Spark plug gapping - How it affects timing - How to gap when burning oil

[MadMax_636]

This is a post asking about what yall are gapping your plugs at. Mainly because Ive done endless research on plug gapping and heard/read mixed stuff. Adding .010 from factory will help with performance and economy, it wont affect timing (Ive learned the bigger the gap. The more advanced the timing is), and so on.


Im wanting to know what yall would, are doing, and have done to your plug gaps when burning oil and keeping idle smooth.

Also, Ive gotten my truck back up and running and ive learned a lot since I was on here last. So, Ive got my carb tuned in away that the lowest I can get the idle (zero vac signal on ported vacuum) is around 1000-1250 rpm. Ive read on here and other places it should be 900... I dont have AC btw... Anything lower it just wants to die and run rough. No matter what I do with timing, idle mix, or anything. So ive tuned timing, curb idle (with a vac gauge on the ported vac port), and have my plugs at .044

 

[gw33gp]

Spark plug gap should not affect the timing. I don't see how a larger gap would advance timing. A larger gap would require more energy to create the spark, so if anything I think it would have a tendency to retard the timing but not easily measurable.

Over my many years of racing I learned that high compression engines require a smaller gap to get a strong spark. I think burning oil would create a similar issue. The problem with oil burning is a tendency for the spark plug to get fouled with carbon build up. A closer gap may foul easier. A hotter spark plug may help with that but I have nothing to back that up.

 

[MadMax_636]

Spark plug gap should not affect the timing. I don't see how a larger gap would advance timing. A larger gap would require more energy to create the spark, so if anything I think it would have a tendency to retard the timing but not easily measurable.

Over my many years of racing I learned that high compression engines require a smaller gap to get a strong spark. I think burning oil would create a similar issue. The problem with oil burning is a tendency for the spark plug to get fouled with carbon build up. A closer gap may foul easier. A hotter spark plug may help with that but I have nothing to back that up.

About the first part. I’ve got the duraspark conversation. Zero original ignition systems.
From my experience widening the gap has caused timing to advance. Probably because of the further distance for the spark to complete.

The second part. I’m running NGK platinums and don’t have fouling at all. Just want to be future proof as well as prevent fouling ever. I’m also on the hottest range of NGK plugs I can find for my motor (mainly my price range). I’m considering going to iridium plugs but they cost way too much for my wallet.

I’m mainly trying to future proof, get a nice steady, smooth, low idle and not have a surging (drops in vacuum as if it’s got a major vacuum leak but clears up. I am running corn gas) after starting up from sitting.

atm, she’s running good but always want to learn more and improve on my stuff. That’s kinda the bad part of me. Don’t know when to leave well alone.

 

[rubydist]

My understanding of physics says that increasing the plug gap will very slightly delay the timing, definitely not advance it. It will take a few milliseconds longer for the voltage to build up to the point where the spark will jump the gap.

If your plugs are clean, then I would not adjust the gap. If there is enough oil in the combustion chamber that the plugs want to foul, then I would decrease the gap a little.

 

[Uncle Gump]

Increased spark plug gap will have zero effect on base timing. It may increase the duration of the firing line but has nothing to do with turning the primary side of the ignition coil on and off.

 

[19Walt93]

Spark plug gap does not affect timing, the spark moves at 186,000 miles per second. Too wide a gap will weaken the spark, that's why high compression engines need a tighter gap. The idle mixture should be adjusted with the vacuum gauge attached to a manifold vacuum port, not the spark port, and with the engine running at the desired idle speed or as close to it as possible. If the throttle is open far enough at idle to get vacuum at the spark port, that's a problem.

 

[MadMax_636]

From my experience a bigger gap has affect timing. Not base timing but I’ve noticed changes. thanks for the new info on that area.

When I get home and the engine is warmed up. I’m gonna fine tune it. That is the idle.

 

[cbxer55]

Similarly, on a supercharged engine, you need to tighten the gap if you are going to increase boost. I went from 8 pounds on my Lightning to 10. Not much, but the recommendation was to tighten the gap up a bit from factory. I am also running NGK TR-6 racing style plugs in it. My 98 3.0 Ranger just turned 185,000 yesterday, and I've run nothing but the factory style plug and factory recommended gap. I've tried various of the multi electrode plugs in the past, including those E-3. JUNK. All of them. Just run the Motorcraft Double Platinum plugs at the recommended gap. The truck will fall apart around them.

