Distributor question?

[fredlp]

Hi Guys,
I have a 68 Mustang 6 cylinder 200, I put this basket case together two years ago. Since then I’ve only gotten 16 mpg so I decided to start checking things. What I found is the distributor centrifugal advance works fine but when I hook the vacuum line to the distributor there is no further advance. I am holding the rpm between 1500 and 2000 when I am checking this. I have put vacuum gage on the distributor line and found it to be only 5-6 inches of vacuum at this rpm. What is going on, why won’t this advance further? Some other people said it was the SCV carburetor. Is there any way to correct this? I know the exhaust manifold does not have a heat port and was designed for a hand choke. I have converted to an electric choke.
Thanks,

Fred

http://i532.photobucket.com/albums/ee32 ... C01745.jpg
http://i532.photobucket.com/albums/ee32 ... 1252243509

 

[Frankenstang]

Welcome aboard. Is your engine original to your '68? I'm not positive, but I think '68 if the first year of the non-scv carbs. It looks like your carb is in fact an scv carb in the first pic...the little 6-8 sized spark control valve w/ a hole in the center (to the left of your ported vacuum connection). But your distributor does not look like an SCV dizzy (aka load-o-matic). It actually looks like a dual vacuum advance dizzy. Does it have a second connection for a vacuum line on the advance canister? If so, IIRC that dizzy needs it's main vacuum signal the one piping into the center of canister (not on top where the black hose is connnected) to come from the manifold connection, not the ported connection on the carb...I'm not 100% on that. Hopefully David/CZNL6 (the carb/dizzy matching expert) will see this post. He could help you clear this up.

 

[fredlp]

Welcome aboard. Is your engine original to your '68? I'm not positive, but I think '68 if the first year of the non-scv carbs. It looks like your carb is in fact an scv carb in the first pic...the little 6-8 sized spark control valve w/ a hole in the center (to the left of your ported vacuum connection). But your distributor does not look like an SCV dizzy (aka load-o-matic). It actually looks like a dual vacuum advance dizzy. Does it have a second connection for a vacuum line on the advance canister? If so, IIRC that dizzy needs it's main vacuum signal the one piping into the center of canister (not on top where the black hose is connnected) to come from the manifold connection, not the ported connection on the carb...I'm not 100% on that. Hopefully David/CZNL6 (the carb/dizzy matching expert) will see this post. He could help you clear this up.

The vehicle and engine were a basket case when I got them, who knows what kind of pieces I was given, it is supposed to be a 68.
The carb is a SCV design, and the plug you are looking at in the dizzy was there when I bought it, you think it should have full manifold at that port? if so I can easily run a line to it from the intake.

 

[JackFish]

Yeah I'm no expert on these, but that nipple on the cannister is for spark retard.
I think there would normally be a hard line going to the front of that dizzy.

 

[Frankenstang]

Yeah I'm no expert on these, but that nipple on the cannister is for spark retard.
I think there would normally be a hard line going to the front of that dizzy.

After looking at your picture again, it looks like you do have vacuum to the correct nipple that (if you think about it) would be in front of the vacuum canister bladder.

According to these posts, the nipple that is 'plugged' with a reddish/pink cap in your picture, some folks leave open (not plugged) or hooked it to full manifold vacuum (which I believe was the oem routing...but this is the part I'm not positive on). According to what I've read/heard you should at least remove the pink cap from the 'plugged' nipple on the canister, as it could negatively affect vacuuum advance ability. Hopefully these posts will help clear this up.

viewtopic.php?f=1&t=45787

viewtopic.php?f=10&t=57890

EDIT:

Does it have a second connection for a vacuum line on the advance canister? If so, IIRC that dizzy needs it's main vacuum signal the one piping into the center of canister (not on top where the black hose is connnected) to come from the manifold connection, not the ported connection on the carb...I'm not 100% on that.

