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Thread: my 258 is spitting oil into the carb (through breather)

  1. #1

    Default my 258 is spitting oil into the carb (through breather)

    Ok, here's an ongoing problem.

    Whenever I drive my CJ5 long distances, it likes to fill the carb up with oil. The oil is coming from the PCV breather. All my knowledge and research points to some vacuum leak somewhere, but I can't find it. I've replaced the PCV valve, and, with the engine running, it has a nice vacuum to it. When I block that same tube, I can hear the engine speed change, which also points to NO vacuum leak. I've also removed the vacuum cylinder entirely at this point, since my current carb (a holley, w/ manual choke) has no need for it.

    Anyways, yesterday, after about 40 miles of 65 mph, I downshifted to pull into the house, and it sputtered and spirted and stalled! I started it back up with my momentum, but it would no longer hold an idle! Pulling into the driveway got a big laugh from everybody, because all the oil in the air filter box was dripping on the hot manifold and smoking like crazy.

    Today, it won't hold it's idle at all. Something's worse. I'm stuck. Help.

    (1980 CJ5, btw)

  2. #2

    Default

    It sounds like you have blow by and the vacuum from the carb is not keeping up (which is why it blows into the air filter through the back vent. Excessive crank case pressure would be the culprit. Does the exhaust smoke any?
    '79 CJ5 with not much '79 left to it

    SOA on Wagoneer Dana 44s locked
    T18/D18 with OD drive train
    258 with HO 4L head and OBD1 Fuel Injection
    Still fixing and building after almost 20 years

  3. #3

    Default

    no smoke in exhaust, but it seems like I'd be able to see that happen even when throttling it when it's out of gear and i'm staring at it. Does the blow-by issue require it to be under load?

    Any easy fix, here?

  4. #4

    Talking

    Mainstreet,I had the same problem.Your power plant has alot of blowby and the pcv system isn't taking care of it.You will need to install a second pcv valve in the original intake opening at the back of the valvecover.This valve needs to be teed into the original and sent to a good source of manifold vacuum.Since you will be drawing so much vacuum you will need to go to parts store and put a push in breather into the oil fill instead of the oil cap.If you can get a breather w/a nipple on it to hook into your aircleaner you'll have a source of filtered air.Just did this to my '83 and I've got aton of suck from the system now,no oil anywhere

  5. #5
    Registered shays4me's Avatar
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    Default

    Quote Originally Posted by mainstreetmark

    Anyways, yesterday, after about 40 miles of 65 mph, I downshifted to pull into the house, and it sputtered and spirted and stalled! I started it back up with my momentum, but it would no longer hold an idle!

    Today, it won't hold it's idle at all. Something's worse. I'm stuck. Help.

    (1980 CJ5, btw)
    It sounds to me as if you lost the carbs power valve when it sputtered, which is quite common on Holleys. That would explain why it won't idle now. I'd change that and see if it helps the idle. Also, they sell a power valve saver for the Holleys, so you won't have to change it again!
    13 JKUR Stock mall crawler

    84CJ7 SBC, T19, D300, D30/AMC20HD, 3" Black Diamond lift, ground up Almost done!

  6. #6

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    Color me stupid, but I thought blow by was a sign of bad valve seats? I have the same problem with my 83, 258. Is it possible to fix this without pulling the head? I am running a Weber carb. The Jeep runs Ok, hard to keep the idle steady. It dose smoke a little a first start up, but clears out after about 10 seconds if that long. I figures it's just the oil from the intake. I would love to get this solved without pulling the motor appart. I am trying to keep it running until I get my 304 finished. Anyway, any help would be great.
    James

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    Default Blow By

    40 miles at 65 mph? Really? My 7 gets pretty squirly at about 50. I can't imagine trying to keep it on the road at 65. I don't think these Jeeps were designed to be long distance cruisers.

  8. #8
    Registered dillonjm's Avatar
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    Quote Originally Posted by bluewater
    40 miles at 65 mph? Really? My 7 gets pretty squirly at about 50. I can't imagine trying to keep it on the road at 65. I don't think these Jeeps were designed to be long distance cruisers.
    If your vehicle (in near stock form, or even with a lift and larger tires) can't go 65 down the highway straight then you have some worn steering components or are out of alignment. If everything is set up within spec and isn't worn then you shouldn't have any problems on the highway @ 65mph.
    91 YJ 4.0, lifted, so on

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    Registered cjmike's Avatar
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    Default

    I had a similar problem with the exception of the oil collecting in the air cleaner and not being sucked into the carb. Give the rubber line running from the PCV valve a squeeze all along its length and see what kind of condition its in. It runs along the top of the exhaust manifold under the stock air cleaner assembly and will collapse after years of sitting close to such high heat. With improper venting I had all the pressure trying to come out the CCV and even experienced seepage around the distributor and the oil fill plug. Even though you have an aftermarket carb and air cleaner, the original set up was on there at some time so I wouldn't be surprised if the hose has collapsed on itself. I replaced all but the first couple inches (off the PCV) of the rubber with copper and now have no problems with blow by.
    84 CJ-7: 92 YJ tub, 4.2L w/MC 2100 & HEI, 4" BDS lift, 1" Daystar BL, 35" X-Terrains, Warn 8274, flush mount tail and marker lights and a stereo!....FINALLY!

    Jeep girl wanted.....Only the dirty and topless need apply!

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    Default

    Quote Originally Posted by Gorillajeep54
    Color me stupid, but I thought blow by was a sign of bad valve seats? I have the same problem with my 83, 258. Is it possible to fix this without pulling the head? I am running a Weber carb. The Jeep runs Ok, hard to keep the idle steady. It dose smoke a little a first start up, but clears out after about 10 seconds if that long. I figures it's just the oil from the intake. I would love to get this solved without pulling the motor appart. I am trying to keep it running until I get my 304 finished. Anyway, any help would be great.
    James
    From your description the problem is oil leaking through the valve guides, down the valve stem into the cylinder when the engine is off. Then when the engine starts up the oil is burned and blown out the exhaust.

    It does not, however, become blown into the air cleaner via the valve cover PCV.

    You can replace the valve guides without pulling the heads. You have to keep the valves closed. You can do that with compressed air, or using a soft cotton rope compressed in the cylinder against the valves.

    The other option for blow-by, of course is installing a puke tank between the air cleaner and the PCV.


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