Clean spark plug, oil on threads - Chevelle Tech
Engine General Engine Discussion.

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  • 1 Post By hjdca
  • 1 Post By 68elky396
  • 2 Post By GuysMonteSS
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post #1 of 10 (permalink) Old Jul 30th, 19, 9:03 AM Thread Starter
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Steve
 
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Clean spark plug, oil on threads

I'm reaching out to the team to get some thoughts on my recent findings. I have about 550 miles on my newly rebuilt 396. I was doing some plug readings the other day, just to find that the #2 spark plug has oil on the threaded portion. The plug is burning clean and indicated it was slightly lean, so I corrected that by fattening up the jets by two sizes. Also, the ground strap indicated that the plug was too cold. What would cause the oil on the threads of the plug? I'm running 10w30 royal purple break in oil.
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post #2 of 10 (permalink) Old Jul 30th, 19, 9:53 AM
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Re: Clean spark plug, oil on threads

Quote:
Originally Posted by 68elky396 View Post
I'm reaching out to the team to get some thoughts on my recent findings. I have about 550 miles on my newly rebuilt 396. I was doing some plug readings the other day, just to find that the #2 spark plug has oil on the threaded portion. The plug is burning clean and indicated it was slightly lean, so I corrected that by fattening up the jets by two sizes. Also, the ground strap indicated that the plug was too cold. What would cause the oil on the threads of the plug? I'm running 10w30 royal purple break in oil.
Your intake manifold may have loosened slightly during break-in and might be sucking some oil from the lifter valley and throwing it on the plugs. Also, valve cover gasket might be leaking a little bit. I would tighten both the intake manifold and the valve cover.
Also, are you running a correct PCV valve for your cam ? if not, you may be getting some light crank pressure that is pushing some oil out at WOT, which is hard to figure out at idle.
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post #3 of 10 (permalink) Old Jul 30th, 19, 10:34 AM Thread Starter
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Those are all good possibilities that I had not thought of. I will be retorquing the manifold and checking the valve covers as well. As for the PCV valve being correct, I'm not sure. The one that's installed is for the stock configuration for the L34 350HP. The cam profile has been changed and I get about 17 inches of vacuum at idle. Thanks for your input!
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post #4 of 10 (permalink) Old Jul 30th, 19, 1:14 PM
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Re: Clean spark plug, oil on threads

As Harry indicates, slightly leaky VC gaskets can do this.

Gene
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post #5 of 10 (permalink) Old Jul 31st, 19, 2:47 PM Thread Starter
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I'll have some time to spend on my engine this weekend and will let you guys know what I find out.
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post #6 of 10 (permalink) Old Aug 7th, 19, 7:19 PM Thread Starter
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Here's the update on my 396/402. This thread was addressing the oil on my #2 sparkplug threads. I checked for leaky VC gasket and loose intake bolts, no leaks at valve cover and no loose intake bolts. I did however notice that at idle the PCV valve is rattling and not staying closed. The engine is producing around 17 inches of vacuum at idle. Should I buy another valve for this particular engine, or should I buy a valve that has a different rating? Suggestions or part numbers would be appreciated. Steve
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post #7 of 10 (permalink) Old Aug 8th, 19, 6:38 AM
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Re: Clean spark plug, oil on threads

If you don't mind spending a bit of $$$$$$ there is the ME Wagner adjustable PCV valve;
Dual Flow Adjustable PCV Valve ? M/E Wagner Performance Products
It is a very nice piece and you can adjust it to your vacuum.
Guy
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post #8 of 10 (permalink) Old Aug 8th, 19, 1:55 PM Thread Starter
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Thanks Guy, I don't mind spending big money when I have to, but I'm not willing to part with that much money for a PCV valve. I'm going to have to search for a different pcv valve that operates at lower vacuum. Maybe the one I have went bad?
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post #9 of 10 (permalink) Old Aug 8th, 19, 2:15 PM
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Re: Clean spark plug, oil on threads

PCV are not created equally. Run a search in this forum for the right part number as I cant remember if mine has an "A" or an "F" on the bottom, But it will make a diff and should NOT rattle at idle. Beleive I asked for one for a 1969 Corvette 427/435 HP application.
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post #10 of 10 (permalink) Old Aug 9th, 19, 2:40 PM Thread Starter
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Thanks for chiming in 427,
I took your advice and searched for a PCV valve for a 427/435hp and it turns out that I have the same one in there now that I just bought this morning. There is an F stamped on the bottom of the valve. It still slightly rattles at idle. Is that normal? Here is a photo of my 396/402. It's not as awesome as some of your engines I see on this site, but I built it along with the rest of the car, and I'm pretty happy with it. Thinking of changing the valve covers to orange.
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