Has anyone ran into this issue on their FE? My passenger runs about 470° at idle operating temperature and driver side runs around 350°, from what my grandfather says is its possibly a "partially" internally collapsed manifold, he's ran into that issue before. So am I looking at another excuse for headers or another issue? All exhaust port temperatures are similar to the manifold temperature.
Note that no matter where I measured the temperature it was always a 100° difference (give or take 15°)

 

Disconnect the mechanical fan blowing air around the engine and re-shoot the temperature.

Collapsed manifold? I've got a bridge to sell him...... what about a raccoon?

 

Maybe the heat flapper butterfly (EFE for you techys) is stuck shut. That would mean most of the exhaust from one side is going up under the carb through the cross over to the other side.

 

Tested with fan disconnected and still got about 90° difference.

 

I would think with a partially blocked manifold you would see a difference in plug color side to side. And would experience a poor running engine.

 

So the left bank is running a bit leaner then the right bank(at idle). I doubt the manifold has anything to do with it. Trying resetting the idle mixture screws on the carb.

Try holding the rpm up to like 1500 rpm and see if the temps balance out.

 

Have you checked for lean on one side? Like an intake manifold gasket sucking wind?

Do a vacuum check and compare plugs from right to left bank.

Manifolds do not collapse. Gaskets do, and mixtures from right to left change temperatures.

Another cheap diagnostic would be to have a smog shop compare hydrocarbons on each bank, if you have dual exhausts. And access to a smog shop.

 

Just to be clear, while it is true that the two barrels of the carb only service 4 cylinders each, they cross in the intake (dual plane) so each barrel services two cylinders on each side. I don't think adjusting the lean/rich of the idle mixture screws will change your heat issue. If you do have the flapper valve after one of the exhaust manifolds I would test it to see that it does in fact move freely.

 

check carb mixture , if one side is lean /rich

 

opps you beat me to it

 

What other symptoms does your rig have? What led you to checking their temps?

 

Don't have any valves on my exhaust or in my intake, as it's a C9AE so I don't believe there's anything

 

My carb was boiling over and pressure was really building up in the line, noticed no ( forget the term but the exhaust circulating in intake to heat the carb/fuel) so led me to think of a restriction in the exhaust/manifold

 

Pressure high in the fuel pump to carb line? If it's too high then the needle and seat can't hold the gas from entering the carb's bowl. And that fuel will come out the bowl vents. If you have an electric fuel pump then maybe the pressure regulator not working right. If mechanical pump then isolate heat from the pump to carb line. I have heard heat in the gas in that line, on the verge of vapor lock, can cause higher pressure.
On the different temp exhaust manifold, my 1st reaction was plugged,smashed, or kinked R/S exhaust pipe or muffler if you have duals. Did you run over something in the road recently?

 

Still sounds like a flapper. It doesn't matter if the part # is 1969, they've used the heat crossover butterfly since at least 54 when the first Y block came out.
The flapper isn't exactly part of the manifold, it's sandwiched between the manifold and header pipe.