I'm not only not 100% sure...I'm 100% wrong in this statement Sorry Fred, hope I haven't made this too confusing for you, and hopefully the other posts above will help. The main problem as I understand it, is your carb and dizzy are not a match. However, what I believe is correct is that you can get by using your main vacuum advance signal taken from the carburetor port with the secondary signal unplugged/open...I'd give that a shot. One other thing, it looks like you have a steel line at the carburetor port, but a rubber line at the advance canister. Hopefully that is just a spliced together connection, as I don't think you want the carburetor port feeding vacuum to anything other than the dizzy.

 

[CZLN6]

Howdy Fred:

And welcome to The Forum. Robert's got you pretty well up to speed on the mismatch between you SCV carb and your non-Load-O-Matic distributor. I just have a couple of FYIs and some more questions.

FYI- there are several good stickies at the top of this forum on both the function of the SCV in your Autolite 1100 carb and on the function of the Load-o-matic (Not yours) distributor. Your distributor is an upgrade over the L-o-M in that is utilized both centrifugal and vacuum advance. The down side of this distributor is that is has a vacuum advance/retard function built into it to aid in reducing emissions. It was part of a multi-part system that only worked marginally well when all parts were present and working. To get the most out of this distributor, check to make sure that the vacuum advance is working by sucking on the hose from the outside port of the vacuum cannister. A HandyVac is a useful tool for this step, but I never got around to getting one so I just suck on the line while watching the arm inside the distributor for movement. If the arm, which advances the point plate, doesn't move there is something else wrong. Either there is damage to the vacuum diaphram or something is stuck. To work, vacuum applied to the vacuum hose must activate the advance mechanism. Verify that the vacuum advance is working.

I'm also concerned about the low vacuum readings you got at a steady rpm of 1,500 and 2,000. At these engine speeds you should be getting 12 to 20 inches, depending on the condition of your engine. This is true even if you used the ported vacuum source, which would, roughly, be the same at these rpms. For a comparison you should hook the vacuum guage to a manifold vacuum source. Were there any vacuum leaks anyway in the system? Is this a manual trans or auto? Is the 16 mpg reading on in town driving, highway, or both? What do you have the initial advance set at? What is your elevation? How long does it take for your electric choke to fully open on a cold start-up?

Again, welcome to the forum. Keep the info coming. The more you give the more likely we can help.

Adios, David

 

[Lazy JW]

.....

I'm also concerned about the low vacuum readings you got at a steady rpm of 1,500 and 2,000......

I just re-read his post and I interpret him as saying the vacuum reading is coming out of the SCV and NOT manifold vacuum. I may be wrong though.
Joe

 

[CZLN6]

Howdy:

Joe- I wasn't sure either. In any case, at those rpms, that vacuum reading should be higher, even from the SCV port. For diagnosis and comparison, I recommended that he get a manifold vacuum reading as a baseline and go from there.

I'm waiting for more info from Fred.

Adios, David

 

[fredlp]

The vacuum reading I am talking about is from the SCV port, I will check the manifold vacuum later today and let you know.
Thanks Fred

 

[Lazy JW]

Dunno if that carb has a "proper" ported vacuum port; if not, I would use manifold vacuum.
Joe

 

[fredlp]

One final question, what should the vacuum reading be at the dizzy port on a SCV carb? ..at different rpm's ie 1500 and 2000 rpms.

 

[CZLN6]

Howdy Fred:

There is a sticky in that section at the top of this forum that explains the function of the SCV on vacuum. In a nut shell the SCV would show little or no vacuum at an idle, but at cruise speeds should show close to what manifold vacuum would be. That is why you will need to know both manifold vacuum and SCV readings at and idle and at cruise speeds. Keep it coming.

Adios, David

 

[Lazy JW]

..... at cruise speeds should show close to what manifold vacuum would be.....

Interesting. I wouldn't have expected venturi action to develop that much vacuum, but then I have never actually measured it in a properly running system.
Joe