Re: reverse rotation gear drive for cam
Lots of potential issues that need to be addressed here.
First... you do not mention which engine this is.
Not all reverse rotation engines use a camshaft gear drive.
Many older ones, yes!
Today, most are chain driven, and the cam rotates with the crankshaft direction.
It's all part of the camshaft profile.
The procedure to check phasing, should be similar to that of a std LH Rotation engine.
To check #1 TDC accurately, the PPS (positive piston stop) procedure is used.
You can check and eliminate an issue with a balancer that may have slipped and is no longer aligned for #1 TDC.
I'd start there, and move forward from that point.
A balancer that is not accurate, will throw off your ignition timing.
Bad ignition timing may be part of what's giving you the low vacuum reading at idle.
Rick ... aka Ricardo
28' SDN F/B w/ twin Volvo Penta 5.7L DP's