38plymouth Posted October 29, 2021 Report Share Posted October 29, 2021 I'm getting super frustrated. I got my car running really good at idle. I set the timing and mixture screw with a vacuum gauge and I'm getting 19-20 psi. I have new plugs, newer wires, cap rotor and points and condenser. I pulled the distributor and double checked everything. The carburetor is rebuilt and I run ethanol free fuel. I triple checked the float level and I have an aluminum Fenton head and a split manifold with dual exhaust. When I Rev the engine it starts to miss/ stumble at around 1700 rpm and up. It did this years ago and I suspected it was running lean and partially closed the choke and that solved the problem. That doesn't do anything anymore. I'm stumped and feel like it's a carburetor issue but don't know where to look next. Quote Link to comment Share on other sites More sharing options...
38plymouth Posted October 29, 2021 Author Report Share Posted October 29, 2021 Edit....It starts running rough at 1200 rpm and closing the choke a little smooths it out until around 2000 rpm. Quote Link to comment Share on other sites More sharing options...
38plymouth Posted October 29, 2021 Author Report Share Posted October 29, 2021 I just pulled the carburetor again and cleaned it out, I thought maybe I found the issue, there was a little gray gunk in it again. The idle orifice tube and step up piston had a little crap that I cleaned out. That definitely made it idle even better and now I have a solid 20 on the vacuum gauge. However it still will not rev up without missing unless I close the choke a little then it doesn't start missing until over 2000 RPM's. Quote Link to comment Share on other sites More sharing options...
chrysler1941 Posted October 29, 2021 Report Share Posted October 29, 2021 Mixture too lean. If carb is cleaned by ultrasonic, then probably your float needs adjustment. Quote Link to comment Share on other sites More sharing options...
38plymouth Posted October 29, 2021 Author Report Share Posted October 29, 2021 (edited) Can someone explain to me what the emulsion tube does? I don't have the proper tool to pull it out and clean it and it never taken it out of the carburetor before. So, I popped the plug out and flushed that area with carb cleaner and no change. Is there a guaranteed way for me to know if I'm running too lean? I thought maybe closing the choke was helping but now I'm not so sure it still seems to start missing a little over 1000 rpms. If it seems like it's lean I'm about ready to start drilling out the jet. Worst case scenario I'm buying a different carburetor. I'm so tired of this. At what RPM do these carburetors switch from the idle circuit? Edited October 29, 2021 by 38plymouth Quote Link to comment Share on other sites More sharing options...
Bryan Posted October 29, 2021 Report Share Posted October 29, 2021 Carburetor Emulsion Tube - Why it is needed - How it works - What they do? - YouTube Quote Link to comment Share on other sites More sharing options...
Bryan Posted October 29, 2021 Report Share Posted October 29, 2021 I can't imagine if some of the little air inlets were stopped up it would run leaner...if this tube has an o-ring sealing the tube check it. Check if the main jet (or this tube) is stopped up. Idle jets and idle mixture shouldn't affect mid & upper ranges (at least on moped carbs). My dealing with moped carburetors - low float level will make them run lean.. BUT I have seen carburetors with a stopped up air filter on a moped run fine til it reached higher rpm then it would stumble - too rich. But since in the past you had to pull the choke to run good, probably being too lean is affecting it. Do the standard spray around shafts & base to check for air leaks. Quote Link to comment Share on other sites More sharing options...
38plymouth Posted October 29, 2021 Author Report Share Posted October 29, 2021 Well I can't believe I figured it out. I was talking to an older gentleman today who knows a lot about these cars and he suggested I checked the vacuum advance. It sure seemed like it was running lean but I couldn't find a vacuum leak. Apparently my vacuum advance diaphragm has blown and it won't hold vacuum. I put a pipe plug in the carburetor and now it runs great until about 2,800 RPMs then it starts to miss a little. I'll take that as a victory for now. So now where do I find a diaphragm? 1 Quote Link to comment Share on other sites More sharing options...
Loren Posted October 29, 2021 Report Share Posted October 29, 2021 This is not your problem of course but when I read the title it reminded me of another problem I've encountered. I am glad you found the leak in the vacuum advance which is related. The symptom I was tasked with finding the cause of was a miss on the highway at cruise speed. There is a ground wire between the breaker plates and when it is broken or missing the electricity has to pass through the pivot between the plates. In this case the wire had been gone so long the pivot point had been eaten away from the current going through it. Every time the engine throttle closed a little the vacuum advance pulled on the top plate breaking the circuit and causing a miss. Once I replaced the wire the problem went away but it still wasn't fixed as now the breaker plate was sloppy and the timing was too variable. A good tune up used to mean removing the distributor and running it on a synchrograph (distributor test machine). The synchrograph has a vacuum pump to check that whole system and a vary-speed motor to test the centrifugal advance. However you only see those in private collections nowadays. Since 3/4 of the time the problem was found in the ignition a synchrograph was a good investment for a shop. Carburetors always TRY to work and sometimes you can clear a problem by putting your hand over the inlet of the carburetor causing vacuum to pull the crud through. But if you can't light the fires a perfect fuel/air mixture isn't going to burn. Just sayn' Quote Link to comment Share on other sites More sharing options...
OUTFXD Posted October 30, 2021 Report Share Posted October 30, 2021 Try Seafoaming your engine. Both the Fuel system and the Oil. get ALL the gunk out of your system. only costs $10, Makes a world of difference! https://seafoamworks.com/ Quote Link to comment Share on other sites More sharing options...
38plymouth Posted October 30, 2021 Author Report Share Posted October 30, 2021 My distributor ID tag is missing, any idea how I can confirm what distributor I have so I can order a vacuum advance? I think it's original but who knows on a car this old. Quote Link to comment Share on other sites More sharing options...
