I heard someone once saying that if you use colder plugs in the middle 4 cylinders (3,4,5 and 6), idea being there are 2 exhaust ports right next to each other and these cylinders run hotter, and hotter plugs on the other 4, the engine will run more efficiently and smoother, changing some over looked engineering flukes. Anyone heard of his, or tried it?

 

There's a whole lot you can do for more power before you start trying that kind of stuff.

 

Havent heard of that but kinda makes sense in theory but motors dont seem to have issues. On serious race stuff, guys will run coolant lines into the side of the head between exhaust ports to keep things cooler. I wouldnt mess with plug heat range by cylinder unless you knew exactly what each intake port was doing regarding air and fuel distribution. If you know what each cylinder is doing you shouldnt run into any issues like detonation/preignition or any reason why you would need different plugs per cylinder. Just my guess and experience with a few motors.

 

I know installing a cam is a lot more cost and labor-effective, but this idea does work, right? And not so much for power gains, but for effeciency.

 

On a street engine you'd never see a difference.

 

Spending countless hours on a dyno can find all kinds of small gains if small gains can win a race. For just about everyone else, you'll never notice a difference. Just install the coldest plug possible that doesn't foul up.

The proper heat range will show a slight bluing about half way down the ground strap. It's only easy to see on new plugs.

 

Thanks for the input, guys. I didnt know if I'd see a difference or not, but I figured I'd ask. The Delco 43's in there now constantly look black, so I think Im gonna go up a range.

 

Plugs are cheap. Standard copper plugs should be changed every few years anyway. Platinum plugs etc cost more but don't need to replaced as often. That's the only advantage to a platinum plug. They don't wear out as fast.

 

If they're completely black then you're running way too rich.

 

I generally change the plugs every spring. And they're not as black as I made them sound, they arent fouling out or anything. Just consistantly black, if you know what I mean. I should add, it's time for a tune up.

 

Fouling will have deposit buildup on them because they are not hot enough to burn off the deposits. Soot is normally from running too rich but that can also be affected by timing. Adjusting the timing can change the fuel requirements.

When tuning especially on a dyno, timing is the first thing that needs to be determined. Every engine is different and no matter what else you do for tuning, the timing the engine wants will never change. Changing major component will change what the engine wants but not not tuning (jets, plug gap etc)

It's not uncommon to have different heat range plugs in an engine that has other issues. If you have leaking valve seals in one head, going up 1 heat range just in that head to help burn off the oil deposits will work until the seals can be replaced.

 

Maybe a dumb question, but how do you determine what timing the engine wants?

 

timing light

 

No. That is how you can SET the timing, NOT determine where to set it.

 

On a dyno. Timing is adjusted to where the engine makes the most power.

You can experiment on a dragstrip as well but it takes a lot longer. Timing is set where you make the most MPH. You make multiple passes adjusting only the timing until you can't make any more MPH then go on to other tuning.

 

apologies for my previous post. yes timing light is setting timing not determining. alky is right only way to really do it right is on a dyno. that and time

 

Also can check plugs to verify timing mark on the ground strap is in the right position

 

Awesome info. Thanks, gents!