Who here is good at reading spark plugs?

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jcolman

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I pulled one of my plugs just to take a look after putting about 900 miles on my car with a Holley Sniper and Hyperspark distribuitor. My intial thoughts are that I have a touch too much timing but otherwise I think it looks pretty good.
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What plug is it? For pump fuel that isn’t too much timing. FWIW it is rich at idle and probably cruise too.
 
What plug is it? For pump fuel that isn’t too much timing. FWIW it is rich at idle and probably cruise too.
Champion RC12YC. I think you might be right about it running too rich as I can smell it at idle while in an open garage.
 
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What heat range is it? What’s your compression ratio, car weight, gear ratio and converter stall speed if you have a converter?
 
What heat range is it? What’s your compression ratio, car weight, gear ratio and converter stall speed if you have a converter?
I'll have to look up the heat range of the plugs. EDIT: heat range is 12. 10:5 CR. Car is light at around 3000 lbs give or take. I have aluminum heads, glass fenders and hood. 3:23 gear, 2400 stall.
 
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What fuel?
They're pretty close, but without knowing the fuel used..
Check out the specs on the porcelain ,does it ping or surge?
 
I always use premium unleaded. No pinging or surging. Plugs are Champion RC 12YC
Premium here is 91.

93?

Tim is right about the rich spot, somewhere.
The base isnt sooty though, the porcelain is a hair dark for today's fuel..so that's rich showing imo
 
I watched a video 318willrun has on youtube about reading spark plugs.. I found it very informative. Hats off to him for taking the time to do it! Maybe he can repost the link to it as I can't seem to find it now.
 
Speaking of rich....the plug I posted above is from cylinder #4. This one is #2. Looks way too rich or maybe I might have a slight oil seepage from the valve seals??

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Hmmm.....#1 does't look too good either.

View attachment 1715854990


You have to tune to the leanest cylinder. You may have to live with that depending on your manifold and some other things like overlap and how well your headers work. You need to look at them all and make sure you know which plug came out of what hole and find the leanest one. And tune from there. And you have to check every plug, every time. When there is excess fuel blowing around in the intake any change you make may change the distribution characteristics.

If you have port EFI then you should be able to clean it up pretty good.
 
You have to tune to the leanest cylinder. You may have to live with that depending on your manifold and some other things like overlap and how well your headers work. You need to look at them all and make sure you know which plug came out of what hole and find the leanest one. And tune from there. And you have to check every plug, every time. When there is excess fuel blowing around in the intake any change you make may change the distribution characteristics.

If you have port EFI then you should be able to clean it up pretty good.
thoughts on running a smaller jet in the corner of the number 1 cylinder if it's a carb?
 
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You have to tune to the leanest cylinder. You may have to live with that depending on your manifold and some other things like overlap and how well your headers work. You need to look at them all and make sure you know which plug came out of what hole and find the leanest one. And tune from there. And you have to check every plug, every time. When there is excess fuel blowing around in the intake any change you make may change the distribution characteristics.

If you have port EFI then you should be able to clean it up pretty good.
Thanks for the advice, much appreciated!

The Holley Sniper acts like a carb in that the fuel/air is combined in the "carb body" itself before it reaches the intake manifold for distribution to the cylinders. So whatever changes I make to the mixture will affect all cylinders.

If I understand correctly, Port injection sprays fuel into the intake port of each cylinder making it easier to adjust A/F mixure to a particular cylinder.

I'm running a Weiand intake and Hooker headers, Edlebrock heads. I'll pull all the plugs and, like you said, tune for the leanest one.

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thoughts on running a smaller jet in the corner of the number 1 cylinder if it's a carb?


Yup. Or, you can start playing with the boosters to correct distribution. You can also work with the plenum floor, but certainly corner jetting is much easier.
 
Thanks for the advice, much appreciated!

The Holley Sniper acts like a carb in that the fuel/air is combined in the "carb body" itself before it reaches the intake manifold for distribution to the cylinders. So whatever changes I make to the mixture will affect all cylinders.

If I understand correctly, Port injection sprays fuel into the intake port of each cylinder making it easier to adjust A/F mixure to a particular cylinder.

I'm running a Weiand intake and Hooker headers, Edlebrock heads. I'll pull all the plugs and, like you said, tune for the leanest one.

View attachment 1715855024


Ok, you have a DP intake and a Sniper. I missed that. I haven’t a clue how to clean up distribution with that set up. If it was a carb you could start by corner jetting, but I don’t know if you can change the bandwidth on a particular barrel or not.

You may want to look into a different intake that is a single plane, but your choices are pretty limited with your gear and converter.
 
Is your spacer Open? As in it's not a 4 hole or split plenum (2 large oval holes) spacer?

I have a Stealth as well and did some reading where folks that have tuned them at the track found the deep side of the plenum runs leaner and that side of the carburetor need jetted more.
 
The OP is running a sniper (TBI) I do not believe it has the ability to tune by bank. It's a blanket afr change.
 
Is your spacer Open? As in it's not a 4 hole or split plenum (2 large oval holes) spacer?

I have a Stealth as well and did some reading where folks that have tuned them at the track found the deep side of the plenum runs leaner and that side of the carburetor need jetted more.
Open spacer feeding into a split plenum. I do have a 4 hole 1" spacer that I plan on putting in next month when I do the transmission swap from auto to 5 speed.
 
Open spacer feeding into a split plenum. I do have a 4 hole 1" spacer that I plan on putting in next month when I do the transmission swap from auto to 5 speed.

I've read hit a miss with TBI and dual planes with no balance port between the plenum divider. Holley just says to use the provided gasket but there is no picture of it. I'm not saying this is or could be your issue but worth looking into.

Have you data logging to see what you AFR is at idle, cruise and WOT is?
 
I've read hit a miss with TBI and dual planes with no balance port between the plenum divider. Holley just says to use the provided gasket but there is no picture of it. I'm not saying this is or could be your issue but worth looking into.

Have you data logging to see what you AFR is at idle, cruise and WOT is?
Not yet. I'm changing shops and plan on having the car chassis dynoed and tuned after the tranny swap next month. But at the moment, I'm simply going by what the hand held wizard device is set to regarding A/F ratio across the spectrum.

Also, there is a plenum divider in the manifold. I'm planning on swapping out to a four hole 1" riser, replacing the open riser I'm currently using.
 
Does the Sniper hand held show you the A/F ratio when its running? If not, have you considered installing an A/F gauge?
 
Does the Sniper hand held show you the A/F ratio when its running? If not, have you considered installing an A/F gauge?
Yes. However I've only looked at it while idling. I need to take a friend for a drive and have them monitor it while running at cruise and open throttle.
 
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