NEW cast iron exhaust manifold HOT within 1 minute of starting jeep! HELP!

[76cj7chick]

I upgraded to a 2 bbl carb intake manifold (off a 85 CJ7 ) and NEW cast iron Exhaust Manifold... I also just installed a rebuilt (by me) MC 2150 Cab with 1.08 venturi...

I had to crank over the engine a few times until the fuel reached the carb but on FIRST within a minute the NEW exhaust manifold started to smoke so I turned off the jeep.

The exhaust manifold was also hot to the touch but everything else was cold still..


ANY ONE KNOW WHY THE EXHAUST MANIFOLD GETS SOO HOT??? -It is a new Cast iron exhaust manifold.. Am I too lean with the carb (1.08 venturi and 48 jets 1.5 turns on idle mixture screws)

I also changed the radiator fluid and don't have any in the heater core and new/used intake manifold jacket yet... But the intake is cool to the touch...

PLEASE HELP!!!

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[Jimbos76cj]

Ummm.. Hard to not be a smart ***. The exhaust is a result of a small explosion so it will hear up really quick. If its idling at 800 Rpms that means each cylinder has had about 400 gasoline induced explosions in it. Each explosion can be between 700-1000 degrees. Normally with a new manifold or freshly painted manifold it will heat up and smoke very quickly and even burn off the paint. I've seen cars with bad map sensors or way to lean actually turn thief pipes cherry red.

So to some it up.. It should be hot.

 

[Torxhead]

If you are concerned about the air/fuel mixture, check the deposits on the spark plugs. There are charts/pictures in most repair manuals to check them with. Not having any coolant running thru the intake manifold will give you a lean mixture as the manifold heats up. A leaky valve cover will make an exhaust manifold smoke.

 

[76cj7chick]

Ummm.. Hard to not be a smart ***. The exhaust is a result of a small explosion so it will hear up really quick. If its idling at 800 Rpms that means each cylinder has had about 400 gasoline induced explosions in it. Each explosion can be between 700-1000 degrees. Normally with a new manifold or freshly painted manifold it will heat up and smoke very quickly and even burn off the paint. I've seen cars with bad map sensors or way to lean actually turn thief pipes cherry red.

So to some it up.. It should be hot.

Thanks for the suggestion. Perhaps you are correct.

I tried to see if the choke pull off had too much vacuum so I turned the screw on the choke pull off in to 5 turns then restarted the jeep. The jeep wouldn't idle down and fuel was coming out of the float bowl vent hose as well as between the gaskets on the carb. I tightened the carb to intake bolts which were not very tight. What could be doing this? I know I am a newb- and never had a vehicle with a carb... Any smart remark IS okay too.

 

[76cj7chick]

If you are concerned about the air/fuel mixture, check the deposits on the spark plugs. There are charts/pictures in most repair manuals to check them with. Not having any coolant running thru the intake manifold will give you a lean mixture as the manifold heats up. A leaky valve cover will make an exhaust manifold smoke.

Thanks for helping me trouble shoot....

Any suggestions on why a newly rebuilt (by me a girl ) carburetor would spew gas out the float bowl vent (I didn't replace float as it looked good ) AND gas coming out between the gaskets of the carb and intake.

 

[elwood blues]

The exhaust manifold is going to smoke and smell funny, there is an anti-rust coating on them, it's going to burn off and smoke and smell like hell for a day or two.

If your exhaust manifold is glowing red hot, obviously way hotter than normal, your timing WAY, WAY off. You are probably way to far advanced on your timing, it should be somewhere between 8 & 12 degrees Before Top Dead Center (BTDC).

 

[elwood blues]

I'm going to address your carb leaking issue; if you have fuel coming out of the bowl vent, there is way to much fuel in your fuel bowl. That can be adjusted by correctly adjusting the float inside the fuel bowl. The fuel coming out between the carb and the manifold is probably from the bowl, same as the fuel spilling out of the bowl vent. The problem is, once the gasket between carb and manifold gets soaked with fuel, most of the time they are no longer any good and should be replaced.

 

[elwood blues]

Another thing to look at, when you rebuilt the carb, did you replace the needle and seat? Also, for the next time, you should ALWAYS replace the float when you rebuild a carburetor, plastic or brass doesn't matter, but you should ALWAYS replace the float. There could be pin sized holes in the float that you can't see, allowing it to fill with fuel and overflow your fuel bowl...

 

[76cj7chick]

Another thing to look at, when you rebuilt the carb, did you replace the needle and seat? Also, for the next time, you should ALWAYS replace the float when you rebuild a carburetor, plastic or brass doesn't matter, but you should ALWAYS replace the float. There could be pin sized holes in the float that you can't see, allowing it to fill with fuel and overflow your fuel bowl...

Thanks for all of the great pointers.
I did adjust the float to 7/16" from the instructions on line and that is when it flooded. I took the top off (air horn) and the float was floating at the top..
I took the accelerator pump diaphram off (the rebuild kit had the wrong one) and it appeared to have a small hole in it.. So, I plan on going to the store to replace it..
Also, I tested the choke pull off and when I suck on the end the arm barely pulls in and won't stay.. So, will replace it too..
I may get a float while I'm at the store...
Thanks for your help.

 

[Fastatv]

Ummm.. Hard to not be a smart ***. The exhaust is a result of a small explosion so it will hear up really quick. If its idling at 800 Rpms that means each cylinder has had about 400 gasoline induced explosions in it. Each explosion can be between 700-1000 degrees. Normally with a new manifold or freshly painted manifold it will heat up and smoke very quickly and even burn off the paint. I've seen cars with bad map sensors or way to lean actually turn thief pipes cherry red.

So to some it up.. It should be hot.

Well said Jimbo They get hot.....very hot....and very quickly!