Clean air package

Andrew Douglas

Andrew Douglas

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I have a 67 T&C, 383 4bbl and it has cap on it. Timing on it is 5 degrees btdc. Both the carb and distributor are cap. Vehicle runs and drives but when in park or neutral it idles real high. I have rebuilt and adjusted the carb and it still idles high.
I have tried looking up a new carb but i cant find any that are cap. What does the carb have that makes it cap? I know the distributor has certain springs in it for cap.
 
The original CAP System consisted of a modified distributor advance curve, not quite so much initial base timing, and a leaner carb calibration. There could be some other vacuum-operated delay valves and such in the mix, too. There should be a Chrysler Master Tech training film on it, via either the www.imperialclub.org website. Click on "Literature", then "Repair Manuals", then the "Chrysler Master Tech Conference", and scroll down to #241 that is "67-12" on CAP Systems. Once there, you'll need to click from page to page.

There might be a vacuum-bias valve that could be having a problem.

The base idle speed was generally a little higher than the non-CAP cars. For example, 750rpm rather than 550rpm, or something like that. In those earlier systems, the timing advance curve was a little "later" than normal, meaning "slower", up to a point as most of the "controls" took place below about 2000rpm.

in your case, just how high is "high", in relation to the base idle speed?

I'd look for vacuum leaks on any and all of the vacuum lines related to the carb AND at manifold vacuum sources. You might double-check how the gaskets in the carb are positioned and such, for good measure.

CBODY67
 
When i bought the car the idle air control valve was missing at the timing was set to 12 degrees btdc running real rough. I got a new control valve replaced all the vacuum lines and set it to the correct timing and it runs awesome now. It just idles high when i put it into park after driving. Im gonna say maybe 1100 rps. Iv tried adjusting the carb so mamy times but it still does it
 
Andrew Douglas said:
I have a 67 T&C, 383 4bbl and it has cap on it. Timing on it is 5 degrees btdc. Both the carb and distributor are cap. Vehicle runs and drives but when in park or neutral it idles real high. I have rebuilt and adjusted the carb and it still idles high.
I have tried looking up a new carb but i cant find any that are cap. What does the carb have that makes it cap? I know the distributor has certain springs in it for cap.
Click to expand...

Which carb is this, a Carter 4BBl or a 2BBL? I think some models for Ca also might have had the Holley 4BBL.
Overall, the main difference in the carbs for the California emissions, aside from the special markings will be in the metering rods and jetting.
I would check a few things before giving up on your current carb. First, are the idle screws in the throttle plate set to factory specs? Next, check the fast idle cam and be sure it is not stuck in the deployed position. A choke that does not fully release will leave the fast idle cam in the deployed position. There is also a fast idle adjusting screw that engages the cam, if this screw is set too far in, the car will not idle down. If your car came with a vacuum valve, check it to be sure it is not the source of your fast idle (Disconnect it and see if the car then idles down). Next, take the carb off the engine, drain the fuel out of it and put a light source under the throttle plate. You should not see much light around the radius of the butterfly valves. If you see more light on one side or other of the butterfly plates, you have a warped throttle plate that will have to be replaced. If you can see a lot of light on both sides of the butterfly valve, you have something blocking the throttle plate from closing. Next check the base plate gasket for the carb to be sure it is not interfering with the motion of the throttle valves and has a good seal, a vacuum leak at the base of the carb can also cause a fast idle condition. Remount the carb and check the throttle linkage to be sure that it is not set too short and holding the carb open. Try these things and report back.

Dave
 
Its the carter AFB 4bbl

1517695200309489389501.jpg


15176952423621636952876.jpg


15176952750662073008067.jpg
 
The Holley 4160 was on the 440/350 New Yorkers. The 383 4bbls were the small pattern AFBs.

When the power brake booster on my '66 Newport failed, every time I pressed the brake to stop, the engine started missing. No brake, no miss.

Seems like there might be some sort of adjustment on the vac valve?

Usually, at base idle, the pcv plunger is held in the "closed"/"low flow" position by manifold vacuum. Still some flow through the internal orifices, but never have seen one that's stuck open, due to the way it's designed internally. Not to say it can't happen, though, if it rattles, it should be ok.

