Lotus Elan and Lotus Elan Plus 2 Forums

I am rebuilding a twincam motor that does not have the steel sleeves for cam followers. My machine shop tells me the bores look good and do not need the sleeves installed. Is it unusual for a cylinder head this old not to have worn tappet bores? I thought tappets riding in the soft aluminum was a weak point in these cylinder heads.
Thanks
Chris

Aluminium is a very good bearing metal and many modern similar engine designs run the followers straight in the Aluminium. The new SAS made twink head does that also.

My understanding is that Lotus started putting in sleeves due to warranty claims due to casting sand or other contaminants left in the head during manufacture scoring the soft aluminium excessively and that the sleeves got them through the warranty period at least

If your follower bores are straight and not worn into an hour glass shape and clearance with new followers within specification then no real need to sleeve until wear gets to that point

cheers
Rohan

Chris

Having overhauled and machined many early heads over the last few decades its certainly not uncommon to find that some still have surprisingly good cam follower bores after 55 years. Even some heads that show the obvious signs in other areas of having had many miles of use or abuse, I?ve found the bores to have little wear.
I have had to fit sleeves into early cylinder heads but not disproportionately more than l?ve had to replace the sleeves in later heads. As Rohan has stated, the problem of excessive wear was due to contamination in the manufacturing process, not the suitability of the aluminium as a good bearing surface.

Nick

I always thought it was an exhaust side problem and only that side is sleeved on my engine. After 280,000 miles there doesn't seem to be any difference to tappet fit.

Thank you all so much! That's good news as I plan to upgrade the cams, valves, springs etc..but didn't want to fit them to a marginal cylinder head or have to go to the expense of sleeving the bores.