Brand New Lotus Twin Cam Engine From 1964

[2cams70]

The reason you don't see locknuts of any type in most engines is because the fasteners are tightened to a level where the stretch in the bolts/studs is sufficient to keep things so they won't come loose. For those cam cap studs the industry standard for that size fastener is 21Nm but Lotus only specifies a figure of 12Nm (probably to save the threads in the head stripping). At 12Nm the stretch in the studs is insufficient to prevent things coming loose and so locknuts rather than regular nuts are specified in this location

[Andy8421]

On the subject of cam caps, they have been numbered - typical of a machine shop prior to disassembly. I guess Lotus could have done this, but neither of my heads has numbered caps. This would lend more weight to Rohan's observation about the numbered valves - which are possibly in the wrong cylinder.

It is still an interesting find, but it does look like the head is a bitsa.

[rgh0]

On the subject of cam caps, they have been numbered - typical of a machine shop prior to disassembly. I guess Lotus could have done this, but neither of my heads has numbered caps. This would lend more weight to Rohan's observation about the numbered valves - which are possibly in the wrong cylinder.

It is still an interesting find, but it does look like the head is a bitsa.

The cam caps should be numbered 1 to 10 and should match the numbers stamped on the head top surface adjacent to each cap. Some cam cap sets have other identical numbers on them also on early heads which appears to have been to keep the cam caps sets together. I have always presumed this was done during manufacture and not after during servicing due to the quality and consistency of the extra number stamping

cheers
Rohan