Hello All,

I recently acquired a 1965 F-250 with a 352 in it. It doesn't smoke, and has plenty of power to get me cruising comfortably down the superslab at 80 mph. It makes really decent power, probably better then the chevy 350 I had in a 1/2 ton 1990 chevy I had a while back.

But I do have a vibration. The motor just "feels" unbalanced. It doesn't vibrate the mirrors (although, the exhaust note does when I idle at 800 rpm, the cab resonates...I think I need to lower the idle), but it does feel like the engine is 'missing'.

I can feel it in neutral or under load. I've changed rotor/cap, plugs, wires...triple checked all my connections and wire order. The engine has a lot of power, but I'm hesitant to give it more then 65% throttle....due to the vibration. But the truck runs well even using the limited throttle.

While the truck is running, I pulled each plug wire off the spark plug and checked for spark delivery (and also to see if the engine cadence changed). Nothing conclusive, other then it seemed every plug was getting fire. I'll have to check it again.

I'm no mechanic, but I'm ready to try some other things. I've read that I need to check for vacuum leaks, check compression to see if one of the cylinders is significantly lower then the others, check timing. Also thinking about installing a vacuum gage.

I guess I need to come up with a checklist.

Any thoughts or suggestions would be appreciated.

d

 

Check you carb adjustments, idle. An ill adjusted carb will make on idle rough. When check timing are you plugging the vacuum advanced? And check to make sure the timing advanced diaphram is not leaking. If not your timing adj will be off. Yes on the manifold vacuum. Should be in the 18-22 range at idle, 650-700rpm. While your running a compression test, may want to run a leakage test too if one is out of line.

 

Well I checked the compression last night. They ranged from 168 to 183. I changed the idle by adjusting the two forward facing screws on the edelbrock carb. I went in half a turn on each. Now idles at 500 rpm, instead of 800. Is that too low? I'll look for vacuum leaks and check timing tonight.

 

If your talking about fuel/air ratio mixture screws.. you dont want to be guessing at this. Get a vac gauge! In means leaner, and leaner (too lean)can create a serious issue in a short period of time ...way short! KEEP AN EYE ON THE PLUGS FOR SIGNS OF WHITE!!

 

Just turning the air/fuel screws blindly is not a good thing. You should have a throttle stop on the side to adj your idle RPM. Get a vacuum gage and connect it to the manifold side. Then turn the air/fuel mixture screws to get max rpm and vacuum. If you were idling at 800 you may/will need to back off the idle stops, and re adjust the air/fuel mixtures screws. Move these (real slow, so you can watch the change) cw till the rpm/vacuum starts dropping then ccw to max rpm and vacuum. Then do the other one. It's common to have to re-adj the idle RPM. Some say to go a 1/4 turn lean, I prefer the smoothest (highest reading) setting.

Others have reported that some of the air/fuel screws were way off, others not. So it is a good idea to adj them for your engine.