3 replies to this topic

[minkus]

My engine is currently out and I've cleaned and lapped all my valves. Ive also had the pistons out to check for broken piston rings. Is there any reason why i cant put the head back on and manually crank the pistons and do a compression test before i put it all back together?

The problem I'm having at the moment is that i cant get much compression when doing this, not sure if I'm just being stupid!!

[Cooperman]

You can't do a comp test by hand. If the engine is out, re-fit the head without the plugs, fit the engine onto the gearbox and fit the flywheel and starter motor. Then get a fully charged battery and after spraying some light oil into each bore, with all the plugs out and no carb fitted (or with the throttle fully open if carb is fitted), use the battery to turn the engine over whilst doing a full compression test.

[minkus]

When hot wiring the stater motor does it need grounding or anything? I think my battery is dead do you reckon it would be safe to test it off another car?

Cheers

[dklawson]

The starter motor gets its earth connection through the clutch cover and therefore, the engine block. If you connect the earth from another car battery to the engine block and then in turn connect the "hot" from the other car to the post on the starter motor, it will turn the engine over so you can check the compression.

This all assumes you have the engine bolted to the gearbox again and that you have secured it somehow so it won't walk around on you while doing this work. Be careful.

Also, use a socket on crank pulley first just to make sure the engine can be turned over freely before you put power to the starter motor. In addition to having the starter motor hooked up, have oil in the sump, an oil pressure gauge attached, and NO spark plugs in any of the ports.