Doug&Deb Posted October 30, 2021 Report Share Posted October 30, 2021 Do you have a service manual and parts manual for your car? If so there should be a picture that you could hopefully match up to see if you have the original distributor. I got a rebuilt vacuum advance from Kanter. Quote Link to comment Share on other sites More sharing options...
Sniper Posted October 30, 2021 Report Share Posted October 30, 2021 46 minutes ago, 38plymouth said: My distributor ID tag is missing, any idea how I can confirm what distributor I have so I can order a vacuum advance? I think it's original but who knows on a car this old. There is an Autolite catalog in the downloads section. Is shows drawings of the various vacuum canisters, points, condensors, caps and rotors that can help you sort out what you have. I'd start by looking in that catalog for the distributor you are supposed to have then see if the parts match what you have. Quote Link to comment Share on other sites More sharing options...
38plymouth Posted October 30, 2021 Author Report Share Posted October 30, 2021 (edited) 56 minutes ago, Sniper said: There is an Autolite catalog in the downloads section. Is shows drawings of the various vacuum canisters, points, condensors, caps and rotors that can help you sort out what you have. I'd start by looking in that catalog for the distributor you are supposed to have then see if the parts match what you have. Thank you! Looks like mine isn't from 1938, the points are the 1939 and up style. I remember having a problem ordering points and getting the wrong ones when we looked for a 38. Edited October 30, 2021 by 38plymouth Quote Link to comment Share on other sites More sharing options...
DJK Posted October 31, 2021 Report Share Posted October 31, 2021 Had my vac. advance repaired at Terrill Machine Inc. DeLeon, Texas. $83.00. Just don't be in a hurry!!! Andy Bernbaum also does them. Quote Link to comment Share on other sites More sharing options...
Sniper Posted October 31, 2021 Report Share Posted October 31, 2021 Terrill Machine Inc. (254) 893-2610 terrillmachine@yahoo.com Quote Link to comment Share on other sites More sharing options...
38plymouth Posted November 2, 2021 Author Report Share Posted November 2, 2021 I adjusted the free play in my clutch this morning and I swear it still feels like it slips in 3rd gear when stepping on the gas hard. That's the only time it feels like that. It also kind of feels like maybe they'll float or something strange. I set my timing with a vacuum gauge and it is turned more counterclockwise than it used to be for years. The book says four degrees after top dead center. I'm going to try to attach a picture. If the left side of the photo is the front of the car which side is 4° after top dead center. Also since my vacuum advance is leaking should I still set it by the book until I get it repaired? The vacuum advance is unhooked. Quote Link to comment Share on other sites More sharing options...
38plymouth Posted November 9, 2021 Author Report Share Posted November 9, 2021 (edited) I am happy to report that my car is running great now. I adjusted the clutch freeplay and the slipping is gone. I also backed off the timing, setting it to highest vacuum was way advanced. I backed it off to where it used to be and it runs really good now. I do still need a new vacuum advance. I called bernbaum to see if they could help me and they asked for emailed pictures. It's a week later and no response. They list 2 different ones, 1935-1941 and 1942-1948. My distributor tag is missing and all I know is my points look like 1939 and later style. Does anyone know the difference between those 2 vacuum advances? Edited November 9, 2021 by 38plymouth Quote Link to comment Share on other sites More sharing options...
Sniper Posted November 9, 2021 Report Share Posted November 9, 2021 the Autolite catalog in the download section ought to have that info. Quote Link to comment Share on other sites More sharing options...
38plymouth Posted November 9, 2021 Author Report Share Posted November 9, 2021 26 minutes ago, Sniper said: the Autolite catalog in the download section ought to have that info. But I don't know my distributor number. The tag is long gone. Quote Link to comment Share on other sites More sharing options...
Adam H P15 D30 Posted November 9, 2021 Report Share Posted November 9, 2021 @38plymouth What's your total mechanical advance at about 2500 RPM? Quote Link to comment Share on other sites More sharing options...
Sniper Posted November 9, 2021 Report Share Posted November 9, 2021 (edited) 1 hour ago, 38plymouth said: They list 2 different ones, 1935-1941 and 1942-1948. The Autolite catalog should have the info on THESE advance cans. 35-41 is VC-1039A 42-48 is VC-2082R pictures are show in the catalog and they do not appear to interchange Edited November 9, 2021 by Sniper Quote Link to comment Share on other sites More sharing options...
38plymouth Posted November 9, 2021 Author Report Share Posted November 9, 2021 18 minutes ago, Adam H P15 D30 said: @38plymouth What's your total mechanical advance at about 2500 RPM? I don't know, both of my timing lights stopped working. I need to pick up a new one. Quote Link to comment Share on other sites More sharing options...
38plymouth Posted November 9, 2021 Author Report Share Posted November 9, 2021 3 minutes ago, Sniper said: The Autolite catalog should have the info on THESE advance cans. I just went thru the whole catalog and it looks like most of my distributer components fit into the 1938-1950 category except my points look like 1939-1950, vacuum advance "looks similar" to 1938-1942 and coil looks like 1938-1941. I'm going to guess that my car was built with a 1939 distributor. The car is very original and untouched with low miles. Quote Link to comment Share on other sites More sharing options...
38plymouth Posted November 9, 2021 Author Report Share Posted November 9, 2021 14 minutes ago, Sniper said: The Autolite catalog should have the info on THESE advance cans. 35-41 is VC-1039A 42-48 is VC-2082R pictures are show in the catalog and they do not appear to interchange Quote Link to comment Share on other sites More sharing options...
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