vacum secondaries question
Thread Starter
Racer
Joined: May 2001
Posts: 418
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vacum secondaries question
Should my secondaries open up if,
a) engine is warm, choke is off
b) air cleaner is off
c) car is sitting in neutral, in garage
d) when the gas pedal is punched from idle to 3000 rpm
new 502, new Holley 850dp, vacum secondries.
I was in the garage with these conditions and secondaries did not even move.
a) engine is warm, choke is off
b) air cleaner is off
c) car is sitting in neutral, in garage
d) when the gas pedal is punched from idle to 3000 rpm
new 502, new Holley 850dp, vacum secondries.
I was in the garage with these conditions and secondaries did not even move.
Tech Contributor
Joined: Aug 1999
Posts: 14,370
Likes: 6,364
From: At my Bar drinking and wrenching in Lafayette Colorado
Re: vacum secondaries question (2nspire)
No. It is virtually impossible to get the secondaries to crack open on a Holley Vac Sec carb by "winging" the throttle in neutral. The secondaries are pulled open only when mass airflow through the primaries exceeds a preset limit. You cannot flow enough air mass through the primary side with the car in neutral without grossly over-revving it.
If you want to see if the secondaries are opening, and how much, you can take a weak paper clip and clip it onto the rod that connects the diaphragm to the secondary throttle shaft lever on the passenger side. Slide the paper clip all the way up against the bottom of the diaphragm housing. Now, take the car out and give it a good, wide open throttle (WOT) run at least through second gear. Then take a look at the paper clip (after you pull over and stop...). If it has moved down on the shaft, the secondaries were open by that amount during your WOT blast.
If you want to see if the secondaries are opening, and how much, you can take a weak paper clip and clip it onto the rod that connects the diaphragm to the secondary throttle shaft lever on the passenger side. Slide the paper clip all the way up against the bottom of the diaphragm housing. Now, take the car out and give it a good, wide open throttle (WOT) run at least through second gear. Then take a look at the paper clip (after you pull over and stop...). If it has moved down on the shaft, the secondaries were open by that amount during your WOT blast.
Thread Starter
Racer
Joined: May 2001
Posts: 418
Likes: 0
Re: vacum secondaries question (lars)
Thanks for the replies.
I'll try do that paperclip test but it'll have to wait for a couple of days.
Thanks again all.
Should the secondary butterflies open so they get to be staight up and down or how far should they open?
I'll try do that paperclip test but it'll have to wait for a couple of days.
Thanks again all.
Should the secondary butterflies open so they get to be staight up and down or how far should they open?
Le Mans Master
Joined: Mar 1999
Posts: 6,744
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From: delmont pa
Cruise-In I Veteran
Cruise-In II Veteran
Re: vacum secondaries question (2nspire)
the secondary linkage have a wide open stop on the base plate,just put a small amount of grease at this spot and look after a full throttle run for a mark in the grease.
Team Owner
Joined: May 2001
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From: Exiled to Richmond, VA - Finally sold my house in Murfreesboro, TN ?? Corner of "Bumf*&k and 'You've got a purdy mouth'."
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St. Jude Donor '06-'10, '13
Re: vacum secondaries question (2nspire)
Should the secondary butterflies open so they get to be staight up and down or how far should they open?
Just my assumption......
