[BillKnight]

Lots of carbon is a sign of a rich fuel mixture or engine running too cool? Take a quess.

[ December 31, 2002, 12:17 AM: Message edited by: BillKnight ]

 

[Larry N. Johnson]

EFI or carb?

 

[Ophitoxaemia]

not enuf time at red line. when i opened up my motor to do heads there wasnt a trace of carbon. hehe

-james

 

[BillKnight]

EFI and carbon all through intake manifolds as well.

 

[BillKnight]

Valve seats had small pits although I had a 97% leak down test result. I believe pits were caused by carbon.

 

[Larry N. Johnson]

Carbon in the intake manifold sounds like a bad thing!

The only way I can imagine that is if the valves are not seating and combustion is getting by the valves into the intake.

The car must have low power to boot?

Sounds like expert advise is needed.
lnj

 

[forrest1]

It can get into the intake manifold via the EGR valve recirculating exhaust gases.

 

[davidk]

I'd bet it is just coming from exhaust gasses coming back in through thermactor or EGR or whatever route it takes. Owned my 89 doner since new and there was more carbon than I expected from the throttle body back. Had 148,000 miles on it, used name brand fuel, tuned regularly, and driven somewhat aggressively, but not hard. The cylinders all had a band of carbon around the top, but no ridge.

 

[steve card]

If you have a lot of camshaft and dont run it hard enough, this can show up as carbon on the floor of the intake. There is a time between exhaust closing and intake opening that is an "overlap period" in hot cams, during which they are both slightly open. This can cause carbon in the intake.

[ December 31, 2002, 01:55 PM: Message edited by: steve c. ]

 

[BillKnight]

This is a stock motor.Stock cam. The car has alot of power. I did a leakdown test and the results were averaging 97.5% per cylinder.This was much higher than I expected. My quess is that the engine was running too cold. I have a 180 t-stat.
There is alot of empty room under these cobra hoods. I always assumed that the cooler the engine ran the better. This condtion can also be caused by a too rich a mixture???? (That's a Question).
It maybe a combination of both!

[ December 31, 2002, 03:51 PM: Message edited by: BillKnight ]

 

[Jim Smith]

Cooler is definitly not always better with EFI.For the most part they want to run at about 190-210 deg.I wouldnt call a 180 deg. T stat too cold though.

 

[BillKnight]

Its going back together with a Kenne Bell installed so this may make it run a little hotter!
I think I'll get a accurate temp gauge and monitor it.

Drive it like you stole it.........
You goota love that line!

 

[RacingRob]

I think the EGR system brings alot of carbon up into the manifold.
RR

 

[Ophitoxaemia]

i was told that one can find significant amounts of carbon in the intake, and on the pistons, valves, etc.

cooler isnt better!

-james

 

[LT1FFR]

Forged pistons, standard tension oil rings, and running rpm's while cold will recirculate carbon throughout the system. No way to avoid it short of going with a cam with very little overlap plus plugging the egr and pvc. Anything with a bunch of miles will look pretty nasty inside.