Motor Smoking F-head

Picked up a 71 cj5 pretty cheap. Has sat a while. Got a new/rebulit head for it. Water in exhaust-head gasket was leaking. Anyway, put on new head and engine runs like a top, just can't get a way from the smoke. It does look blueish/grayish but honestly doesn't smell like oil. I have the same (very little difference) cylinder pressure hot/cold. # 1 is 115 psi, #2 108 psi, #3 110 psi, #4 110 psi. So pressure looks good. THe cylinders leak down some, but not much. Maybe 10 percent so not bad. I have new points plugs coil electric fuel pump with 2 psi regulator. Have new solex carb. When pulled head off cylinders were very smooth and no scoring. Small lip at top, but that can be normal, at least for the racing motors I have built. I have no problems tearing this sucker apart and rebuilding it, but really don't want to to that right now. Where could oil be getting in at, plugs do not look wet. block face was .001 flat, new head was .000. Have not dealt with a motor (car) with exhaust valves in the block. Could something be happening here? I would assume there are seals? Any help would be greatly appreciated. I just want to have a god trail/hunting jeep, which I have, but don't want the smoke. Thanks to all you guys helping me out.

PS. I have been steadily reading posts and history for the last 2 weeks after work and before bed. Usually aroung 2-4 hours a day. Please help

 

F-Head motors can suck oil from the crankcase into the intake manifold through the vacuum pump. If you still have one mounted, it's just possible it needs a rebuild. Try disconnecting the line to the intake.

Or maybe valve guides are loose. Does it smoke more during idle or other high manifold vacuum conditions? I believe valve seals are a retro-fit option IIRC.

Pete

 

Thanks for your reply, I need help with the motor, don't know everything about the FHEAD yet!


I think it was originally an emissions motor, however there seems to be none now. Vaccuum pump should be on a bracket and connected to a belt right? I have the hole under the carb plugged off, the hose on the filler neck closed off and the vent from the valve cover is just open. There is a line running from the crank case to the head behind cylinder #4. It is hooked up. I am assumig this is for head lubrication.

It doesn't smoke at idle, you can see a hair of color out the exhaust at idle, but next to none. Just looks like condensation. But, when you give it the gas. It smokes pretty good the entire time the throttle is applied and quits when you let off the gas.

I know all motors are different, but what general cylinder compression should I find. Am I low on all cylinders and just don't know it?

 

Mickey,

I was referring to the combination fuel pump/vacuum pump mounted on the block at the lower left side, near the front motor mount. This assisted the old vacuum wipers on early CJ's. Your case sounds different. I'm not so familiar with late F-heads or emissions set-ups.

Now I'm wondering if you need a PCV valve to lower any excess pressure in the crankcase. Seems you have some vent tubes missing.

Your compression numbers seem excellent to me.

Sorry I can't be more helpful.

Pete

 

your compression and leakage numbers don't seem out of line
the oil line at the rear of the head is for rocker arm lubrication
could have some stuck rings from just sitting so long
is crankcase pressure blowing out the valve cover vent ?
what weight motor oil are you using ?

 

Rings were initally stuck. I had much lower compression #'s than that. Let Marvel oil soak for about a week and the rings freed up then got the compression #'s I have now. I pulled the head off and cleaned the excess MMO out of the cylinders. I have ran it long enough for all the MMO to have burnt off, I think. Several hours since. I continue to show the compression #'s. That is why I am stumped. I had 20 w 50 in it after freeing the rings. I tried staight 30w last night to see a change. smokes the same. Crank case pressure is blowing out of the valve cover vent.

THanks for the continued insight!
Mickey

 

It does sound like you do not have a PCV valve or it was capped off. I would fix that first. Here are pics of mine. Mine was not plumbed correctly. I used adapters and brake line. The connection below the carburator has a vacuum line off the backside for my heater control. That would be capped off there in your case. Here is a good thread as well.
http://www.film.queensu.ca/CJ3B/Engine/Rebuild8.html

 

Will get this done to mine asap! Thanks

 

I have same problem, scratching my brain also.
Posted via Mobile Device

 

Mine is doing the exact same thing as well.

Compression figures are all between 120-130.

Had the head rebuilt, new valve guides, new valves, and had them modify it to accept the new style valve seals. Head resurfaced flat as well.

I've run it with and without the PCV line hooked up, no difference.

Still smokes like mentioned above. I don't mind the smoke so much, but the oil consumption is killing me. I need to get more than 10-15 miles to a quart of oil, lol.

I'm thinking the Jeep sat for a long time before I bought it and the rings are still not completely un-stuck. Compression figures rock, but I have oil on the inside of my intake going to the carb. When the head was off, the cylinder walls looked pretty good. No scoring or anything.

With the head before, it was burning a lot of oil past the worn valve guides. The plugs were soaking wet when I bought it. I think I have a LOT of buildup around the rings at this point that I need to get out of there.

Hopefully reviving this thread a bit will help me or anyone else having this issue. I'm avoiding a rebuild right now since work has been slow and there's no way I can afford to do one right now.

Going to try Seafoam today and see how it does through the week (improve or not). I'll post back my results in case anyone is having this issue, the info might help.

 

This won't help you much, but years ago I had a full rebuild just as you describe.

Shortly after, I left the jeep idling for a few minutes and when I returned the entire neighbourhood was filled with blue smoke from the tail-pipe.

Of course, I was flipping out, wondering what I had screwed up in the rebuild. Thing is, it never did it again! Ran fine ever after.

I still don't know what it was, guessed maybe a stuck valve seal or such. I wish you luck!

 

Well, the Seafoam did not help at all with the oil consumption or the smoking. I was hoping it was gummed up rings (a longshot, but for $8 I had to try) which I believe the Seafoam would have helped. Oh well.


But the Seafoam did wonders for cleaning out my combustion chambers though. Holey moley. It runs and starts noticably better now. Had to lower the idle down as it idled higher afterward than before. Interesting. I used it as directs. 1/3 in the gas, 1/3 in the oil, and 1/3 down the carb throat (slowly) at a fast idle.

Didn't fix what I was going for, but it was a good $8 spent non the less.

 

google bonami and decide for yourself
have seen it work before, on new engine where the rings didn't seat

 

New rings could be installed with engine in jeep, a little harder than pulled, but rings are cheap. I have an almost complete set of rings(out of a full set one ring is busted) If you can figure out which piston is causing the problem I'll send you these rings.
I bought them from JCwhitney for $6, turns out they're the same USA MFG rings that Walcks sells, that I paid $45 for. STD size.

Anyway If you want them

 

Just got a swamp buggy built on a 1958 jeep chasis and running gear w/F134 engine. It was smoking like mad when I got it. New plugs would foul in 5 minutes. When I drained the crankcase 2 1/2 gallons of fluid came out, about 1 1/2 gallons was gasoline. Had carb rebuilt and replaced all fluids. Carb was putting out so much gas that it was running down the cylinder walls into the crankcase. I checked that gas wasn't coming thru fuel pump. Now it runs like a top without any smoke at all.