I have a bog off idle on my 283 with a rochester 2G carb. Maybe this will narrow it down. It doesn't bog with the manual choke partially closed. I tried everything I've read on this subject. I haven't had any success. Thank you in advance. When I adjust the idle mixture screws the engine doesn't respond quite like how I have read it should. Even adjusted all the way in the truck still runs. Is that right?
I bought the carb rebuilt and it was running good on the 236 it was on before. I have confidence in the builder. Do think it may need some adjustment? There is an "atmospheric valve" located on top of the float bowl. It has a flap that opens just off throttle. It operates off of the movement of the accelerator pump linkage. I've never seen one of those in my unlimited experience with carbs. What does that do?
I had a '65 C20 V8 AT that I bought when it was only six months old. After a couple years of driving I figured the truck was due for a tuneup, took it to the local dealer. Within a short period of getting the truck back it started to stumble on acceleration. I took the truck back to the dealer, they had it for a couple of days, called and told me there was noting wrong with the truck. On my way home I noted that the truck was still pausing and/or stumbling on acceleration, back to the dealer. Was again told there was noting wrong with the truck. I went home got out my factory manuals that I had bought when I bought the truck. Reading through the tune-up section I noted a section about the PCV and how it should be serviced during a tune-up, IE, cleaning the valve in solvent and checking the valve for operation. I serviced the valve and reinstalled it, the truck ran fine. The purpose of the PCV is to provide vacuum through the engine to draw out the blow-by, introducing same to the combustion chamber. Upon acceleration the valve with-in the PCV snaps closed switching open to closed and thereby providing vacuum for the vacuum advance. I went back to the Chevy dealer to explain the problem to them, the service writer did not understand the issue and the importance of servicing the PCV.. Hmmmmm factory trained tech's ? Wm.
That is pretty sad. The mechanic should have known that. It's good you had the manual. I need one for my specific truck too. I forgot to mention. My truck doesn't have a PVC valve. Thanks for the response though.
1960 Chevrolet C-10, 1/2 ton, long wheel base fleetside. I read on here it would be a S&M 22. I have one for a 1961 passenger car and it is a S&M 32. I like that manual. It's very good but many things obviously aren't pertinent to my truck.
Does anyone know what the atmospheric valve is? Or what it does?
There is an "atmospheric valve" located on top of the float bowl. It has a flap that opens just off throttle. It operates off of the movement of the accelerator pump linkage. I've never seen one of those in my unlimited experience with carbs. What does that do?
No. I've tried changing the ignition timing numerous times. Change a couple degrees. Test Repeat. I will change when the atmospheric valve opens. Don't know if that has anything to do with it or not but I will try anything at this point. I will experiment making it close sooner by bending the tab. My bog goes away when I close the manual choke about halfway. I keep changing the idle mixture screws. Seems to me I should set them richer since the choke is essentially making it run richer. Does that seem logical?
Thanks. Information like this is invaluable. I've watched dozens of videos on rebuiding carburetors but I've never seen anything on this valve. I wish I could find information like this on the web. I appreciate you taking the time to send it.
I still have my bog issue. I think I previously described the issue incorrectly. It's not necessary only at idle, it can be at any RPM. It seems only to bog when the throttle plate is closed. If I hold a steady speed and punch it, the truck accelerates with no bog. If I let off the gas and then punch it, the truck bogs. Timing, dwell is all correct. The truck performs great other than the bog. Good acceleration, starts and idles well. Any suggestions are appreciated. The carburetor has recently been rebuilt and was operating fine on a 235. Thanks. Mark
I bought a new one for it. It matched the gasket that was under the Holley I replaced. I'm pretty sure all the holes were uncovered. I'll check it again. Is it safe to assume you might think a circuit may be covered with an incorrect gasket? If so, what circuit would that be?
