1970 Ford Ranger with 302 vibration after spark plug change

[5feeney]

Hello all
I am new and first post. And still have an awful lot to learn
Just bought this truck and it was running but working thru issues.
Started and drove ok but rough. PO added headers with 3” collectors that were all jammed up against trans case and they even had to cut a piece of cross member to work it in.
I started by replacing the headers with a 2.5” collector to get the clearance I need, fixed the cross member and put in new 2-1/4 inch exhaust, mufflers and back tailpipes.
I changed the spark plugs but kept the wires as they seemed in decent shape. I have now double checked all the plugs and wires and know all to correct plug. Tuned the Edelbrook carb and now she starts right up, and idling at 930. I did notice the left set screw on the carb may not appear to be working properly, all the way in our out not resulting in any change in how she runs.
But how after the plug change as soon as I put her in drive she starts vibrating hard. thought it could be a misfire and why checked all plugs and wires multiple times now. Yesterday I checked timing and adjusted the HEI distributor. She still starts right up and idles good but same hard vibration in drive.
I have not driven her like this so not to cause any damage so not sure what happens at higher speed.
It was not vibrating before I did this work. Figure I could change the spark plugs wires next but if it’s not that wondering what I need to look at next? I am a newbie and learning as I go so any advice would be appreciated. Thanks
Jim

[cep62]

Did you set the gap on the plugs?

You can remove the idle screw and give a shot of carb cleaner and burst of air , there might be a spec of crud in there.
Also that's idling pretty fast , it might be bypassing the idle circuit , so the screw might not be effective.

You can also check resistance of the plug wires with an ohm meter , just in case you damaged an end removing them.

[5feeney]

Thanks for getting back @cep62.
I used Autolite ap5145 plugs, same as PO had in there.
They are gapped at 54 out of the box and how they were with old ones? Should I close that gap? I was seeing mixed opinions
On what the gap should be. Truck was running much better before I changed the plugs although in the rough side.
I will try removing the idle screw and the carb cleaner as well as
Check the resistance on the wires and report back.

Also related to the other post On a similar topic by Drewski
I have a Edelbrock 1405 600cfm with manual choke.
I noticed that other issue was resolved because the tach was set at 4 instead of 8 but I am not sure where this switch is and if something I should also check?

[tsherry]

I'll go for the obvious stuff, because I've made these mistakes before myself:

1) Double check your firing order and that you've reinstalled the wires to match.
2) Just because its new doesn't mean it's good, or working. I've had both bad plugs out of the box and bad wires. And bad caps and rotors for that matter. And points, condensors, Duraspark units, and ECU's.


You may have a cylinder not firing. If you have one of those laser temperature guns, you can check your exhaust manifold temperature at each cylinder and those that are cooler than the others are highly suspect. You could pull plug wires while running to determine if there's any difference--that'll get you in the neighborhood of finding one not firing, but not always.


If it ran OK before without a misfire, it's an ignition problem, not fuel. Don't go looking for a problem where there wasn't one before.

[5feeney]

Thanks tsherry. I did go looking in other places to solve before i read your reply, still dealing with the hard vibration when I put it in drive ( or reverse)
I did take it around the corner today and once i'm moving the issue stops, only when i come to a stop and still in gear. Vibration stops in neutral.
I checked and tightened all motor mounts and forward and tranny cross member, and some were pretty loose, but no change.
from an earlier post I did remove the non working air fuel screw, spray carb cleaner and brush / air it out, still not working.
I noticed today when i am in drive but not moving, if i turn the wheel the truck stalls out (have power steering), no issues restarting.
I also replaced the spark plus wires, did not help. I dont have a laser temp gun but will get one of it helps diagnose the issue.
I will also try pulling plug wires while running. Will reply back with these next results, thanks for your help

[Terry Veiga]

Hello, I’m a bona fide novice, but here goes…

…idling at 930. I did notice the left set screw on the carb may not appear to be working properly, all the way in our out not resulting in any change in how she runs. … hard vibration when I put it in drive ( or reverse).

Don’t these symptoms indicate a vacuum leak? Also, is your timing set near to factory specs?