Ran the 511 down the track yesterday. How's these ngk8's look. Pump gas with 2gals of 110.

Do they look like proper heat range and mixture. Some have brown specs.

If the specks aren't purple and shiny it's just carbon blowing off the inside of shell. Kind of hard to see that in a picture. As to heat range, you are about right on. The other thing to look at is the fuel ring at the bottom of the porcelain. How wide is it?

Forgot to add your intial timing looks about spot on. From the angles you posted it looks like you may have a skosh (and by skosh I mean maybe, maybe 2 degrees) too much total.

On pump gas you want the total line on the ground wire close to the shell. It's hard to tell how close you are in that picture, hence my skosh remark.

I did not cut the shell of the plug off yet to read that. I was running 36* total timing til I pulled a plug and seen it speckled, I then reset timing to 34* for the rest of the runs. It did slow down .5mph on next run set at 34*. The specks look to be brown in color. The color change on the ground strap was right on the bend with 36* timing.

What times did it run ?

It ran the same times my 408 SB ran. 10.40 was its best at 129mph. Actually my SB was faster.

What do you read on the plug for proper heat range? I also thought fuel mixture could be read from the ring at the bottom of the threads?

Very nice job! MPH overrules all else

I can't read a used plug accurately after the tune up has been changed, can you
Put one new plug in # 7 cylinder and make one pass and get it out of the motor ASAP before returning the car to the pits and post a picture of that plug on here
I'm thinking the mixture is to lean but changing the timing may have put the spots on the center proclyn I'm seeing from the first pass

pic 1 and 4 are the same plug after 3 passes with 36* of timing. Thanks cab.

Unfortunately, You can't learn much from reading a plug with multiple tunes and multiple passes on it.

Buy yourself a bunch of plugs from rockauto.com (very cheap NGK prices!), and make one pass. Click the car off at the finish line, take the plugs out, and cut one apart to see the fuel ring down at the base of the porcelain.

Driving it back, or multiple passes will give you bad information, and could just lead you in the wrong direction.

Ok, I was told by another racer that you need 3 passes on a new plug to get enough to read on the plug. I'm really curious to reading the heat range and timing(pic 1 and 4) of this plug as I have some brand new 7's I can throw in for next testing. As far as mixture reading, the wide band was showing rich at 12.5 thru the traps and was showing leaner with every pass with a 13.2 on the last pass being the fastest pass, so looks like I need to lean it up just a bit with a HS bleed change. Thanks guys

If the specs are brown, it's carbon, either coming off the inside of the shell, or from the combustion chamber. If they are shiny and purple. That's detonation.


You don't need to put new plugs in every run, unless you are tuning for wide open throttle. A plug will show changes in one pass. If you can't see changes in one pass, you are way off or something else is wrong.

I wonder if the race gas was affecting the AFR readings due to mixing with the pump gas better from being sloshed around from the runs, hence the time slips difference in MPH
Where you monitoring the density altitude?
With no jetting changes the AFR should have remain the same
All Information is good

Cab, the temp dropped fast from 6pm till 9:30, 72 to 58 on last pass. Was not watching density. The cooler air with low humidity 48% helped with every run. I just cut a plug for sh!ts and giggles. 7 runs with idle time in line and on and back off trailer.

Ok, brown in color. Thanks mad

The fuel was 12 or 13 gallons 93 to 2 gals 110. I calculated 96 octane with that mix. Tank is now down just under half, so i'll fill back up with 93 and shouldn't have much 110 in it. I have seen in the past 110 knock the crap out of your number with pump gas engines. My 408 lost 3 tenths once with straight 110 vs straight 93. It was 11.3:1 compression. Over octaning may be good for the engine, but not so good for your time slip IMO. There's a balancing act there for sure.

The fuel ring is probably twice as wide as it should be. It should be .060-.080 wide. Looks like more than that in the picture. Also remember you have to keep everything happy, so the fuel ring may need to be .100 wide for best MPH and that's ok. But of you can get the fuel ring narrower and still keep the MPH going up or at least not losing, the better off you should be. You may be a bit rich at idle and cruise as well and again, that depends on your combination. If you can get the color on the upper end of the porcelain to lighter brown or get it off there all together it may like it. Or...with your intake/carb/air cleaner etc it may not like to be that lean

Only testing will tell you. And not running a vacuum advance may mean you can't get much leaner if you aren't running a VA.

Going back to the track with timing bumped back up to 36*, had some new 7's on the bench, so put them in. They are a champion race style plug with cut back ground strap. See if it likes them. If it runs a little fat Dom tells me to change the HS bleeds to a 30. Looking to gain another 10th or 2, but 9's or a 10 O is not gonna happen without changing some hard parts. I thought I had a good combo of parts here to make 680-700hp, but its just not there. Dwayne spec'd the cam and its in at 105.5. Lenny freshened the 8" 5100 vert and it calcs to a 6% slip thru traps. Seems soft off the line with a 1.45 60 foot braking to 2500rpm and worse at 2000rpm. Maybe advancing the cam more would help?
No vac advance. A fast curve only 30* initial and 36* total.