Okay got a 70 350 with Pertronix III and coil. New plugs, wires, and distributor cap. Rebuilt the 2 BBL carb and adjusted idle mixture screws to get full RPM out of them.

My sitting idle before putting vehicle in reverse is approx. 1000 rpm. After I put it in reverse with brake applied or no brake applied the RPM drops about 500 rpm and acts likes it wants to stall or stalls.

I have tried this with the distributor vacuum line plugged and unplugged with the same results.

The car runs fine once I get it on the highway. But at low speed and reverse the motor cuts out intermittently. There is no consistency with it at all.

Anyone have any ideas what else I can check...

d1

 

Well I have never messed with a 2-barrel, but like a 4-barrel, it should have 2 idleling speeds, one in park, one in gear. Sounds like your slow idle speed is set too low, so when you put it in gear, it is dropping too far in RPM. You should set the low idle to the specified RPM, in drive, with the parking break ingauged, or if your more concerned about saftey, have someone sit onthe car with their foot on the break. If you don't have the service manual for your car, you should get it, it's worth it's weight in gold! It has step by step instructions on how to set up your carb correctly. But in the end, even if you have everything set to "stock" recommendations, you may still have to tweek it. These things are old, and depending on your location/weather, you may need more idle, less idle, more or less timing..etc.

 

Did you replace the carb. base gasket. If not I would.

It could also be the float needs adjustment.

 

The instructions I used to set slow idle were off the carb rebuild kit instructions. It had me setting the slow idle (900 rpm) while car was in neutral. I will find the manual instructions for the car and set it to that specs and see what happens.

I just tested the base gasket with carb cleaner and when I sprayed a bit of cleaner at the base the RPM picked up. So, I am assuming I have a leak around the front of the carb somewhere.

I did adjust the float (like 5 different times) as it was consistently flooding the carb. Maybe I went too far and am starving the carb of fuel. While I have it off looking at the gaskets I will check it out.

Can I use silicone or gasket maker, or high tack on a carb to get it to seal? Anyone ever do that or am I asking for trouble?

 

Yeah that's' your problem then. The only thing you can do is just replace the gasket with a new one.

 

Yeah that's the problem I had when I put on my rebuilt q-jet. Also when you replace the gasket ( don't use any sealer or anything) just make sure you don't torque it down too tight. I did that and it warped it so much that it leaked. Check the torque recommendations. They are usually surpisingly low, meaning they aren't torqued too high, only like 10-12 ft lbs.

 

Check the link below your idle should be set to 550 rpm, sometime with air I go as hi as 600, dwell should be st to 30, timing 6-12 Btdc with vacuum advance disconnected. Good luck!

http://www.oldsmobility.com/tuneup.htm

 

Got it done. Apparently the 3 screws that hold the base to the main portion of the carb worked loose. So I retightened them (probably too tight) and through it back together.

Seemed to do the trick but we will see. Before this it was running fine after I rebuilt the carb but after a hundred miles or so it start acting up. So hopefully the screws stay put.

Thanks for everyone's help.

d1