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post #1 of (permalink) Old 08-27-2002, 03:36 PM Thread Starter
 
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CJ Carbon build-up on S/S valves

How much is to much? New S/S values with 5000 miles showing a significant amout of carbon build-up on the intake valves. Is this normal or should they be as clean as the exhaust. What causes this build-up and is it causing me a loss of performance? Thanks for your support Fran

P.S. I discovered this while changing the intake gasket.
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post #2 of (permalink) Old 08-27-2002, 04:06 PM
 
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Re: CJ Carbon build-up on S/S valves

How much is "significant"? Are we talking just a change in color or can you notice a thickness? You might try running some fuel system cleaner through your tank periodically.
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post #3 of (permalink) Old 08-27-2002, 05:05 PM Thread Starter
 
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Re: CJ Carbon build-up on S/S valves

Hello J-D, Glad to hear from you! Build-up is best described in this case as scaley, rough, burnt on carbon deposits, between an 1/16 and 1/8 inch in height. A whole lot more than you would have ever thought could accumulate in 5000 short miles. I first noticed it while changing my intake gasket. At first thought I was thinking that running the ccv valve (came from Clifford on their 4.0L cover) rather then a true PVC valve was the problem. To much oil mist entering the intake camber at low rpm's, hense the build-up. But I'm not sure just how much build-up should take place if any? I only burn hi-test fuel 92 octane or better. Pinging can be a problem with this engine on poorer quality fuels. Thank for your help.
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post #4 of (permalink) Old 08-28-2002, 02:39 AM
 
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Re: CJ Carbon build-up on S/S valves

If that was a used 4.0 head you put on there, it's quite possable the build-up is caused by oil running down the worn intake valve guides and seals.
At this point, if I am correct, I'll have to defer to others on whether a new set of valve guide seals would help.
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post #5 of (permalink) Old 08-28-2002, 04:17 AM Thread Starter
 
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Re: CJ Carbon build-up on S/S valves

That was a brand new Clifford 4.0L Head Conversion. The thing came as a kit. That is why I'm puzzled to the build-up on the new stainless steel valves. The engine shows none of the typical valve stem problems that you mention. Thank you for your support. You have a great web site. Fran
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post #6 of (permalink) Old 08-28-2002, 06:26 AM
 
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Re: CJ Carbon build-up on S/S valves

Fran, is the buildup on all the valves or possibly just the ones where you had the intake gasket leak? I wouldn't think that a leak generating a lean condition could cause that, but I don't know for certain.

On a brand new head ('specially a high$ one from Clifford) you should not be having that kind of buildup. It might not be the head though... could be caused by your fuel mix and timing not being set right.

Have you hooked up a digital voltmeter to your O2 sensor? That was how I wound up tweaking and tuning mine. It was a lot more convenient that checking plugs because I could run the leads inside the Jeep and watch it while going down the road. .5 volts is "perfect mix". Toward 0 is lean. Toward 1 volt is rich.

From some previous posts, it seems like I remember you were getting pretty sad mileage... something like 11-12? Sounds to me like you just have a fair amount of tuning to do. I know I did, and it really surprised me the difference in performance and mileage I got out of it. I am now getting 19mpg and have awesome power delivery everywhere vs. 15mpg with detonation and holes in the power when I started.

I also wound up changing out one of the mechanical advance springs in my distributor to slow down the advance. This helped eliminate my detonation. I would suggest getting out there with a DVM and play with your jet sizes, idle mixture screws, and timing. You might be surprised at the difference it makes.

Let me know if you want more details about what I did to mine.
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post #7 of (permalink) Old 08-28-2002, 10:38 PM
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Re: CJ Carbon build-up on S/S valves

How would one hook up a VM to a three lead O2 sensor? I'd like to use mine to try to get my pro-jection "close" to good. Then I can hook it back to the pro-jection.
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post #8 of (permalink) Old 08-29-2002, 06:17 AM
 
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Re: CJ Carbon build-up on S/S valves

I am guessing that a three lead O2 sensor is one of the heated ones. If that's the case, then my next guess is that two of the leads would be for power and ground for the heater. The remaining lead would be your signal. When you turn the Jeep on, check if one of the leads is seeing a continuous voltage (and probably more than 1 volt [img]images/icons/smile.gif[/img]) and if one of the others sees ground.

I'm guessing here - I haven't fooled with a three lead O2 sensor before. But I can't figure out what else the wires would be. I also don't know if the signal will still be in the 0-1 volt range, but maybe we'll get lucky [img]images/icons/laugh.gif[/img].
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post #9 of (permalink) Old 09-01-2002, 11:49 AM Thread Starter
 
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Re: CJ Carbon build-up on S/S valves

J-D lets get started on the tuning I think that will be a major step forward. Do you want to use e-mail to communicate?
Fran
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