Author Topic: 66 429 no vacuum from carburetor to vacuum advance.  (Read 3538 times)

Offline jules

  • Posts: 11
  • Name: gjules
66 429 no vacuum from carburetor to vacuum advance.
« on: February 18, 2013, 08:05:12 AM »
I have a 1966 429 and just recently had the Carter AFB rebuilt as there was no vacuum from the base of the AFB to the vacuum advance. After installing the rebuilt AFB, I still don't have any vacuum and the engine doesn't idle well at all. Tried adjusting the idle and air mixture screws with no luck. Changed out the points with a Petronix unit, new plugs and spark plug wires. The air mixture screws bottom out with no change in engine idle. Any ideas?????

Offline Dave Shepherd

  • Posts: 2422
Re: 66 429 no vacuum from carburetor to vacuum advance.
« Reply #1 on: February 18, 2013, 09:02:01 AM »
Make sure you have the proper base gasket to begin with, also are you using the ported vacuum port or manifold vacuum port.

Offline TJ Hopland

  • Posts: 10183
Re: 66 429 no vacuum from carburetor to vacuum advance.
« Reply #2 on: February 18, 2013, 09:23:18 AM »
Does that vacuum port turn on if you open the throttle?  If so it may be a 'ported' vacuum source which is a common way to connect the distributor and off at idle is normal. 

If the idle mixture screws can bottom out and don't make any difference either the carb is screwed up or the throttle blades are open too far.   Open too far seems unlikely because they would have to be really open to have it running off just the main jets.   I don't know those carbs at all so I'm just guessing but maybe there is a float or fuel pressure issue and its dumping fuel directly out the bowl?
StPaul/Mpls, MN USA

73 Eldo convert w/FiTech EFI
80 Eldo Diesel
90 CDV
And other assorted stuff I keep buying for some reason

Re: 66 429 no vacuum from carburetor to vacuum advance.
« Reply #3 on: February 18, 2013, 09:50:33 AM »
Jules,
Do you have the Stainless Steel shim installed under the carb?
The order of installation for the AFB, starting from the intake manifold is base gasket, stainless steel shim, base gasket and then carburetor. As clearly mentioned in the service manual "Engine will not idle without shim  on Carter carburetors". Although there is some discussion of using gasket cement on the top of the second gasket, in 20 years of changing my carb on my '66 I never had an issue with the gasket going on "dry"
Greg Surfas
Cadillac Kid-Greg Surfas
Director Modified Chapter CLC
CLC #15364
66 Coupe deVille (now gone to the UK)
72 Eldo Cpe  (now cruising the sands in Quatar)
73 Coupe deVille
75 Coupe deElegance
76 Coupe deVille
79 Coupe de ville with "Paris" (pick up) option and 472 motor
514 inch motor now in '73-

Re: 66 429 no vacuum from carburetor to vacuum advance.
« Reply #4 on: February 18, 2013, 11:25:33 AM »
Jules,

I think Greg identified the most likely culprit. Carter’s will not run properly without the shim. I would add that you should use the stock type set up with the brown Bakelite insulator under the carburetor. It’s there to keep the carburetor body from getting too hot and boiling the gas, and it’s the inlet port for the PCV breather line. Using the insulator, the sequence is: manifold, gasket, insulator, gasket, shim, carburetor.

Ralph
1966 Fleetwood Brougham-with a new caretaker http://bit.ly/1GCn8I4
1966 Eldorado-with a new caretaker  http://bit.ly/1OrxLoY
2018 GMC Yukon

Offline TJ Hopland

  • Posts: 10183
Re: 66 429 no vacuum from carburetor to vacuum advance.
« Reply #5 on: February 18, 2013, 11:30:41 AM »
So what does this shim do?   It must block or change some of the ports?  This could also explain the vacuum ports not working correctly?
StPaul/Mpls, MN USA

73 Eldo convert w/FiTech EFI
80 Eldo Diesel
90 CDV
And other assorted stuff I keep buying for some reason

Re: 66 429 no vacuum from carburetor to vacuum advance.
« Reply #6 on: February 18, 2013, 02:45:26 PM »
Where is my mind gone to? Of course you have the insulator with the nipple for the PCV that goesd between the manifold and the shim.
Thanks Ralph.
TJ you need to look under the AFB to best explain why the shim, by cuttiong off direct communications with the intake manifold, allows the venturi vacuum signals to go where intended.
Greg
Cadillac Kid-Greg Surfas
Director Modified Chapter CLC
CLC #15364
66 Coupe deVille (now gone to the UK)
72 Eldo Cpe  (now cruising the sands in Quatar)
73 Coupe deVille
75 Coupe deElegance
76 Coupe deVille
79 Coupe de ville with "Paris" (pick up) option and 472 motor
514 inch motor now in '73-

Re: 66 429 no vacuum from carburetor to vacuum advance.
« Reply #7 on: February 18, 2013, 05:37:52 PM »
Greg,

Completely understandable. I have my clothes monogramed 'cause sometimes I can't remember my name......

Ralph
1966 Fleetwood Brougham-with a new caretaker http://bit.ly/1GCn8I4
1966 Eldorado-with a new caretaker  http://bit.ly/1OrxLoY
2018 GMC Yukon

Offline jules

  • Posts: 11
  • Name: gjules
Re: 66 429 no vacuum from carburetor to vacuum advance.
« Reply #8 on: February 19, 2013, 01:21:40 PM »
Thx all for the info. I currently only have one gasket, then shim, then AFB. I'll have to look more closely at the AFB, as I thought the PCV valve was part of the AFB base. As described below, is it what you are calling the Bakelite insulator?

Re: 66 429 no vacuum from carburetor to vacuum advance.
« Reply #9 on: February 19, 2013, 02:52:04 PM »
The Bakelite insulator should have a nipple at the front.  This is for the PCV hose from the valve.
Greg Surfas
Cadillac Kid-Greg Surfas
Director Modified Chapter CLC
CLC #15364
66 Coupe deVille (now gone to the UK)
72 Eldo Cpe  (now cruising the sands in Quatar)
73 Coupe deVille
75 Coupe deElegance
76 Coupe deVille
79 Coupe de ville with "Paris" (pick up) option and 472 motor
514 inch motor now in '73-

 

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