Cam Timing

[arthur67]

Hi I have bought a +2s130/5 the compression on number 4 cylinder is a bit low IE 130 PSI the rest are between 170 and 190 PSI.Someone has told me it is a classic Lotus twin cam fault and is caused by worn camshaft sprockets.
This is my fourth Lotus and I have never heard of this has anyone? The valve clearences are a little out 3 inlets are between 2 and 3 thou and the other OK at 5 thou.The exhausts are spot on at 10 thou.
The car seems to run OK but I have only done 5 miles it has been off the road for 16 years.
Any advice would be great Regards Arthur

[rgh0]

I don't understand how worn cam sprockets could cause low compression in just one cylinder. If wear or other valve timing problems occurred I could see compression being affected a little but it would be small and it would be the same across all cylinders.

cheers
Rohan

[john.p.clegg]

Arthur
You've checked the valve clearances,next is to do a compression test wet,tip a little oil down the spark plug holes and repeat the test.....bore wear or valve leak?

John

Edit


P.S you are doing the test with Wide Open Throttle ?

[arthur67]

Thanks for the advice great forum. Arthur

[twincamman]

Low compression in one cylinder may just be the rings stuck in the groove from lack of use through long storage and may improve with a bit of driving ....Ed

[arthur67]

Hi John
Yes I am doing it with all the plugs out and the throttle wide open.When I get it on the road next year I will see if it improves . Thanks again Arthur