401 and oil burnoff

[donsjave]

Something of mystery here has cropped up with my 401 and may need some vertication of what I think is wrong here. I overhauled (with some help) an 401 and the engine is currently running good except for the fact that at highway speeds it uses oil like there is no tomorrow. Here is what I have done to try and locate where all the oil is going: Removed the spark plugs and took a close look at them. I am using just over a quart per 100 miles. There is no deposits on the plugs. They are normal with no unusual wear. I did a compression test and all cylinders are normal (160 PSI) and there is no variation between the cylinders. I check and replaced the PCV valve and hose going to the carb, although I did not see any problems with old PCV or the hose. After doing the above checks, it still is using oil at highway speeds and not using any oil at city driving speeds (under 45 MPH). I suffer no leaks at he head gaskets, valve covers, or the intake, and there is no oil mixed in with the antifreeze. I am using an Edlebrock performer intake with the Edlebrock performer carb. Here is what I came with: The heat sheild under the intake is allowing oil burnoff to occur due either being loose or has fallen off somehow. This would account for the non usage of oil at city drives considering that the RPM would be low and the oil pressure being somwhat lower (at about 45 PSI) verus that of highway speeds where my oil pressure is just above 60 PSI and the RPM nearing or topping 3,000. It is my feeling that with the above description as stated above that this would be the more likely reason for the oil burnoff. Note: there is no smoke from the tailpipes at any speed. I sure would welcome any comments from the experts in this field of mechanical experts. :confused:

[304_dude]

If you are burning oil you will notice. Try parking your car over a clean piece of cardboard. While in park, pull on the throttle linkage till the engine revs about 2500 - 3000 RPM and watch the exhaust.

After running it for about 1 minute move the car so you can look at the cardboard. My hunch is that your loosing it through the timing cover where it mate to the engine block. There is not much surface area for the oil passage and gaskets seem to blow out there.

My first 304 had this issue... fortunately the oil was a little dark and noticable. Depending on the leak, it may spray at an angle below the alternator and away from the steering linkage. This would keep you from noticing the leak when looking for it. At highway speeds having the air blow most of what your looking for away on to the road or under the car.

The timing cover is easy to install but difficult for even the best to aline and seal properly. This is why I do not use a stock oil pump setup anymore since I will remove the cover every once and a while.

A nother note all engines will burn oil when newly rebuilt... depending on the circumstances you will need to add a quart or two before your first 1,000 break in.

[donsjave]

If you are burning oil you will notice. Try parking your car over a clean piece of cardboard. While in park, pull on the throttle linkage till the engine revs about 2500 - 3000 RPM and watch the exhaust.

After running it for about 1 minute move the car so you can look at the cardboard. My hunch is that your loosing it through the timing cover where it mate to the engine block. There is not much surface area for the oil passage and gaskets seem to blow out there.

My first 304 had this issue... fortunately the oil was a little dark and noticable. Depending on the leak, it may spray at an angle below the alternator and away from the steering linkage. This would keep you from noticing the leak when looking for it. At highway speeds having the air blow most of what your looking for away on to the road or under the car.

The timing cover is easy to install but difficult for even the best to aline and seal properly. This is why I do not use a stock oil pump setup anymore since I will remove the cover every once and a while.

A nother note all engines will burn oil when newly rebuilt... depending on the circumstances you will need to add a quart or two before your first 1,000 break in.
I took a real close look at the timing cover and could not deteck any leaks at all. The fast idle test was done and I forgot to mention it. The motor has about 1800 miles on it. The other day, I was talking to the guy that intially installed this intake on the car (when it had the 360 in it) and told me that he thought that the intake was warped or something. It just didn't seem to fit right (wish he would have told me this sooner) and it kind of felt the same way to me, but I thought maybe it just my imagination or something. So what I did was that I found another Performer intake that I know is good and am going to try it instead of trying to reseal the current one that is on the car now. There is a possibility that either the intake on the car now is slightly warp (never heard that one before) or the heads are not straight across like they should be. Will find out here in the next couple of weeks or so.

[glennrock]

304 Dude...........read your post and am getting ready to rebuild my 401, and have the usuall concerns. What type of aftermarket oil pump set up do you use? This is going to be a high$$ total resto and hope to avoid as many issues as possible. Thanks, Glennrock

[donsjave]

Believe it or not, nothing real special as far as fancy setups. The one thing I did do was install a new timing chain cover. They can be purchase at your local Jeep stores. I also installed a new set of gears (since all AMC engines are gear driven external pumps incorportated with the timing chain cover). I checked the tolerances as per the service manual of the gear to cover measurements and had the setup that I wanted. My oil pressure is hovering right at 60 PSI warm and almost 75 PSI cold (the 75 is when the oil relief valve kicks in). :)