oil mist from 427 breather cap

oil mist from 427 breather cap

Joined: October 17th, 2006, 1:02 am

May 23rd, 2007, 12:04 am #1

I'd like to hear some thoughts from the mechanics on this one.

I've posted previously regarding the revitalization of the 427's in my 1973 36' sportfisher. I'm pleased to report that they are running beautifully. The cameraphone photo below shows an aft view at around 3200 rpm / 22mph. (notice the progress on the toe rail)


After running at speed for a few moments, I opened the floor to check for anything unusual. What I found was an oily mist coming from the breather on the oil fill cap of the starboard motor. This cap has some filter material in it, but the mist still flowed out. It wasn't smoke. I had added >.5 quarts of oil to that motor before leaving the dock because the level was just above the bottom end of the range on the dipstick. Compression on the engine is great. All cylinders are within 15lbs of each other and are greater than 175lbs each. I would think that makes blow-by unlikely. There is abnormal no odor to the exhaust (like the distinct smell of oil). Is this as simple as a failure of the filter material in the breather? Should I be concerned? The other side breathes into the flame arrestor.

Any suggestions?


Scott Keefer










<HR WIDTH="100%" COLOR="##666699" SIZE="11">PHOTO OF THE DAY AWARD (During the last week of May, 2007))



(ABOVE) Scott's 427s pushing a lot of water ! This interesting photo and write-up lead to a very good discussion that may help others. Thanks for introducing the subject, Scott, and for the great photo to go along with it too.

Paul,
forum moderator


<HR WIDTH="100%" COLOR="##666699" SIZE="11">









Last edited by FEfinaticP on May 31st, 2007, 9:47 pm, edited 1 time in total.
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Joined: July 15th, 2005, 8:09 pm

May 23rd, 2007, 9:15 am #2


The first thing that comes to mind is the crankcase ventilation valve. Here is what the installation should look like (compliments of Mark Weller, who took the photo of Tim Toth's beautiful motor). If the valve that runs from the crankcase to the carb is not working properly (is stuck) then pressure can build up in the crankcase and the vent becomes the oil breather. It's supposed to breathe, but not in an outward direction.

Do you have aftermarket carbs, or aftermarket valve covers (some of the latter don't have the internal baffles like the stock covers do). Is there anything not stock on the motor? First thing I'd do is to look at the crankcase vent system. It's pretty simple, internal parts just slide back and forth.

regards, Paul




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Roy
Roy

May 23rd, 2007, 6:51 pm #3

I'd like to hear some thoughts from the mechanics on this one.

I've posted previously regarding the revitalization of the 427's in my 1973 36' sportfisher. I'm pleased to report that they are running beautifully. The cameraphone photo below shows an aft view at around 3200 rpm / 22mph. (notice the progress on the toe rail)


After running at speed for a few moments, I opened the floor to check for anything unusual. What I found was an oily mist coming from the breather on the oil fill cap of the starboard motor. This cap has some filter material in it, but the mist still flowed out. It wasn't smoke. I had added >.5 quarts of oil to that motor before leaving the dock because the level was just above the bottom end of the range on the dipstick. Compression on the engine is great. All cylinders are within 15lbs of each other and are greater than 175lbs each. I would think that makes blow-by unlikely. There is abnormal no odor to the exhaust (like the distinct smell of oil). Is this as simple as a failure of the filter material in the breather? Should I be concerned? The other side breathes into the flame arrestor.

Any suggestions?


Scott Keefer










<HR WIDTH="100%" COLOR="##666699" SIZE="11">PHOTO OF THE DAY AWARD (During the last week of May, 2007))



(ABOVE) Scott's 427s pushing a lot of water ! This interesting photo and write-up lead to a very good discussion that may help others. Thanks for introducing the subject, Scott, and for the great photo to go along with it too.

