Oil burn cloud on engine deceleration

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WSUTARD

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My 340 is blowing oil smoke out of the exhaust during prolonged engine braking/deceleration. It does not burn oil at any other times.

This started when I switched from dual breather caps to a PCV and single breather. The engine vacuum was pulling a lot of oil through the PCV so I installed a catch can I pulled off my Ram. That cut the oil getting into the air/fuel mixture for everything but the hard engine braking.

I installed a set of valve covers with baffles thinking that this would eliminate the oil but it didn’t change anything. My previous did not have baffles for some reason.

Now I need some more ideas. My current PCV is a Microguard 2088 or at least 2088 is what it says on the PCV housing.

Should I try a different PCV? Or something else?
 
WSUTARD said:
My 340 is blowing oil smoke out of the exhaust during prolonged engine braking/deceleration. It does not burn oil at any other times.

This started when I switched from dual breather caps to a PCV and single breather. The engine vacuum was pulling a lot of oil through the PCV so I installed a catch can I pulled off my Ram. That cut the oil getting into the air/fuel mixture for everything but the hard engine braking.

I installed a set of valve covers with baffles thinking that this would eliminate the oil but it didn’t change anything. My previous did not have baffles for some reason.

Now I need some more ideas. My current PCV is a Microguard 2088 or at least 2088 is what it says on the PCV housing.

Should I try a different PCV? Or something else?
Click to expand...
are you using oil? do you have a film of oil on the rear of the deck lid after cruisin at freeway speeds? If so, there's a possibility of a vacuum leak on the bottom of the intake to head surface. This is usually due to angular mismatch betw. intake manifold and head intake port surfaces.
I have also seen oil consumption from putting on well sealed heads onto poorly (ring)sealed short block.
 
Have the valve stem seals been replaced?

Changing PCV's would not likely do much. You could try a restrictor in the PCV line, but then that will defeat the large opening setting of the PCV. Seems like we discussed some PCV's before...??

IIRC, this engine has some wear and age on it.
 
Not using any oil other than decelerating down a hill. I’m 99% sure this is coming from the PCV system.

Do PCVs go bad?
 
nm9stheham said:
Have the valve stem seals been replaced?

Changing PCV's would not likely do much. You could try a restrictor in the PCV line, but then that will defeat the large opening setting of the PCV. Seems like we discussed some PCV's before...??

IIRC, this engine has some wear and age on it.
Click to expand...
Engine is relatively new(ish) 5 years on the rebuild. No oil consumption under normal, flat, cruising conditions.
 
Could I test my PCV system by unplugging it and running that way? My engine should still get the normal air by leaving the carb PCV port uncapped.

If I don’t experience smoke on a downhill deceleration then I know it’s the PCV is what I’m thinking.
 
WSUTARD said:
Engine is relatively new(ish) 5 years on the rebuild. No oil consumption under normal, flat, cruising conditions.
Click to expand...
it probably wouldn't be visible at cruising speed, but you would notice the light oil film on the bumper and rear panel, when you wipe the car down. It comes from the exhaust, and gets deposited on the rear surfaces in the turbulence/road draft following your car.
 
Can you put a 5/8-3/4" barb on you air cleaner? I run a non-atmospheric breather with a hose fitting (much like the original Mopar ones) to the air cleaner.

PCV valves can go bad, mainly gummed up but even after cleaning they can fail to seat.
 
1969383S said:
PCV valves are not all equal! Sounds like you have done your homework. Is the catch you installed filling with oil?

They make a fully adjustable piece that may fit your need.

Dual Flow Adjustable PCV Valve – M/E Wagner Performance Products.

IMO you need one and not dual breathers!
Click to expand...
$129!!! It better come with a +5hp sticker for that much.

I just finished a successful test run with no smoke on downhill deceleration. I pulled the PCV from the valve cover and kept it connected to the carb and then put my extra breather on the open valve cover port. This gave me the same air mixture as prior but removed the possibility of oil being sucked through the PCV.

So, I believe this identifies the PCV as the culprit here.
 
dano said:
Can you put a 5/8-3/4" barb on you air cleaner? I run a non-atmospheric breather with a hose fitting (much like the original Mopar ones) to the air cleaner.

PCV valves can go bad, mainly gummed up but even after cleaning they can fail to seat.
Click to expand...
I don’t know what kind of “barb” you are referring to.
 
WSUTARD said:
$129!!! It better come with a +5hp sticker for that much.

I just finished a successful test run with no smoke on downhill deceleration. I pulled the PCV from the valve cover and kept it connected to the carb and then put my extra breather on the open valve cover port. This gave me the same air mixture as prior but removed the possibility of oil being sucked through the PCV.

So, I believe this identifies the PCV as the culprit here.
Click to expand...

