why does the throttle need to be held open? Ensure reasonable air flow into the cylinders?

[philthehill]

Having the throttle open ensures that maximum air is entering the cylinder.

Spin the engine until the indicated gauge pressure stabilises.

[mattyguk1]

Test results after a 10 minute run to warm engine up.... dry all very close at between 170 and 173 and wet once again very close at between about 190 the 192 ?

[philthehill]

Well done.

I would suggest that the compressions are good. The additional lbs when oiled is to be expected so do not read too much into the difference.

Phil

[mattyguk1]

Cheers Phil