DSII vacuum hookup

[Mercury Mike]

If I'm still usin' the holley 1940 scv carb with my DSII setup where should I hook the vacuum up to? I've still got it running to the ported source but I think it's supposed to run at full manifold, right?

 

[Bort62]

Manifold.

 

[jamyers]

I hooked mine to the manifold right below the carb, and plugged the SCV outlet on the carb. Works great!

 

[FalconSedanDelivery]

Manifold Vacuum at first glance would seem to be the way but it usually causes a hesitation on intial aceleration, and then too much when under Part throttle , Most factory setups ARE of a Ported source , still unless you recurve your dist ( and light springs do not a recurve make ) experiment to see what works best for you,

 

[66 Fastback]

Most factory setups ARE of a Ported source

That's true in the emission era. But before they started tuning carbs to reduce emission, the cars were using manifold vacuum. Ported source was not used to enhance drivability and performance. But emissions era distributors that used ported vacuum are often curved differently than pre-emission distributors the used manifold vac. Mixing one with the other can sometimes cause problems.
Doug

 

[fordconvert]

Some of the emissions cars had a thermal switch that would change between ported and manifold depending on coolant temp.

 

[FalconSedanDelivery]

Most factory setups ARE of a Ported source

That's true in the emission era. But before they started tuning carbs to reduce emission, the cars were using manifold vacuum. Ported source was not used to enhance drivability and performance. But emissions era distributors that used ported vacuum are often curved differently than pre-emission distributors the used manifold vac. Mixing one with the other can sometimes cause problems.
Doug

Ive been Rebuilding and Recurving Distributors since 1976 , longer than most on this forum have been driving , I am a Regular on Ford FE.com where I gladly givin advice and recurved over 100 of their Dist's, with nothing but great feedback , here in 6cyl land I am running up against a click , no matter I will just watch . and smile , and ocasionally hear something intersting and enlightining ( other than repeated qotes from repair books )I was hoping to meet open minds ( and I am sure there are some here ) but for now and the percievable future I will not post.

 

[wsa111]

Faron, not everyone on this forum is aware of the difference in distributor requirments.
There is a big difference in vacuum advance & mechanical advance requirements depending on the camshaft & many other variables.
I like you have probably driven most past daily drivers with high compression & a non stock camshaft.
What that requires is an advance curve to have the mechanical advance by 2500-2800 rpms. Vacuum advance was controlled by full manifold vacuum & the amount varies with the application.
However if you have a very mild camshaft or a stock one, ported vacuum might benifit you. If you have a mild engine too much vacuum advance at idle will cause the engine too flutter because of too much vacuum advance.
I understand what you are saying, but many members of the forum need to get professional advice for proper advice on distributor advance class 101.
This forum needs your experience & professional help on this & many questions in other areas.
Experience is paramount, Bill

 

[FalconSedanDelivery]

And enjoyed our chat a few weeks back , but for now I still perfer to remain in the background , perhaps I will feel different givin some time , untill then thank you , Faron

 

[wallaka]

And enjoyed our chat a few weeks back , but for now I still perfer to remain in the background , perhaps I will feel different givin some time , untill then thank you , Faron

Thanks for your participation in the forum.

I guess the problem is trying to figure out who to listen to...random guy #20 is more trustworthy than random guy #21 because of why? It is especially difficult when the subject isn't fully understood by the questioner. I don't think that contrary opinions are a slam against you, but is that "random guy" principle at work. It is all too easy to get frustrated because people won't listen. It happens to all of us.

I, for one, enjoy hearing the thoughts of someone with experience in whatever field is brought up. For my part, I have no problem with refuting things I know to be false or misleading, no matter the subject. Your initial comments that I saw were a bit brisque, and that may have been where a bit of indignation from some members came in. For my part, I hope you stick around.

 

[Bort62]

It doesn't take a genius to understand how a distributor works, and it doesnt take 32 years of curving them, either.

But, what is difficult - is understanding what your particular combination will benefit most from. Once you have that under control, getting your distributor to give it to you is fairly straightforward (altho having the right tools makes it easier.)

Of the cuff, IMO, manifold vac gives you a better result w/ a stock curved DSII. It gives you full advance at idle, which helps a smooth idle as well as lower temperatures. Advance falls w/ load, as you would want, to prevent detonation (altho, naturally, it rises w/ RPM as a product of the mechanical advance)

The only real difference between manifold and ported vac advance is that you get the manifold advance at idle... which, IMO, is a good thing.

At WOT, they are both the same anyway - 0... and I know the only part of the performance curve I care about on my car is WOT anyways

 

[Mercury Mike]

I drive this car with a pretty light foot just because I drive it every day, all day, everywhere. I want a smoother idle and better performance from light to mid throttle. Manifold, then? =)

 

[Bort62]

I would suggest manifold then.

 

[jamyers]

It doesn't take a genius to understand how a distributor works, and it doesnt take 32 years of curving them, either.
...
The only real difference between manifold and ported vac advance is that you get the manifold advance at idle... which, IMO, is a good thing.

Dead on, both counts.

The only reason GM used ported vacuum advance was to retard the timing at idle to increase combustion temps to reduce emissions. That is all. Once the carb opens up beyond idle, the vacuum signals are identical.