DuraSpark Conversion Confusion

[I66coupe]

I have a '66 200, stock. I am planning to do the DuraSparkII conversion.

I am confused about the vacuum supply to the DuraSpark distributor. As I understand things, the SCV in my 1100 will deliver too much vacuum and so the advance will come in too soon and too far.

So, how do I supply proper vacuum to the DSII while retaining my SCV carb?

 

[Lazy JW]

Manifold vacuum

 

[CZLN6]

Howdy Rande:

You might understand the differences better if you were to read the stickie at the top of this forum- both on the SCV and on the Load-a-Matic distributor function.

The DS II is designed for a carb with a ported vacuum source. JW's suggestion of using manifold vacuum will work to some extent, but not as designed. The only real correct solution is to adapt a carb with a ported vacuum port.

If you want to stick with a stock appearing, carb, linkage, fuel lines, and air filter your only choice is the Autolite 1100s from '67 and '68. They have not SCV and do have a ported vacuum source. They are also down on CFM- from 185 to 150. Another option is the 1101 Autolite carb from a '69 Mustang 250. it will require flairing out the carb hole to match the larger throttle bore. all else will be the same as the 1100.

Adios, David

 

[mugsy]

Actually the SCV send only 5 in. Hg to the dizzy I think. A stock dual advance dizzy can take more than that. So using the original carb would acutally result in less vacuum which means less advance. And finally, the SCV send an increasing level of vacuum (my shop manual states that the carb can select which vac is greater between the manifold and venturi and sends that to the dizzy) while the ported source will increase then decrease as the throttle blade is open.

Bottom line, the SCV carb should only be used with the LOM dizzy.

tanx,
Mugsy 8)

 

[jamyers]

I'm running straight manifold vacuum to my DS dizzy, and it runs like a champ. I put a "T" in the PCV tap and draw from there.

(I like manifold vacuum on all my old engines)

 

[kspageddie]

I am running manifold vacuum for my DII as well. Runs fine for me. If you use manifold vacuum it will adv the dist. at idle. You will just have to lower your idle screw at the carb.