Pulled the plugs yesterday and they look like no other plug I have seen. Keep in mind I have never seen plugs that were run on a mix of race fuel etheir. Below are two pictures in lighting that gives the best color represention as possiable. The plugs are 1-6 from left to right. 2,3,6 have a floresent yellow color and plug# has tiny little brown dots on the insulator.
I went to the track with plugs in hand to have some "experts" take a look. They say the mixture looks close, maybe a touch lean. I told them about the black smoke trail this car leaves and they looked confused having just looked at the plugs. They also think that I should back the timing down a little and again confusion when I tell them its 25* total. I realize there not used to slant6's and their want for less timing, but they say that what the plugs say. They also suggested maybe a colder plug. I am running the Autolite 64 which is two ranges colder than the stock 66. Is there a colder plug than the 64?

Pic of the plugs
http://tinyurl.com/2lofsx
http://tinyurl.com/37hhyd

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67Cuda,FAST EZEFI,340cu,CR=10.25,RollerCam&Rocker (XR268HR,#20-810-9)(#1622-16)(EddyRPM#60779,#7576), (MSD6AL,#6425) A904, GearVendorsOD, 8 1/4,3.55:1, ClassicAir

This is what I think.
Your exhaust is to "small", you should have at least 2 1/2" where the front exhaust meets the rear exhaust (Y-pipe?).

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Lasse

Signet -66 225
Holley 600 Offy-5270 Dutra Dual,regrind. cam 272 0,420 110, head shaved 0.100 slight.ported
MSD6A
A904
7 1/4 3.23

I don't think you can relate old timers reading plugs to your engine, with your bildup, fuel, comp, cranking pressure readings, etc...

They look fine to me... the black smoke trail when you nail it can be due to the large(r) accel pump nozzle youre running...

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Juan Ignacio Caino

Please use e-mail button istead of PM'ing. I do log in sometimes but I'll be answering quicker thru e-mail.

The smoke trail is not just at the beginning, it is black all the way down the track.
The exhaust has been redone and it looks about the same as before except the bottle neck is gone. 2 in pipes dump into 2 1/4 pipe and flow through a 2 1/2 dyna max muffler back to 2 1/4 in pipe through a resonator and then crome tip.
What do you think of the timing marks on the plugs? Is there a colder plug than the 64 Autolite. What are the symtoms of running to cold of a plug?
The electrode tip (center) looks like it has some miles on it. It rounded just a little. There about 600 miles on this motor and the plugs maybe have 400miles on them.

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67Cuda,FAST EZEFI,340cu,CR=10.25,RollerCam&Rocker (XR268HR,#20-810-9)(#1622-16)(EddyRPM#60779,#7576), (MSD6AL,#6425) A904, GearVendorsOD, 8 1/4,3.55:1, ClassicAir

If you have black smoke the whole 1/4 mile you are running too rich, but the plugs don't seem to indicate that. How far off of stock are the secondary jets? Primary jet? Does the engine oil smell of fuel? What's your total ignition advance and what RPM is it completely advanced?

If memory serves there are Autolite 63 spark plugs. Too cold a plug will lead to fouling.

What was the reason for the 2 1/4" exhaust? It seems a little small for as much motor as you have. You can buy 2 1/2 and 3" tailpipes to fit your car from TTI. They sell individual pipes, BTW.

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Joshua

Did you pull the plugs RIGHT after the 1/4 mile pass? If not, they would have had time to clean themselves off if the carb runs right or lean at part throttle or idle. It's also hard to read plugs on the track that are not essentially new. The readings you have are some sort of average over the last 400 miles of running, and not what happens at WOT.

My guess is that you are quite rich on the secondary circuit, as Josh suggested. Changing secondary springs to delay opening would be a good start. If you have a metering block on the secondaries, then jetting down would be another thing to try.

If you are getting black smoke all the way down the track, then chances are you can gain quite a bit more power by leaning out your mixture.

I have seen gains of more than 0.5 sec by leaning things out when it was too rich.

