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Old 10-25-2010, 12:40 AM
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Help with spark plug selection, currently running autolite 25

I have a 388 sbc with world product sportsman heads, holley street dominator carb and 650dp. Upon pulling the plugs the car has been running rich and it has been suggested that I run one step hotter of a plug. Is this wise or could this cause me trouble? Thanks.

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Old 10-25-2010, 01:42 AM
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its probabily something else but use a Champion RV12YC for normal street duty.
Use a RV8C for Street strip racing or moderate nitrous.
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Old 10-25-2010, 08:01 AM
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Quote:
Originally Posted by IntrstlarOvrdrve
I have a 388 sbc with world product sportsman heads, holley street dominator carb and 650dp. Upon pulling the plugs the car has been running rich and it has been suggested that I run one step hotter of a plug. Is this wise or could this cause me trouble? Thanks.
Just throwing in a hotter plug will not fix a too-rich carb calibration, and in a worst case scenario could cause detonation.

So, what you need to determine is if the engine is running rich or if you have too cold of a plug heat range. Also you need to be sure that what you're seeing isn't oil fouling.

To begin with, set the idle mixture w/a vacuum gauge. The timing curve has to be correct as well. Be sure the air filter is adaquate and the lid isn't too close to the vent tubes.

To do a quick check for primary calibration, you need to run the engine up to where it's mostly on the main circuit (~2500 RPM) and partially choke the air flow into the carb. If it picks up speed, you're on the lean side, slowing is on the rich side. A little lean or neutral is where you want to be.

Do a plug chop to see what the secondary side "looks" like.
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