Spark plug range???

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88bluestar
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Spark plug range???

Postby 88bluestar » Wed Sep 13, 2017 11:09 am

Small block Chevy
9.5:1 compression, 355 cid
246, .498 lift advanced 4 degrees Elgin cam
91 octane pump gas - Holley 750/850 base
Vortec head with 1.95/150 valves
RS12YC spark plug. 1 3/4" headers

Idles blowing black exhaust and even on the throttle still black smoke regardless of where timing is set, is this to cold or too hot of spark plug? 74 jet on primary. 84 secondary

Schurkey
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Re: Spark plug range???

Postby Schurkey » Wed Sep 13, 2017 11:44 am

I'd be looking at fuel curve, not heat range of the plugs. But maybe I'm wrong.

Plugged air bleeds?

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Re: Spark plug range???

Postby Firedome8 » Wed Sep 13, 2017 12:06 pm

88bluestar wrote:Small block Chevy
9.5:1 compression, 355 cid
246, .498 lift advanced 4 degrees Elgin cam
91 octane pump gas - Holley 750/850 base
Vortec head with 1.95/150 valves
RS12YC spark plug. 1 3/4" headers

Idles blowing black exhaust and even on the throttle still black smoke regardless of where timing is set, is this to cold or too hot of spark plug? 74 jet on primary. 84 secondary


check float levels, look down carb at idle you shouldn't see fuel coming from boosters.

F-BIRD'88
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Re: Spark plug range???

Postby F-BIRD'88 » Wed Sep 13, 2017 2:12 pm

It is not the spark plugs. RS12YC is correct for this one.

Probabily issue with the base plate gasket.
Or something else non standard.

6.50camaro
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Re: Spark plug range???

Postby 6.50camaro » Wed Sep 13, 2017 3:16 pm

X2 on float level. Have you checked for the correct power valve and is it good. Make sure the secondary PV is plugged and the gasket is good. Dan

88bluestar
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Re: Spark plug range???

Postby 88bluestar » Wed Sep 13, 2017 7:44 pm

Still was dripping out of booster with a low float setting. Installed a 4177/TR6 NGK plugs in with a .035 gap, seem to clear up quite a bit of the exhaust issue but still slight smoke especially on throttle. One thing I found that may have been a culprit was I did not have a proper gasket in between the intake, and spacer. Had an open gasket on a 4 hole spacer so there was a noticeable gap in between. Just as a precaution, rebuilding Carb to weed out any small trash that got in there, clearing lines and replacing filter as well. Haven't dealt with 4bbls much so any help is appreciated

88bluestar
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Re: Spark plug range???

Postby 88bluestar » Wed Sep 13, 2017 7:45 pm

Where do you all preset dry the float level?

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MadBill
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Re: Spark plug range???

Postby MadBill » Wed Sep 13, 2017 8:06 pm

Dripping from a booster (just one?) at a normal idle cannot logically be a sparkplug issue. Sounds more like maybe a plugged idle air bleed...
Felix, qui potuit rerum cognscere causas.

Happy is he who can discover the cause of things.

Geoff2
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Re: Spark plug range???

Postby Geoff2 » Thu Sep 14, 2017 5:00 am

Dripping booster can also be throttle blades open too far at idle, accessing the main system. Remove carb & make sure there is 0.040" or LESS of transfer slot showing below the blades in the idle position. Less slot is better.

F-BIRD'88
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Re: Spark plug range???

Postby F-BIRD'88 » Thu Sep 14, 2017 7:17 am

To preset the holley float, turn the float upside down in your hand. Hold level and adjust the float level so the float is parallel with the float bowl casting roof (which is on the bottom of the upside down held float.
(Fuel pressure 6psi)

allencr267
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Re: Spark plug range???

Postby allencr267 » Thu Sep 14, 2017 10:34 am

They're a symptom, not a cause, forget about the plugs!


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