 

[Angie]

So, Ive got my carb tuned in away that the lowest I can get the idle (zero vac signal on ported vacuum) is around 1000-1250 rpm <<<<<<


0 vac on idle is a problem .... when the engine is increasing RPM's the vac should drop ... recheck your hook ups, as walt said, you have something wrong.

 

[franklin2]

So, Ive got my carb tuned in away that the lowest I can get the idle (zero vac signal on ported vacuum) is around 1000-1250 rpm <<<<<<


0 vac on idle is a problem .... when the engine is increasing RPM's the vac should drop ... recheck your hook ups, as walt said, you have something wrong.

I think he meant he has zero vac on the ported vacuum port, which is good.

I think he needs to get some brake cleaner and spray it around here and there and around the base of the carb. I think he is sucking air in somewhere besides the carb throat.

 

[MadMax_636]

I think he meant he has zero vac on the ported vacuum port, which is good.

I think he needs to get some brake cleaner and spray it around here and there and around the base of the carb. I think he is sucking air in somewhere besides the carb throat.

That’s what I mean the ported vacuum port.
move sprayed brake clean all around and nothing affects the idle. I was thinking that maybe lower the spark gap. On the 70s pinto and mustang 2 the gap is 35.

 

[Uncle Gump]

From my experience a bigger gap has affect timing. Not base timing but I’ve noticed changes. thanks for the new info on that area.

I'll say it again... plug gap has zero effect on spark timing.

Why are you running the hottest plugs you can find anyway. You having fouling problems... gas or oil?

If so... did you root cause the problem and correct it? Or are you stuffing hot over gapped plugs into it in an attempt to cover it up?

 

[franklin2]

That’s what I mean the ported vacuum port.
move sprayed brake clean all around and nothing affects the idle. I was thinking that maybe lower the spark gap. On the 70s pinto and mustang 2 the gap is 35.

Like the others said, the sparkplug gap will not affect your problem. When you slow the idle down till it's idling rough, have you then tried to tune the idle mixture screws?

Also the EGR valve. Is it still on there? If it is, I would take it off and make a solid block off plate to put underneath it to block it off and see if that affects it. They are famous for getting pieces of carbon stuck in them, causing them to leak. If they leak they are like a big vacuum leak and will cause a rough idle and stalling.

 

[MadMax_636]

Like the others said, the sparkplug gap will not affect your problem. When you slow the idle down till it's idling rough, have you then tried to tune the idle mixture screws?

Also the EGR valve. Is it still on there? If it is, I would take it off and make a solid block off plate to put underneath it to block it off and see if that affects it. They are famous for getting pieces of carbon stuck in them, causing them to leak. If they leak they are like a big vacuum leak and will cause a rough idle and stalling.

yeah, I’ve done everything. I removed the spark plugs to see how they looked and they were dark/fuel fouled. The #1 plug cracked so I’m gonna have to replaced it….
I took the carb off to see if the PV was leaking and the cover had a little fuel in it.
So I replaced the gasket. Then I put the carb back on and tried to tune it. I then got it to idle around 75-900 but the vacuum was low and the timing was way out of wack. I then tried to adjust timing and it would move but randomly it would fly way too advanced. So I tried to adjust it. Same thing. It did this before and after the power valve adjust them.

for the person that said spark gap doesn’t affect timing…. Whatever. I had to adjust it after I tried over-gapping once….Also my plugs are NGK platinums. The only heat range for them are 5. I’m not looking for the hottest. My gaps 0.044. Factory setting.

 

[MadMax_636]

Like the others said, the sparkplug gap will not affect your problem. When you slow the idle down till it's idling rough, have you then tried to tune the idle mixture screws?

Also the EGR valve. Is it still on there? If it is, I would take it off and make a solid block off plate to put underneath it to block it off and see if that affects it. They are famous for getting pieces of carbon stuck in them, causing them to leak. If they leak they are like a big vacuum leak and will cause a rough idle and stalling.

For things Ive left off. The EGR is gone. Theres a block off plate with a gasket under it. I used a OEM style EGR gasket for it. I was thinking about removing it to replace the gasket in case it was leaking