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Discussion Starter · #1 ·
I have blow by only on the highway i have a weber carb so i have an after market filter in there it is fine around town and driving places that is under 50mph
I was woundering if any one alse had this problem after installing a weber carb or just having this problem in general
 

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Well when I did the Weber swap on my old 258 it was ok. She ran sweet and it did not have any blow by.

But wait You have my old Motor!!!!

WHAT DID YOU DO TO HER?
/ubbthreads/images/graemlins/burnout.gif /ubbthreads/images/graemlins/burnout.gif /ubbthreads/images/graemlins/burnout.gif /ubbthreads/images/graemlins/burnout.gif
 

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Discussion Starter · #4 ·
it only happens around 55up it blows out the aftermarket filter i have replaced it and it still does it the pvc valve is good driving on the highway for 3 hours it will blow out a half court of oil. like mach2_nh said it never did it to him we put it in mine and it started doing it as soon as i brought it on the high way and most of my driving is on the highway
 

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I have blowby too. It is definately worse on highway trips. I have a bottle rigged up to my battery tray bolt with a hose clamp holding it. I have ran like this for two years with no decrease in power....yet. Just run a hose from the rear grommet to a hole in the lid w/ a grommet and a hole in the side near the top with a grommet and run the hose under the jeep for excess vapor/pressure. It's simple just empty the jug every few hours on long trips and top off the oil. I use an orange juice jug -- Simply Orange or something like that but it is a clear tall bottle that has worked for me.

Your rings are bad. If the power is still there you have nothing to lose. I have a 4.0 head at the machine shop right now anticipating a rebuild of a spare block but I am not in a hurry! I have driven 30,000 miles with what some might say is Bad Blowby but it still pulls hard and gets me to where I'm going. Rig something up and you'll get use do it.
 

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Check for vacuum leaks and make sure your crank case vent is under vacuum. Crank case vacuum helps to seal the piston rings to the cylinder walls.
 

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I had a similar problem.

Ran a puke can - it ended up being more trouble than it was worth.

I put a breather on the back of my valve cover and everything cleared up.



Scott
 

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[ QUOTE ]
Tell us more about your symptoms...A carb has nothing to do with "blow by". When you have blow by...you have it...at any speed.

[/ QUOTE ]

Blow-by can occur at different speeds, different RPMs, and at different start-up conditions. Blow-by can be caused by any number of problems. And... a carb can, in fact, cause blow-by.
Gnarls.
 

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""""And... a carb can, in fact, cause blow-by."""""

OK, I give up -- how can the item that mixes fuel with air on top of the engine cause the rings to no longer seal properly? Are you thinking he dropped a bolt or something down and broke a ring?


The only possible difference caused by switching carbs that I can think of is the size of the intake manifold port may be smaller or restricted, affecting the PCV system, not evacuating the crankcase enough - if it's taken off the base of the carb.

Q - when the carb was switched, of course you did provide for fresh air into the crankcase at the opposite end to create a draft through the engine. And, did you change the rocker cover at all? Sometimes aftermarket ones don't have a baffle inside - the PCV sucks out oil splash.
 

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[ QUOTE ]
""""And... a carb can, in fact, cause blow-by."""""

OK, I give up -- how can the item that mixes fuel with air on top of the engine cause the rings to no longer seal properly? Are you thinking he dropped a bolt or something down and broke a ring?

The only possible difference caused by switching carbs that I can think of is the size of the intake manifold port may be smaller or restricted, affecting the PCV system, not evacuating the crankcase enough - if it's taken off the base of the carb.
Q

[/ QUOTE ]

How about a too rich air/fuel mixture??
Gnarls.
 

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It would have to be really dumping huge amounts of fuel in to wash enough oil off the rings to cause blowby - rings not sealing, pressurizing the crankcase.

If that were the case, I'd think the complaint would be more of clouds of black smoke, poor running, terrible mileage, smell, hard starting etc. rather than blowby.

Maybe if we had more specific information about what he means by "blowby" we could help more.

What's happening? - You changed what filter? What's the "smoke" look like, where's it coming out of etc. And what else was done at about the same time?

Take the oil filler cap off - run it fast and slow - is smoke coming out of the filler hole?
 

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Discussion Starter · #14 ·
there is plenty of vac for the pvc it works great i did not switch the carb on it was on when i bought the engine. The carb is a out of adjustment its runing kinda rich and i the same set up as 84 cj7 except the fuel regulator.

