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Old 03-21-2010, 03:47 PM   #1 (permalink)
XTRMTOY
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Join Date: Feb 2001
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Location: Ontario, Canada
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4.3 engine diagnosis

With the Rausch Creek KOH qualifier around the corner, I need to make some engine upgrades to my buggy. The ~180 hp 4.3 TBI will not be enough.

I'm finally adding a few ponies to my 4.3L V6, so I took off the heads off to do an upgrade to some Vortec head, a Comp cam, an Edelbrock intake and a Whipple blower.

When I started the teardown, I took the plugs out and noticed #2 and #3 plug looked quite different than the other 4 plugs. When I took the heads off I noticed the exhaust valves on those cylinders to be a much lighter color than the others.

The engine definately was not running 100% at the Rausch race in November. As a matter of fact it ran like crap at first but cleared up with some full throttle passes. At the time, I had tried to fix things by putting new plugs, a new rotor, a new cap, a new O2 sensor and going back to a 195 thermosat. I had also tested the plug wires with an ohm meter and they all looked good. None of this seemed to really make any difference.

Any thoughts what might be causing this? leaking exhaust valves? ignition problem? Cylinders running leaner than the others?

Oh! As well, I see no signs of detonation and the top of the pistons look great. There was no engine overheating during the Rausch ~3 hour race.

Let's hear your thoughts guys.

Thanks,
Mat
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