Lotus Elan and Lotus Elan Plus 2 Forums

Just curious, what is this threaded hole on the inlet side of the cylinder head for and why is it threaded?

Thanks,
Sherman

Hi

This vent hole is part of the engine breather arrangement and is machined down into the breather chamber. It is not normally threaded.
Your Cylinder Head may at some time during it?s life been used on an engine where for some reason the builder chose not to use the block to head rubber breather tube. If this was the case then the oil thrown up by the cams that would enter this hole, cannot then find its way back into the crankcase and would spill out of the external holes of the breather chamber. Hence the need to block this hole with a threaded bung.

It?s not uncommon on race engines to find that the engine builder may chose not use the existing breather arrangement . The hole that takes the rubber tube in the block would be blanked off, as would this hole. The use of a breather fitted to the front of the cam cover is found to be more effective.

Nick

Thanks for your reply. It is very informative.

The engine has 24,000 miles on it and is original to the car (Europa Special). The car was last driven in 1980 and then stored in a barn. However, I'm in the process of rebuilding the engine and I did have the head redone by John McCoy at Omnitech so it is possible that he threaded the hole as a just in case for the future.

Regards,
Sherman