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Old 06-08-2005, 11:40 AM
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diagnosing blow by issues with 460

While on the Power Tour the minor blow-by I had been experiencing for some time with my Ford big block seems to have worsened quite a bit. I'm getting significant oil out the breather, a bit out of the dip stick tube, and I think it's even pushing out the rear of the oil pan gasket since I have some oil drips in that area. During the trip I lost a quart of oil in 1,200 miles - which is significant for that motor. My immediate diagnosis was bad rings or rings not properly seated in one of the holes (11K since the rebuild). So this morning I ran a compression test and got:

140
141
150
145
146
140
150
150

Unless I'm mistaken, these readings do not indicate bad rings or valves on any particular cylinder and lead me to believe it may not be a typical blow-by problem at all. The simple "rattle" test on the PCV valve also seemed okay. I may replace it this afternoon anyhow since it's cheap but I don't think that is the culprit either. Also the plugs are clean and the engine is not smoking or showing signs that I am burning the oil. I am almost certain it is simply pushing the oil of the motor.

Any ideas where I should be looking next? Might a leak down test (I have to have this done at a shop since I don't have the equipment) still prove the rings are a big enough problem to cause that much oil being pushed out?

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Old 06-08-2005, 11:57 AM
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A static compression test will not necessarily point out a broken(s) oil ring. You may still have good compression and have a faulty oil ring. A leak-down test may not show it either.

How do your plugs look? Are they (or any) oil fouled? Do any (or all) have a brownish tinged deposit (indicative of poor valve seals)?

Have you done a thorough PCV System check? Is it pulling vacuum? Is it OEM designed or an after thought? A free valve does not mean it is OK.
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Old 06-08-2005, 12:04 PM
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Also look to see if the crankcase air inlet is plugged. If it is, it will act just like a faulty PCV.
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Old 06-08-2005, 12:43 PM
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Quote:
Originally Posted by sbchevfreak
Also look to see if the crankcase air inlet is plugged. If it is, it will act just like a faulty PCV.
Where is that located on a 460?
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Old 06-08-2005, 12:55 PM
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Kultulz,

Here's a pic of the plugs just as they came out of the engine. No oil at all and to my eyes, no brown coloration...but you would be a better judge. I still haven't touched them so if blow ups of each plug would help I can still do that.

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Old 06-08-2005, 02:06 PM
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After looking over the plugs more closely, I would say that if any have a brownish deposit, it would only be among the three lower plugs on the left in the prior picture. So I took close up shots of those three plugs as shown below. To my untrained eye, these plugs look fine...but it's sure possible that I could be missing something.





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Old 06-08-2005, 02:32 PM
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The plugs actually look very clean (except maybe for a few cylinders running a little rich). You have what appears to be wet oil on the threads. Is there a rocker cover leak that is leaking onto the plugs and maybe smoking from the exhaust manifolds? Also be advised that what may appear as a bad valve seal deposit can also be an additive in the fuel.

The crankcase ventilation sytem draws fresh outside air into the crankcase to rid it of blowby fumes which are harmful to it's well being. In the PCV design, engine manifold vacuum provides the source of this ventilation. Outside air is drawn into the system via a ventilated oil cap (Open Emission) or through the air cleaner (Closed Emission) (oil filler cap non-ventilated).

It is then drawn by engine vacuum (via PCV valve) throughout the crankcase through the PCV valve ( usually on rocker cover on late applications)(grommet must be tight) through the valve and into the carburetor plenum where the fumes and vapors are burnt.

Is your system setup in this fashion and is it operable (requires periodic service)?
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Old 06-08-2005, 02:42 PM
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These are also fairly fresh plugs? You may need to run them for a few weeks to get a better reading.

I see black on the insulators. Are you using dialectric compound in the plug boots to prevent shorting/arcing (resulting in less cylinder spark)(may be cause of rich plugs) or is that exhaust gas leakage from the headers?
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Old 06-08-2005, 04:59 PM
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Quote:
Originally Posted by KULTULZ
You have what appears to be wet oil on the threads. Is there a rocker cover leak that is leaking onto the plugs and maybe smoking from the exhaust manifolds?
Definitely oil on the plug threads, but it's perplexing because I can find no exterior source for it and no signs of oil dripping on the headers from the valve covers or elsewhere. Also, these plugs have been in the motor since it was rebuilt so they have a little over 11K on them.

Quote:
The crankcase ventilation sytem draws fresh outside air into the crankcase to rid it of blowby fumes which are harmful to it's well being. In the PCV design, engine manifold vacuum provides the source of this ventilation. Outside air is drawn into the system via a ventilated oil cap (Open Emission) or through the air cleaner (Closed Emission) (oil filler cap non-ventilated).

It is then drawn by engine vacuum (via PCV valve) throughout the crankcase through the PCV valve ( usually on rocker cover on late applications)(grommet must be tight) through the valve and into the carburetor plenum where the fumes and vapors are burnt.

Is your system setup in this fashion and is it operable (requires periodic service)?
My system has a oil filler/breather cap (no vent holes) on the driver side valve cover with a hose connection to the air cleaner. On the passenger side there is a pcv valve inserted in the the valve cover (appears to be a tight grommet seal) with a hose running to vacuum outlet at the rear base of the carb. This sounds like the "closed" emissions variety you described.

