Chevrolet Nova Forum banner
1 - 20 of 29 Posts

·
Registered
Joined
·
18 Posts
Discussion Starter · #1 ·
On the Holley,which is the best place to hook up the vac line to the vac advance? There is a place at the bottom of the carb and one in the upper part?
 

·
Registered
Joined
·
1,197 Posts
SuperSport said:
Upper part.

my understanding is that that would be a ported connection...what you want is an unported connection and that is what the bottom one would be....you want a connection that gives you full manifold vacuum at idle and the port above the throttle plate would only give you vacuum after the throttle plates begin to open while the one below the plate would give you full vaccum when the plates are closed...like i said thats my understanding of it...I could be wrong:)
 

·
Registered
Joined
·
43 Posts
Yo, 69. I believe the lower ports are sucking on idle and the top ports suck on acceleration.
Wow, more confusuion or I am just an idiot? (I am leaving myself open to some serious smack talking if I am wrong).
 

·
Registered
Joined
·
43 Posts
Holley's website has the insrutions on there. I do not know why this site does not let me cut and paste the link here. It shows the distributor vacuum line to the top.
 

·
Registered
Joined
·
1,197 Posts
SuperSport said:
Yo, 69. I believe the lower ports are sucking on idle and the top ports suck on acceleration.
Wow, more confusuion or I am just an idiot? (I am leaving myself open to some serious smack talking if I am wrong).

thats what I said and thats what you want....you want full vacumm at idle....you will only get that from the lowest ports...so as Johnny said hook it up there...the ported vaccum is what GM and others switched too in an effort to help MPG and emissions(in the 70's sometime)....but based on the vacuum advance 101 thread at Steves it didnt work worth a damn...
 

·
Registered
Joined
·
1,197 Posts
SuperSport said:
Holley's website has the insrutions on there. I do not know why this site does not let me cut and paste the link here. It shows the distributor vacuum line to the top.

Based on ignitionman that would be wrong (if my memory is right)

Hey John...you wouldnt happen to have a copy of that doc somewhere?
 

·
Registered
Joined
·
43 Posts
Well, like I said holley is showing you to connect it on top. It was my understanding that you want vacuum on acceleration for the dist. . But, hey it's only holley's instructions I am going by.​
 
G

·
i might have it... i have the Link-Library saved in my own files... it's not up to date, but i have 99% of it. i think it's in there...


unless i deleted it when i reposted it in "Best of Tech" for Paul/Mike...

i'll look...
 

·
Registered
Joined
·
43 Posts
69NovaSS said:
the ported vaccum is what GM and others switched too in an effort to help MPG and emissions(in the 70's sometime)....but based on the vacuum advance 101 thread at Steves it didnt work worth a damn...
I'll have to check that out. Hope you can find it Johnny, I am interested in that. Let me also, add that according to Aaron at Bad Ass Racing Engines he also hooks them at the top (I have a really good carb video from them).
 

·
Registered
Joined
·
1,197 Posts
SuperSport said:
Well, like I said holley is showing you to connect it on top. It was my understanding that you want vacuum on acceleration for the dist. . But, hey it's only holley's instructions I am going by.​
Well look at it this way normally when you set the timing the vac line is disconected but then you hook up the vac line which WILL normally advance the timing EVEN at idle...and then as you accelerate the vacuum will fall off of the lower port but at the same time your mechaniical advance will take over and give your total advance...

Just set the timing normally (depending on your setting you will have 10-12 degrees advance) then hook up your vac line...now I bet you will have closer to 20 degrees of timing...and that IS with the motor idling...

To me it just seems backwards to hook it up to the upper port but hey thats JMO...I'm not Holley after all:rolleyes: :D
 

·
Registered
Joined
·
43 Posts
I am not Holley either. So, there is your answer Jr. If, you want Holley's answer = top. If, you want the these guys answer = bottom (and, in no way am I saying these guys are wrong).
I own a Holley still in the box and to be honest I will try both and see wich one my engine likes.
 

·
Registered
Joined
·
43 Posts
Thanks for posting that Johnny I will read that later. I got an appointment to catch. Thanks, for refraining from the name calling. We have a chat room for that now.
SS<--- Who will have homework to do later today.
 

·
Registered
Joined
·
1,197 Posts
thanks for the links John...very helpful;)
 
1 - 20 of 29 Posts
Top