PLUG READING FOR A NITROUS MOTOR

[John_Heard]

Put a fresh one in it before your pull and then yank it out afterwards (ideally all eight but do what you can). Then cut the threads off so we can see the base of the porcelain. If you have time on the dyno you might also try a pull with a degree of timing out and see if that gets rid of the tiny speckles and if you see any HP difference.

[Craig W.]

I found this year that my combo will slow down if I try to clean up every last bit of fuel off the plug. Could it be telling me that something else is not quite perfect with the tune? Timing is close but might like a degree one way or the other in certain conditions.

[John_Heard]

Might be just the plug heat range, as in colder than necessary for that shot? A hotter one might look cleaner, but not really mean the tune up is off. A degree one way or the other is pretty normal I think depending on air conditions.

[Craig W.]

I started the year with a -10 plug but had to move to -9 to see any heat in the plug. What I was seeing with the -10 didn't correspond to the timeslip. Adding timing would slow the car down but still no heat so I knew I had to move to the hotter plug. Now I can see a timing mark.

[Clutch]

Hello,

Need some help, I have build this engine and everything is okay, no smoke, no oil consumption, pull's very nice etc. After 500 miles I went to see the plugs and the cylinder 4 is very different from others. Is it possible to give me some tip guys?

I think is some extra fuel on this cylinder but I don't know why. I already change the injector number 3 with number 4 and still do the same.






Thanks in advance

[John_Heard]

I'd start with a compression test and see if that cylinder has sealed up ok as compared to the others, it looks dry but that's good thing to do for starters.

Next perhaps ohm that plug wire and/or swap it out, maybe weak ignition on that hole. I don't know if it has a solid lifter cam or what it uses, but maybe check the valve lash too.

[Clutch]

I did a compression test every cylinder equal at 15bar.

I will check the wire and valve lash.

Many thanks John

[Clutch]

After 2000 miles and a reduced 2% in fuel in this cilinder the car pulls very strong but this spark plug continues a bit dif from others.


It doesn't burn oil and I made another cilinder pressure test and all cilinder are in the 18bar range.

Spark cables ok and valve lash ok.

[grandville455]

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