exhaust manifold backfiring

[baxsom]

ok so i have been doing a good deal of work on the car lately.

new carb from jet performance.
recurved distributer using the mr gasket parts that lars suggests.

here is the thing.
when i rev the engine literally there is a pop and a flame coming out from the joint of the exhaust manifold and the pipe.

i have read here that it could be valves, timing, etc.

timing is set at 12 degrees with the vacuum line off and plugged.
the condition of the exhaust is horrible.
i dont think that there is any of the donut actually left in the seam.

i know that every valve works, i took both valve covers off and each of them go up and down the same amount.

valves are adjusted just to where they stop ticking and then 1/2 turn

i am hoping that it is coming from the bad joints between the manifold and pipe but please dont let this get any more expensive.

i already have a set of hedman headers and 2.5 inch exhaust from corvette central ready to go on so i am hoping that once all that is on it solves it.

what are the chances of that being the case.
i really really cant afford to pull the heads and valves right now

 

[minifridge1138]

Here is one possibility: you're running too rich.

If you're running too rich, then there is unburned fuel being passed out of the head on the exhaust stroke. This unburned fuel is very hot, but there is not enough oxygen in the combustion chamber for it to burn (because you're too rich). With the seal gone between the header and the pipe cool oxygen-rich air can mix with the exhaust fumes. The exhaust fumes have unburned oxygen and are very hot. When exposed to fresh air there is enough heat, oxygen, and gasoline to ignite.

That is just one possibility.

 

[TimAT]

Here is one possibility: you're running too rich.

If you're running too rich, then there is unburned fuel be passed out of the head on the exhaust stroke. This unburned fuel is very hot, but there is not enough oxygen in the combustion chamber for it to burn (because you're too rich). With the seal gone between the header and the pipe cool oxygen-rich air can mix with the exhaust fumes. The exhaust fumes have unburned oxygen and are very hot. When exposed to fresh air there is enough heat, oxygen, and gasoline to ignite.

That is just one possibility.

erd:Right on the money. I'll bet the gasket between the manifold and pipe is gone. Either put a new donut and sleeve in the pipe or go ahead and install your new exhaust. Your troubles will be history.

 

[LVMYVT76]

You have probably seen the fire from the NASCAR cars when they let off going into thecorners, etc. Thats what is happening with your can except they have a little more HP. Headders are nice on a car, and the sound you want comong out the exhaust will depend on the pipes, whether you "X" them or not and the type of mufflers. I wanted a quiet sound this time, so I went with a muffler that did not have much back pressure, but was a sound of a meatty stock sound. Its up to how you want it.

 

[Hib Halverson]

The pop and flame is normal.

What's not normal is you're seeing that at the joint between the manifold and the head pipe.

Repair the joint.

You won't hear the pop.
You won't see the flame.
The engine will be quieter.

 

[baxsom]

thanks guys
looks like its time to bug dad to use his car lift and get the new pipes on.