1970 C10 Spark Plug Read.

[Gasbuggy]

I bought a 70 C10, it's a 307 4 speed truck with 39,000 original miles. A friend of mine owned it for over a decade. A rancher ordered it new and used it rarely for trips into town.

The truck drove great but I thought the idle was just a little odd. I know it had a complete tune-up not that long ago maybe 2,000 miles. So I pulled a plug to get an idea what's going on and I removed an old Motorcraft. They were only finger tight, no ratchet needed. Mentioned this to my buddy and
he said oh yeah the mechanic said GM discontinued the plug for this truck so he left the old ones in there. And this is actually true, AC Delco discontinued the 44 heat range and unfortunately most systems are recommending the colder 43 when you should run 45s. Which is what I used. R45S. Runs and idles great now.

This truck has a happy engine in it. But I have a hunch it still has the original nylon timing gear.

 

[PontiacHO]

It’s running right where it should. Not rich or using oil. Did you replace points, condenser, rotor, cap, and ignition wires? Remember to disconnect the vacuum advance hose when checking-setting the timing. Nice truck!

 

[Tman220]

Beautiful truck! My dad had a 1971 C10 growing up, would love to find one again.

 

[Chris142]

Glad to see the correct plugs in it. 70 was the last year for plugs with sealing washers. 71 they went to the taper seat peanut plugs.

 

[JHZR2]

Nice truck, nice plugs!

 

[Astro14]

The plugs look good. I would do the timing set. It’s not that the gear itself is nylon, it’s that it has a nylon shell around the teeth, to dampen the noise. If that nylon cracks and starts to break off, the truck can jump time.

And even one tooth off it won’t run.

I had a 1970 Ford, very similar timing gears, with nylon, and that’s exactly what happened to me. I could not figure out what was wrong with it. Finally, I went through the very basics and I noticed the distributor was off by 15°, which made no sense until I realized that cam gear had jumped a tooth.

New timing set took a couple hours, and it fired right up.