I don't see the point in colder plugs if you are not getting detonation or pinging.

Lou

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Home of Slant6-powered fun machines since 1988

accel 262 are the coldest i know,yours look like n14y champions, i wouldnt run anything hotter than a n11y, n9y would be the best. as for the smoky exhaust, have you tried leaning it out 2 size jet at a time untill the plug change color or the exhaust clears, if that doesnt work the check the float level you might be getting fuel pull over from the fuel bowls. try it your air/fuel ratio meter is only a tool to help you get close to your best tune up, just ask seymour.

A closer look would be better, but from what I can see, the heat range looks OK. Forget the center porcelain for now: what does the base of the shell look like? This is what the side electrode is attached to. Is there a build up of ash? Heat range is determined by the location of the annealing ring on the side electrode. Half way down to the base shell is OK. Race gas often has a very different stoichiometric value and, therefore, requires a different A/F ratio.

Mitch

I think you need to take the plugs and cut the metal off of thems so you can really see what is going on. But from what I can see you are way to rich, to hot on the range, and the timing I would not even begain to guess untill you get it burning alot better. You can take a wizz wheel and cut the plug apart. One thing is for sure, your tune up is no where close.

Are you still running the same carb. You should take a vacume gauge and see if the carb is to small ( it will read vacume when WOT , sould be 1.5 or less). I believe I would try to barrow a bigger carb, seems to be choking for air with that one.


Jess

Its a 570 Street Advenger and the vac drops to zero at full throttle.
Exhaust was based on everyones advice here that anything over 2-1/4 is a waste.
Ive installed a new set of Autolite 64's and will do some testing.

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67Cuda,FAST EZEFI,340cu,CR=10.25,RollerCam&Rocker (XR268HR,#20-810-9)(#1622-16)(EddyRPM#60779,#7576), (MSD6AL,#6425) A904, GearVendorsOD, 8 1/4,3.55:1, ClassicAir

That should be good on the vac, one thing, is that reading at the intake. If its reading at the carb its not giving the reading you need. But still, a 570 is probably plenty. Get some readings on the new plugs & cut them apart and see what they show. Or atleast one of them.

Jess

I would pay heed to the thought that if it is blowing black smoke, it is too rich at that point. Way too far off to even think about trying to start reading plugs. As already pointed out, plug readings are almost useless unless the plugs are new and the engine is shut down right at the end of or during a full throttle run. Running unleaded fuel or mostly unleaded makes reading them even harder.

So, I would look at your jetting and power valve setup. Is it OK at part throttle and cruise? Take care of them first. Possibly only too rich at full throttle? I would try cutting back the accelerator shot until it hesitates and work back up from there to get it right, then jet back the secondarys.

You have a wide band don't you? That is the tool to be using. I would seal up the exhaust and not get too concerned about what look like too rich readings at light throttle and low rpm, not with your cam. Tune that by performance. Then pay close attention to those readings at full throttle and pretty much forget about trying to read the plugs, aside from the heat range being correct and that they are all similar from cylinder to cylinder. And don't get too obsessive about targeting a certain, exact ratio, tune it to run. The ratio will fall into place and you will have a reference from there on. The way to track it down is to start rich (like you seem to be) and then try to go to the lean side, just don't run it too hard for too long, you should feel it nose over. Then, knowing what is too rich and too lean it is easy to find the spot in between.

If you want to look close at your plugs, use a small flashlight and a magnifier if you need it, I have never heard of cutting up plugs to try to read them, I would not try to invent a new procedure. An abrasive wheel would just contaminate the surfaces anyway.

ditto, i wouldn't be timing guessin...

also: why don't you shut close your secondaries with the hardest spring, do a 1/4 pass and read there?

another important thing to know is what kind of additives is your fuel being loaded with... with unleaded AND oxygen additived fuel, you can't use the normal color range.

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Juan Ignacio Caino

Please use e-mail button istead of PM'ing. I do log in sometimes but I'll be answering quicker thru e-mail.