GEO
Sarcasm Inc.
What is that strange shadow behind the valve , looks kinda like a crack to me?
My oil burning pig. Pics too!
- Thread starter Ironmike
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dano
Evil Handy Man
This post and picture alone should be a sticky.
moper
Well-Known Member
Not reversion unless the rings are shot. If the seals were installed without the plastic guide in place over the valve stem they should be replaced again - and this time use it. Just the process of sliding the valve through can damage the seals like 9s said earlier. Cracks from porting rarely - very rarely have any oil ssociated with them unless it's the port roof. Most everywhere else there are water jackets. You'd be leaking water, not oil. It's a guide problem unles the rings are not working but the leakdown is "ok". 3% to me is a lot for gapless, but that doesn't mean it's pumping oil up there. Pull the heads, have a good performance shop look at them.
Ironmike
Well-Known Member
OK Mope, I plan to replace seals, again. Where can I get the plastic guide for installation? Also, exactly how far down should the seals be installed on the guides?
So if the seals are good, wouldn't they stop oil flow even if your guides are shot? Is there a way to check my guides with the heads on, and springs off?
Also.. I ordered all the parts required for a PCV system, BUT I'm hoping I can run it to a nipple just under my carb. There is no ports on the HP950.
Here's the big one, and I know it sounds stupid: I've run quite a few motors in my day and all of them have just had a breather on each valve cover. I just don't grasp how the PCV system can do more.....I'm hoping you guys can explain the "workings" of the PCV. I always thought it was just a pollution thing. I need a thorough explanation of the benefits.
I guess I've just been lucky all these years without one, but I sure believe you guys about needing one now!
Sorry so many questions, fellas. I'm friggin' lost on this issue.
So if the seals are good, wouldn't they stop oil flow even if your guides are shot? Is there a way to check my guides with the heads on, and springs off?
Also.. I ordered all the parts required for a PCV system, BUT I'm hoping I can run it to a nipple just under my carb. There is no ports on the HP950.
Here's the big one, and I know it sounds stupid: I've run quite a few motors in my day and all of them have just had a breather on each valve cover. I just don't grasp how the PCV system can do more.....I'm hoping you guys can explain the "workings" of the PCV. I always thought it was just a pollution thing. I need a thorough explanation of the benefits.
I guess I've just been lucky all these years without one, but I sure believe you guys about needing one now!
Sorry so many questions, fellas. I'm friggin' lost on this issue.
PCV = Positive Crankcase Ventilation
A pcv is a good system to run but it is not going to stop your oil consumption . IMO and that's all it is .
Ironmike
Well-Known Member
So excactly how does it do any more than just breathers?
It creates a vacuum which actually sucks the pressure out of the crankcase.
Breathers are just "there".
The PCV system is a good one. But if your breathers open the crankcase to atmosphere preventing a pressure buildup (no one way valves, etc.), it may do little to curb your oil burning IMO. That is, there is no internal pressure to drive extra oil thru the valve seals, leaking intake gasket, etc. other than already wants to happen via existing leak paths and intake port vacuum.
The slightly negative pressure provided by the PCV might reduce oil consumption however by lowering crankcase pressure to the oil rather than allowing it the natural path (under atmospheric pressure) if you get what I mean.
I still believe you have something else going on. But no response so far to my questions. So I wish you luck.
yellow rose
Overnight Sensation
It's either guides or rings. Possibly both
Ironmike
Well-Known Member
DC, I kinda agree with your thinking. I can't see how the PCV is going to help, at least in my case. But I'm gonna give it a go.
And YR, I think the root of this whole thing may indeed be my guides.....I hope. Can't be rings, though. I don't see how new rings are going to push oil through the intake valve and puddle there. I can't even see how BAD rings can cause that problem...It's not reversion.
I would love to know if there's a way to check my guides with the heads still on....springs off. When I changed my seals, I sure didn't notice any "wiggle" in the valves, but then I wasn't really looking for it.
I plan to pull off the rockers and springs, take another look at the seals and pay attention to the spring pocket, under the shims. Heard about some problems that could be there, too.
And YR, I think the root of this whole thing may indeed be my guides.....I hope. Can't be rings, though. I don't see how new rings are going to push oil through the intake valve and puddle there. I can't even see how BAD rings can cause that problem...It's not reversion.
I would love to know if there's a way to check my guides with the heads still on....springs off. When I changed my seals, I sure didn't notice any "wiggle" in the valves, but then I wasn't really looking for it.
I plan to pull off the rockers and springs, take another look at the seals and pay attention to the spring pocket, under the shims. Heard about some problems that could be there, too.
Keep the piston near TDC so the valves don't fall too far into the cylinder, put a dial indicator (with magnetic base (mount it to the head or block)) on the valve stem and wiggle it to get a reading. There's a clearance spec on valve guides. Based on your valve stem distance (where you're measuring) from the guide, use geometry to figure the actual clearance. I don't have the specs at hand, they're packed in a box somewhere (I'm moving : )). It's in the service manual though if you can get your hands on one.
AJ/FormS
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I can think of 3 ways to check the guide seals on an assembled engine.
