Compression test pressures

[gprentice]

Hi folks,
Anyone know what compression test pressures should be for 1.7 Ital engine should be?
Graham

[old_n_notpastityet]

Re: Compression test pressures

Hi folks,
Anyone know what compression test pressures should be for 1.7 Ital engine should be?
Graham

Found this on the net, may help. It says 9.1 compression ratio on the full specs page for a 1981 1.7 Highline model.http://www.automobile-catalog.com/ma...ital/1980.html. If you scroll down the page it lists all models and there is the option to check out other full specs clicking on the links at the bottom of details for each model. Hope it may help you,good luck

[stevejgreen]

Re: Compression test pressures

I would expect an engine in good condition to be:
HC 9.0:1 around 190psi
LC 8.0:1 around 170psi

Acceptable tolerance on a used engine around 15% across the cylinders unless there is a serious oil consumption problem.
Strangly not all manuals quote figures or agree!

[gprentice]

Re: Compression test pressures

Thanks Guys, I getting between 155 and 165 across the 4 cylinders sounds as if it may be a bit low.
However my main problem is getting the engine to run properly.
Went back to basics and checked the pulley markings that the belt was on correctly, removed and re-timed the distributor with a strobe, checked the plug gaps, the points and inside the distributor cap.
The engine starts on the choke but backfires when the accelerator is pressed. Tried adjusting the mixture screw that was not making much difference, decided the carb might be to blame (single SU),changed the carb but still getting the backfire but not as bad.
Any ideas anyone.......?

Regards

Graham

[lil_red_roadster]

Re: Compression test pressures

Manifold leak perhaps..?
Check the gasket...not unknown for them to go between the ports.

[dogoncrazy]

Re: Compression test pressures

Manifold leak perhaps..?
Check the gasket...not unknown for them to go between the ports.

I was once told that a rough guide for compression figures was to multiply compression ratio by atmospheric pressure then add 1 atmosphere ----
Are you sure timing is correct and not 180 degrees out?

[gprentice]

Re: Compression test pressures

Thanks for your help.
I was thinking along the lines of this as an inlet would need to be open as combustion was taking place for it to fire back up to the carb, but did not think it would run at all if it was 180 out, I was wondering if an inlet valve was not seating hence the compression test.
However good shout, if I move the leads round 2 positions on the distributor cap would this be right?

Regards
Graham

[stevejgreen]

Re: Compression test pressures

Easy check is to remove the dizzy cap, spark plug from number one, and rocker over.
When piston is at TDC, checked with long shaft screwdriver down the plug hole, check that both valves are closed, and dizzy rotor is pointing to number one plug lead position.