Blow By Catch Can???

[Gladiator Brad 704]

A friend of mine recently had to have the intake gasket replaced on their JL. Would a MISHIMOTO Oil Catch Kit (MMBCC-JLP-18BPE) have made a difference? Would this be a good thing to have on my Gladiator? Anyone have any experience or thoughts about this. Thanks.

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[ShadowsPapa]

A friend of mine recently had to have the intake gasket replaced on their JL. Would a MISHIMOTO Oil Catch Kit (MMBCC-JLP-18BPE) have made a difference? Would this be a good thing to have on my Gladiator? Anyone have any experience or thoughts about this. Thanks.

You don't have blow-by if your engine is normal. A normally aspirated engine, even those with mild mods, run a vacuum in the crankcase so there's no "blow-by".
The catch cans are for situations where you have such extreme angles that the oil gets to where it should not normally, or can't drain back.
If the intake gasket was bad, it was bad, no band-aid will fix a bad gasket.

They market the heck out of things like this for geeks and those who think it's a cool performance thing, but unless you have a problem or run extreme angles, it's just a "gee, that's cool" sort of thing.
Makes it look like you crawl up steep cliffs even if you don't because you have one.
It's a fix looking for a problem, IMO.
Now if you do extremes with the Jeep - it's a consideration IF you see oil where it shouldn't be or burn oil or see blue smoke (but if I saw blue smoke I'd be talking to an engine guy about repairs, not a band-aid)

 

[WranglerWillys]

You don't have blow-by if your engine is normal. A normally aspirated engine, even those with mild mods, run a vacuum in the crankcase so there's no "blow-by".
The catch cans are for situations where you have such extreme angles that the oil gets to where it should not normally, or can't drain back.
If the intake gasket was bad, it was bad, no band-aid will fix a bad gasket.

They market the heck out of things like this for geeks and those who think it's a cool performance thing, but unless you have a problem or run extreme angles, it's just a "gee, that's cool" sort of thing.
Makes it look like you crawl up steep cliffs even if you don't because you have one.
It's a fix looking for a problem, IMO.
Now if you do extremes with the Jeep - it's a consideration IF you see oil where it shouldn't be or burn oil or see blue smoke (but if I saw blue smoke I'd be talking to an engine guy about repairs, not a band-aid)

The way the PCV system works is to draw oil vapors from the crank case. Catch cans will keep the intake clean.

All vehicles have blow by by design also... most is very minimal.


Catch cans do work, but it has zero to do with intake manifold gasket failure but clogged up intake runners and valves.

 

[ShadowsPapa]

The way the PCV system works is to draw oil vapors from the crank case. Catch cans will keep the intake clean.

All vehicles have blow by by design also... most is very minimal.

Catch cans do work, but it has zero to do with intake manifold gasket failure but clogged up intake runners and valves.

No, they do not have blow-by by design. Do I need to once again post the info from my engine building and design books?
A normal crankcase with an operational PCV or other vent system will run a VACUUM in the crankcase - there are even specs for that!

I have 4 vehicles with Jeep engines. I won't count the JT 3.6 because it's too new to have a history, but of the others -
One is my wife's JGC 3.6 - oil does not drop between changes - no blow-by
Then there's the 4.0 in the WJ I bought from my father's estate - a 4.0 with 125,000 miles - oil drops minimally between changes, intake remains clean.
And the 4.0 I rebuilt and put into my SX4. It has about 34,000 miles on it since I rebuilt it. Clean running, vacuum in crankcase, oil level does not drop between changes, intake remains clean.
I could add the built 377 hp 360 in my other car - dual quad carbs, cam, horrible vacuum at idle, not enough for the PCV to work really well, runs almost 0 vacuum in crankcase so some oil does make it to the intake. I've had the intake off of it twice in the last year - shines with some oil and you can feel it when you run your fingers in the intake runners, but it's certainly not plugged and it's been that way for who knows how long - I've had the car since 2015 and drive it quite a bit but swapped speedometers a while back so lost track of miles on it. The whole car I believe is a 100,000 mile car.

How many engines have people built here? I've built more than I can count. I've got the factory Dana/Perfect Circle information on rings, crankcase design, as well as technical service manuals that cover three shelves in my library.

The PCV is not to draw "oil vapors" but the byproducts of combustion that may make it in, plus the pumping effect of the pistons would actually build pressures in the crankcase just by that effect. So the PCV or other vent system runs a vacuum in the crankcase. This helps SEAL the engine as well because the rings seal best with the pressure differences above vs. below the rings. Run a vacuum below the rings and it aids in sealing rings AND the crankshaft seals as well. Rings are made to twist and flex - that forms the seal.
Intake runners don't get clogged up! Want to see some I can show - I have about 8 intakes in my shop on shelves - that I've pulled from engines with various wear and mileage.
I've rebuilt engines with so much ring wear the piston fell out once the rod cap nuts were removed - there was oil pooled in the air cleaner it was so bad, but the intake was clean. Oil plugs nothing.

