Vacuum readings

[Roddster]

Anyone know why my vacuum is a steady 12 inches while the truck is in park, then drops down to 8 inches when put in gear? The idle is rough and the tranny shifts very hard into second gear, chirping the 31" tires. All the vacuum lines were checked for leaks, as well as the intake manifold and carb base. The engine is a 350 of questionable vintage. Could the modulator on the tranny be bad? Also, where is the reverse light connection on a Turbo 350?
Appreciate any help, as I am finally done with school and now have the time to work on my projects.

 

[BUD]

IT SOUNDS TO ME THAT YOUR VAC IS ALITTLE TO LOW PUT YOUR VAC GAGE BACK ON AND TURN YOUR DIST. UNTIL YOU GET THE HIGHEST VAC READING I THOUGHT IT SHOULD BE ABOUT 18

BUD

 

[coilover]

If timing doesn't do much for it I think your 350 of questionable background has been visited by a long duration cam. This is not easy to check with engine in vehicle and you really need a dial indicator with one inch of travel and degree wheel to procede. All the major cam grinders have literature on the procedure. On anything I've had experience with and IF you have power brakes, a long cam will give you good brakes at 60 or so mph and decrease to really lousy by 30 or so. Very unscientific but has been my observation. An engine with stock cam and valves, seats, and rings in good shape should show 19-21 inches of vacuum. Good luck--hope the timing does it for you.

 

[Roddster]

I'll try messing with the timing...I think it may be advanced too much right now- sometimes I have engine run-on when I shut it down. I have power drums and an HEI distrubutor. The brakes work good- as far as I know. The pedal is firm, but the truck stops nicely. The vacuum booster and the hose going to the manifold don't appear to be leaking.
Thanks for the advice, I'll give it a try.