Need Distributor Specifications

[AR67GTX]

You don’t count vacuum. Its in and out, it’s transitional, it’s dependent on too many things (cam, engine throttle, acceleration, closed throttle). Total timing usually referenced in terms of initial and centrifugal only.

My 67 will only tolerate about 33 - 34 degrees without pinging. But it has 68 heads on it - might make a little difference.

 

[Dragon Slayer]

You don’t count vacuum. Its in and out, it’s transitional, it’s dependent on too many things (cam, engine throttle, acceleration, closed throttle). Total timing usually referenced in terms of initial and centrifugal only.

My 67 will only tolerate about 33 - 34 degrees without pinging. But it has 68 heads on it - might make a little difference.

Since vacuum is one with your set up i would disconnect it plug port on carbs and set initial at 2. Plug distributor back to port and read initial. That will tell you what vacuum is being added at idle

 

[67 GTX]

Since vacuum is one with your set up i would disconnect it plug port on carbs and set initial at 2. Plug distributor back to port and read initial. That will tell you what vacuum is being added at idle

I can try that at specifically 2, but last month (back on page 1), with my initial set at 12.5 without vacuum, there was no change to timing when connected the vacuum advance.

 

[67 GTX]

You don’t count vacuum. Its in and out, it’s transitional, it’s dependent on too many things (cam, engine throttle, acceleration, closed throttle). Total timing usually referenced in terms of initial and centrifugal only.

My 67 will only tolerate about 33 - 34 degrees without pinging. But it has 68 heads on it - might make a little difference.

What type of vacuum do you run, if you do? Manifold or ported?

 

[AR67GTX]

On my 66 Hemi it’s run to ported as that is all I have - no other ports on the manifold or carbs to connect to.

I was running manifold vacuum advance off of an 800 Edelbrock AFB-type carb on my 67 GTX. But, I had a correct 67 Carter AFB 4327 restored and I installed it last spring and again hooked it up to manifold advance. I do this by “T” into the choke pull off vacuum hose which comes off a low port on the right side.

I have a long history with a BB 66 Corvette and the Corvette forums. In the Corvette and the Chevy world in general, few people consider running ported vacuum advance - virtually everyone converts over to manifold to help engine cooling and street performance - in contradiction to the Mopar world. Mopar guys in general remain in favor of ported advance to a considerable degree. But I remain a proponent to manifold vacuum advance when possible for the engine cooling, it smooths out the idle, and it seems to help throttle response off idle. Both systems help fuel economy on the highway but who keeps track of their mpg in these things anyway.

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[67 GTX]

On my 66 Hemi it’s run to ported as that is all I have - no other ports on the manifold or carbs to connect to.

I was running manifold vacuum advance off of an 800 Edelbrock AFB-type carb on my 67 GTX. But, I had a correct 67 Carter AFB 4327 restored and I installed it last spring and again hooked it up to manifold advance. I do this by “T” into the choke pull off vacuum hose which comes off a low port on the right side.

I have a long history with a BB 66 Corvette and the Corvette forums. In the Corvette and the Chevy world in general, few people consider running ported vacuum advance - virtually everyone converts over to manifold to help engine cooling and street performance - in contradiction to the Mopar world. Mopar guys in general remain in favor of ported advance to a considerable degree. But I remain a proponent to manifold vacuum advance when possible for the engine cooling, it smooths out the idle, and it seems to help throttle response off idle. Both systems help fuel economy on the highway but who keeps track of their mpg in these things anyway.

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Beautiful engine!
Thank you for that detailed explanation. I was wondering how you ran manifold vacuum with the original setup. Very interesting.

 

[Dragon Slayer]

Mopar makes a variety of fittings for the rear of the manifold that operates power booster and such. The AC some with multiple fitting you can change that and have a port for distributor. Your just adding a lot of extra initial timing.

 

[67 GTX]

I was running manifold vacuum advance off of an 800 Edelbrock AFB-type carb on my 67 GTX. But, I had a correct 67 Carter AFB 4327 restored and I installed it last spring and again hooked it up to manifold advance. I do this by “T” into the choke pull off vacuum hose which comes off a low port on the right side.

I was thinking about this today. Wouldn’t that choke pull off port have to be carb vacuum? If it’s manifold vacuum and that drops off, wouldn’t the choke flap bounce back and forth after the choke spring loses tension?
Don’t you need a constant vacuum on the pull off diaphragm to keep pulling the plate open?

 

[AR67GTX]

The choke pull off is primarily to index the choke correctly once the car initially fires, to give it enough air to maintain the fast idle. Once the manifold heats up, the thermostatic coil takes over and opens the choke up the rest of the way and and holds it open. The slotted linkage on the rod connection to the vacuum pull off prevents it from having any more influence even If the vacuum falls out on acceleration.

 

[67 GTX]

No unless the points are wrong, or the cam on point arm worn. You should not have vacuum at idle. If you do you are on the transition slot and blades open more than stock exposing the timed vacuum port. So you would have to factor that into your initial timing.

Do you have the correct PN for the points for this distributor?
I believe I have the correct dual points, but they are different than single points correct? As in you can't use two single points in a dual pt. distributor?

Are there any measurements of the rubbing block?
My points are new.

So if the points are ok and my cam is ok as well, any idea what would account for the low dwell?

 

[67 GTX]

The choke pull off is primarily to index the choke correctly once the car initially fires, to give it enough air to maintain the fast idle. Once the manifold heats up, the thermostatic coil takes over and opens the choke up the rest of the way and and holds it open. The slotted linkage on the rod connection to the vacuum pull off prevents it from having any more influence even If the vacuum falls out on acceleration.

Thank you. I was thinking the diaphragm was responsible for opening the flap.

 

[Dragon Slayer]

2421173 CH-8V. Don't know why your dwell is so low. Maybe a faulty wire/connection to the coil and it goes open.

 

[AR67GTX]

I just noted in my post 30 above I said my vacuum advance was hooked to ported vacuum. That’s incorrect and it’s hooked up to manifold vacuum as I showed in 45 above. Guess I was thinking about the Hemi dual point.

What are you measuring dwell with? I know with my Innovia timing light/ meter I have to set it to the correct # of engine cylinders. Could yours be set on something other than 8? Do you have another meter you can check the dwell with. Some auto multi-meters will measure engine dwell and rpm too.

 

[RJRENTON]

Beautiful engine!
Thank you for that detailed explanation. I was wondering how you ran manifold vacuum with the original setup. Very interesting.

Out of curiosity, perhaps you could have put a "Tee" fitting in the vacuum pulloff source, that way you could have the manifold vacuum to the distributor AND the choke pull off would be functional.....if you want/need the vacuum source to be manifold supplied. Just talking out loud....
BOB RENTON

 

[AR67GTX]

Yes, that’s what I’ve done on a couple of cars. I described it above in #45.

 

[67 GTX]

What are you measuring dwell with? I know with my Innovia timing light/ meter I have to set it to the correct # of engine cylinders. Could yours be set on something other than 8? Do you have another meter you can check the dwell with. Some auto multi-meters will measure engine dwell and rpm too.

I have a meter that I'm using. It can also measure rpms, among other things. I tried another meter, which I believe is faulty.
I will try again with another meter and see if it matches the main meter that I've been using.

 

[67 GTX]

2421173 CH-8V. Don't know why your dwell is so low. Maybe a faulty wire/connection to the coil and it goes open.

Thank you. I'll double check what I have to that.

And in terms of the connection, anything is possible at this point.