VCCA Home Forums TECHNICAL - GENERAL Mechanical - Engine, Trans, etc Car Wont Stay Running in gear.

My brother has a 1970 Impala with the optional 350 with and Automatic transmission. The car is in decent shape but currently we are having problems getting it to stay running while in gear. It has the 2 barrel Rochester carb on it, we have replaced it with a re-manufactored one because we thought the carb was needing to be replaced because it would barely run. It's does run a lot better now but it still won't stay running in gear. We put Cylinder 1 at TDC and made sure the rotor button and the spark plug wires were in the right spots. With minimal adjustments to the distributor it fired right up. The previous owner had the distributor so far advanced/retarded that im surprised it ran, we actually had to remove the distributor to turn it 180 degrees because he had everything so messed up (the plug wires were nowhere near the right spots on the distributor before we timed it). I have already done a vacuum leak around the carb and intake manifold. It has brand new plugs in it and we have tried adjusting the A/R screws on the front of the carb to get it to idle out smoothly. We can get it down around 900-1100 RPMs before it wants to die. It has around 15-20 pounds of vacuum on it as well, I checked it with a brand new vacuum gauge. Im at a stand still and completely stumped right now. Im pretty mechanically inclined and have rebuilt engines and transmissions before but I guess a carb is just to smart for me. Any help is appreciated. Thanks in advance.

I will try to attach some pictures to show you whats going on with it. We have a tach hooked up under the hood and that's what the green wire is in the picture running from the ignition coil to the fender.

Will it idle fine in neutral or park? I had a a 1975 Impala that had a problem with the transmission and it would not idle in gear,
Might be worth checking the points/condenser/fuel filter while addressing tune up items. Make sure the fuel 100% fresh.

Did you check the dwell?

Fuel is brand new, we are putting fuel in, in small amounts just to make sure that the fuel isn't going to go bad while we sit and try to fix it.

Im pretty new with carbs im not entirely sure what dwell is. How and where do I check it?

The dwell is the amount of time (measured in degrees of distributor cam rotation) that the distributor contact points remain closed. It has nothing to do with the carburetor.

You will need a dwell meter. A parts house may have a loaner.

https://nortonsafe.search.ask.com/w...38F-9150-EEA2944EBCF6&doi=2018-03-18

A couple of thoughts first here.

In 1970, the BASE V-8 was the 350 with a 2 bbl.

Only engine belowr the 350, was the 250 six cylinder.

1. Be certain points are set correctly, 28 to 32 degrees dwell.

2. Set timing to factory specs.

3. Adjust fuel mixture on carb.

4. Adjust engine idle speed ........ you did not mention this step.

If all the above has been done, in the order of steps written ......

It then sounds like a vacuum leak. Vacuum is measured in inches, not pounds.

Check the obvious first,

Are all vacuum hoses connected ?

Power brake booster vacuum line connected ?

Is the check valve for power brake booster broken or cracked ?

Was the intake manifold off for any reason ? You said distributor was out, why ?

IF all the above is fine, Do a propane vacuum leak test, but if not CLEAR as to this procedure, ask before you attempt anything.

My apologies about me putting in down in pounds and not inches. From what I understand the vacuum should be somewhere around 15-20. That's what it's sitting at right now. As far as I know all of the vacuum lines are on where they need to be. I pulled the distributor out because it was out 180 degrees and was barely running before. The intake manifold has not been off at all since we have had the car. I have sprayed the entire carb and intake down with starter fluid and nothing happened at all, no rpm changes or anything. No vacuum hissing noises from anywhere.

How do I perform a propane vacuum leak test? I don't have a bunch of money to spend on doing this so I just need to know. I grew up around newer cars but have always had a passion for old cars, just never had the money or time to work on them until recently and I still dont have a lot of time or money but its a hobby and a passion. Thanks for helping.

If you do not have a dwell meter you can adjust the point gap to about .018" WITH THE CAM HOLDING THE POINTS OPEN AT MAXIMUM. AND wHILE IT WILL NOT BE PERFECT IT SHOULD AND WILL RUN ok WITH THAT SETTING..
If there is a vacuum leak spraying carb cleaner or even WD40 into the carburetor throat will make the mixture richer and engine run better.

Old car hobby is difficult without time AND money.

Vacuum gauge needle reading should be close to a steady reading, not bouncing between 15 and 20, if that is what you are indicating here.

With engine running and a propane torch in hand, open valve on propane, BUT DO NOT LIGHT THE TORCH ....... again I repeat, DO NOT LIGHT THE TORCH, but with the open valve on the propane torch, fan the tip of the propane torch close to any source of vacuum, such as the carb base, the intake to head area, vacuum hose area.

See if you have an RPM change.

It has been MY experience that propane seeks out smaller leaks than starter fluid, etc.

If the distributor was 180 degrees out, I cannot imagine it would run.

Right.....especially MONEY!

I had a car a long time ago that the throttle jammed in the wide open position on the way to work. The quickest thing I could do was shut it off. As it was decelerating it had a huge back fire. I got the throttle loose from the overdrive kickdown switch it had jammed on, but then it would not run at all . It had gas, spark, air, but would not run. Had me stumped. My dad came over and we started researching. There was nothing coming out of the tailpipe. We started at the back pulling off the exhaust piping. Worked all the way forward until all there was left was the crossover pipe connected to the exhaust manifolds. That did it. Turned out that the backfire had collapsed the inner lining of the pipe just ahead of the muffler. Looked fine on the outside but was absolutely closed off on the inside. The point is that the spent gasses have to go OUT before new air and fuel can come in. May not be your problem but it needs to go on the lengthy list of things to investigate when trying to get a stubborn rig running. You know a 4 bbl 327 sounds pretty good on the way home with no exhaust piping.