You want vacuum advance, at least until you learn to tune around it. Swap in a new can. It does add better mileage and driveability and engine will run cool in extreme temps. What you can do if that turns out to be the problem and you want to make a repair, is buildup the throttle shaft with JB-Weld or lead-free (hard) solder. Drilling the body out and installing bushings is another. It needs to be an extreme backfire, or backfire through the carb itself, that can blow out power valves, I expect. It's one of those stories that gets told and retold and gets worse every time. It can happen, or Holley wouldn't have modified their carbs.. But. The way to check if the power valve is OK, turn your idle mixture screws all the way in, should kill the engine. If it does, the power valve is not blown.
My recollection is that MoPars of that vintage wear the distributor shaft bushing out. When you looked at the dwell on a scope the dwell line it was impressive how much the dwell varied. The dwell on 8 cylinder distributors was in the 28-32 degrees.
Your distributor cam is shot, its also likely the bushings are bad as well. in addition to having a bad vacuum advance canister as well, throw the dist away and get a good one. Most of your problems will go away. When ever you have a point distributor you can not get the dwell setting within the accepted range, the cam lobes and/or bushings are worn too much. Did I mention to throw that junk distributor away? Until you get that right, nothing else will solve your problems. Gene
I'm not saying there is nothing wrong with your ignition system, but if this problem didn't exist before changing carburetors why would you start looking at anything beyond the fuel system. Ignition problems don't stat with carburetor swaps. When you make a change and a problem pops up, go back to the change you just made before looking at anything else.
I tend to agree with this, but, I have no idea what "the double 2 carbs I had didn't do this. I removed them for rebuild and maintenance." means. I ***ume it meant he had some sort of duel carbs on the motor and they needed to be rebuilt. To me that sets up the possibilities that the problem may have existed before, but with carbs that needed rebuilt, the problem could have been covered up. When you reach a place with a point distributor that you can not get the dwell into specs, that issue needs to be addressed before anything else happens. The posted pictures of the distributor show almost nonexistent cam lobes, and he has a vacuum leak in the advance canister. I will stand on my advice to replace the distributor before anything else is done. Once the ignition system is functioning correctly, there may not be a carb issue. Gene
One thing for sure, you are ******* into the wind and expecting not to get wet by not changing the advance in that distributor. You have to fix the known bad items before sorting out the small details. One thing for sure you can't compensate for a vacuum advance that doesn't work by bumping the timing up higher. Gene-Koning and Truck 64 have both given you solid suggestions to go with and I have never seen Gene lead anyone astray as he always gives solid info and suggestions when he answers a question. Study those suggestions and do what he said and most of the issues should be solved. Shops with distributor machines are few and far between anymore but chucking that distributor in a distributor machine would tell you what's going on with it in less than a minute. Meanwhile Rock Auto has new distributors for that engine for 50 bucks.
Yeah Johnny Gee first noticed the dwell figures. And as Gene points out a loosey-goosey distributor will never allow points to be adjusted properly too much end play or wobble on the distributor shaft. A clean tight distributor will make a big difference in the way it runs from idle all the way up and down.
Seems to me also you are missing 2 screws that hold the base plate on. The 2 larger holes in the center of the plate? Denny
I’ve got a lot of stuff to check and do now based on all this info The reason I took the double 2 off is because the front carburetor has a stripped fuel inlet and was leaking gas. It also needs a choke and a kick down. Otherwise it was a really good progressive set up and worked well. The Holley was supposed to be simple and reliable. It might be and the problem is just me. I’ll know soon I hope as I keep learning about stuff. Thank you for letting me know that the distributor is shot. The turning and bushings seem ok and it seems nice and tight. At this point I’m working on the electronic install. I’ve almsot got that wired up and ready. http://vb.foureyedpride.com/showthread.php?98031-Surging-bog-hesitation-with-Holley-carb This guy had the same exact problem. He changed a lot of things to fix it and still couldn’t find the problem Then changed the carb and it went away. I’ll post more when I run some more tests based on the info here. What does a good points cam block look like. I know this thing was run without grease as when I go it there was none on there for god knows how long. I though there was screws missing as well......but I see more 4160 carbs with those gone. I think it came that way
Try holding the secondary's from opening (any way possible) so it only runs with the primary and run it back up again and see what happens.
Un Hooking the vacuum advance made the stumble in that video, a lot less. I retested the advance canister with a better seal and the diaphragm is fine. Must be in the mechanical prts somewhere. I decided to get the skip white hei distributor. I also bought a tach for inside the car. The actron device I was using for rpm only went to 2000rpm. With this new distributor I should be able to recurve it and get the total timing to 34° with the highest base timing. I was at 12° and ran it to 15°. The engine liked this and gave me 1/2” more of vacuum. Seemed to have better throttle response as well. Once I get this distributor straightened out I’ll then start looking for the stumble again. I think it’s still there but it was much less with the advance unhooked. However......I did drive the car with the advance unhooked and the stumble under load was a lot more pronounced. Getting the timing good and making sure the spark is there should help a lot. There is a mixture screw very slightly with some gas on it. I think it has a small leak. The idle mixtures are now 1 turn out. With 21.5” of vacuum. Turning them out to 1.5 out gave me 17” of vacuum. Turning them down to .5 turns out gave me 19” of vacuum I turned off one side of the mixture screws and turned the other to 1.5 and got 21” of vacuum.......same for the other side. This was all done with the secondaries covered and no air. They are closed down as far as I can get them.
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