60 CDV stalling

[Michael Petti]

My stock 1960 390 stalls when sitting at a light with the brake on and especially when jockeying into a parking place (like at a car show) using the brakes and the power steering at the same time. I've been dealing with this for about 3 seasons. I got a lot of idea from a former post I put up 3 years ago about poor running in general and I am now down to this problem. So far, I have eliminated some small vacuum leaks and tightened the intake manifold to specs and picked up about 1/2 inch of vacuum and wrapped the fuel lines in heat reflecting tape. Had Arthur Gould rebuild the fuel pump which made a huge improvement and rebuilt the carburetor (Carter AFB). Car ran good for about a month then started this stalling problem using the steering and brakes at the same time. Timing is set correctly, and I use ethanol free gas. The engine just seems loose rpm and stall like It's running out of gas, but it restarts right away when I turn the key so there is gas in the bowl. This is worse in hot weather than cool weather. I'm going to tackle this as soon as car come out of storage, and I need some suggestions as I am out of ideas. Thanks in advance. The info here is always good.

[Big Fins]

Have you tried bumping the idle up just a little? Say, 100 RPM's or so. My 390's ran horrible set at the OE specs. I had base idle at 650 with a 4-5 degree bump in the base timing. That corrected a lot of rough running issues.

[James Landi]

Michael,

Does your car model have an accelerator "dash pod"--I think that's what they are called.  Part of the accelerator linkage, the device. mounted on the firewall, was simply a vacuum actuator  connected to the vacuum intake, and when the vacuum started to fail under load at idle, the device would push out its plunger rod and, in turn, push the accelerator to a slightly higher rpm. I'm certain I had such devices on my '56's (that had a/c) but don't recall for certain if my 60 had the device.  Perhaps your car "lost" this device, as, over time, the device would lose it's ability to hold a vacuum, so some folks took the device off and pushed up the idle rpm. James

[Lexi]

My 1956 idle spec was said to be 400 rpm which GM changed to 420 if memory serves, for AC cars. Like Big Fins, my car would never idle at the OE spec without serious issues. 600 seems to be where it is most comfortable and that is with near everything rebuilt or new. I remember being at a GN years ago, where another '56 owner told me his car would never idle at OE spec, and that he also ran his at 600 rpm. His car was also a stock OEM survivor with very low mileage. So, depending on what idle speed your car is currently set at, it may need a "bump". Chasing vacuum leaks is a good idea. If you think most everything is fine, you may want to slowly place your hands over you carb's throat and see if your idle speeds up. If your engine rpms increase, and does not stall, then you have a vacuum leak. Even though your carb is rebuilt, some rebuilders may not tackle the issue of a leaky throttle shaft. Can't remember if yours also has that irritating idle by-pass valve. They can be a source of erratic idle if they leak. Spraying carb cleaner at those points may help to pin point a vacuum leak source, if there. Clay/Lexi

[Michael Petti]

I never thought about timing. It will be worth a try.
I do have a dash pod, and the piston moves. I have adjusted the screw to its maximum position with no change in stalling. Maybe I can go to Ace and get a longer screw to put in there.
I have my idle increased somewhat. I read a post earlier where someone had the idle at 750 rpm in park. Too fast, car dieseled when shut off. Right now, I'm about 700 RPM in park. Is your 600 rpm in park, or in drive?

[Big Fins]

Michael,

Does your car model have an accelerator "dash pod"--I think that's what they are called.  Part of the accelerator linkage, the device. mounted on the firewall, was simply a vacuum actuator  connected to the vacuum intake, and when the vacuum started to fail under load at idle, the device would push out its plunger rod and, in turn, push the accelerator to a slightly higher rpm. I'm certain I had such devices on my '56's (that had a/c) but don't recall for certain if my 60 had the device.  Perhaps your car "lost" this device, as, over time, the device would lose it's ability to hold a vacuum, so some folks took the device off and pushed up the idle rpm. James

I think all of the 365/390 years had the dashpot. It's main objective was to stop the engine from stalling when you released the throttle quickly. It is mounted on the firewall and is adjustable. In the FSM, it is also part of the base set up of the idle and TV rod. If the dashpot was out of adjustment, it would also cause the transmission to shift hard or not at the correct set points. Being as finicky as they are the 4 speed HM's shift points can change with a simple 1/4 turn of the adjusting nuts on the trunion.

[Big Fins]

600 in Park, Michael. Going to reverse or drive should bring it down to 450-500.

[Big Fins]

Many variables can affect the idle settings. Set screw on the carb, set screw on the dashpot, vacuum, vacuum advance where the vacuum advance supply comes from, timing, air/fuel ratio screw settings, air valve (big screw in between the air/fuel ratio screws) A/C or no A/C load and on and on.

[Lexi]

I never thought about timing. It will be worth a try.
I do have a dash pod, and the piston moves. I have adjusted the screw to its maximum position with no change in stalling. Maybe I can go to Ace and get a longer screw to put in there.
I have my idle increased somewhat. I read a post earlier where someone had the idle at 750 rpm in park. Too fast, car dieseled when shut off. Right now, I'm about 700 RPM in park. Is your 600 rpm in park, or in drive?

