What color should a plug be for a street driving motor?

I'm wondering if this is too clean?
These are #'s7+8 and 1+2 were similar.

Tom

By tdavist, shot with DSC-W55 at 2008-10-19

By tdavist, shot with DSC-W55 at 2008-10-19

By tdavist, shot with DSC-W55 at 2008-10-19

How many miles? Ideally the plugs should be light tan. White may indicate a lean condition.

About 1500 miles on these plugs so far.

Tom

I'd say it's lean......

As we have all seen, there are many articles out there for spark plug tuning at WOT but not many about street driving. The article that I like to use describes reading the spark plug as:

* The "Ground Strap" = Heat Range
* The "Plug's Base Ring" = Jetting
* The "Porcelain" = signs of preignition/detonation

For WOT, the bottom of the plug (base ring) should be covered with color for 7/8 to 1 full turn. For street driving, once again, there are not many articles or any that show what this should be.

Your plugs appear to be a perfect color for the WOT plug (see below picture) but it is a street driven car. I am going to say that since you have a full turn of color on your base ring, no signs of black specs on the porcelain (except it does seem to show a tan color down on the around the side of the porcelain), I am going to say that your "street driven plugs" are a tad on the rich side.

I had my plugs looking the same as yours on my streeter and I decided that since they were so close to the typical WOT description, I dropped my main jets down by 2 sizes. This changed the color on the base ring to apx 3/4 color all around (instead of the 1 full turn of color) and I have no signs of detonation on the procelain and no ping at WOT. I also think that the color on the porcelain will change due to the strength/condition of the ignition system on a street car.

Good question and I hope you get more responses explaining the opinions on the lean/rich street plug. I would have no problem with increasing my primary jetting back up two sizes if someone can explain why a steet driven plug should look like a WOT plug description.

BUMP!!

Note: The below shows a WOT plug.

Tom, I cant see the pics.. but Dave (YO7) is a heck of a tuner, and unrelenting in his tweaking...lol. It's also getting colder out... you may want to throw more jet at it.

Thanks so much for the advice. I will keep an eye on them, I have them 2 steps higher on the jetting F+R from stock on my 770 Avenger Carb on my Iron Headed SB Stroker that Moper put together for me.

I don't see much out there for info on a street plug for sure. Racing is fun but most of my time is on the street. I wonder if I swap out the secondary spring that will keep the secondaries closed a bit longer in street driving, I have the Small White spring in there now and the secondaries come in pretty early for a vac sec carb.

Dave, take a look when you get home.....

Tom

Tom,
If David put the motor together, you need to listen to him!
David, if you get a chance to look at the plug pictures, please let us know so I can make some time to put the other jets back in or not.
Tom,
For my own curiosity, could you tell us what the 770 came with from the factory and what jets you have in it now? I am not very familiar with that Avenger.
Note: If you put in a stiffer spring, that will delay the seconds. On my last carb (vac sec), I tested all of the springs right after each other starting with the lightest. As I put in stiffer springs, the motor had more torque off the line, except for the very stiffest. I ended up with the Brown one for my stock stroke 340.

Thanks

I have 74 Primary and 77 Secondary Jets in it now up 2 sizes front and rear from stock. I do notice that if I jump on it from idle on the street there is a slight delay in respnse with the lighter spring, I have been working with Dave on correcting this but haven't fixed it yet since I'm lazy and cheap.LOL

Torque off the line usually isn't a problem.



Tom


By tdavist, shot with COOLPIX S4 at 2008-10-19

for whatever it is worth
spark plug reading
articles:

http://members.uia.net/pkelley2/sparkplugreading.html

http://www.strappe.com/plugs.html

http://web.archive.org/web/20041207125325/http://www.corollaperformance.com/TechInfo/sparkplugs.html

http://web.archive.org/web/20070414112339/http://www.olyonline.com/techngkplugperformance.htm

What kind of ignition system are you running? My MSD setup burn's hotter and i belive that affect's plug burn, the color change on the ground strap look's good. I believe you need to look down in the plug at the base of the porcelin to deterime jetting and like said spec's up higher on the porcelin will show a lean condition with shiny spec's meaning detonation. There are so many different way's i've heard of reading plug's it's hard to be sure and i am no pro by any mean's.

Thanks Guys, there was some good reading in there.

I run an MSD set-up on it, I'll have to pull one again and use a magnifying glass to check it out a bit better.

Tom