I’d certainly try it. 

Yes like you I didn’t initially have one on this engine but it’s so free and quick revving I fitted one.  initially set at 6k but hit it far too often and not far enough peak torque so discussed with engine builder and was set to 6,250 for quite a while now and feels right.    At aintree i typically used 185/70 tyres and this gave top speed and the revs weren’t too extreme.  this time i used my 185/55 tyres and got better corner exit speed thus carried high revs for far longer than usual and I think it’s this it didn’t like.    normally my max revs are very short lived between gear changes and not holding high speed high revs i confess I’m not doing the engine it’s with the original builders.    As an aside -after 3 years competition use  the MaXpeeding rods are still excellent- they were a complete unknown quantity we we went with them.

Do you have a rev limiter Hamish? Didn't bother with the racer initially as I assumed I would watch the rev counter. Then one event I noticed we were a little short of 7800rpm on the 1300. Standard crank, rods and pistons. All balanced but even so. Fitted one with a soft then hard cut and warning light after that, just in case. 6800 shift light, 7000 soft cut with 7300 hard cut

That isn't how the wishbone, trunion, upright system is loaded in use though and so isn't really relevant. The U shaped plate is only there to hold help with assembly. As is the wee bar across the wide end of the wishbone. By having minimal contact they allow for minor misalignment of the moving joints without imparting undue stress on anything. And will almost certainly affect getting the right clamping force on the trunion bushes leading to premature wear of the bushes and/or bolt holes if they are not able to flex a little. Lotus used the Triumph vertical link/trunion/spring/damper on the Seven, Elite, Elan, Elan +2, Europa with separate lower wishbones without any joining bits with no issues. I would recommend NOT welding up the U plate.

The shafts are not interchangeable. The Mk1 2L and 1600 six and 1147 4 cylinder engines have shafts with the same end pedestals as those in the middle and are fitted with external end caps to close off the central oilway. Like this The 2L six and 1300/1500 4 cyl have end pedestals with an extended support for the outermost rockers and are fitted with internal blanking plugs to close off the central oilway. Like this I think it is possible to swap the entire rocker assembly, shaft, pedestals, etc between engines but I've never done it so maybe someone else can confirm.

Yeah in my very unscientific experiment ( jacking up on side of the wishbone ). One bolt is in a pollybush, the other the trunnion both of which move. Combined with the arb only being on one side. There was definitely unnecessary movement, potentially due to some ovaled bolt holes, but i figure why not run a couple of beads along it. I'm not sure it helps, but it can't hurt, can it?

So other than part numbers what is the difference between a Vitesse mk1 rocker shaft and that fitted to the mk2. reason for asking is that my intention (when second hip replaced, hopefully very soon) was to get mk2 head prepared for fitting to mk1 block. I had hoped that it would be a straight swap but there’s obviously something different otherwise everyone would list just one shaft for all the 6’s. Is the difference earth shattering so that it can’t be fitted and I have to get a mk2 shaft/set or is the mk1 shaft going to be ok on the mk2 head?   Any ideas info or tips greatly received.  cheers John 

The others were ok. Looks all good on the compression face once some carbon cleaned off.  possibly over revving stresses as I have a feeling I sensed a change flat out in od 4th at aintree. But reviewed the videos and can’t pinpoint any changes.  nor any clear performance change. Remained free revving till strip down.    trying to get one replacement piston. A set is expensive! full set of rings going in.  new big end shells.  Just lucky I still have an intact block !!

Ahh il have a read through that tonight. Lumps of 7075 aluminium (often called aircraft grade) Are around £100 for enough to do the uprights. 1/4 of which would end up being reclaimed as scrap. Once the 3D cnc file is set up shouldn’t be too silly a price going forward… Another project idea to add to the list.

Thanks both, I removed those anti vacuum things long ago.  Knowing the return isn't excessively lazy is really useful info.  It sounds like I need to continue to be extra sympathetic on 1st to second gear changes.  I'll file it away under "reasons for machining the flywheel" and add that to the savings figure I need to achieve before I pull the engine for the camshaft/piston rings, and now flywheel works.