Lotus Elan

Valve shim adjustment

PostPost by: holywood3645 » Fri Oct 28, 2016 11:17 pm

How often (miles) do most of you adjust the valve clearances on you're twin cams?
James
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PostPost by: Foxie » Sat Oct 29, 2016 12:32 am

James,

I would rephrase your question, "how often do I check my clearances"

When I have done some work on the head involving valve replacement/regrind I will check them every few hundred miles and adjust as required until they settle down. I have found that this takes a little time.

That's why I like to have a cam-cover gasket, glued only to the cam-cover, that stays in one piece

Once they are right I would do it every year as part of a big service. But you can hear when they get noisy !

I've had two head rebuilds this year, one for a pressure test for a problem which turned out to be a porous block, the second for a dropped exhaust valve in Mondello, which luckily jammed in the port and spared the (new) Dave Bean piston (in the new block !). The valve cut-outs were marginally too small diameter for the 1.4 exhaust valves, even though the engine turned freely by hand.......

Leading the Irish Hill-climb Championship Historic Class after the first four events, I ended up third at the end of the year :(

But everything is now go for next year ! :)
68 Elan +2, 70 Elan +2s
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PostPost by: holywood3645 » Sat Oct 29, 2016 4:14 am

Hmmm! I thought the valve clearances got tighter with wear on a twin cam. I found noise came from timing chain needing adjustment
Even so! Thanks...
This is me at Craigantlet in 1974.
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PostPost by: rgh0 » Sat Oct 29, 2016 9:23 am

I check them every 3 or 4 years in my Plus 2 and Esprit ( which uses the same followers and shims). The Plus 2 engine has done about 80,000 miles since its last rebuild back in 80's and I dont think I have ever needed to change the shims, Same story with the Esprit. My race engines for the Elan get rebuilt before there is any sign of change on valve clearances.

The clearances can open up if the cam or follower wears or the shim indents on the valve stem or close up if the valve and seats wear. With modern lubricants and valve materials wear appears to be very very little. Npise from the cams is often worn followers and sleeves in the head rather than excessive clearances.

My Toyota Landrcruiser uses a similar shim system for valve clearance and has done close to 400,000 kms and its valve clearances are the same as when I got it new. The Toyota recommended clearance check is every 80,000 kms

cheers
Rohan
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