i was so excited to receive my gunson colortune in the mail. but i hooked her up today to adjust my fuel/air and was dissapointed. with the colortune in the idle became very rough. with the regular spark plug roughness went away.

it was impossible to use the colortune because the spark would alternate with no order whatsoever between tiny whitish blue flames and huge orange circles. everytime i got an orange circle you could hear the exhaust cough. however, that went away with the regular plug placed back in the plug hole. i tried it on the no 3 and no 4 plug holes, tightened it exactly according to spec and followed the directions like a good mechanic should. does anyone have experience with this colortune?

right now my plugs are carboned up so i am thinking of just tightening the fuel adjust screw on the carb a 1/4 turn at a time and then driving 20 minutes and checking the plugs, and then adjusting again. i will take notes on how far i have turned, get them to white, and then add more fuel until they are right in the middle between carbon fouled and running too hot/lean.

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God took you away, then brought you back to me.

Sounds like either a defective colortune or one that's not gapped anywhere near correctl to support combustion in your engine. I'd check the gap first. When gapped properly (0.035" or so) they work great.

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一期一会
Too many people who were born on third base actually believe they've hit a triple.

the inside of the colortune plug is essentially an L inside a circular housing. I don't know what kind of guage i could get in there to check the gap other than an eyeball guess.

they were specific in the instructions not to overtighten, saying make it fingertight and then add 1/16 of a turn to it.

will checking my spark plug color give me an accurate fuel to air ratio over time?

the colortune says i should be dead center between firing yellow and the point where the engine starts to falter, would dead center between white and black plugs be the same thing?

how long do i need to drive the car at a given fuel/air setting before its "color" is registered on my plug?

just as an aside, after doing the fuel line rerouting, putting in a new fuel pump, adjusting my valve lash and properly setting my timing and idle speed i have the smoothest idle i have ever had. the engine is quiet at stoplights. and i have had no warm start issues. so thanks to all on the slant six board because my success is a tribute to you all. i can't say enough how good it feels to have an online community i feel a part of. i never used to understand why people liked internet chat rooms. but this is too cool

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God took you away, then brought you back to me.

Reading the spark plugs (looking at them after they've been in the engine) gives you an idea of the fuel/air mixture over time, but that can really only detect gross and prolonged overall too-rich/too-lean conditions. It cannot be used for setting the idle mixture, for instance, and it can seldom be used effectively for fine-tuning. Black plugs = way too rich, and white plugs = too lean. There's a LOT of grey-to-brown-to-tan area in between black and white. No, it is not the same as dead center between yellow and falter w/the colortune.

Gap? No gauge, just eyeball it.

Glad your engine's running better!

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一期一会
Too many people who were born on third base actually believe they've hit a triple.

So I need to get this colortune to work for me.

There was a note in the instructions that said if the engine misfires badly with the colortune in it should be sent to Gunson. But I would prefer to find a way to get it to work.

First I check the gap.

Should I try to tighten it a little more than it suggests? I have a 75 which means taper seat plugs, correct? They recommended not using the brass washer with taper seat plugs, I tried it both ways and still had the rough idle.

The blue flashes were tiny little pin prick size. The yellow circles were large, the diameter of the viewing mirror. What size is the spark normally on the colortune? Because the blue was so tiny it was hard to tell how blue/white it was.

I'm going to check gunson's website and see if I can call them for some assistance.

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God took you away, then brought you back to me.