Vacuum Secondary Question
Thread Starter
Racer
Joined: Jan 2012
Posts: 422
Likes: 28
From: Collinsville IL
Vacuum Secondary Question
I am in the process of installing a 200 4r transmission in my 79 Corvette. I am currently running a Holley 650 with vacuum secondaries. My question is will the 4th gear and drop in the rpms have an effect on the secondary spring? I guess I am asking if the drop in rpms will drop the amount of vacuum produced causing me to need a different secondary spring? I look forward to any input the C3 experts may have. Thanks again.
Drifting
Joined: Aug 2005
Posts: 1,682
Likes: 3
From: League City TX
Changing the transmission is not going to change your spring requirements.
The secondaries open when there is sufficient airflow through the primary venturis to create enough vacuum to compress the diaphragm spring.
So if you're in the throttle hard, they will still open up just like they always have.
When your just cruising they wont open, but they never did before either.
The secondaries open when there is sufficient airflow through the primary venturis to create enough vacuum to compress the diaphragm spring.
So if you're in the throttle hard, they will still open up just like they always have.
When your just cruising they wont open, but they never did before either.
Melting Slicks
Joined: Mar 2008
Posts: 2,989
Likes: 198
From: Meriden CT
I did that swap a year ago. I don't have a Holley, but my carb doesn't act any different than with the TH350. The vacuum secondaries will open when the motor needs them no matter what transmission is in there.
