I jetted my 327 up to 70 on my primaries in my Holley 650cfm VS. The metering plate is a 69 jetting. The car runs stronger, sounds better but the plugs are still white. I'm running about 9.5:1 SCR and 7.8 on the DCR with my new vortec heads. I have a 216/228 @0.050 cam and i run it in my 66 chevelle with a 2004R tranny and slightly higher than stock stall converter.

Am I still lean? Is it possible for a plug to run hot enough to keep itself burned clean even in a rich condition? The plug is white, the electrode and tip are clean as a pin but the rim of the plug where the electrode attaches is black and sooty.

I have a set of 72 jets but i don't have a larger secondary metering plate. Will I get into any problems if my primaries are larger than my secondaries? Its usually the other way around. My wife was following me in the car today when I did a WOT run and she said it was smoking. I asked her if it was black, brown or blue smoke and she couldn't tell me. Go figure. Could this possibly be an indication of running rich at WOT but running lean at cruise?

Clyde

Why not go a little richer and see if performance
improves even more.

What are your engine temps doing?

Dave

They say you need a magnifying glass to read plugs correctly. Its hard to judge performance with the butt dyno. Take it to the track and jet for mph or make a full power pass,cut it off clean and look at the plugs,see if that helps you.

Clyde

Dont know if this helps but I just got my 670 street avenger back from THE CARB SHOP in California. They are supposed to know carbs well. I sent them all my specs on my 383,700r4 and
the carb came back with 65's in the front and 75's in the rear and 28 squirter. The front jets are the stock but they went up 7 sizes in the rear. My cam has the same .050 specs (GM HOT Cam) so maybe this will give you ballpark idea. I think your plug color can very greatly dependant upon your driving habits. I know if pull mine in and out of the garage and putter around on short trips they will carbon up some but clear up a 10-20 mile trip.

I look for a heat range that makes the ceramic look white. The only way to read a plug is where the ceramic meets with the metal. Cut the threads off of a plug and slide them off, when you have a good tune you will see about a one MM band of carbon where the ceramic necks down. Just my observations, they may be wrong, but work GOOD for me!

Thanks for the replies. My engine temps range between about 190 when idling in town and 170 or so out on the road. The temps seem to creap up a degree or so in traffic whenever I jet up. I guess its more fuel and therefore more heat.

I don't have a local track to test at so its only short blasts out on the local roads. The butt dyno is the only thing that I have work with.

As for the plugs, they are stock platinum autolite 605's. I chose them because they are the OEM plug for the vortec heads in chevy trucks. I wouldn't have thought that they would be that hot.

It was late last night and i forgot to mention that I lowered my octane from 93 to 89. I wanted to try it to see if i had detonation but from what i can tell, there is none. When i was running the 93 with the 68 jets, then i had a slight coloration on the plugs. I dropped to 89 octain and the plugs cleaned right up. Is this typical for a change like this to require significantly more jetting to make up for the octane change.

Clyde

I just started doing what Pony Hunter is doing. I was told that the ring only shows whats happening at WOT and at the richest condidtion, so if you made a change that leaned out the mixture, you'll still see the results of the richer mixture, Maybe Pony can elaborate more on this. I have pictures I was sent of the rings on a set of plugs, but dont know how to post it on here.
Also this is " assuming " you have the proper heat range plug.

That ring will show up in any throttle range. Put a new plug in there, and run it wot- read and tune. Another plug run it midrange- read and tune. So on and so forth. Isn't WOT the only thing that matters anyway?

My opinion, take it or don't:

With the **** in today's pump gasoline, PLUG COLOR MEANS NOTHING as far as carb tuning for power.

You might be able to see oil fouling, you might see the result of gross errors in fuel curve (blown power valve, jets fifteen sizes off, sunk float) If you see aluminum specks, you know you have problems. BUT! Looking for plug color to get your jetting "right" is impossible.

My personal experience when a plug is bone white with no signs of detonation it is right. There is a possibility of a very rich condition actually washing the plugs and leaving no color. My mild vortec motor has plugs that look like they were just put in and runs fine.