Blow by and Carburetor Questions

[hbabler]

I recently purchased a 1980 Cherokee chief and I am in the process of trying to get everything sorted out on it and I am kind of at a loss with two problems that I have found.
1. I have a large amount of blow by coming out of the oil filler cap, I have checked the compression (all cylinders at 120 except #3 which is at 130) replaced the pcv valve, rerun all the vacuum hoses and to a new carbon canister and removed the rear hose that runs from the valve cover to the air cleaner from the air cleaner and put it in a bottle to catch oil and got no oil out of it. Any ideas where to go next on this?
2. I have a weber 32/36 dgev and an HEI from Z&M jeeps that the old owner installed. I am unable to get this the idle mixture to adjust on this thing, when I turn the idle mixture screw nothing happens. I have a return style fuel filter, do I need a regulator also? Should i rebuild the carb?
Thanks for all the help,
Hudson

[lindel]

While I'm not a 6 banger expert, the numbers don't sound bad. That doesn't necessarily mean that the rings aren't worn, or that perhaps the passages in the intake/head aren't plugged up.

For the latter, I've never messed with a weber carb, so can't help there.

[Stuka]

Welcome to the forum!

It just so happens I have nearly the exact same setup as you!

1: Do you still have the plastic valve cover, or has an aluminum one been swapped on? Or were you lucky enough to still have the steel one (some '80's had the steel cover still).

2: For the carb, that is *NOT* an idle mixture screw. Its an Idle Volume Screw. Its not just a change in name, it has a different functionality. Although even their own manual goes back and forth on the name. Since this is a common issue, I have the instructions scanned in here: stuka.fsjnetwork.com/fsj/carb/weber-manual.pdf

Go to page 8 and follow the instructions. If you try to tune it like a mixture screw, its unlikely that you will get it right. But once you do get it tuned well, it will run like a top. I LOVE mine. Also, I do not run a regulator as I have a return style fuel filter. When running a return style fuel filter you cant run a regulator also, unless you like running out of gas whenever you hit a hill. The return does a good job of preventing high pressure on the needle and seat in the carb. And being I was able to get 18mpg out of mine (with stock lift/wheels/tires/gears), I highly doubt fuel was getting by it.

[hbabler]

Thanks, great site by the way.
1. I actually have a steel valve cover.

2. I followed the instructions that you posted and I am still unable to get a change in the way that the engine runs when I am adjusting the screw. However after reading the rest of the article I am going to try again with a tachometer and see if that will work.

3. When I pulled the spark plugs out of the engine for the compression test I noticed that the two center cylinders had different plugs than the other four. Is there any reason why this would be?
Thanks for the help.

[carnuck]

PCV dumps into the middle 2 cyls on '80 and older rigs. Probably higher heat range to keep them clean.

[hbabler]

So any more thoughts on the blow by issue? I am kind of at a loss on this one. I am assuming that due to the higher heat range plugs on the two middle cylinder this may be an ongoing problem.

[carnuck]

I put 15W50 synthetic in my 6 cyl to cut the blowby down. My 454 too.

[letank]

I put 15W50 synthetic in my 6 cyl to cut the blowby down. My 454 too.

15w50 synth is that the rotella?

Otherwise you can put a "catch can" to trap the blow by to reduce air filter contamination, as an example:

http://www.ebay.com/itm/Universal-Silve ... 66&vxp=mtr

[Stuka]

I have never had an issue of blow-by on my 258. And it has 242k miles on it, and does burn a bit of oil for sure.

If you PCV valve though is working, I am not sure why you would be getting oil past the oil filler.

As for the carb, so when you have the idle speed screw all the way out (So the engine is running very slow, nearly stalling), and you turn the "mixture" screw, nothing happens at all?

Also, not sure I would run 15w50. First because 50 weight oil is very bad for bearings. And having a larger span between weights typically results in the oil breaking down sooner. I have always run 10w30 and it was been great.

[hbabler]

The pcv valve is brand new, and it did reduce the amount of oil coming out of the filler cap. When I adjust the idle speed screw it literally does nothing, I am going to pull it all the way out tomorrow and hope that maybe I can see a piece of trash or something in it, I will also spray some carb cleaner in it to see if that helps. Would reconnecting the egr help with any of this? The previous owner has it disconnected. The thing that puzzles me is that I only have blow by out of the front of the cover. I pulled the rear hose that goes to the bottom of the air cleaner and put it in a coke can and I did not get any oil in it even though I drove that way for about sixty miles. It is almost like it is pulling air through the rear of the cover and pushing it out the front, is that even possible? Would it be worth replacing the valve seals could that be the problem? I thought that since the compression was fine then the seals would be good but at this point I am willing to try just about anything. Thanks for all the help.

[Stuka]

For the carb, its possible you have a vacuum leak. The Weber uses a 2 piece adapter setup. Twice I have had to pull mine apart and re-tighten the bottom adapter. It uses these allens that can come loose.

Push oil out the valve cover typically means the cylinders are pressurizing the crank case and the PCV is plugged, making it go out the other hole. But you have good compression (120 is within factory specs). Strange.

