I have a stock 352 in a 66 f250. When I am cruising down the highway I get this surging and slight miss. If I unhook the vaccum advance hose it runs good at wot but misses on the highway, and If i hook up the hose it runs like crap because the only vaccum port i have is the one at the base of the carb (2100), and it pulls too much vaccum. What can I do, aside from buy another carb that has a ported vaccum port.

 

oh, and the inside of my distributor cap has uneven wear on the contacts.

 

66. you're supposed to have lots of vaccuum there. Ported vaccum is a mistake, and won't cure your problem. Because you mentioned the uneven wear inside the dizzy, you might want to check the shaft for play. If the dizzy bushings are worn, the shaft 'walks' around the inside of the bushing....and timing is frequently not where it should be. Thats a good place to start. Manifold vac advance will not cause the problems you describe.






DinosaurFan

 

OK, that sounds like you may have wear in the distributor bushings, or possibly a bent shaft.

With the truck secured, remove the cap and crank the engine. Watch the rotor: Does it seem to wobble? Without cranking, grab the rotor and try to move it side to side.

It could be that your dizzy is just plain wore out.

FWIW, I snapped a pic to show the spark port. If you have vacuum there at idle, the throttle screw is holding the throttle blades open too much. If that is the case, you have some tuning in your near future.



I'm sposed to be near FoCo one of the next couple weekends. If you don't get things sorted out by then, maybe we can put our heads together.

 

great advice. come to think of it the upper bushing was making some noise a little bit ago, and then stopped. I will check for shaft play and if it's bent. and hypoid thanks for the pic. that helps.
and there is no vaccum to the advance hose at idle. the problem is that as soon as i open the throttle, it advances the timing way too much. so right now the vaccum advance is disconnected, and it runs fine except for when im crusing. then i get the surging and missing.
the dizzy is about 6 months old. it's a reman from napa. if i have to get a new one, where or what should i get. i don't feel comfortable buying another one from napa

 

66, I would have thought NAPA's dizzy would be fine. But check the shaft's paly anyhow. As too the advance, if you have no advance at idle, then you're hooked up to ported spark advance, which is not the best way to go. Try hooking the advance to a full manifold vacuum source and see how it runs. Even if your truck came with ported advance from the factory, and it could have, depending on where it was made, manifold works better. But you will have to change the amount of initial that you have. But neverminding all that about the advance, you should check the fuel ratio- it sounds like you have what I would call 'lean surge'. DinosaurFan

 

Now there is some new info. If the dizzy has no apparent defect, we need to verify the total advance, and the curve. The rule of thumb is 10* advance for every 1000 RPM.

Then again, it also sounds like you might be running too lean. Have you pulled the plugs to check the color?

First things first, verify the igniton and advance. Then move on to fuel.

Edit: LOL Dino, one step ahead of me tonight.

 

great thanks guys, i'll check it tomorrow and post the results.

 

DING DING DING! Give that man a cigar.

With the points closed (or open), push/pull the rotor in the direction of the points, I bet they open and close right before your eyes

 

Not what I would expect from a NAPA product, but that's why they come with a warranty. The dizzy that came with my engine had a Checker's rebuild sticker on it; so far, so good.

 

o.k so I got a new cap and rotor from napa, and began to investigate. I pulled the cap and wiggled the dist. shaft. it had a lot more up and down play, and not much side to side play. I pulled of the rotor and it seemed to "slip" off rather easy. I installed the new rotor and it pressed on better and went further down than the last one. Than the new cap also seemed to fit better. (?) so far so good, than may explain the uneven wear on the cap contacts.
than i pulled some plugs, and you guys were right, the plugs read very lean. white. so I installed #52 jets (had 48 before, because of the altitude).
Than I rechecked the timing, it was at 16 degrees initial, i bumped it back to 12 degrees and took it for a spin. right away it ran better but was running a little sluggish. than i realized i had the air/fuel mixture screws way out because of a previous test. SO i got out re-adjusted them and all of a sudden the planets aligned and I cruised at 50 (it's got 4.56) and life was good.
i realize now this is probably the last thing you guys want to hear, that i did 10 changes at once, but i just wanted it to run right so.....
thanks again to everyone for all the help, this is why i donated to the site. I don't have alot of extra money, but you guys and the site is worth it.


brad

 

oh and i did disconnect the coil wire and remove the cap and watch the rotor spin, and it appeared to be spinning true.

 

o.k, so maybe it's NOT fixed. it was just my imagination. I looked at it again today, and sprayed some carb cleaner around the carb and the idle dropped big when i sprayed it around the throttle shaft. then i was able to wiggle the throttle shaft and actually create an audible sucking vaccum leak! whoppie.
so now I broke down and bought a 350 cfm holley and a set of #56 jets. they will be here this weekend.....so.....we'll see........sorry for the preemptive celebration.

 

Throttle shaft being lose doesn't usually cause problems when driving down the road. Off-idle, idle, trying to get it running when cold, sure.

I still think you might have a loose distributor.

How much did the distributor shaft move side-to-side? Even .010 (or even less) can cause you all sorts of problems when the dwell walks all over the place.

 

I just went outside and popped the cap off and the dist. shaft has a very,very small amount of slop. when the points were closed (on a flat spot on the shaft) i couldn't get the shaft to wiggle enough to effect the points gap. Does this still sound like it could be the problem.
also, the other day when i had the dist. cap off checking the shaft for straightness, i noticed that with the cap off and the coil wire un hooked, when my buddy turned the engine over, i could see a spark jumping between the points (?)
I just want to get to the bottom of this.......