I found a Popular Mechanics article on the 1963 tests Chrysler did in CA, with the pre-cursor of the CAP/CAS system. I put "1967 Chrysler CAP System" in to Google and found an Allpar article on the CAP/CAS system by Daniel Stern. Very informative. What the vacuum valve does is use two sources to put vacuum to the distributor vacuum advance unit. The article shows the vac control valve without the "can" on it, so you can see the spring and the adjusting screw. I suspect that this valve is not adjusted correctly, as is, ans is putting vacuum to the vac advance when it shouldn't be. Of possibly the vac lines might have been switched inadvertently in the replacement process. The dist vac advance should not have any significant vac to it at base idle. IF you find strong vacuum there and the idle speed slows to normal with the vac line at the dist vac advance pulled off and plugged, when the engine idles too high when hot, that's probably what the problem is. The new valve just needs to be adjusted correctly, I suspect. Adjustment is covered in the #241 MTEC training document.

Just some thoughts,
CBODY67
 
Last edited:
No need to worry bout being CAP as you are not being inspected. Also I'd not use the vacuum control valve, just bypass it.
Set you advance to a desired setting and not the book, again not inspected.

The tune up specs for CAP are not desirable.


Alan
 
CBODY67 said:
The Holley 4160 was on the 440/350 New Yorkers. The 383 4bbls were the small pattern AFBs.

When the power brake booster on my '66 Newport failed, every time I pressed the brake to stop, the engine started missing. No brake, no miss.

Seems like there might be some sort of adjustment on the vac valve? Usually, at base idle, the pcv plunger is held in the "closed"/"low flow" position by manifold vacuum. Still some flow through the internal orifices, but never have seen one that's stuck open, due to the way it's designed internally. Not to say it can't happen, though, if it rattles, it should be ok.

Some carbs (not sure about that particular AFB) had a hot idle compensator valve. A bi-metal flat spring with a rubber nub on the end. Under hot idle conditions, it would open to allow more air in to prevent an over-rich condition in hot weather, at idle. Other than the power piston bores and the pcv passages, that's the only other vac circuit in the carb that's open to full manifold vacuum at idle. The vacuum control valve, seems to run off of a vac bias between manifold vacuum and ported vacuum, I believe. Hence the need for some sort of adjustment to ensure it works correctly. I think if you pop the lower cover off, you'll find an adjustment against spring pressure. And I suspect there would be some sort of adjustment procedure in the factory service manual.

Just some thoughts,
CBODY67
Click to expand...

Re: PCV. They sometimes got "stuck" as it were by a piece of sludge or other crud getting pulled into the plunger seat for the PCV valve, which causes the vacuum leak. Most common an vehicles that did a lot of short trip driving. Simple to test, put a piece of heavy gauge tape over the hole in the engine side of the PCV valve. If the engine slows after that, the PCV is stuck and leaking.

Dave
 
I would be with MrMopar on deleting the non-stock vac valve. It's contribution to reducing emissions was negligible, all it does is slightly delay full vacuum advance. Car will probably run better without it and be slightly more fuel friendly.

Dave
 
Gentlemen,
In pix #1, the green colored valve is a deceleration valve. I believe they were used on manual transmission cars not automatic cars.
The purpose was to increase the distributor's vacuum advance to maximum on closed throttle coast down. The purpose was to prevent exhaust back fire due to a lean condition. During normal operation, the distributor received normal ported vacuum signal. If piped incorrectly, manifold vacuum was applied to the distributor, possibly resulting a higher hot idle speed. I believe that the CAP system was California cars only and later all 50 states. Check the FSM for your specific year (not Chiltons or Motors) for for proper orientation and operation.
Bob Renton
 
RJRENTON said:
Gentlemen,
In pix #1, the green colored valve is a deceleration valve. I believe they were used on manual transmission cars not automatic cars.
The purpose was to increase the distributor's vacuum advance to maximum on closed throttle coast down. The purpose was to prevent exhaust back fire due to a lean condition. During normal operation, the distributor received normal ported vacuum signal. If piped incorrectly, manifold vacuum was applied to the distributor, possibly resulting a higher hot idle speed. I believe that the CAP system was California cars only and later all 50 states. Check the FSM for your specific year (not Chiltons or Motors) for for proper orientation and operation.
Bob Renton
Click to expand...
My 1967 Barracuda had one and the car was an automatic.


Alan
 
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