However, this is clearly not the stock set up. This is the way I got it from the builder so there could be something amiss in the system which is causing it not to work properly.

One of the heaviest areas of oil being blown out is at the driver's side oil filler/breather cap. My understanding from your description is that the fresh air from the air cleaner should be being drawn into the valve cover and then on to the crankcase through this breather cap. Instead, oil is being blown out around the grommet of this cap and possibly around where the rubber tube attaches to the cap. I would think if there is enough pressure to blow oil out this breather, it certainly is enough pressure to prevent fresh air from entering the system. Almost the reverse of what ought to be happening it seems.

Quote:
I see black on the insulators. Are you using dialectric compound in the plug boots to prevent shorting/arcing (resulting in less cylinder spark)(may be cause of rich plugs) or is that exhaust gas leakage from the headers?
No, I have not used dialectric compound in the boots..and I don't believe there is exhause leaking from the headers (at least I can't see it or hear it).

My wife just got home with a new pcv valve and some new plugs so I'll replace those items and crank up the motor and try to check all the vac hoses.

If you can think of anything else I should to be checking at this point let me know.
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Old 06-08-2005, 05:49 PM
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Can you post a few detailed photos of the PCV System on the engine (especially the filler cap and rocker covers)? Does there appear to be oil baffles at the oil filler cap opening on the rocker cover?

What type of ignition system do you have?
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Old 06-08-2005, 06:15 PM
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Plugs

Doc here,

What I see on those plugs...

Is an over lean condition...White, with possible detonation (the little "Ball" like deformation on the electrodes)...The Substance around the threads looks more like "Varnish" than fresh oil...But it's really hard to be sure from pics alone...

As for the Blowby, Try a Vented Breather cap, also inspect the air cleaner for oil being sucked in to the element, or air cleaner base..

Also, if you were running a bit Advanced on timing and lean in mixture (read: plug indications) you would see more CONDENSATION from the crankcase, (higher engine temps) not what you may be mistaking as oil burning..

I had an early 460 years ago that we popped from a wrecked tow truck and stuck in a Fairlane 500..

Would always show low after running on oil..but would only blast smoke in the first start up of the day...did not drip oil, nor otherwise smoke..thought it was seals or guides...until I pulled the valve cover off warm..apparently the oil return holes were under-matched to the flow from the heads...AND it had some gunk in there..it would hold up to 1/2 qt of oil in there until it slowly drained back down (like a few hours)..and I guess seep past the guides..

A Coat hanger down the return holes solved the problem quite nicely...

Doc
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Old 06-08-2005, 06:22 PM
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Yeah Doc, that first one looks like it might have piston material on it to me from here.
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Old 06-08-2005, 08:08 PM
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Looks lean to me too.

cboy, disconnect the PVC hose and block it on both ends(the vac source & the pcv itself) so that it is air tight. Then take an old plug wire with a straight boot and remove the boot(plug side) and put it on the dipstick so it is air tight.

Then start it up and remove the oil cap. Put your hand over the hole so it is air tight.

Does it build pressure? When you release your hand does a "puff" of smoke or air come out, if so how much?

Answer those and we'll move on
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Old 06-08-2005, 08:43 PM
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Quote:
Originally Posted by KULTULZ
Can you post a few detailed photos of the PCV System on the engine (especially the filler cap and rocker covers)? Does there appear to be oil baffles at the oil filler cap opening on the rocker cover?

What type of ignition system do you have?
First shot is the oil filler/breather cap. The rocker cover has baffles at the opening, basically two pieces of metal, one on each side placed just inside the diameter of the opening. The grommet I use also has a rubber baffle in it. I've tried an open grommet and this baffled grommet to try to prevent oil discharge out the breather. I've also tried a venter breather as Doc suggested but that allowed even more discharge. This breather is a push in type (not screw in) and fits quite tightly in the grommet. You can actually see in this picture oil standing in the manifold valley just below the hose to the air cleaner. Sorry this pic is a little blurry but there is a clamp on the breather where the hose is attached.

The second shot is the pcv side.

The ignition is a stock ford dura spark II system.


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Old 06-08-2005, 09:21 PM
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Quote:
This breather is a push in type (not screw in) and fits quite tightly in the grommet.
OK...The rocker covers (EDELBROCK or MOTORSPORT?) has a hole (as opposed to fill tube) and in that hole is a grommet that the male filler cap pushes into? There are no oil/fumes being drawn into the air cleaner? I also see the vent tube wraps around the carb and the inlet is on the right underside of the air cleaner. Any chance of this tube collapsing at speed? A PCV hose can be purchased with a formed ninety degree bend in it to prevent this (or a ninety degree plastic elbow is also available). Can the cleaner bottom be turned one hundred eighty degress?

If there are no fumes being drawn into the air cleaner (as evidenced by a clean carb top), then the rubber grommet has to be defective. Remember, most of this stuff is made overseas and the grommet may not be soft enough to make a perfect seal.

Also verify the vacuum signal inlet (at carb base) has no restriction and is drawing full manifold vacuum.

Some of these aftermarket rocker covers oil baffles will not prevent oil spray from being drawn into the valve/oil filler cap.

The one plug that appears to have deposits on the ground electrode, scrape it with your thumbnail and see if it appears to be a metallic deposit. See the clear spot on the electrode insulator? At least you have one indexed correctly...

You are absolutely sure you have the correct heat range?
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