misfiring after losing fight to high speed winds - Spark plug troubleshooting please.
 

1970 c10, original 4bbl 350 points ignition, 84k miles
Thoughts on the misfiring, spark plug conditions and the next troubleshooting steps?

got truck running after 11 years parked from previous owners.
did not change any of the following spark plug, wires, rotor cap, points.
put about 2k miles on it last 6-9 months.
got caught in high headwinds on fwy attempting to go 60-75mph
The truck lost the fight and started misfiring now and lost hp.

This is what the original spark plugs look like when pulled.

I am replacing the plugs and will drive a bit to see what the new plugs look like after.

Left to right is front of engine to back.
3, 4, and 8 are the obviously the ones that concern me the most.

Re: misfiring after losing fight to high speed winds - Spark plug troubleshooting ple
 

I would start with a Compression check.









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Re: misfiring after losing fight to high speed winds - Spark plug troubleshooting ple
 

How much oil is it using? I agree with Getter-Done, start with a compression check and if that looks good do a basic tune up and drive.

Re: misfiring after losing fight to high speed winds - Spark plug troubleshooting ple
 

Also make sure you have the correct heat range plugs. Too cold and they'll foul too.

I'd say headwinds had nothing to do with it. Compression check will tell you a lot more.

Gary

Re: misfiring after losing fight to high speed winds - Spark plug troubleshooting ple
 

If compression is good it probably could use valve seals.
Oh, almost forgot and a tune up.

Re: misfiring after losing fight to high speed winds - Spark plug troubleshooting ple
 

2nd plug from left in pic, top, looks to have a very narrow gap. Possible that is where your misfire came from. Especially if a piece of carbon lodged in the gap during the fight with the wind.

IMO - 1st step is replace points, cap, wires, and plugs. Worn points can cause a misfire.

2nd thoughts on valve seals. If original, very likely they are worn/cracked from age.

Might be worth it to pull the heads and inspect the valves. Pre 75 heads/valves were setup for leaded fuel. Later heads and valves were a bit different to deal with unleaded fuel.

Re: misfiring after losing fight to high speed winds - Spark plug troubleshooting ple
 

Do it in stages. First new plugs. Then try cap, rotor, plug wires, and so on, doing the easier cheaper things first and note what happens in each step.

And I saw the comment about a loose carbon deposit that might have closed a spark gap too tightly... Here's a shameless plug for one of my employer's famous products: Techron Concentrate. Use a bottle at the recommended treat rate of 1 oz per gallon of tank size.

Dump a bottle of Techron Concentrate in your fuel tank and fill it up with gas. In the past I've done lots of lab testing. It's a very gentle and persistent cleaner. It should clean your intake valve and combustion chamber deposits. Run it for a tankful of mild around-town driving. Also, we've seen that the second tank after that, even if you don't add any Techron still keeps cleaning, because of the "heel" left behind from the first tank that had the full dose. One set of experiments I did showed a solid restoration of 5-6% of power and torque. We also checked flow bench with dirty intake valves vs. cleaned ones and vs. new ones. Both flow and swirl numbers were significantly improved and similar to the numbers with brand new valves.

Re: misfiring after losing fight to high speed winds - Spark plug troubleshooting ple
 

If your just going to get it running then fine throw money at it.

If you looking to see the true condition of your engine get a Leak Down Tester.

Your burning oil on three of those plugs pretty apparent by the black soot. That is an indication of leaking valve seals or worse yet completely worn oil control rings.

A compression test will only tell you if your engine will build compression. As opposed to holding it.