View Full Version : Low Engine Vacuum

Captain Billy
06-09-2007, 08:57 AM
I've been readying my 64 Lark for the trip to South Bend, and during my tune up I see that the engine vacuum is only about 16", I've tried adjusting the timing to get a change but it seems 'happiest' in the low number range. I've listened and sprayed for leaks and have not found any, I've set the valves and the result is the same, before and after.
I'm running an Edelbrock 1406, on a 259 with a stock presolite distibutor,new wires, points,plugs, cap and rotor. I purchased this car last fall and it appears the engine has been rebuilt, or at least recently assembled.
I've also checked the pvc valve, it appears to be free and operating.
What else can I check, my days are numbered?

06-09-2007, 07:06 PM
Are you removing the 3/8" pipe plug in the intake manifold to "read" the vacuum? That is where Studebaker recommended checking it.

Studebakers Northwest
Ferndale, WA

Captain Billy
06-10-2007, 06:29 AM
Short answer: YES

06-10-2007, 09:19 AM
What's wrong with 16?

Tim K.
'64 R2 GT Hawk

06-10-2007, 03:50 PM
Agree, 16" is on the low end of OK. It's not really a problem, but if you want to confirm it can/can't go higher, remove the lines and plug every opening from the intake. Does it have power brakes? That can be a leak. What about your PCV valve? Have you confirmed your RPM setting. Some tachometers are not accurate at low RPMs. Same with vacuum gauges. I have a 5" brass industrial gauge. One small aftermarket dashboard-type gauge I checked was off by 3". Also, run a restrictor in the vacuum line. If you run the full diameter line, the needle will flutter and not be as accurate as if it has a 1/16" or smaller diameter hole restriction in the line.

thnx, jv.


John Kirchhoff
06-11-2007, 12:36 PM
When you said you adjusted the timing, were you going strictly by the timing marks? If so, try ignoring those and adjust the timing going strictly by the vacuum gauge. Just be sure to have the vacuum advance disconnected and plugged. Mine was running about 16 inches also when going by the marks. It now runs around 21" and seems much happier.