Engine exhaust issues

My 1948 CJ2A is at my trusted mechanic. I have been having issues with the engine starting and not wanting to run after 10-15 minutes of use. My mechanic is old school and loves to work on old jeeps, he rebuilt much of the jeep for me over the last 13 years. However he is stumped over this issue. In mechanics terms, the plugs are running rich and the exhaust is running lean. The plugs are sooty and the exhaust manifold is turning white from heat. He has removed exhaust pipe and the exhaust manifold (I guess its call a shutter ) is frozen wide open, but the engine is not seeming to want to vent all the exhaust gasses. He is thinking the valves need adjusting and that would require removing the intake and exhaust manifolds. Also when running, jeep will not get above 32 miles an hour, he said it should be able to reach at least 50 MPH. He has replaced all the fuel lines, filter, fuel pump and gone through the Carter Carb. and checked coil, coil wire. Any comments please.

Heat riser in exhaust manifold is stuck open , muffler and exhaust pipes are clear. exhaust system has been removed and checked. Any comments  welcomed !

Edited by R P Williams - 18 Apr. 2017 at 5:27pm

I also would have guessed a mouse nest in the exhaust.

Just for grins, is there any chance that the intake manifold is from a welder or any other stationary engine? Those have a smaller inlet than the CJ ones have. I had a customer that had a welder engine installed in his '53 Willys pickup. It could hardly get out of its own way. The top speed was 35 MPH as well. When I installed the correct manifolds, it ran quite well & could achieve 55 MPH.

One way to tell if it has a stationary engine in it is that most of them had the carburetor clocked 90 degrees off from what a CJ would have. The sure way to tell would be to remove the carburetor & measure the OD of the hole it feeds into.

I am assuming that the mechanic has tested all of your electrical components. The problem is that there are a whole bunch of bad condensers that have been sold to good folks by a bad manufacturer or two. Some of these condensers fail right away, while others wait until you are confident in them & then fail at the most inopportune time.

Coils also do not last forever. Most of them fail completely, however, some fail just enough to give one fits. These can cause a mechanic all kinds of frustration. It is easy enough to test them on a machine. Finding an old school mechanic that has that machine, & know how to use it, may be a trick though. If their test takes less than an hour, & they say it is good, find another tester. Try this, get the engine running & warmed up well. Next, using the back of your hand & moving slowly, test the temperature of the coil. If it will sear your flesh when you are 3" away, the coil is bad. If it is about the same temperature as the engine, it is probably good. No guarantee on this though. I will guarantee that the hot one is bad!

IHTH, Cpt Logger.

Thank you all for the  info. I will pass onto my mechanic.

Edited by R P Williams - 19 Apr. 2017 at 1:09am

Problem solved. The heat riser in the exhaust was only about 70% open and frozen tight. The camera that was sent in showed it was open but it did not show it was about 30% closed. It is now 100% open, carb was worked on and new fuel pump installed, valves were slightly adjusted too. Runs better than ever now.  Will make over 40mph with 5.38 gears. that is about as fast as I want to run this old girl .

Edited by R P Williams - 23 May 2017 at 7:59pm