Engine running ok but................

If you are using a timing light with an adjustment control on it, it can end up delivering its light flash at some steady but not expected time. Thats the message for today.

Its all about how that 40 degrees is measured - if it was done by the marks on the timing scale with a basic ignition triggered timing light then it really is 40 degrees.

If it is done using a gun with a rotary dial on the end, then that gun can be adding more or less timing than you expect if the gun is faulty.
For instance my gun which I could set to 60 degrees and get the mark being lit at zero time on a working engine.

I could tell it was wrong because if I rotated the control to zero degrees and back again, the position timing mark on the pulley only moved about 5 degrees while the control on the timing light was moved from 0 to 60.

There were mysteries in that engine when it was "running" at TE, like the cylinder doing the least work was NOT the cylinder with a massive head leak, based on pulling ignition leads one at a time..
And the time the timing suddenly jumped 40 degrees and it stopped as the distributor popped out of lock.

 

I've been camping at a home made Reading and Leeds festival all weekend so I haven't looked at my laptop all weekend. In answer to all the point raised the cam is definitely timed correctly using the dots, I checked it several times and kept turning the crank to make sure so I'm 100% sure that's correct. The valve clearances have been set and are all good. There's no air leaks as I've sprayed carb cleaner over the manifolds and carbs when it's running and nothing changes. The distributor was 180 degrees out in the drive slot which is why it kept jumping out as @mikedjames said. My timing light is an old Gunsons one from the 70's so doesn't have a rotary dial. I've also swapped the distributor with a spare and it makes no difference.

I've taken it for a run and it's driving better than it ever has done and it isn't getting too hot either I'm going to borrow an endoscope device and confirm the pulley mark at TDC, if it really is in the right place it's going to end up as one of lifes little mysteries.

 

Are you going to trailer it again this coming weekend, Paul? I am sure the folk at TE would be able to get to the bottom of it.

If it makes you feel any better my air leak came back again just after leaving the campsite this weekend, so I am back to figuring out why it keeps coming back after a couple drives. Thinking out loud, I think the new linkage, which is quite stiff, is causing a rotation moment against the manifolds and carbs pulling a gap open somewhere, job for tomorrow.

 

I had thought about trailering it down Andrew but I'd forgotten that my MOT expires tomorrow so I took it in on Friday and it failed! It needs a couple of rear wishbone bushes, (bloody roads around here are awful), and they won't be here until Thursday when I'm going to T/E. I daren't risk pulling an (overweight) trailer without an MOT so it's either drive the bus or get back on my bike and bring a tent.

 

That's annoying, Paul. To me, it feels quite odd to drive it so far with something so obviously unaccounted for/unexplained, without getting to the bottom of this, I'd be worried about damaging it.

 

If it makes it past the first 20 miles it will probably make it to TE. ..