not sure on power valve, I haven't ripped into the carb yet. However, idle vacuum is around 10inHg, so I'm thinking it's a 6.5 or 5.5
help me read my spark plugs
- Thread starter khan0165
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yeah, she idles at 13inHg out of gear 850rpm, and about 9 to 10inHg at 750rpm in gear. So thinking power valve is something like 5 or 6.
Those plugs show that out of idle it's running lean out of idle but with a 750 cfm holley with 73 jets it shouldn't be lean. It could be the pictures don't give us the accurate colour of the plugs...the ceramic looks white except for 2 and 3
isn't the ceramic supposed to be white?
I think the pictures are pretty accurate. I took them in the sun and then compared to what I saw with my eyes.
... you can see a few of them, the straps are greenish gray, and the colour has moved passed the bend. So I agree, they look a little lean.
But then, the base circle is black, and that's usually an indication of rich?
#2 looks wet, but that could be when the car shutoff, the intake valve was open and plug got some fuel on it after a run.
could it be leaning out due to excessive heat? I was talking to Larry454, and he suggested a cooler plug.
... these were oem 14 heat range spec'd
but with my added compression, excessive heat, I think I need to run a cooler plug.
I think the pictures are pretty accurate. I took them in the sun and then compared to what I saw with my eyes.
... you can see a few of them, the straps are greenish gray, and the colour has moved passed the bend. So I agree, they look a little lean.
But then, the base circle is black, and that's usually an indication of rich?
#2 looks wet, but that could be when the car shutoff, the intake valve was open and plug got some fuel on it after a run.
could it be leaning out due to excessive heat? I was talking to Larry454, and he suggested a cooler plug.
... these were oem 14 heat range spec'd
but with my added compression, excessive heat, I think I need to run a cooler plug.
the carbon on the base is from a rich idle ....the ceramic should be a light brown, white indicates a lean condition
First off are you tunning your car for street or track cause you need to decide that first. So f you havent been to the track since last fall then your reading plugs after just running around town. Next time you go to the track put in a new set of plugs and pull them out after a run and read them then. And you might want to close up the gap a little.
PS what kind of 350 are you running ?.... I think its in backward 1357 is on left bank 😀
PS what kind of 350 are you running ?.... I think its in backward 1357 is on left bank 😀
well, I was tuning for street + track... but I'm scrapping that idea, and I will keep one set for street and another for track (hotter for street, cooler for track?). These plugs have seen a mix of track and heavy street, so I thought it'd be a good idea to see where my tuning is going.
I've installed NGK FR4s after pulling these, which are at the same heat range. But it's clear I need to go cooler, so I'll likely change those out too.
the Champions were tuned on some WOT runs up and down the street near my house... maybe got to 5000rpm in 2nd gear. But they did see maybe 10kms of normal street driving after that.
it's a chubby (chev 350), L98 heads, air gap single plane intake, holley 750 double pumper 2 corner idle with 73/83 jets.
... you are right, left bank is 1357, I was just orienting from front of car.
I've installed NGK FR4s after pulling these, which are at the same heat range. But it's clear I need to go cooler, so I'll likely change those out too.
the Champions were tuned on some WOT runs up and down the street near my house... maybe got to 5000rpm in 2nd gear. But they did see maybe 10kms of normal street driving after that.
it's a chubby (chev 350), L98 heads, air gap single plane intake, holley 750 double pumper 2 corner idle with 73/83 jets.
... you are right, left bank is 1357, I was just orienting from front of car.
I would suggest to read up on how to read plugs cause plugs can tell you alot about the set up and the engine...depending on where the marking is on the electrode that can tell you what your timing is. It's an art to read plugs and some guys can really surprise you with the info they get off a plug
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