My son gave me a timing light for my birthday and I was checking the timing on my 1976 390 and when I pulled the vacuum line of the vaccum advance to plug it off I didn"t get any suction. It was on the port on the passenger side of the Edel 600. So I plugged the port on the passenger side and hooked the line to the port on the driver side of the carb. The engine idled up about 200 more rpms. I took it out on the highway and couldn"t believe how much more power it had. I bought the truck from my son and he had the carb put on it and had it tuned by a machanic. The timing was set by trial and error. It was suppose to be set so it ran better. He marked it at 25 degrees. I know this sounds really high. It had 3 paint marks and I could not tell which one it was set at. The timing marks are really rusty. So I cleaned them with rust remover and I ran out of time before I could remove the paint marks. But when I removed the vacuum hose and put it back I could see about 15 degree change. I am going to clean the paint marks off and try to see what the timing is set at. The decal on the motor show 6 degrees at 550 rpm. But I think I will keep adjusting it until it runs better. Is the carb port on the driver side the right port for the vacuum line. Also can anyone tell me how the timing numbers are spaced. thanks for any help

 

the passenger side is ported or timed and has no vac at idle, the other is a manifold source and pulls vac until the throttle blades are mostly open. The ported or timed port is what most people run.

The timing marks are 10-0 atdc, then o-30 btdc. There are 2 degree increments. You want 6-14 btdc for timing.

 

Thanks fordeverpower. With the vacuum advance connected to the manifold source the truck ran a lot better on the highway. Is there a problem with my dizzy? Or did the engine builder put the wrong cam in the engine. The engine was rebuilt before my son bought the truck and I have not been able to find out what was done to the engine. But it does idle rough. Like it has a high cam in it. Thanks again for the info. I am trying
to learn all I can about the fe engine. It really help when people like you take the time to explain things.

 

At highway speeds the ports should have equal vacuum on them. The difference is at idle and just off idle only.

 

I have the same engine and carb but run the driver side port. Truck runs great. Should I be using the other? Why or why not? Now you got me wondering if mines hooked up right. Thanks.

 

The ported vacuum was developed for the vacuum advance systems to give you a low initial advance (no vacuum) to idle properly and then give you extra advance at highway speeds under light loads for improved fuel economy. If you need the extra advance of the manifold vacuum to make the motor idle properly then something isn't right somewhere. Ported vacuum is the proper place to connect your vacuum advance to.

 

I retimed the truck and switched vacuum ports...you guys were right as always. Seems to be smoother and guicker when hitting the gas from idle. I just made a trip of 250 miles with it...didn't see any difference in mileage, but it's so hard to drive 65...it wants to go 90!

 

I found the paper work for the carb and it said the same things you guys said. So I put the vacuum hose back on the port side. When checking all the vacum hoses I found 2 manifold ports caped with plug that had splits in them. So I replaced the plugs and it make the vacuum a lot stronger. I checked the timing and it wasn't set on 25 btdc like it said on the fan gard. It is set on 6 btdc. This was with the vacuum hose off and plugged. I set the #1 piston a tdc and the timing mark was on 0. With the hose hooked up and the engine at 2500 rpms the timing advances just like the book says it should. I want to adjust the timing up a little to see if it runs better. But I didn't have a wrench that I could get to the dizzy nut. I know it takes a special wrench, but does anyone know what size wrench and where I can but one. Thanks for the all the info. It's good to know that there is a place where you can find out anything about a fe engine.

 

Actually a short 1/2" universal socket (or a cut doen standard depth socket) on an extension will reach if you don't have or have access to a dist. wrench.