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My 390 is burning a huge amount of oil since my latest rebuild. This time I had the cylinder heads decked. I used moly rings and honed the cylinders. Valve seals are new. I pulled the intake twice to make sure it was sealing. I even put RTV around all the intake ports this time. I've tried various manifold vaccum sources for the PCV. The truck runs very good but uses a ton of oil. I put my bore scope down the spark plug holes and verified that there is oil pooled on top of some of the cylinders. I tried to view down the intake but wasn't very successful. I then did a compression test.
Same question what valve seals ? teflon = oil burning
Also what have you done with the guides ? wiped out guides can't be fixed with any seal.
For future reference you never use RTV on intake ports or anywhere that fuel is present. but this isn't your problem in this case it doesn't happen that fast.
I do not remember. They were the flexible orange ones.
I forgot to mention that the oil is burnt on acceleration only and the drivers side bank sometimes gets better. The valve guides had no problem before but maybe when he cleaned the heads at the machine shop it knocked some carbon off or something?
I do not remember. They were the flexible orange ones.
I forgot to mention that the oil is burnt on acceleration only and the drivers side bank sometimes gets better. The valve guides had no problem before but maybe when he cleaned the heads at the machine shop it knocked some carbon off or something?
What type did you install umbrella or positive type? and did you measure the valve stem to determine if they were standard size ?
Umbrella and yes they are the correct size. I also have the Holley jets in the heads. No drainage trays though because they wouldn't work with roller rockers.
With moly rings being used was the end gap set? The critical part of this is were the bores finished to the specifications of the ring manufacturer normally 15 to 20 RA. Next step is did you miss the critical break in period on the rings? Moly rings require heat and high pressure also to seat, hopefully you didn't go light on the throttle.
Positive crank case pressure will gunk up your motor and turn your hair grey.
Good point. How does your motor breathe through the valve covers? My motor sat for 20 yrs when I got it running again and my plugs after 10k mi never look like that.
The only seals I've had problems with are the white teflon ones use with positive valve seals. they're worthless. if you have umbrella seals it should be okay.
So with that eliminated it put rings and valve guides more in the spotlight. you say the valve guides had no problem , does that mean they weren't replaced ? since you can see oil on top of the pistons this is where I'm leaning.
If you're drawing your PCV from the valve cover is it baffled under the PCV valve ? it must be or you'll pull oil.
Oil pooled on the tops of the pistons seems extreme. Your compression values seem reasonable. I'm assuming that the skirt on the valve stem seals was tall enough to keep the oil from dripping on the stem above the top of the guide. I'm also assuming that when you installed the stem seals you pushed them down to the tops of the guides with the valves in the closed position. Also be sure that the return oil drains in the heads are not obstructed.
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