I've been chasing this issue for a while, I'm absolutely sick of the way the car runs. I'm fairly certain it's an ignition issue. It vibrates all the time in every gear moving or not. It's worse above 1800 RPM.

I have a fleabay HEI distributor, and a clear clue cap and rotor I got from a swap meet. I used the wire for the ignition coil before I knew it was 9 volts. I ran a 12 volt source but it didn't change anything. All 8 spark plugs are wet with fuel. I wonder if the issue would be fixed with a good 12 volt source and new plugs. I also wonder if I maybe messed up the coil by running a 9 volt source for an extended period.

The car is a '70 with a 302 and 5 speed. It vibrated when it was still automatic. I also have a Holley 600 CFM. I would really like to fix this issue once and for all, it's almost unbearable to drive the car any longer than to the grocery store and back.

 

All the plugs are wet with fuel? I dont understand how it could even run at all and have wet plugs?

Did the car ever run right since you owned it?
If yes when did it stop running good and what changed?

Does it just dump black smoke when you stomp on it?

Its a holley so thats cool..What size jets are in it?
How old is the carb?

Could the firing order be wrong? If its running a cam that you are not aware of that cam may use a different firing order

if the engine is cold and you start it up and measure the temp of each header with a non contract ir temp gun which headers are warming up quickly and which ones are staying cold or warming up much slower?
OR do they all warm up at about the same rate?

-Gun

 

Here are 2 of the plugs:





The motor has always run this way, it doesn't dump black smoke. It's not a timing issue, any more advance makes the starring slow, any less and the car hesitates on take off. The Holley is less than 2 years old, I'm not sure what jets are in it, I picked it up from advance auto parts. I'll see if I can borrow a heat gun from work. I put the cam in, I believe it is a lunatni bare bones 268 but it was 7 years ago so I could be wrong. I remember looking for one that was for a '70 302. The way to check this would be to swap 2 plug wires wouldn't it?

 

Those plugs look pretty darn good. Your fuel mix should be good enough to get it to run okay. Do all 8 plugs fall within that color range?

1) Try switching to the 351w firing order (the distributor rotates counter clockwise) Try switching to the 289 Firing order (but try to verify which one you are using before you switch)

2) you could remove a plug wire one a time and see which ones make it run worse or produce no change...any removed plug wire that makes no change is suspect.

3) The heat gun would tell you if a cylinder is not firing or not firing as well as another...a slower increase in temp would indicate no or slow burn.

4) Does your damper wheel have the proper balance weight on it? aftermarket damper wheels have removable weights which could be the improper weight installed or not installed at all!

 

^^^ good advice from Gun Jam- those are the things I would look at first and in the same order.

 

All 8 plugs are similar. I swapped to the 13726548 firing order from 15426378 firing order and it made the engine run worse. I did suspect the harmonic balancer before and swaped it for a new one, no change. I am positive it is matched to the flywheel because I had a hard time finding a flywheel with the correct number of teeth and balance because I have a 3.8 bell housing. I forgot to check on the heat gun, I'll check on it today.

 

What is the gap on those plugs? Do I see a crack in the insulator through the 45 on the top picture? Have you run it at night and look for arcs?

 

depnding on if your engine is pre 1982 or 1982 or new will depend on what flywheel and balancer you need. pre 1982 uses a 28oz flywheel and balancer. anything 1982 and newer needs the 50oz