Hemi motor vacuum advance

[AR67GTX]

What are most Hemi stock engine owners doing with their vacuum advance, running it ported, running it on a manifold vacuum source, or plugging it off?

It looks like stock must have been ported and connected to the back of one of the carbs. It looks like there are some low ports on the right front of the carb that are probably manifold vacuum if the bolt is removed and a threaded nipple installed. I normally like to run full time vacuum advance to smooth out and strengthen the idle and help the engine run a little cooler. But I have the distributor set up with an FBO mechanical advance limiter plate in order to increase initial timing so it may not matter much. Running manifold advance on my 440 has been working well.

 

[Fran Blacker]

There should be fitting on passengers side front of carb near idle screw.

 

[Fran Blacker]

In the second picture you can see fitting on rear carb. https://www.ebay.com/itm/194479132515?hash=item2d47dc0f63:g:0HcAAOSw~JRayWPq

 

[AR67GTX]

That is plugged with what looks like a manufacturers bolt on my 66 carbs. That’s the one I said I would need to find a treaded vacuum nipple to use. So Fran, it sounds like your car is hooked up and running on manifold vacuum that pulls in advance at idle?

 

[AR67GTX]

Fran, not my car but

if you can zoom in on this front carb, both of mine have the front, right vacuum port pugged by a bolt. Guess I need to remove a bolt and see if I can find a threaded port that fits

 

[Fran Blacker]

Stock they run the vacuum advance. They tap manifold at the carb. You can run without vacuum advance, did that when I had xram on my Satellite. Whether to run vacuum has debated, guys said better drivability . Think another was gas washing cylinders without vacuum, not positive.

 

[RJRENTON]

IMO....
As the primary carb is the REAR carb, the ported vacuum advance connection should be connected to this carb. As to which vacuum source to use is open to serious debate: ported source -vs- manifold source. Without any serious engine modifications (cam, compression ratio or ignition system), the OEM source was the rear carb, ported vacuum source. Not saying that this way was is "best" or the only way. Experimentation is the alternative as everything can be "improved upon", as the factory settings were for a large percentage of the population. The "best way" can be defined as what ever works for you or what ever you (the owner) thinks as best. Just my opinion of course.
BOB RENTON

 

[AR67GTX]

Thanks Bob - that would seem to match or confirm my observation they must have run ported advance stock off of the rear port of the rear (primary) carb. I guess if I want to experiment with full vacuum advance I’ll need to open up the front port.

 

[64BEL]

Mine is coming off the primary (rear) carb on the passenger side.

Edit: I found a good pic.

 

[AR67GTX]

Mine is coming off the primary (rear) carb on the passenger side.

Any chance you have a picture of it? Does the nipple look pressed in, or threaded in?

 

[64BEL]

Here's a pic of it on the bench while I was rebuilding them. It's threaded.

 

[Fran Blacker]

This the piece it was on a 4140s I sold.

 

[AR67GTX]

That’s exactly what I was figuring. Now if I can find one of those. My carb may have had one at one time but it had a non-vacuum advance distributor in it when I bought it and they may have plugged off the port with a threaded plug.

thanks

This looks promising - need to check size.
https://www.summitracing.com/parts/...MI2pS-pq2L9AIVESM4Ch1WbwfCEAQYDSABEgIS6fD_BwE

Thanks

 

[gtx6970]

Mine is coming off the primary (rear) carb on the passenger side.

Edit: I found a good pic.

View attachment 1190956

Same as mine

 

[gtx6970]

If i had to guess,,
I would say 1/8" NPT

 

[AR67GTX]

That’s what I’m thinking too. Looks like Summit has it.

 

[gtx6970]

https://www.mcmaster.com/pipe-tubin...ssure-barbed-tube-fittings-for-air-and-water/



https://www.mcmaster.com/pipe-tubin...ssure-barbed-tube-fittings-for-air-and-water/


https://www.mcmaster.com/tube-fittings/pipe-size~1-8/thread-type~npt/pipe-size~1-16/