What is considered a good vacuum level at idle.I have a cc qjet on a 305 lg4,
and warmed up,with a idle of 900,i'm getting 21" of vacuum,and idle of 600 in drive gives me 17 to 18".The gauge is hooked up to the bottom rear port on the carb,which is manifold vacuum I presume.Are these good levels?.

Thanks,
Alicat.

 

Vacuum levels are determined by several aspects of the engine combo.

Depending on the valve timing, runner volumes, exhaust flow and many
other things, you can determine whether the vacuum reading is sufficient.

If you are reading 16-18 in./hg. of vacuum, on a 305, I would guess it's
fairly stock and the level indicates a fairly sound motor. Looks good!

 

Yes it's stock as far as I know,and seems in good condition,although my oil pressure at idle is only 25 psi,but it runs strong,and does'nt leak or lose any oil.

 

25 PSI is more than enough at idle. With the proper bearing clearances
and volume, even 10 PSI is enough pressure.

Everything is fine, don't worry. Your engine is healthy according to those
values.