Michael, my 600 rpm idle is in park. Drops a chunk when put into drive with emergency brake on. Although my engine is a 365, (and not a 390), for mine to idle at 700 that would be wayyy...too fast. Clay/Lexi

[Lexi]

I think all of the 365/390 years had the dashpot. It's main objective was to stop the engine from stalling when you released the throttle quickly. It is mounted on the firewall and is adjustable. In the FSM, it is also part of the base set up of the idle and TV rod. If the dashpot was out of adjustment, it would also cause the transmission to shift hard or not at the correct set points. Being as finicky as they are the 4 speed HM's shift points can change with a simple 1/4 turn of the adjusting nuts on the trunion.

"You got that Pontiac"! Clay/Lexi

[Lexi]

My stock 1960 390 stalls when sitting at a light with the brake on and especially when jockeying into a parking place (like at a car show) using the brakes and the power steering at the same time. I've been dealing with this for about 3 seasons. I got a lot of idea from a former post I put up 3 years ago about poor running in general and I am now down to this problem. So far, I have eliminated some small vacuum leaks and tightened the intake manifold to specs and picked up about 1/2 inch of vacuum and wrapped the fuel lines in heat reflecting tape. Had Arthur Gould rebuild the fuel pump which made a huge improvement and rebuilt the carburetor (Carter AFB). Car ran good for about a month then started this stalling problem using the steering and brakes at the same time. Timing is set correctly, and I use ethanol free gas. The engine just seems loose rpm and stall like It's running out of gas, but it restarts right away when I turn the key so there is gas in the bowl. This is worse in hot weather than cool weather. I'm going to tackle this as soon as car come out of storage, and I need some suggestions as I am out of ideas. Thanks in advance. The info here is always good.

Hello Michael. Attached are 2 tune up spec sheets for your car. These are actual scans from my original set of AEA engine specification cards. Hope they help. Clay/Lexi

[Big Fins]

That's a nice set of spec sheets!

[Lexi]

I thought it would give Michael a good base line in which to further investigate his idling issue. Keep in mind these specs are from 1960, using gasoline that was properly formulated for cars of that period. Some deviation will be necessary I imagine to accomodate today's fuel. So put them to good use guys. I copied all AEA spec sheets on Cadillac from 1954 - 1968, so if anyone wants a spec sheet from these years, let me know. Clay/Lexi

[Michael Petti]

Thanks so much. I will print them for use and as an addition to my shop manual

[Lexi]

I think my original images are larger in file size, and should print better. Downloading pics to the Forum must compress them a bit. If you want better quality, message me and we can work out a way to send sharper images to you. Clay/Lexi

[tcom2027]

In the course of your vacuum testing did you disconnect and plug the vacuum booster? A leak there combined with the load of the trans in drive and the PS pump, especially when moving the front end on pavement or soft ground at low speed or stopped with the pump against the bypass. Those cars have heavy front ends wide (ish)and tires and fairly low tire pressures. Lots of drag.

Just a thought.

tony

[59-in-pieces]

Michael,

Some pretty sharp suggestions so far.

Since your car has 2 vacuum canisters behind the left wheel well, did you test them for pin holes and vacuum hoses leaks (often at the clamps of any connection if the pieces have any movement).

Like someone had said - there are many places for vacuum leaks.
A couple more came to mind:

The vacuum emergency brake release
The vacuum door lock mechanisms
The anti-backflow valve leading to the Brake booster from the manifold held at the firewall.
Often times the single and double vacuum valves (silver colored flying saucers) on the heating and A/C assembly housing leak.
In the neutral switch cluster on the lower steering column.

HOPE YOU FIGURE IT OUT SOON.

Have fun,
Steve B.

[Jon S]

I never thought about timing. It will be worth a try.
I do have a dash pod, and the piston moves. I have adjusted the screw to its maximum position with no change in stalling. Maybe I can go to Ace and get a longer screw to put in there.
I have my idle increased somewhat. I read a post earlier where someone had the idle at 750 rpm in park. Too fast, car dieseled when shut off. Right now, I'm about 700 RPM in park. Is your 600 rpm in park, or in drive?

The dash POT is designed to prevent stalling at higher speeds when you suddenly release the gas pedal and hit the brakes. It has no effect while parking the car. Personally I would advance the timing 2 degrees and bump the idle to 550 RPM.

[Cadillac Jack 82]

I remember having a similar issue and the 59-60s like to idle higher than other years for some odd reason.  Dash pod working is a must as others have said before.  Fresh plugs and wires also helped MASSIVELY with my 59.  She runs so smooth now after adding the correct parts/correcting adjustments you can barely hear her run.  Keep us posted and hopefully you can get her running right.

[Roger Zimmermann]

The dash POT is designed to prevent stalling at higher speeds when you suddenly release the gas pedal and hit the brakes. It has no effect while parking the car.

It has also an effect while parking the car: when near stalling, the vacuum is reduced, allowing the pin to come out and open a crack the butterfly.