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Old 03-21-2010, 03:47 PM   #1 (permalink)
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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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Old 03-21-2010, 07:23 PM   #2 (permalink)
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Its kinda hard to tell from the pics, but from what I see, cyl's #2,3 are running slightly lean and the rest are running rich.
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Old 03-21-2010, 07:59 PM   #3 (permalink)
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Quote:
Originally Posted by mrboyle View Post
Its kinda hard to tell from the pics, but from what I see, cyl's #2,3 are running slightly lean and the rest are running rich.
I did a little research on this and i think your right, I have two cylinders running lean or reasonably ok and the other four cylinders are rich. After looking at the TBI intake, I think the intake is not providing good fuel distribution and I'm also running a little too rich.

The new Edelbrock intake should solve that problem.
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Old 03-21-2010, 08:31 PM   #4 (permalink)
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Hey the CPI heads flow better then the vortec heads. And Edelbrock intake or boat intake flow way better then stocker.
I have a bud thats a old 3.8 turbo and 4.3tbi gearhead. He found a cam that keeps the motor from booging down. I plan on putting one in mine. If it ever lets go or i get the cash to rebuild it.

Hes on 4th motor. Hasnt liked the way they ran. Plus he was using old parts the 4th one was all new parts.

Older style block stonger lower end. Bored .035 over, Better pistons, Stock rods, CPI heads P/Polished with roller rockers, after market push rods. And his custom cam he found. And some custom garge chop up headers. Reflashed computer tbi-350T/body and home build harness.
This thing run little a champ. I was shocks by the way it ran. Didnt have the skinny pedal stomp lag. And this is in a 91 4-runner and 60's/5.13's and 39.5"s. Pretty heavy rig. And it rans. Even at high way speeds.
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Old 03-22-2010, 09:09 AM   #5 (permalink)
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Something ain't right. The intake manifold shouldn't be the reason for 2 out of 6 cylinders to run right. All 6 of my 4.3 TBI sparkplugs look like your two good ones. You should have run a compression check before removing the heads. However, with that being said, I would NEVER run Champion plugs, EVER. Plain jane AC-DELCO spark plugs work the best. My $0.02.
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Old 03-22-2010, 11:51 AM   #6 (permalink)
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Seam here on the ac-delco plugs. But i started run the wires, cap and rotor. And have alot better running motor.
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