Paul,
forum moderator


<HR WIDTH="100%" COLOR="##666699" SIZE="11">








Scott, my first thought is a malfunctioning crankcase vent system, but we need to know more. How much vapor are you seeing? Also, if you disconnect your PCV system, are you getting any suction from the carb side of the tube, and then from the pcv valve itself.

Also, are you seeing any steam from your exhaust? Well, lets rephrase that. Are you seeing any UNUSUAL amount of steam from your exhaust? If so, it can only be coming from a few places, and the steam and the oil film can actually be related.

A malfunctioning head gasket can leak pressure into the oil sump. A malfunctioning head gasket can also leak water into the cylinder or exhaust outlets. Leaking exhaust manifold will also cause steam.


Here is a good reference, go to the vac gauge site and look up example #13 for head gasket. http://www.network54.com/Forum/424840/m ... cuum+gauge

If the sump is pressurized it is coming from the head gasket, the head (possible crack) or the intake crossover (crack, hole, or bad gasket at the intake. Yes, the intake (few people realize the intake manifold is connected to the exhaust system via the crossover, and it could be a bad intake or bad intake gasket, which produces the same results of adding pressure to the oil sump.


Roy
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Paul
Paul

May 24th, 2007, 12:30 pm #4

I'd like to hear some thoughts from the mechanics on this one.

I've posted previously regarding the revitalization of the 427's in my 1973 36' sportfisher. I'm pleased to report that they are running beautifully. The cameraphone photo below shows an aft view at around 3200 rpm / 22mph. (notice the progress on the toe rail)


After running at speed for a few moments, I opened the floor to check for anything unusual. What I found was an oily mist coming from the breather on the oil fill cap of the starboard motor. This cap has some filter material in it, but the mist still flowed out. It wasn't smoke. I had added >.5 quarts of oil to that motor before leaving the dock because the level was just above the bottom end of the range on the dipstick. Compression on the engine is great. All cylinders are within 15lbs of each other and are greater than 175lbs each. I would think that makes blow-by unlikely. There is abnormal no odor to the exhaust (like the distinct smell of oil). Is this as simple as a failure of the filter material in the breather? Should I be concerned? The other side breathes into the flame arrestor.

Any suggestions?


Scott Keefer










<HR WIDTH="100%" COLOR="##666699" SIZE="11">PHOTO OF THE DAY AWARD (During the last week of May, 2007))



(ABOVE) Scott's 427s pushing a lot of water ! This interesting photo and write-up lead to a very good discussion that may help others. Thanks for introducing the subject, Scott, and for the great photo to go along with it too.

Paul,
forum moderator


<HR WIDTH="100%" COLOR="##666699" SIZE="11">








Well, we have the PHOTO OF THE DAY feature here on the forum, so why not the RAMBLE OF THE DAY?

Thinking this through again, Roy makes some good points about the intake gasket, etc., but unless you really have a seriously pressurized crankcase, it's probably blow-by. I think I'd pull the crankcase vent valve out of the valve cover, and would try to plug each opening in the valve cover temporarily just to see what kind of a pressure build-up you have. There is a small natural pressure build-up because most motors allow a SMALL amount of pressure to leak by the rings and into the oil sump. This is, in effect, blow-by, even from a new motor, albeit very small. It's small, but it is still large enough to require PCV valves on new cars to control it.

--->NOTE<--- If you disconnect a vertical PCV valve that is intended to stay closed until vacuum increases, then you are sending in way too much air to the carb at idle speeds and it won't run very well. Therefore, at slow idle testing like this, that PCV valve should remain in the vertical position, or be plugged for the test.

If you are running at a slow speed, you are not generating much heat in the motor, and there isn't much blow-by at all. Therefore there isn't much of any need for the PCV system to be working. The PCV valve may allow "some" pre-determined evacuation of the crankcase at slow speed, but it's essentially closed at slower speeds.

