.

Jump to content


Hello, Allpar Forums member or visitor! If you were an active member (more than two posts) or subscriber, you would not see this ad!

Register for a free account or Sign in (see top right of page for Facebook/Open ID login icons).


Photo
- - - - -

Vacuum Diagram 318


This topic has been archived. This means that you cannot reply to this topic.
5 replies to this topic

#1 jaguarxj88

jaguarxj88

    318 V8 rocks!!!

  • Inactive
  • 1,669 posts

Posted July 21, 2006 at 11:10 am

Hello. I have three ports on my 1969 Carter BBD for a 318 for vacuum hoses.

One have to go to the choke diaphragm

The second has to go to the PCV valve

And the third has to go to the exhaust manifold.

But my car originally came with a vacuum advance distributor

But some people here at Allpar told me there should not be any vacuum present at idle to the vacuum advance canister, so I have to take a hose that is connected under the throttle valve, this way there won't be any vacuum

But only the PCV valve hose is connected under the throttle valve.

The previous owner, or at least, my car came with the vacuum advance connected to a T-fitting in the hose that connects frop above the throttle valve to the choke diaphragm

Supposed the previous owner (he's dead now, I can't ask him :( ) screwed my vacuum diagram, can someone tell me exactly what to connect where?

as soon as I plug back my vacuum advance hose, the ignition timing goes from 4 BTDC to... 12-13 BTDC... at idle in neutral.....

Thank you!

#2 68RT

68RT
  • Active Member
  • 4,701 posts

Posted July 21, 2006 at 01:14 pm

On many older cars, you had to disconnect the vacuum line and plug it to set the timing as they were open at all times. The hose to the choke unloader diaphram MUST have vacuum at all times as it partially opens the choke as soon as the engine fires up. The PCV valve is always below the throttle plates as it too must work at all times. The vacuum advance on the distributor is the only one that above or below was optional depending upon the manufacturer. The reason for the vacuum advance is that the engine can use additional advance during light engine loads to run better and enhance fuel mileage. It cannot be there when the engine is under full load or the engine will be damaged. In either case (hose above or below the throttle plate), when you step on the throttle the vacuum drops and the distributor retards back to the mechanical advance system only. If the car runs fine with the advance on at idle, so be it. If not, then you need to find a port that is just above the throttle plate. It will still be located in the base area of the carb.

#3 Bob Lincoln

Bob Lincoln

    "CHECK FAULT CODES"

  • Supporters (L2)
  • Others:Forum Leader
  • 25,779 posts

Posted July 21, 2006 at 01:47 pm

Unless I goofed, I believe I told you (or should have) that there should be NO vacuum at idle to the distributor. So the vacuum advance for the distributor should be hooked up to a port ABOVE the throttle plate, not below it. This will block vacuum at idle and give it vacuum above idle, as it should be. No car I know of should have vacuum to the timing advance at idle.

#4 Webslinger60

Webslinger60
  • Inactive
  • 990 posts

Posted July 21, 2006 at 05:45 pm

Any vacuum fittings below the throttle plate, regardless of diameter are full-on at idle, and decrease with engine speed, and load. (You can actually tap-off just one PCV fitting using plastic "tees" and run all your vacuum accessories if you had to). There are TWO exceptions the Distributor and the EGR valve, you cannot run these off of manifold vacuum. Thats why for the dist & EGR we use vacuum fittings above the throttle plate, because those work just the opposete (very little vacuum at idle, but increases with RPMs).

Is the BBD you're using original?
An older-style BBD designed for cars with vacuum advance distributors will always have a small-diameter nipple-fitting on the right side about halfway up the throat of the right barrel. This is for the distributor.
Unless it's broken-off it should be obvious. Look again.

If for some reason you have a BBD designed for a Lean Burn System, then it will NOT have a distributor port. However some models had another fitting above the throttle plate, used for the EGR or Canister purge. These were sometimes located at the rear of the carb. You can probably tap into one of those lines with a plastic "tee" to run the distributor.

If you have no fitting, or it's broken-off, take it to a carb shop, they can re-install, or tap & affix a distributor nipple for you. This is something you dont want to do yourself, cause the fitting may fall-out, leaving a vacuum leak and no active advance.

#5 68RT

68RT
  • Active Member
  • 4,701 posts

Posted July 21, 2006 at 10:58 pm

According to the manual I looked up. You should have a fitting on your carb that is on the right hand side about choke diaphram height and slightly forward of the choke shaft. There should be a round boss that it comes out from. AND it is taken above the throttle plates on yours.

#6 jaguarxj88

jaguarxj88

    318 V8 rocks!!!

  • Inactive
  • 1,669 posts

Posted July 22, 2006 at 10:05 am

According to the manual I looked up. You should have a fitting on your carb that is on the right hand side about choke diaphram height and slightly forward of the choke shaft. There should be a round boss that it comes out from. AND it is taken above the throttle plates on yours.

really? I will take a look at this. I had the confirmation my vacuum hoses setting were not original: the previous owner is the one that put a T-fitting at the choke hose, but when I rebuilded the carb, I just still tought it was original. Actually, his son is still alive and I called him. But he never knew why his dad did this!

Thanks a lot guys for your helpful help :)

Edited by jaguarxj88, July 22, 2006 at 10:06 am.



.
Allpar

Home · Cars · Engines · Repairs · Tool and Car Reviews · News

Please read the terms of use and privacy policy. We are not affiliated with Chrysler Group, makers of cars, minivans, trucks, and Mopar (TM) parts. We make no guarantees regarding validity or applicability of information, opinions, or advice. Posts may be edited and used in other parts of allpar.com and affiliated car-related sites. We have the right to remove or modify any message, and to ban or suspend any user without notice. Logos and site-specific information copyright © 2001-2014 Allpar LLC; Chrysler PR materials remain property of Chrysler Group.