Modifying the SCV to produce ported vac signal?

[wallaka]

We disabled the load o matic by putting a spring on the valve as we screwed it in making it not operational. The vacuum for the distributor is pulled off the port on the carb just like when it was stock. We are running the stock 1967 Califonia distributor with a pertronix. 1967 200ci California cars did not have the load o matic and had a smaller carb.

So if I'm reading this right I can just put a spring in the SCV to make it operate like a ported vacuum source? It seems so simple...anybody else have any experience with this? I want to get a DS2 and don't want to switch carbs (mine runs perfectly).

 

[Jett's_Pony]

Think of it as keeping The scv valve from operating. There are two sources of vacuum to the valve. When there is enough vacuum to pull the plunger the valve seals off the source of vacuum that all the later model distributors need and give to much advance. Just put something between the operating plunger on the valve and the carb body when you screw it in to defeat the valve. I had a spring that fit over the end of our valve, cut it to fit, and it seems to work fine.
If I am wrong someone correct me.
Greg

 

[wallaka]

It makes sense to me.

 

[fordconvert]

For what its worth:

Im running a rebuilt DSII from Napa for a 78 fairmount with a blaster2 coil and HEI module, stock plugs at 45. I have no idea what the total advance is because I dont have an advance light. Base is around 12. Im guessing its around 18 at idle on manifold vac. It seems to run overall better hooked to manifold vac. It ran fine on the 1100's port but the idle was better on the manifold. My engine and exhaust is stock and I have not had the car that long. The performance seems simalar to the points except there is much more range in the idle. My timing method: max vac and rpm at idle then retard till it didnt have signs of pinging. I never looked at the weights in the dizzy.

 

[nachoman]

I just went through this. You need to plug the vacuum source in the venturi of the carb. The valve seems to operate in reverse logic - when the vavle is closed (the way it would be if you glued it shut), the vacuum source is the venturi. It only gets the ported vacuum source if the valve is open (extended). When the manifold vacuum source is high (the ported source just above the throttle plate), the valve opens and allows this vacuum source to operate the advance. If the ported vacuum source goes to low vacuum at WOT, the valve closes and allows only venturi vacuum. post 1967 distributors need the ported source, not the venturi source. Sticking the valve in its closed position will allow only venturi vacuum - what you don't want. I plugged the tiny hole in the venturi with a dab of JB weld. I then gutted the SCV so that it is always a through-flow. This may be unecessary.

kevin