Vacuum port for distributor?

[TommyK]

The only difference between manifold vacuum and ported vacuum is at idle. When hooked to ported vacuum, once the throttle blades have opened enough to expose the vacuum port, the vacuum the advance mechanism sees is the same.

Hooking a distributor hat has been set up to run on ported vacuum to manifold vacuum can cause some grief in the form of excessive advance at idle.

 

[ManniB]

Guys,

thanks for all the great help and information in this thread. I must say: as usual!!!

With your help, I managed to get the Cleveland running much better than before. I have set it to 12 degrees initial and 22 centrifugal advance which gives me a total of 34 degrees at the crankshaft. Idle is a lot more stable now and so is vacuum.

I have connected the vacuum advance to ported vacuum because with manifold vacuum, idle and vacuum became again more unstable.

Regards, Manfred

 

[c9zx]

Manni, Thanks for providing us the feedback, it is helpful to others. I'm glad you have the engine running well. Chuck

 

[will e]

Very helpful. And I learned there is a third vacuum, 'ventri' vacuum, which is used to pull the secondaries open on Vacuum operated secondaries. I always assumed this was the same as ported vacuum and did not know that ported/manifold would equal out at wot. Learn something new every day!

 

[c9zx]

Very helpful. And I learned there is a third vacuum, 'ventri' vacuum, which is used to pull the secondaries open on Vacuum operated secondaries. I always assumed this was the same as ported vacuum and did not know that ported/manifold would equal out at wot. Learn something new every day!

And then there is Chevy vacuum it doesn't do anything except _ _ _ _.

I know that is bad, I just couldn't resist. Chuck