No 1, and by far, the easiest, is finding oil on the back of the intake valves.
No 1, and by far, the easiest, is finding oil on the back of the intake valves.
The plastic guide comes with fel-pro valve seals.
Its just a piece of clear tubing that slides over the tip of the valves to prevent nicks in the seal on installation.
Breadburner
Well-Known Member
So the heads are cracked but its only leaking oil and not coolant......???
moper
Well-Known Member
As Sire said - they come with the seals in many cases (factory and aftermarket). The seal goes on until the guice contacts the inside "top" of the seal. Take a measurement on a new seal if you need to know exactly how far but mine always just stop. If you force it, ot hit too hard, they'll just break.
Worn guides can be felt by removing the seal and opening the valve ti mid-lift and trying to wiggle it in the direction of the path it follows as it opens and clsoes. They can also be measured, which is what I do if I think there's a problem but I can't feel any slop in the first test. Bronze guides don't use a lot of clearance so measuring may be the only way to get a real picture of them. Just measure the ID of them in the direction of travel.
A positive type seal will not stop oil from going down a bad guide because the valve stem is allowed to move too much in that case. Umbrella seals can be stuck on anything and provide some sealing. Positive seals only work with limited lateral valve stem movement.
The PCV won;t stop your issue. Because it's not made to dispose of excess oil... But it will go a long way to helping the seals do their job. They are designed to seal liquid oil under no pressure. Yours is pushing liquidf oil under pressure down the guides. At least i think so...
Worn guides can be felt by removing the seal and opening the valve ti mid-lift and trying to wiggle it in the direction of the path it follows as it opens and clsoes. They can also be measured, which is what I do if I think there's a problem but I can't feel any slop in the first test. Bronze guides don't use a lot of clearance so measuring may be the only way to get a real picture of them. Just measure the ID of them in the direction of travel.
A positive type seal will not stop oil from going down a bad guide because the valve stem is allowed to move too much in that case. Umbrella seals can be stuck on anything and provide some sealing. Positive seals only work with limited lateral valve stem movement.
The PCV won;t stop your issue. Because it's not made to dispose of excess oil... But it will go a long way to helping the seals do their job. They are designed to seal liquid oil under no pressure. Yours is pushing liquidf oil under pressure down the guides. At least i think so...
Rustedwrench
Well-Known Member
A crankcase should always have negative pressure in it, by which I mean lower than atmospheric pressure. That is what the pcv system is for. On a normal vacuum gauge you will not see a vacuum until you raise the engine speed and then not much. Crankcase pressure is typically measured with a magnehelic gauge because is it so low. If the crankcase has pressure in it the pressure will attempt to force oil out past any gasket or seal that presents the path of least resistance. Pushing oil past the intake valve seals is aided by the vacuum in the intake port because the pressure drop across the seal there is the greatest.
That oil on the back of the intake valves is very common on BMW V-8 engines with more than 50-60,000 miles on them. Valve seals on those are junk. Match the rest of the car.
Ironmike
Well-Known Member
How do you figure it's pushing oil UNDER PRESSURE, down the guides?
Hipo65
Yeah I'm "That Guy"
Silly qustion,you say you upgraded cam at the same time correct? Well by chance is it more lift? I ask because are the spring retainers hitting the seals? Just another idea to rule out. Had same issue on my old 340 until I installed a good se of Manley viton valve stem seals very & carefully put them on my 340 & it quit using any oil at all!
Ironmike
Well-Known Member
Nah. Spring retainers not hitting seals. Wish it was something that easy to fix.
I think it is something simple, have you hooked up a proper pvc system yet?
Rustedwrench
Well-Known Member
The oil is not under pressure. The pressure under the valve cover is the same as in the crankcase, which you stated was above atmospheric. The pressure in intake port is below atmospheric. So if you have 3 psi gauge pressure above the intake valve seals and negative 15 psi gauge pressure below in the intake port the 18 psi pressure difference tries to equalize past the valve seals and takes some of the oil vapor under the valve cover with it.
Ironmike
Well-Known Member
OK. the 3 psi I got was doing a diagnostic test with the valve cover ports PLUGGED, and a vacuum guage in the dipstick thing. I'm sure there's no pressure normally, with the breathers on.
I have not yet installed the PCV system. I just don't think it's gonna help in this situation, but I do plan to give it a try. I probably should be running header evacs, if anything.
I'm going to take a look at my seals, check the guides......if nothing looks odd there, I'm not sure what my next move will be.
I've had quite a few higher HP engines over the last 30 years or so and have never run a PCV set up. Never had this problem.
I have not yet installed the PCV system. I just don't think it's gonna help in this situation, but I do plan to give it a try. I probably should be running header evacs, if anything.
I'm going to take a look at my seals, check the guides......if nothing looks odd there, I'm not sure what my next move will be.
I've had quite a few higher HP engines over the last 30 years or so and have never run a PCV set up. Never had this problem.
nm9stheham
Well-Known Member
Just as an additional thought/observation: the guides look to have been cut off some and look to be kinda short in the pix of the intake port. Did the porting guys says anything about that? A shortened guide is going to be subject to faster wear and more wobble of the valve stem.
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