I have a 302 ford that I can only get 12" vacuum at idle and idles rough. Autolinte 4100 carb freshly rebuilt, new plus, wires, cap, points, and condenser. Plugs run nice chocolate brown. I removed one wire at a time and all are firing. Spark is bright white not blue. Timing is 6 degrees BTDC, dwell is constant 31. I'm confident there are no external vacuum leaks. Vacuum will vary from 10 to 12" while idling. Idle screws are set for max vacuum at 2-2.5 turns out. Cam is unknown as I just purchased the car. Am I missing something?
Is your vacuum needle steady or bouncing?Possible burnt valve.Check compression on all cylinders cranking and running.
can you adjust the timing while it is running with the guage hooked up? A low vac reading may be late timing... here is a good read. http://www.secondchancegarage.com/public/186.cfm
Looking at the various scenerios my vacuum gauage was reacting more like retarded timing than any other. I'll advance it tonight and see if it improves.
be careful if you advamce it to the highest reading you will have timing that is too far advanced,,,,you can advance to the highest reading of vacuum and back it off 2 inches...then check it with a light
I may be dealing with multiple issues here. Put the timing light on again andit had moved to about 15 degrees. It would not run a 6 degrees as it did last night. I could advance it up to 30 degrees on the damper and seemed to run fine in the garage....was afraid to drive it so backed it down to 15 degrees. Ran good for about a block then started missing and running rough again. Wondering if my damper is shot or if the timing chain is stretched. Have never experienced this before....vacuum went up to 15"at the 30 degrees.
Ported or manifold vacum. I find manifold vacum works best on my 302's for som reason. One with a holley the other edelbrock.
Check to see if TDC #1 is the same as the damper. I have seen the outer ring slip or even come off. What cylinder are you using as #1?
#1 is on the right even though it is not the most forward cylinder. A Ford thing don't ask me why. Jim Ford (55willys)
If you are going to use a timing light, and it is good to use one !!! But if you do you need to be sure the marks are correct, that the balancer hasn't slipped and all that stuff. You need to confirm the marks with a piston stop test. Otherwise you are unsure that the timing light isn't telling you stories that make you chase your tail You could just time it by ear, vac gauge and seat of the pants dyno too. But you wouldn't be able to say its at 6*.
I would double check your timing mark and also have another look for vacuum leaks. I had a similar problem on my mopar 383 recently, rough running and severe advance to get it running okay. It turned out to be a vacuum leak at the intake (even after I thought I had resealed it well) Good luck.
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