3.0 Distributor for carbs

justinp71 · 05-12-2008, 10:01 PM

Ok Contiplating a carb conversion on my '81 sc motor with dc19 cams.

If I understand correctly I need to re-curve my 81 distributor or I can buy a '78-'79 distributor and leave it stock???

Also, why is everyone getting rid of the vacuum on the distributors? Most older v-8 cars you want the vacuum on the distributor to give you better part throttle acceleration and more mpg. Does the Porsche distributor work differently?

And finally does anyone have a good contact to re-curve the distributor?

Steve@Rennsport · 05-12-2008, 11:34 PM

Justin,

A few things,......

SC distributors were set up and configured for emissions, not performance. While the early ones were a little better, both '78-'79 & '80-'83 ones should be recurved for best performance.

These are all somewhat limited in range but they can be improved and I do recurve all of these motors that receive carburetor conversions.

You can retain a functional vacuum advance but it requires that all branches of the manifold be tapped and plumbed into a vacuum reserviour for this to work. Remember, V-8 engines are different, they usually have a single, common-plenum manifold (dual or single plane) that provides sufficient vacuum for the distributor as well as power brakes,...

justinp71 · 05-13-2008, 06:33 AM

Ok thanks for the info steve, I guess that the vacuum advance doesn't help as much on porsche b/c you are normally revving them higher and into the full advance spectrum.

I have seen the vacuum advance on some car make a big difference in mpg and streetability... It would be a nice experiment, but not maybe on a good set of carbs.

RoninLB · 05-13-2008, 07:19 AM

to me the traditional vacuum advance works only by advancing spark at cruise a few degrees when engine is not pulling.

justinp71 · 05-13-2008, 08:44 AM

Believe me I know that Porsche is a completly different animal, but I've seen alot of cars get about 14-17 degrees advance from the vacuum on the dizzy.

I've seen cars go from a stinky exhaust and gas thirsty to burning cleaner and more efficient for the street.

I would have to say it is probably not worth it on a carbed Porsche otherwise people would be doing it. But I bet it would give you 10% or more mpg for freeway cruising, I mean for a cleaner burn to happen internally inside the engine you must have a more complete combustion...