R. Shackleford
Active Member
This brings me to my confusion. Something is preventing the vacuum on the non ported line during idle.
1965 Belvedere II 318 poly tuning
- Thread starter R. Shackleford
- Start date
Geoff 2
Well-Known Member
The man vac port will be the lower one on the carb body. Nothing to do with the brand of carb either, Holley or Carter [ Carter is better ]. A little known fact is that the engine can need as much as 50* of idle timing with big cams, & anywhere in between. The simplest/best way to do this is by using vac adv connected to man vac adv [ MVA ].
The 264 cam with 9:1 CR is probably going to need 25-30* of idle timing for best idle/highest vacuum/best tip-in performance.
You can test this easily in 5 min: engine warmed up, VA disconnected, idling, in gear if auto, turn dist SLOWLY CCW. Keep going until you get the highest rpm. Now see what the timing is.
Report back with results.
The 264 cam with 9:1 CR is probably going to need 25-30* of idle timing for best idle/highest vacuum/best tip-in performance.
You can test this easily in 5 min: engine warmed up, VA disconnected, idling, in gear if auto, turn dist SLOWLY CCW. Keep going until you get the highest rpm. Now see what the timing is.
Report back with results.
I should have the diistributor parts for you. PM me what you need.
R. Shackleford
Active Member
Thank you for all the info and I will definitely head this direction.... However my question still remains as to why the ported and non ported vacuum ports on my carb do the exact same thing. Manifold should show vacuum at idle but theres nothing until I open the carb and if thats not working properly is there something wrong with it. I've always been a Holley guy and this is my first Carter so don't know if this is a known issue or an isolated case.
R. Shackleford
Active Member
These are the 2 vacuum ports I'm talking about. On mine they both act the same way which doesn't seem right to me.
71Beeper
Well-Known Member
- Local time
- 8:50 AM
- Joined
- Nov 28, 2010
- Messages
- 1,149
- Reaction score
- 1,816
- Location
- Stoney Creek, Ontario
I wonder if your metering rods are lifting high enough that it's dipping slightly into the main circuit thus pulling some vacuum into the ported circuit nipple?
moparx
Well-Known Member
one needs to run as much initial as can be tolerated by the engine, then limit the mechanical weight slots so there is not too much advance that pinging/detonation occurs.
then tailor the vacuum advance curve to get the maximum advance possible under cruise conditions [very light load] as possible.
E-booger did an excellent article on this very subject in Mopar Action magazine many years ago, and if one follows his suggestions, quite an improvement in engine performance can be obtained.
i really recommend one read this article if possible.
just my opinion. [and i'm old, so don't beat me too hard !]
your mileage will vary.
then tailor the vacuum advance curve to get the maximum advance possible under cruise conditions [very light load] as possible.
E-booger did an excellent article on this very subject in Mopar Action magazine many years ago, and if one follows his suggestions, quite an improvement in engine performance can be obtained.
i really recommend one read this article if possible.
just my opinion. [and i'm old, so don't beat me too hard !]
your mileage will vary.
Now we're gettin somewhereone needs to run as much initial as can be tolerated by the engine, then limit the mechanical weight slots so there is not too much advance that pinging/detonation occurs.
then tailor the vacuum advance curve to get the maximum advance possible under cruise conditions [very light load] as possible.
E-booger did an excellent article on this very subject in Mopar Action magazine many years ago, and if one follows his suggestions, quite an improvement in engine performance can be obtained.
i really recommend one read this article if possible.
just my opinion. [and i'm old, so don't beat me too hard !]
your mileage will vary.
Geoff 2
Well-Known Member
Post #26.
If both ports act the same [ & you have them correctly marked ], it is most likely that the pri t/blades are open too far, exposing the P port to vacuum at idle.
The carb needs to be removed & the T slot position checked. Should not be more than 0.060" at idle, & I am expecting it will be more than this.
Until you get this relationship [ the amount of T slot showing below the blades at idle ] correct, you will never get the carb/ign tuned properly. Ideal amount of T slot showing is 040-020, & 020 is better.
If both ports act the same [ & you have them correctly marked ], it is most likely that the pri t/blades are open too far, exposing the P port to vacuum at idle.
The carb needs to be removed & the T slot position checked. Should not be more than 0.060" at idle, & I am expecting it will be more than this.
Until you get this relationship [ the amount of T slot showing below the blades at idle ] correct, you will never get the carb/ign tuned properly. Ideal amount of T slot showing is 040-020, & 020 is better.
R. Shackleford
Active Member
Thank you for the advice however I am not getting any vacuum at idle from either port. I did a little internet digging and from what I heard the manifold vacuum port on the "competition" series carter carbs that line is blocked off and to use a drill bit and ream it out. I'm all about doin crafty modifications to parts but don't want to do anything to make the issue worse.
Geoff 2
Well-Known Member
To make matters worse....there are two lots of 'Competition Series' AFB carbs. There is the later #963X for GM, Ford & Chrys.....& the original #4758-4762 carbs. There should be no reason for these vacuum ports to be blocked...unless purposely blocked by someone.
R. Shackleford
Active Member
Thank you very much
Similar threads
