I recently had to replace the EGR valve in my 91 Z28 5.7L. At the same time i knew the intake gasket was leaking so I went ahead and ordered the kit to replace that also. Well when I got the intake off I had noticed in one of the intake ports there was a solid piece of carbon build up about the size of a spoon. I broke it off and looked at the rest of them and looked inside to see what else might be there and I found nothing. Also along with that when I start my car there is a cloud of white smoke. I was told that it could be from bad seals. That I can understand but what about the carbon build up? Any info would be greatful. Thank you for your support!

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Leaky seals shouldn't build up carbon right at the entrance of the intake port.

EGR and PCV really scum up the intake tract, especially on a well worn motor from increased blowby. Add to the fact the intact tract is dry flow, there's no solvents to break it up. Misting water or ATF fluid during a tuneup helps some.

 

Probably a leak from the lifter valley, the intake pulse will suck up the oil mist.


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"Question with boldness even the existence of a *** ; because, if there be one, he must more approve of the homage of reason, than that of blind-folded fear."

-Thomas Jefferson

 

The size of a SPOON??? Holy cow!

Well, if it's only in one intake port it's almost certainly a leak just on that port- likely into the lifter valley. Valve guides don't go bad one at a time, generally.

Suck in oil vapor from the lifter valley into the port, mix with general dirt and gunk that makes it past the air filter (or comes through the EGR) and you get...... CHARCOAL BRIQUETTES!

Clean it out, make sure the intake seals up well when you put it back on and don't worry about it for another 50K miles.

 

Thanks for the help. It's nothing that I can fix right away but I know what to look for and do now.

 

You sure the carbon build-up wa in an intake port?

Maybe it was in the EGR/crossover port?

 

I honestly couldn't tell you. The EGR valve was bad. If it was the EGR port how come there wasn't carbon build up in all the ports instead of just the one?

[This message has been edited by Sinister (edited September 04, 2001).]

 

Which port was it actually in? The intake ports are tall, most of the height of the flange that the intake bolts to; the exhaust port is smaller, right in the exact center of the head from front to rear.

What part of Vista are you in? I actually live in Vista myself now, in Shadowridge; my car is a silver 83 HO Z28...

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