440-6 engine surge

I have 45 miles on this engine. I was rebuilt to standard specs, nothing fancy or special. Everything is new on the engine and the six pack is correct in every way for the 440. I replaced the dist. with Mopar perf pointless and a flame thrower coil. At 10* BTDC the car is pretty much undrivable, at 18*BTDC it runs much better but still has a surge. I also notice a backfire through the exhaust on deacceleration and ocassionally during idle. I have been told to don't use the vacuum advance and otheres tell me bull I need the vacuum advance. I am trying to get the car on a dyno machine but they are out about four weeks. Does anyone have any kind of an idea? Should I try 20*BTDC. I haver a car show today and another tomorrow and the car is not much fun driving right now. If anyone want to call me collect my number is 920 667 4377 ask for Roger

I am certainly not a mechanic, so I will be interested in seeing what others say.

However...I just finished going through this on my 440-6.

My suggestions, in order...

Since you are using a Mopar electronic distributor...initial advance is pretty much meaningless. Set it at 38 degrees at full advance, using a timing light that can dial in advance...for this distributor it is at about 2300 to 2800 rpm (once you see it stops moving when using the timing light). With the vacuum advance disconnected and plugged.

Turn your vacuum advance all the way counter clockwise so it barely contributes, you can come back to it later. Hook it back up.

Then you need to go after the carbs. There are great previous posts on how to set up a 6-pack. Your issues sond very much like carb to me, once the timing is set right. Again in order...check floats, have outboard carbs set at about 3/4 to 0ne turn out on the four mixture screws and then work the mixture screws on the center carb. I am assuming your linkage is set right. What size jets are in the center carb? Is your car an auto or stick? Read the previous posts on this site...use the search tool...they are very helpful

You should have 34 degrees total advance with the vacuum advance unhooked. After setting total advance I would try it with the vacuum hooked and unhooked, you want the vacuum advance hooked up if it doesn't ping with it.
The surge is most likely coming from a lean condition, you most likely have a vacuum leak somewhere, could be a leaky manifold to head gasket or an open vacuum orifice somewhere. I would check the vacuum tree at the back of the manifold to make sure all your vacuum lines are hooked up correctly.

Sheldon

I had the same problem with my 440-6, drove me crazy for months, I had a vacuum leak in the power brake booster diaphram, brakes worked so I did'nt suspect it originally. Vacuum gauge showed low vacuum (15-16) and fluctuating, replaced booster vacuum is now 20-21 and no more surge.