B85 Spark Plug Question

[Robb]

I recently acquired a 1956 B85 and we need to replace the spark plugs. I've heard that both sides take the same plug and I've also heard the opposite. Can someone confirm which it true. The service information I have doesn't mention using 2 different ones but I'd like to be sure.

Thanks!

Robb 

[41chevy]

Twin ignition 707 engine my info show the same plugs for both.

[Robb]

Thanks, what plugs do you prefer?

[41chevy]

AC, NGK or Bosch as a 3rd choice. I've had so so luck with Champion over the past few years. Had to many fail for no reason.

Edited August 19, 2020 by 41chevy

[eddeere]

I agree with 41 chevy . Stay away from Champion. I have put new Champion plugs in a few two cylinder tractors in rebuilt engines ran the tractor for an hour or so, Then a few months later the tractor would not start until the plugs were replaced. 

[Robb]

Thanks everyone, I appreciate the help. It starts, runs and idles well but it's not running real smooth at higher RPM's. We are replacing all of the plugs and installing a new set of spark plug wires, which it needs anyway.

Thanks again and I appreciate y'all sharing your knowledge.

 

Robb

[1958 F.W.D.]

3 hours ago, Robb said:

Thanks everyone, I appreciate the help. It starts, runs and idles well but it's not running real smooth at higher RPM's. We are replacing all of the plugs and installing a new set of spark plug wires, which it needs anyway.

Thanks again and I appreciate y'all sharing your knowledge.

 

Robb

What kind of gas are you running and if it is ethanol-formulated, how long did it sit? You may have snot in the carb and fuel system; you may have to rebuild the carb. 

Strongly recommend you run non-ethanol if you can get it. 
www.pure-gas.org

 

[Robb]

Thanks. Carb was rebuilt and the gentleman we got it from always used non-ethanol and we're doing the same. I appreciate the information though. If he hadn't made me aware, I probably wouldn't have thought of that.

 

Robb

[41chevy]

After you do the plug wires and road test it, if it still rough at hi speeds a few things can cause the issue. Point bounce, the flat springs do  lose tension with age,  ohm the primary and secondary winding's in the coils out. They can break down and at higher RPMs can cause a slight misfire.  Check Primary side ohms from + to - terminals should have a value of .4 to 2 ohms.  Check secondary ohm from + terminal ( - side if the system is still positive ground) to coil wire tower values should be from 6000 to 12000 ohms.

I only mention how to check it because most techs are not familiar with old school systems.  Paul

[Robb]

Thanks, I will check that as well.

Robb

[yarnall]

When I was looking into replacing the plugs on my father’s B85 I talked to a lot of people.  I believe Info from the mack museum said Champion D14 and D16 (I think that was the number).  A mack restorer told me to use all D16. That is what I did.   
i have also had trouble with Champion now and am buying Autolite    Mike. 

[Robb]

Thanks Mike, I appreciate the reply!

[Firemack]

The other option is go electronic ignition, I did a write up on that a few years ago when I swapped the points out on a 707 in a B95. 

You can search for it on the site and find all of the info and I purchased the high quality cap rotor wires and other parts from John Brillman. He actually has the template to make up the original wire sets with the Packard 440 original type wire and Pertronix electronic igntion. His number is 540-477-4112 or www.brillman.com. He also has the old truck disease (Autocar). 

Firemack

 

 

Edited September 4, 2020 by Firemack

[Robb]

Thanks for the advice. We actually got plug wires and a couple of new coils from him. We did discuss the electronic ignition and I’m sure we’ll switch at some point in the future. Had we not already bought the new plug wires, we probably would have switched it over then. 
 

Thanks again!