Just remember that PCV actually helps promote ring seal. You have a dilemma, go buy 10 different valves and experiment or drop some cash for something you can actually adjust to meet your needs.

What covers do you have and can you use a factory resto piece? Still seems you have and inadequate baffle setup. Glad you have your finger on it and sure you will make the best decision for your needs. You have shown great troubleshooting skills in your diagnosis!
 
If you have paid much attention to the baffles on these era engines on the factory covers they are long and cover the full width of the cover! The aftermarket covers are weak here!
 
I have cheap Mancini chrome covers. Hey have a tiny baffle just wider than the hole in the cover.

The amount of oil in my catch can has dramatically decreased since installing the baffles but I still get some in there.
 
WSUTARD said:
I have cheap Mancini chrome covers. Hey have a tiny baffle just wider than the hole in the cover.

The amount of oil in my catch can has dramatically decreased since installing the baffles but I still get some in there.
Click to expand...

You are on the right track and a few decisions to make. BOL!

Maybe save up and chrome some original covers?
 
WSUTARD said:
I don’t know what kind of “barb” you are referring to.
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Hose nipple perhaps? Something like below that Edelbrock sells.

Edelbrock Crankcase Ventilation Hose Connection Kits 1205

upload_2017-10-2_17-38-43.jpeg

You should be routed this way.
upload_2017-10-2_17-44-19.gif
 
Smoke from oil in the exhaust during deceleration/high vacuum usually indicates bad intake valve seals. The pcv valve should be almost closed under high vacuum. Pull your carb and see if the intake is oil soaked.
 
WSUTARD said:
My 340 is blowing oil smoke out of the exhaust during prolonged engine braking/deceleration. It does not burn oil at any other times.

This started when I switched from dual breather caps to a PCV and single breather. The engine vacuum was pulling a lot of oil through the PCV so I installed a catch can I pulled off my Ram. That cut the oil getting into the air/fuel mixture for everything but the hard engine braking.

I installed a set of valve covers with baffles thinking that this would eliminate the oil but it didn’t change anything. My previous did not have baffles for some reason.

Now I need some more ideas. My current PCV is a Microguard 2088 or at least 2088 is what it says on the PCV housing.

Should I try a different PCV? Or something else?
Click to expand...

The very first thing I would do is to compression test this thing.
High vacuum conditions oil consumption can also be caused by a bad ring seal, as well as excessive blow by.
You may not want to hear it, but it still may be.
 
let's see them sparkplugs. I bet those will tell the story.
 
when I used to do valve jobs, I always checked the ports for vacuum. There is a Souix tool, that works kinda like a leak down tester in reverse. It works by means of compressed air creating a vacuum, you calibrate the gauge with your finger over the opening("perfect" reading), and then you exert that same vacuum on a sealed intake port, exhaust port, or combustion chamber surface, and read the amount of vacuum on the gauge. You then take that reading, divide it by the perfect (max vacuum possible) reading, and that is the percentage sealing. That way you'll know if you have a sealing problem before the heads are installed. I don't recall ever finding a problem with my work, but it was just a check for quality control. I did find problems on other people's work. On both occasions, it was Serdi style valve seat jobs.
 
Not sure if all the recent posters saw my update. The smoke went away once I removed the PCV from the valve cover.
This tells me that the oil was finding its way in through the PCV during the heavy sustained deceleration.

Now I need to figure out the correct PCV for my application.
 
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Makes baffles that are farther away from the base of your PCV and longer to block any oil splash. The guys who make tge adjustable made an article about it and they did testing
 
WSUTARD said:
Not sure if all the recent posters saw my update. The smoke went away once I removed the PCV from the valve cover.
This tells me that the oil was finding its way in through the PCV during the heavy sustained deceleration.

Now I need to figure out the correct PCV for my application.
Click to expand...

Small Block Mopar Engine

Look at this thread. Can you fashion a larger baffle as well?
 
1969383S said:
Small Block Mopar Engine

Look at this thread. Can you fashion a larger baffle as well?
Click to expand...
Yes, you may have told us. What valve covers do you have? All valve covers need a baffle for any plug in that vents or has vacuum. A solid non-vented oil fill cap doesn't need a baffle. Everything else does.
 
WSUTARD said:
Not sure if all the recent posters saw my update. The smoke went away once I removed the PCV from the valve cover.
This tells me that the oil was finding its way in through the PCV during the heavy sustained deceleration.

Now I need to figure out the correct PCV for my application.
Click to expand...

I saw it, but I still have to wonder if it's just a PCV issue.
That said, I had to orifice down my PCV to get it to quit pulling oil, but it did it all the time and not decel only. (which makes me question ring seal and intake stem seal condition.)
 
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