I chagned the breather filter on the back of the valve cover because i thot it was just old and dirty there is no smoke blowing out of the tail pipe its all blowing out of the breather ontop of the valve cover and driping down onto the exhaust pipe.
 

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"""""I was woundering if any one alse had this problem after installing a weber carb or just having this problem in general """""

AHA! Then it isn't related to the carb - you had us going - thought you switched carbs, then got it.

Could be the engine's just getting tired.

But - the filter in the rear - normally that hole is connected to the air cleaner inside the filter ring via a hose. It allows fresh filtered air to be drawn in the crankcase - you don't want dust in the engine, that's why the filter.
That air then sweeps through the engine, taking the normal hot oil fumes with it. Then it gets sucked in through the PCV valve into the intake and the fumes get burned.

At high speeds, the normal blowby is more than the PCV can handle, so then that same hose reverses the flow - blowing the excess into to the air filter.

That's absolutly normal at higher R's. The older and more worn the engine is, the more fumes it has to handle.

But yours - sounds like it's been modified by someone that doesn't understand the system. They put on a little filter in the back. Possibly because they put on some other carb airfilter. Now at speed the oil fumes get trapped in the small filter, overloading it, causing your concern.

2 things - check inside the cover's hole for a baffle - it has to have one. The cheapie valve covers don't have them. You can make one easy enough.
And - see your parts house - the chrome goodie stuff. You'll find an adapter that screws onto the air cleaner housing - underneath or on top. It's made to run a tube into it. Make sure it's going into the INSIDE of the filter ring so it sucks clean air.
Get the needed grommet for the valve coverhole and a hose fitting that fits it. Run a hose from that hole to the adapter.

Then, normally it sucks in clean fresh air to keep the engine clean. But at high R's when the volume of blowby is too much, the excess goes into the INSIDE of the air cleaner. You might even want to put a little filter inside the air cleaner like many stock aircleaners use.

Or - get the correct air cleaner and run the hose properly.

Not a biggie, but a common problem with the aftermarket stuff "made to sell, not to use."
 

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Discussion Starter · #17 ·
the system never had a problem from the po it sat for 2 years and then we put it in my jeep and got it fired up i dont have the stock air cleaner or any thing like it i have the air cleaner that came with the weber carb the gromit is new and the right size and the filter is not to small i will put a pic of my top half of the engine and i have a baffle in the valve cover

http://www.fourwheelsolutions.com/Photos/Projects/Adam/Motor_Swap/100_2048.jpg

http://www.fourwheelsolutions.com/Photos/Projects/Adam/Motor_Swap/100_2046.jpg
 

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I guess you didn't read what I wrote about tossing that round filter in the back and setting it up correctly with a hose.
The way you have it will always cause trouble.

I'd ditch that tiny street type filter on the carb too. I'd get something that will catch the dirt and dust effectively, without causing restriction. I'm sure K&N has something that'll fit. But it'll still clog up the round filter like that.

Or get a big supply of the round filters so you can change them often.
 

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Discussion Starter · #19 ·
I dont understand what you mean buy runing a hose from the breather to the air box there is no spot in the air box for one The filter is not tin that is k&n the only tin part is the cover over the filter and the base for the filter to sit
and its not a round filter its a square shhape filter
 

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Round filter - look on the back end of the valve cover -- that's the round filter I referred to. The filler cap - isn't that the one you said you replaced too often?
Other than that round filter and the air cleaner, what other filter is there that you replaced?

Get a cap to replace that cap that's not a filter, it should be solid inside, and it should have a hose connection - $5. That's where the hose will come from.

While you are at the parts house - where you found the new cap - look in the chrome goodies rack. You'll find a little adapter that's designed to bolt onto something to attach a hose. Get one!

That tiny little mickey mouse air cleaner you have on it is pure trash. It will almost instantly clog up with dust off road. If it doesn't, dust is going in your engine!

Yes, I can clearly see it's not a K&N. I suggest you get one, or at least a bigger filter and housing to protect your engine.


Yes, the only metal part is the top and bottom of that tiny POS. The bottom doesn't have any place to put the hose adapter - not enough room.
But the top does. Drill 1/2" hole in the top, and 2 small mounting screw holes for it. Connect the other end of the aforementioned hose to it.

Then it will draw clean fresh air in to the engine, taking the fumes with it when it goes through the PCV Valve. At high speeds any excess fumes will go into the air cleaner. Just like it's supposed to!

Or - bring it here, I can do it all in about 10 minutes.
 
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