72 vette vacuum whoa's
Thread Starter
Instructor
Joined: Dec 2002
Posts: 174
Likes: 1
From: brandon florida
72 vette vacuum whoa's
I have a 1972 corvette with a 350, i installed a
Performer RPM intake (7101) and cam (7102 hydraulic)
kit and now have trouble with vacuum. I currently am
using the stock distributor and stock vacuum advance,
in order to get the car to idle/run properly with the
car in gear (500-600rpm), it has to idle at 16-1800
rpm while in park.
With the vacuum advance hooked up and the car running
when you remove the line there is verry little change
in the way the motor runs. I have had the vacuum
advance checked and it is fine. At idle i am getting
very little vacuum pressure thus the car labors while
at idle in park and in gear, however when given some
gas the vacuum advance kicks in advancing the timing
to about 22 degrees and there is 18" of vacuum however
the car idles at 1800rpm standing still and 600rpm
while in gear. The engine performs very well while
driving however when idling the motor is racing. When
the carb (edelbrock 1405) and timing are adjusted to
counter act the problem it idles poorly and
performance is hindered until the engine gets gas and the rpm's
are increased at which time it works as it is supposed
to however once the rpms return to normal the engine
labors, vacuum seems to bleed down and there is very
little vacuum pressure. Not sure, is there a vacuum advance that you can buy that is adjustable as to the pressure required to open the diaphram? I'm open to suggestions/solutions anyone can provide!
:crazy:
:chevy
Performer RPM intake (7101) and cam (7102 hydraulic)
kit and now have trouble with vacuum. I currently am
using the stock distributor and stock vacuum advance,
in order to get the car to idle/run properly with the
car in gear (500-600rpm), it has to idle at 16-1800
rpm while in park.
With the vacuum advance hooked up and the car running
when you remove the line there is verry little change
in the way the motor runs. I have had the vacuum
advance checked and it is fine. At idle i am getting
very little vacuum pressure thus the car labors while
at idle in park and in gear, however when given some
gas the vacuum advance kicks in advancing the timing
to about 22 degrees and there is 18" of vacuum however
the car idles at 1800rpm standing still and 600rpm
while in gear. The engine performs very well while
driving however when idling the motor is racing. When
the carb (edelbrock 1405) and timing are adjusted to
counter act the problem it idles poorly and
performance is hindered until the engine gets gas and the rpm's
are increased at which time it works as it is supposed
to however once the rpms return to normal the engine
labors, vacuum seems to bleed down and there is very
little vacuum pressure. Not sure, is there a vacuum advance that you can buy that is adjustable as to the pressure required to open the diaphram? I'm open to suggestions/solutions anyone can provide!
:crazy:
:chevy
Drifting
Joined: Sep 2001
Posts: 1,427
Likes: 1
From: Boxford Mass
Re: 72 vette vacuum whoa's (1972vettman)
I'm not an expert, but could you have a minor vacuum leak in your new intake along the gasket somewhere? How bad is your vacuum at idle? A vacuum leak could cause a very rough idle.
Sounds like you have something else going on unrelated to the cvacuum advance...
Sounds like you have something else going on unrelated to the cvacuum advance...
Melting Slicks
Joined: Aug 1999
Posts: 3,123
Likes: 13
From: Hollywood, Florida
Re: 72 vette vacuum whoa's (Jack71)
I agree with Jack 71.
Please check and double check for a vacuum leak. That cam is NOT that radical. It should not cause the issues you describe.
You can use the spray carb cleaner trick. Spray it around the base of the carb, fitting, etc with the engine running to see if the idle speed changes (indicating a vacuum leak).
If you have NO vac. advance at idle, which I believe is correct for our years, you are hooked up to ported vacuum.
Good luck, and let us know what you find :cheers:
Please check and double check for a vacuum leak. That cam is NOT that radical. It should not cause the issues you describe.
You can use the spray carb cleaner trick. Spray it around the base of the carb, fitting, etc with the engine running to see if the idle speed changes (indicating a vacuum leak).
If you have NO vac. advance at idle, which I believe is correct for our years, you are hooked up to ported vacuum.
Good luck, and let us know what you find :cheers:
Team Owner
Joined: Jul 1999
Posts: 65,492
Likes: 230
From: Orange Park Florida
Re: 72 vette vacuum whoa's (shoptek)
Take s and pinch the rubber vac lines to the main cannister, the two way vacuum diode silver thingy, and the master cylinder,.....
of not that, you most assuredly have an open vacuum port on there somewhere....listen for the sucking sound using a hose to your ear....
GENE
of not that, you most assuredly have an open vacuum port on there somewhere....listen for the sucking sound using a hose to your ear....
GENE
