Red hot exhaust manifold!

[earlroots]

1985 chevy G20 5.0L 4bbl quadrajet 3 spd trans.
ok the thing bogs under load and pops and exhaust comes out the carb. i did plugs wires cap rotor wires and fuel filter. then drove it with the doghouse off and noticed the top of the Y pipe and both manifolds getting cherry red hot. so i figured it was a plugged cat. replaced the cat and the problem is still there. i cant check the timing because when i unplug the 4 wire connector the thing won't start. when i unplug the 4 wire con. while van is running it dies. as of now i am stumped i have never seen manifolds get that hot before without any exhaust restriction. any suggestions??

[sierrap615]

i have never worked on this system, but have read about it. IIRC the car should run with the 4-wires disconnected, i wonder if it is way off(over-advanced i beleave), to the point the computer has to adjust just to keep it runing? i would hook up a timing light with the 4-wire connected, to see if it is at all close, then maybe adjust it (still connected) so you can get it to run with the 4-wires disconnected and then set the base timing.

its just a theory, distributors at not my strong point

[Pewter'01SS]

I'm going to completely go out on a limb. Could it be something wrong with your valves? The only reason I say that is I'm thinking that the exh. valve might be staying open a bit and allowing unburned fuel into the manifold, and its detonating there.

[slimone]

Hi, most of the time its from a stopped up ex.pipe or cat,and even muffler, try dropping the cat off and let it run for a while an see what it does , also if your running to lean pipes will get hotter , which ever it is thats Hard on valves Good luck Slim

[Mikes Mechanics]

Here is the reason you are having a problem. First stop playing with the Catalytic Convertor. It costs a lot of money and thats not the problem. The problem is one of two things. First the 4 wire connector when you disconnect it the engine wont start. Thats because some one in the past set the timing without disconnecting it. That cause the timming to retard extremely. What you should do is disconnect the 4 wire connector. Loosen the distributor and advance it a little at a time till the engine starts. Once the engine starts set the timming to factory spec and if I remember correctly it should be somewhere between 12 and 15 degrees before top dead center. Once you have done this then reconnect the 4 wire connector. Right now what you have is an engine that is so retarded that it is pushing unburned fuel thru the exhaust and it is burning in the pipes causing them to glow. Remeber that timming controls how long the fuel is burned in the cylinders.

Now the other possible problem could be if the first thing I said dont pan out. The timming chain maybe stretched to the point of almost breaking. This I have seen. The way to tell this is remove the distribtor cap and get a socket and breaker bar and turn the engine backwards then forwards by hand and watch the rotor. Remember that there should be no hesitation between the crank and the rotor. They should turn together.

Check both of theses things I mentioned. I can bet you breakfast that one of these things will be the problem.