Not the exhaust

Dropped the exhaust off the car and tried to start it last night. Still no firing and the plugs still bone dry despite fuel making it to the carb chokes. There seems to be a lack of vacuum plus the crankcase still appears to be getting pressurised.

I tried a compression test and albeit a cold test (not exactly easy to do a hot compression test if you can't start the car!), the readings were identical at 150psi on all 6 cylinders which sounds about right, especially cold,

Most likely culprit seems to be the valve timing, could be that the cam chain is slack and has been jumping teeth. It has been suggested that the tensioner could have failed. I will also double checkthe distributor   drive pin, however this doesn't seem a likely cause as it wouldn't explain the crankcase getting pressurised.