Lotus Elan

valve clearances

PostPost by: gjz30075 » Sun Mar 20, 2011 9:06 pm

No action in the 'Common...' section so I'll repost over here.

I'm trying to track down a ticking noise and as part of the 'journey', I noticed the valve clearances are quite wide: Intakes are .010 and exhaust are .014 to .015. The cams are reground with specs of, intake: .417 lift, .105 ATDC lobe center, 247.4 duration. Exhaust: .416 lift, 105 BTDC lobe center, 247.7 duration. Valve overlap of 37.6 crank degrees. This all from the cam spec sheet.

I asked the engine builder if I can close up the clearances and he said those are in spec per the cam grinder, but he couldn't tell me the consequences if I closed them a somewhat, especially the exhaust. Actually the exhaust clearance calls for .012-.014, still a bit wide for my tastes, in regards to tracking down the ticking noise.

So, the question: Can anyone tell me what the consequences might be, if any, if I close up the specs to something like .008 on the intake and maybe .009 - .010 on the exhaust, based on the cam grind?

As an aside: the shims in it now are really big, using the top hat style on the exhaust side and I did purchase some shims to cut the clearance to .012 but I had to take off about 2mm of the skirt of the shim to not hit the keepers, which tells me there's not a lot of tip left. Maybe one of the shims could be 'rocking', causing the ticking?
Just another thought.

Thanks!
Greg Z
45/0243K Sprint
36/5727 pre airflow coupe
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PostPost by: twincamman » Sun Mar 20, 2011 9:12 pm

If you mixed up the cam followers or you may have one thats loose in its bore -it is very important not to mix the cam followers up and return them to the bore holes they came from ===ticking lifters are not bad if you hear the valves you wont have to see them -[old axiom ]--ed
dont close your eyes --you will miss the crash
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PostPost by: gjz30075 » Sun Mar 20, 2011 9:26 pm

Thanks Ed. Cams haven't been out since the build, about 5k ago. Ticking has been there from nearly the beginning.
Greg Z
45/0243K Sprint
36/5727 pre airflow coupe
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