It's a M110 Euro engine. The vacuum seems low. I get pops from backfiring. The airplate often begins to flutter in conjunction with engine running faster at idle. I checked for leaks. Furl pressure seems OK. The PSI in the cylinders is around 125 psi. One is little lower at 110. Is this abnormally low and potentially causing the intake vacuum problem, please

bm:

Begin by adjusting valve clearances: Cold, In. .004", Ex. .010"
Recheck cranking compression pressures

Disconnect all vacuum lines from distributor
Set idle timing to 10* BTDC

What are the results?

Suggestion: Post Once

Hi Frank, the valves were adjusted a couple of weeks ago. They should be just about correct. The timing is at 13 with the vacuum line, around 10 without. The flywheel marker isnt super-steady and moves around a little. I also put in a new exhaust cam, thinking that one of the lobes might be flat. The engine has also had new exhaust valves and guides. What makes its strange is that it'll idle smoothly, then abruptly become uneven with the air meter flutter and higher revs I describe...