no 6 seems lean?

[yetterben]

Getting my car dialed in to perfection. All my plugs are tanish except no 6 it looks new. It is firing verified spark. I dont get why it would look new. Compression is fine. 4, 5 tanish 6 white electorde looks new with a slight discoloration. When i pulled the old plug out it was dark. Sooty. 4 5 where as well. I am wondering if i need to just up the mixture a tad. Does #6 run lean normally?

[WarrenZ]

You don't say what carbies you are running?

If it is the standard SU's then generally the front 3 should be very similar and the back 3 should be very similar as each 3 run off a single SU. If one of the 3 looks lean may be you could check tappet adjustments on No.6, the inlet clearance could be too small and not letting in the right amount of fuel or a sticking inlet valve.

Could be higher resistance spark plug lead reducing spark and fuel burn

If you are running triples or FI then that is a whole difference ball game

Cheers

Warren

[yetterben]

Sorry about that i am running su's. Will check valve clearance on no 6 and post back. I pulled the choke on that carb and the plug turned black so it is getting fuel when i choke it.

Edited July 27, 2009 by yetterben

[yetterben]

valve clearance is fine i am stumped.

[Curtis240Z]

Did you double check to make sure all the spark plugs are the same model number and gap?

[WarrenZ]

You could swap the No.6 plug to another cylinder and see which ones runs lean, it may just be a off spec plug.

If it stays on 6 then it has got to be either poor spark or poor fuel delivery.

You could check the no6 post inside your distributor cap for corrosion or excessive wear

You could measure the resistance of the plug lead compared to the others.

Warren

[yetterben]

i Doubled checked all that and most of it is new. in the end i turned the mixture knob another half a turn. It made the 4 and 5 slightly darker more chocolate and number 6 turned mocha. I guess you cant really have even burn?

Today was the first time my car ever revved to 7 grand

Is this normal though? can you have even burn? intake mani is a e88 zx motor 3 screw su's zx dizzy flamethrower coil. plugs gapped to .44. the history of the motor is unknown to me.

Long term goals are to blowthough the carbs. I have done it on many rx7's with the nikki and with webers just not duals or tripples. I will find a way with oers i am sure. maybe individual hats.

[WarrenZ]

Good work.

I'm running the Flamethrower coil with the Pertronix ignition (but triples) and I have not gone out to that bigger gap, I think high 30's from memory, if your not happy with what you have done you could experiment with the plug gap for no6.

But if you can pull 7K smoothly that very good.

Warren