Plug tuning for street driving?
#138758
10/19/08 05:54 PM
10/19/08 05:54 PM
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Joined: Jun 2006
Posts: 824 NH
72challorange
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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
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Re: Plug tuning for street driving?
[Re: 72challorange]
#138762
10/20/08 06:51 AM
10/20/08 06:51 AM
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Joined: Jan 2003
Posts: 5,444 Indiana
YO7_A66
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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.
1970 YO7 A66 [Canadian Export] F8 Challenger 340 (Currently in shop for stroker assy.)
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Re: Plug tuning for street driving?
[Re: YO7_A66]
#138763
10/20/08 11:54 AM
10/20/08 11:54 AM
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Joined: Feb 2003
Posts: 12,675 Columbia, CT
moper
I Live Here
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I Live Here
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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.
Well, art is art, isn't it? Still, on the other hand, water is water! And east is east and west is west and if you take cranberries and stew them like applesauce they taste much more like prunes than rhubarb does. Now, uh... Now you tell me what you know.
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Re: Plug tuning for street driving?
[Re: YO7_A66]
#138764
10/20/08 06:45 PM
10/20/08 06:45 PM
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Joined: Jun 2006
Posts: 824 NH
72challorange
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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
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Re: Plug tuning for street driving?
[Re: 72challorange]
#138765
10/20/08 08:48 PM
10/20/08 08:48 PM
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Joined: Jan 2003
Posts: 5,444 Indiana
YO7_A66
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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
1970 YO7 A66 [Canadian Export] F8 Challenger 340 (Currently in shop for stroker assy.)
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Re: Plug tuning for street driving?
[Re: YO7_A66]
#138766
10/20/08 09:16 PM
10/20/08 09:16 PM
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Joined: Jun 2006
Posts: 824 NH
72challorange
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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
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Re: Plug tuning for street driving?
[Re: 72challorange]
#138767
10/24/08 09:17 AM
10/24/08 09:17 AM
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360view
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