Rough idle issues and Carb gaskets

chope97

chope97

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Today was a beautiful day in the D.C. area. I drove my car to the exhaust shop it drove well and it was nice and fast but the idle was not good. When I got back I decided to check the timing. My car has no ball or marks on the fly wheel that can be seen from the little hole. I adjusted it by ear and watched the idle go up or down on my sears tune up box from the 70's. It was running better but not where it should be, next I decided to check the cabs to see if they were in sync. Turns out they were a little off but I could not get them to adjust. I decided to spray some carb cleaner at the base of each carb by the spacer. One carb got no reaction. The other carb by the firewall caused the idle to go way up. Question, I have taken the carbs off before is there something better than the cardboard gaskets I can use that will seal better? Should I use two gaskets together? Should I use gasket seal?

P.S I also found that the on the manifold closes to the firewall the vacuum port that had a cap on it the cap had come off so this was causing a big problem also
 
Usually one paper gasket is enough. I would check to see if the surface is cklean and the crb base is flat. Once you have the vacuum cap back on you should check again and pay attention to the throttle shaft area.

You may want to clean and lubricate the linkage so that each carb can be adjusted to come off the fully closed throttle plate together.
 
This was a common problem with the Zenith's. 40+ years ago I used a wet/dry sandpaper on a piece of glass to sand the cab bottom mating surface perfectly flat. Same with the spacer blocks.
 
Yep. Agree with Sven. I have 2-32/36s on my M30, and went through all this vacuum leak stuff and sundry other gremlins several years ago. Tightening down the mounting nuts did not help me feel I had taken up any gaps at the carb base. And these Webers are old! So, removing both carbs, placing them on sheet of glass, sanding just a bit, then using a light to see if there was still any leakage, then finally removing a bit more material. New gasket, and finally a satisfactory fit. I will add that I also replaced the throttle shaft bushing in both carbs as this is a typical wear/leak area. Good luck, and let us know what worked.
 
I had a rough idle issue a month or two ago. Make sure to check your idle stop solenoids are functional properly. I took mine out and cleaned up up with some carb cleaner since they were clicked on and were getting 12v. Try getting that timing in order using a timing light. Sounds like you have a vacuum leak at the base though. That ought to be your main culprit though.
 
Update, got car running real well, plugged vacuum port, adjusted timing, it was running sweet. Then it started loosing power, then it would pick back up. Seemed like it was running out of gas, tank is full. I swapped in a new gas filter, then a new fuel pump from my parts stash. It starts right up ran well but then the power lose came back. If I stopped at a stop light power would come back seemed like the more I drove the more the power lose would come back. Next I checked the coil it was out of spec for ohms. I reached into my parts depot and got a coil swapped it in once again car started right up then ran well for a while. Got it back home, checked everything again, now I am thinking it is my electronic ignition system. When you start the car it uns well then after a couple of miles of driving it starts to loose power. Currently there is an Allison Electronic Ignition module in it not sure how old it is. I just order a new Pertronix kit. Any thoughts?
 
Have you checked your timing with the timing light again? I run an Allison E-Ignition as well. It's nearly impossible to time properly my feel/ear. We are talking a cm or two too car clockwise or anti-clockwise will throw it off.

I would recommend trying timing properly before your rip and replace with the Pertronix.

What plugs do you have in the car? Platinum plugs were NOT the way to go for me. Opted back to a stock-like copper NGK plug and those have been working flawlessly for me.
 
Thanks for you response. My car has no ball or timing marks on the flywheel as far as I can see so I can not check timing by the normal method. I have copper NGK plugs. My car runs fine until I have driven it a few miles then it starts to loose power. If you stop at a light the power may come back So this is an intermittent problem.
 
The flywheel marks (ball and lines) can be hard to find after all the years of rust and dirt. Recommend that you pull the valve cover and then turn the engine over to find TDC on #1. Once there you will be able to look for the TDC mark and then 22 degrees later you will find the second mark.

This may help, see post 11 & 12.

Once you find them you can clean them with some emery cloth or a skotch brite pad so they will show up when you need to time it again.
 
Some of your symptoms are familiar to me. I had a lot of heat-soak vapor lock...which was a form of fuel starvation.
I tried replacing the original Pierburg mechanical fuel pump with several "new" Pierburg mechanical pumps...but the issue persisted. I finally went to an electric fuel pump mounted at the tank. Functional problem solved; no more fuel starvation or vapor lock problems.

But the electric pump is sometimes very very loud; like a large bee's nest in the trunk... other times it is just a little bit loud...
I suspect the Carter P4070 pump I have in there may be slightly defective; but I have not yet got around to replacing it in kind, or substituting a different brand/model.
 
mosearch said:
Some of your symptoms are familiar to me. I had a lot of heat-soak vapor lock...which was a form of fuel starvation.
I tried replacing the original Pierburg mechanical fuel pump with several "new" Pierburg mechanical pumps...but the issue persisted. I finally went to an electric fuel pump mounted at the tank. Functional problem solved; no more fuel starvation or vapor lock problems.

But the electric pump is sometimes very very loud; like a large bee's nest in the trunk... other times it is just a little bit loud...
I suspect the Carter P4070 pump I have in there may be slightly defective; but I have not yet got around to replacing it in kind, or substituting a different brand/model.
Click to expand...
I helped a buddy put an electronic pump in his Volvo 122 - the first one was a piston-style pump and it was loud like yours. We swapped it for a rotary style pump and it was much quieter.
 
Not too surprising that the rotary style was quieter than the piston-style...But my Carter P4070 pump is a rotary-vane pump (not a piston style). Do you happen to know exactly which rotary style pump you found to be quiet?
Others have recommended Mr. Gasket 42S pumps; but they are referred to as "gravity pumps" which seems to not be appropriate for my tank geometry and it's top mounted port. I'm actually thinking my best "fix" might be to convert my Carter pump to a switched "priming pump" and re-install my old mechanical pump as the main supply.
 
mosearch said:
Not too surprising that the rotary style was quieter than the piston-style...But my Carter P4070 pump is a rotary-vane pump (not a piston style). Do you happen to know exactly which rotary style pump you found to be quiet?
Others have recommended Mr. Gasket 42S pumps; but they are referred to as "gravity pumps" which seems to not be appropriate for my tank geometry and it's top mounted port. I'm actually thinking my best "fix" might be to convert my Carter pump to a switched "priming pump" and re-install my old mechanical pump as the main supply.
Click to expand...
Unfortunately I do not, it was a few years back. If I can find out from my friend I will pass it on.
 
Update info, since last weeks episode, I replaced Allison ignition for a new Pertronx, can ran much better, but loss of power came back after 5 miles of driving, next I found a leaking vaper tank connecting hose that appeared to be about 50 years old and leaking, next I replaced the plugs from wdc8's to the ngk, car got smoother again almost perfect but once again the lest of power comes back after a couple of miles of driving. I open the hood and started disconnecting things while the car was running badly and ah ha I disconnected the idle jet cutoff switch of the carb closest to the firewall and there it was there was no difference in how the car ran, I disconnected the other carb and the car cut off. I took the carb top off and there was no gas in the bowl. Time for a new topic
 
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