Now crank it up and run hard for a while, generate a lot of heat, let those 4-bbl carbs open up create a lot of vacuum. Now we're running around 3000 RPM and creating a monster wake like your photo! (Great photo by the way!)
Under these conditions the PCV valve is being opened by vacuum to the carb and NOT PRESSURE in the crankcase. This is true because you have an open vent on one side of the motor (Port) and the PCV installation on the other side. They both connect to the crankcase so it's impossible to pressurize the motor (unless you bought an aftermarket un-vented device, and this certainly has happened more than once.)

At speed when the vacuum creates suction on that PCV valve and pulls it open, this also sucks air FROM that open vent on your valve cover, through the motor, and out the PCV valve. In this way the natural blow-by created by a hot motor is evacuated out of the crankcase and into the carb where it's burned. If you see smoke or fumes coming out the valve cover vent while under way at higher rpm, then your PCV valve is not necessarily working properly and it needs to be cleaned out(they vary in design, but most are required to be in a vertical position, because they work on gravity, just a given weighted plug that is pulled up when suction gets to a certain point). If the PCV valve is working properly, then you may have more blow-by than the PCV system will tolerate, or you may have a leak somewhere in the head, head gasket, or as Roy pointed out, in the intake gasket where it hooks to the exhaust port. Personally, I think what you have is blow-by.

So here you are, running at 3000 RPM or so for a while, heating everything up, and all of a sudden you throttle back, raise the hatch and take a look at the motor. You're horrified to see smoke coming out of the breather. Guess what? It may be there because the vacuum on the running motor just shut down and the PCV valve is now closed. The result is a belch or two of smoke coming out the breather because things are still hot and there is still some blow-by (or otherwise hot oil motor smell, etc., cooked oil, whatever you want to call it) in the crankcase.

Now I'm interested in what oil you are using. I'm the first to tell people "you can not get a mechanic in a can", but oil quality, prices, and performance will vary widely. You generally get what you pay for. I've been running Mobil-1 15W50 in my 427s for years. They love it. The 15W quality allows fast starting, and the 50W quality comes into play when things get good and hot. It's not as simple as "50W runs like cold 30W when it gets hot". The engineered quality of this oil allows good oil pressure at all times. AMSOIL HD DIESEL/MARINE (synthetic) is probably the best oil you can put in a boat motor of this type, but the Mobil-1 is a good choice too. I think they're both "the gold standard". The motors run clean, they get superior lubrication. The AMSOIL HD Diesel/Marine will have more detergent to handle diesel soot.

You might consider changing oil and see what happens under the exact same condition. This is just a hunch. I'd hate to be responsible for you wasting an oil change, but it may help, if (IF) your present oil is not doing its full job.

Anyway, sorry for the ramble. I love problem-solving and the diagnostic challenge. These old motors are pretty simple, most of the issues are able to be explained and solved. My hunch here is probably the fact that the big motor is a bit loose from normal wear, you're getting a pretty normal blow-by and other fumes generated by a hot motor, and the PCV system isn't able to handle all the load. Things could be a LOT worse!

Keep us posted on this, Scott. I'm interested in hearing more about this one from you and the others.

Regards, Paul



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Joined: October 17th, 2006, 1:02 am

May 30th, 2007, 10:20 pm #5

Thanks to all for the feedback.

Naturally, I like Paul's assessment best. I was away on another boat for the weekend and did not get a chance to follow up with this investigation. I will try to observe the condition while still under speed. I did not expect blow by could be an issue when compression is so good.

There is slightly more steam from this motor than the other, but not so much that it seems an issue. I will try the vacuum checks when I get an opportunity.

Current motor oil is Castrol 30W HD. It is new this winter.

Conditions are year-round boating on TN river in AL.

Scott
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Paul
Paul

May 30th, 2007, 10:48 pm #6

Castrol is a good brand, I'm familiar with their 20W50, which I used pretty much exclusively until I got on the synthetic band wagon ten years ago or so. I always hesitate to make recommendations that would potentially put someone at financial risk or personal peril, of course, but if it were me, I'd try the Castrol 20W50 and see if you could see any difference. The 30W is what CC recommended "back when", but oil technology has come a long way since those owners manuals were printed.