You won't have any difference in intakes with or without a catch can - because if you do have blow-by it's raw oil and it flows just like pouring it out of a bottle or can. It doesn't plug the intake.

IF anyone really has to have proof, I'll be happy to scan some of my college engine building books and show the intake runners of the manifolds I have sitting in my shop and on the three engines i have waiting to rebuild. I think I also have pictures of an intake from an engine that didn't seal well and it was drawing in oil. Moist but no plugging because oil plugs nothing - otherwise the oil passages in the engine would get plugged up.

 

[WranglerWillys]

No, they do not have blow-by by design. Do I need to once again post the info from my engine building and design books?
A normal crankcase with an operational PCV or other vent system will run a VACUUM in the crankcase - there are even specs for that!

I have 4 vehicles with Jeep engines. I won't count the JT 3.6 because it's too new to have a history, but of the others -
One is my wife's JGC 3.6 - oil does not drop between changes - no blow-by
Then there's the 4.0 in the WJ I bought from my father's estate - a 4.0 with 125,000 miles - oil drops minimally between changes, intake remains clean.
And the 4.0 I rebuilt and put into my SX4. It has about 34,000 miles on it since I rebuilt it. Clean running, vacuum in crankcase, oil level does not drop between changes, intake remains clean.
I could add the built 377 hp 360 in my other car - dual quad carbs, cam, horrible vacuum at idle, not enough for the PCV to work really well, runs almost 0 vacuum in crankcase so some oil does make it to the intake. I've had the intake off of it twice in the last year - shines with some oil and you can feel it when you run your fingers in the intake runners, but it's certainly not plugged and it's been that way for who knows how long - I've had the car since 2015 and drive it quite a bit but swapped speedometers a while back so lost track of miles on it. The whole car I believe is a 100,000 mile car.

How many engines have people built here? I've built more than I can count. I've got the factory Dana/Perfect Circle information on rings, crankcase design, as well as technical service manuals that cover three shelves in my library.

The PCV is not to draw "oil vapors" but the byproducts of combustion that may make it in, plus the pumping effect of the pistons would actually build pressures in the crankcase just by that effect. So the PCV or other vent system runs a vacuum in the crankcase. This helps SEAL the engine as well because the rings seal best with the pressure differences above vs. below the rings. Run a vacuum below the rings and it aids in sealing rings AND the crankshaft seals as well. Rings are made to twist and flex - that forms the seal.
Intake runners don't get clogged up! Want to see some I can show - I have about 8 intakes in my shop on shelves - that I've pulled from engines with various wear and mileage.
I've rebuilt engines with so much ring wear the piston fell out once the rod cap nuts were removed - there was oil pooled in the air cleaner it was so bad, but the intake was clean. Oil plugs nothing.

You won't have any difference in intakes with or without a catch can - because if you do have blow-by it's raw oil and it flows just like pouring it out of a bottle or can. It doesn't plug the intake.

IF anyone really has to have proof, I'll be happy to scan some of my college engine building books and show the intake runners of the manifolds I have sitting in my shop and on the three engines i have waiting to rebuild. I think I also have pictures of an intake from an engine that didn't seal well and it was drawing in oil. Moist but no plugging because oil plugs nothing - otherwise the oil passages in the engine would get plugged up.

wrong.. plus you do not know in whom you argue with...


Vehicle cannot be perfectly sealed in the combustion chamber. The oil and compression rings will always have blow by. Pop your oil cap off. You won't have a vacuum.

 

[ShadowsPapa]

wrong.. plus you do not know in whom you argue with...


Vehicle cannot be perfectly sealed in the combustion chamber. The oil and compression rings will always have blow by. Pop your oil cap off. You won't have a vacuum.

Yeah, I do run a vacuum in my engines - I've not tried the Jeep engine yet, but I do the others.
I have a degree in automotive. I have the specs for the crankcase vacuum. Maybe the current JT has sealing issues, but I DO run a vacuum in my car and other engines. I know, I have measured it.
If the 3.6 doesn't then that's their issue - all others have a vacuum and I could video the testing if I must to show it.
I measure with a jig and vacuum gauge as well as the palm of my hand over the oil fill hole.

 

[WranglerWillys]

Why the pentastar isn't a GDI... it shows you how much is building up. Lucky the injectors clean the valves.

 

[Elwenil]

A catch can on a naturally aspirated engine is pointless and a waste of time and money.

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