13 inches

[steve from staten island]

Eric, i think if i remember correctly all the cylinders were within 10 to 15 PSI of each other. 120 to 130 maybe. I do know none were very low or there was a big difference between them

 

[eric383]

Also check for a vacuum leak at the vacuum advance canister on the distributor if it has one, and if you have power brakes the booster unit.

 

[dvw]

Another thought. Possibly one or more of the valves may not be completely closing. The push rods may be bottoming the lifter plunger. It's possible if the heads were sufaced and the seats were ground deep enough. You may have to shim the rocker shafts up.
Doug

 

[Don Frelier]

Another thought. Possibly one or more of the valves may not be completely closing. The push rods may be bottoming the lifter plunger. It's possible if the heads were sufaced and the seats were ground deep enough. You may have to shim the rocker shafts up.
Doug

It could be a geometry problem following the head work. Were your compression test results from before or after the heads were done?
What Doug describes would give a loud lifter noise as well.

 

[PRHeads]

The stock 383 2bbl cam is pretty small, and pretty wide.
In a stock 383 that has reasonably close to the stock CR it would have noticeably more vacuum than 13”(closer to 18-20).
The cranking compression should also be higher than 120-130 for a fresh motor with a cam that small.

My guess is one or more of the following in varying degrees......
-cam timing retarded
-valves not sealing optimally
-replacement pistons that have lowered the compression ratio