On my 427s, I've been using Mobil-1 15W50 with good results. The 50 weight factor comes into play when the oil really heats up, and you should have a thicker viscosity at hot running temps with the heavier oil, which would most likely reduce blow-by and cook off too. What you are seeing and smelling may well be a cook-down by product (too). Since there are few applications for straight 30W these days, I wonder about the quality of the stuff.

Just a few addl thoughts.

regards, Paul
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Joined: October 17th, 2006, 1:02 am

May 31st, 2007, 12:09 am #7

Since the rest of the specifications re valve lash, plug gap, etc. are still applicable, I've never thought that the recommendations for oil might be dated.

No worries about the endorsement of a non-specified oil product. Your advice on 427's has been sound. I will shop it around for triangulation with some of the mechanics I trust at the yacht club. The decision and its potential results is ultimately mine alone.

Scott
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Paul
Paul

May 31st, 2007, 5:50 pm #8

Hi Scott,

I began wondering about the specifications on your oil, and thought I would look it up. It sparked my interest in doing a comparison, which I have added to the forum at this link.

Check it out, I think you'll see why I recommended trying the Castrol GTX 20W50 as a reasonably priced non-synthetic (which is near the bottom of the chart and not highlighted). It's a good product with some potential advantages over what you are presently using. It has the same zinc content, which some people equate to long life in camshafts (I believe there are many things working together for long life of cams, and not just the zinc content, so I check out those wear tests when they're available).

http://www.network54.com/Forum/424840/m ... 1180631150

One of the other things that is not apparant on the referenced chart, is the synthetic oils actually run cooler due to less friction. I think all these things add up, even with old engines that have some wear on them, becuase they still need all the protection they can get.

Does the synthetic oil really make a difference? I think so. I have a particular Porsche transaxle that was really making a pronounced gear whine, and it was tough to shift when cold. I was using THE BEST and MOST EXPENSIVE German approved natural gear lube I could find. (Gear lube, not motor oil). I tried some AMSOIL gear lube and I was astounded. The gear whine went almost away, and the transaxle shifts like butter when cold or hot. It transformed the car! In that instance, there was a huge difference I could notice. With a motor it's going to be harder to notice something that significant, but with a transaxle you can "feel" the pressure on the synchros, etc., and hear the gears. Now when I use a gear lube it must be synthetic.

Scott, when you look at the referenced chart, look at the last segment for the 20W50 oil. Within that category alone, there is one huge difference in real performance, so the 20W50 designation really has little to do with how good an oil is. Note the .39" scratch in the AMSOIL 4-ball wear test, but the .79" scratch for Quaker State (ouch !) I would expect the Castrol GTX to be much better, even though it's rated at 625 along side the Quaker State. Anyway, food for though, eh?


Regards,

Paul
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Joined: March 24th, 2008, 11:02 pm

March 24th, 2008, 11:18 pm #9

Paul what would you feel normal oil consumption should be on these 427" .....Chris
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Paul
Paul

March 25th, 2008, 2:29 am #10

My marine engines have consumed so little oil with the Mobil-1 15W50, I have not really kept track of the hours. My particular motors seem to like that oil. Equivalent to automotive use, at 50-mph a 100 hour run would equate to 5000 miles, and it's not unheard of to go through a quart in 5000 miles with older motors, especially if you are pushing it when you're running, along with a lot of startups an shutdowns. I dare say there are some that will go through a quart in half that much.

If you are consuming a noticed amount of oil, I would check the compression to see if the rings really are the culprit, and then I'd look at those valve seals. You can lose a lot of oil down the valve stems, the motor can smoke, and the rings could still be in good shape.

If the rings are on their way out, you can bump up to a thicker oil and use plugs that will help with the burn. I'd be sure to get an oil known for low ash when burned, not unlike the two cycle outboard motor oil. In the end, you'll have to solve this problem by getting into the motor and seeing exactly what the tolerances are, etc.

regards,

Paul












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