[hbabler]

I will check the adapter for tightness. On the blow by I have another thought I purchased an oil cap on the way home from work this morning and I realized that the one that is currently on it has a homemade gasket spacer to make it seal tighter. When I drive it on the freeway is when I have the blow by problem and it covers the front top of the valve cover with oil. I know it is not likely but I wonder if the compression numbers would drop when it is hot?

[Stuka]

Compression numbers cold/hot and dry/wet are different. So that is quite possible.

[carnuck]

I have never had an issue of blow-by on my 258. And it has 242k miles on it, and does burn a bit of oil for sure.

If you PCV valve though is working, I am not sure why you would be getting oil past the oil filler.

As for the carb, so when you have the idle speed screw all the way out (So the engine is running very slow, nearly stalling), and you turn the "mixture" screw, nothing happens at all?

Also, not sure I would run 15w50. First because 50 weight oil is very bad for bearings. And having a larger span between weights typically results in the oil breaking down sooner. I have always run 10w30 and it was been great.

I've run 100W Aeroshell with no probs. 15W50 is the same as 15W40 except it's synthetic. The 50 part is the additive package that makes it protect like 50W at (IIRC) 100 degrees F. When cold it flows like 15 weight. It may not be good for subzero temps, but it's fine around here. I put 160 K on my 454 with that in it.

[carnuck]

Compression numbers cold/hot and dry/wet are different. So that is quite possible.

Generally though numbers go up when warm. If they go up drastically, then there is heavy wear.

[carnuck]

The pcv valve is brand new, and it did reduce the amount of oil coming out of the filler cap. When I adjust the idle speed screw it literally does nothing, I am going to pull it all the way out tomorrow and hope that maybe I can see a piece of trash or something in it, I will also spray some carb cleaner in it to see if that helps. Would reconnecting the egr help with any of this? The previous owner has it disconnected. The thing that puzzles me is that I only have blow by out of the front of the cover. I pulled the rear hose that goes to the bottom of the air cleaner and put it in a coke can and I did not get any oil in it even though I drove that way for about sixty miles. It is almost like it is pulling air through the rear of the cover and pushing it out the front, is that even possible? Would it be worth replacing the valve seals could that be the problem? I thought that since the compression was fine then the seals would be good but at this point I am willing to try just about anything. Thanks for all the help.

Really sounds like the valve cover vent in the rear is clogged. Can you blow into the cover? (put a clean rag over the end so you don't get oily lips) Valve seals only seem to do backpressure like that if the exhaust is clogged too. EGR doesn't do anything for or against blowby.

[carnuck]

For the carb, its possible you have a vacuum leak. The Weber uses a 2 piece adapter setup. Twice I have had to pull mine apart and re-tighten the bottom adapter. It uses these allens that can come loose.

Push oil out the valve cover typically means the cylinders are pressurizing the crank case and the PCV is plugged, making it go out the other hole. But you have good compression (120 is within factory specs). Strange.

I put double star anti-rattle washers to keep those from coming loose.

[hbabler]

Okay more updates, the carb adapter was not loose. However when I pulled it off and opened the throttle plate oil ran out of the inside of the carburetor. If you look down into the intake there are puddles of oil. Currently I am at a loss as to what the heck is going on here. I will try to blow into the rear hose and see if it is clogged. I was told today that even though the compression test was good it was still most likely that the oil was getting past the rings and being forced past the valves and into the crankcase. Another symptom that I have is that for the first ten minutes of driving at highway speeds my oil pressure is up around 65 psi and then it drops to about 30 and finally settles out slowly to 20 or so. Do you think this could be related?

[Stuka]

For the carb, its possible you have a vacuum leak. The Weber uses a 2 piece adapter setup. Twice I have had to pull mine apart and re-tighten the bottom adapter. It uses these allens that can come loose.

Push oil out the valve cover typically means the cylinders are pressurizing the crank case and the PCV is plugged, making it go out the other hole. But you have good compression (120 is within factory specs). Strange.

I put double star anti-rattle washers to keep those from coming loose.

The ones I have come loose are recessed allens. You cannot put washers on them unfortunately.

[Stuka]

Okay more updates, the carb adapter was not loose. However when I pulled it off and opened the throttle plate oil ran out of the inside of the carburetor. If you look down into the intake there are puddles of oil. Currently I am at a loss as to what the heck is going on here. I will try to blow into the rear hose and see if it is clogged. I was told today that even though the compression test was good it was still most likely that the oil was getting past the rings and being forced past the valves and into the crankcase. Another symptom that I have is that for the first ten minutes of driving at highway speeds my oil pressure is up around 65 psi and then it drops to about 30 and finally settles out slowly to 20 or so. Do you think this could be related?

Well, if oil is getting passed the rings, then it would be getting burnt, and you would have blue smoke coming out. Even if you pushed it passed the valves somehow (Extremely unlikely unless the valve train is shot), it would not pool in the intake. It would get sucked right back out when the valve opened.

I think the oil is coming through the breather hose. Its either going to be a plugged PSV line, or you are getting a ton of crank case pressure that is pushing oil up through the vent line and then into the intake.