I know this sounds crazy, but hear me out.

Is it possible that my car would run better with slightly fouled plugs because I have too much timing?

My motor is a 383 LT1 w/ 11.8:1 compression and .035 quench. I also have a Delteq ignition. I was running TR6 plugs gapped at .040 and when I pulled them after about 7k miles they were kinda pretty fouled and the gaps spread to 48-54 but were running really strong until about 100 miles ago when they started to buck the whole car at low rpm.

The new plugs are Autolite 103s gapped at 48 and they dont buck and cruise well, but feel that there is less power.

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I guess my main question is can a fouled plug run better when you have too much timing? Then clean plugs run worse because they are getting better burn rates?

Thanks,
Stu

 

I've never heard of old plugs making more power. Unless you motor liked the larger gap they opened up to as they wore out.

In any case it's usually a matter of perception. It runs smoother (maybe a little quieter) which sometimes makes it feel less powerful. I bet if you ran it on a dyno I bet it would be putting down equal or stronger numbers. Or it's possible something's not right with the new plugs- a manufacturing defect or just not the right ones for your application, different design than the old ones, etc.

Plugs are a one way street. They get only worse the longer they're in the motor, never better.

 

Thats the way I see it, but could it be that the more fouled they became, the weaker the spark and the more advance it wanted?

A weaker spark would want more advance right? Could I be putting TOO MUCH advance with the newer plugs but it runs fine with the old plugs?

Im just confused as to why it feels different. It feels like it is taking out more knock retard.

 

I would think the gap is the difference. Take a gap measuring tool and check the plugs and see if they are different. I have had the same thing happen before with my snowmachine. It was the gap that made the difference in that situation.

 

Well I measured the gaps and they were between 48-54. The new ones were all gapped at 48.

 

103s? 106s are stock heat range... TR6's are one cooler than stock. The 103's might be too cold.

 

Almost seems like a contradiction.... the plugs are badly fouled (possible sign of a too cold plug), yet the gaps eroded from 0.040" to 0.048/0.054" (possilbe sign of a too hot plug).

 

Well what else could cause the gaps to grow like that? Too much timing?

Im just trying to figure things out. I doubt the plugs are too hot. They were TR6s in a 11.7:1 383 making ~420 rwhp.

The plugs werent fouled bad (I can take some pics) but the gaps did grow from 40 to 48-54 in no more than 7k miles.