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one header tube glowing red?!?

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4x4orbust

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last night i was checking all the fluids and what not on the plow truck, and i noticed one of my primaries was glowing red while idling. (#6 cylinder)

any ideas of what would cause just one primary to glow red?

on a 1982 k-10, 355 ci mild cam, stock heads, performer intake, q-jet that needs a rebuild.
 
that stinks, i just put these heads on when i re-did the top end last year. i checked compression in the cylinder just for laughs and it reads 110 psi.

what would cause this to happen? i want to remedy the problem before i throw another set of heads on.
 
The chances are its a burnt valve,but valve might not be burnt ,it could be a lifter has pumped up and is holding it open slightly or its sticking in the guide,but usually you'll be able to detect the engine not running smooth or performing as well as before..I've seen cylinders # 5 and 7 "crossfire" and that can make one cylinder fire out of sequence and burn the fuel in the exhaust manifold...one cylinder running lean can make that happen too..

...my 400 small block had real rusty exhaust manifolds that were very thin in the center and you could see them glowing after a highway run,and the engine ran great,had excellent compression...
 
you can't
it's low cause the exhaust valve isn't holding compression and is allowing fuel/ combustion through into the headers, where it's burning, instead of inside the cylinder. It's glowing because of that reason alone.
Time for either new heads or a valve job/replacement.

EDIT: damn, little slower than ^^, good points too. :)
 
I've always heard that running way to open of an exhaust IE open headers with no long collector can burn exhaust valves.
 
these heads were never run on an open exhaust. at the same time i did the heads, i did the headers and true duals (2 1/4").

the truck has seemed to develop a miss above 2300 rpm, but i thought it was cause the carb needs a rebuild.

so some new heads, huh? any good recommendations? i'm not gonna have these heads redone again. might as well upgrade a little.
 
4x4orbust said:
these heads were never run on an open exhaust. at the same time i did the heads, i did the headers and true duals (2 1/4").

the truck has seemed to develop a miss above 2300 rpm, but i thought it was cause the carb needs a rebuild.

so some new heads, huh? any good recommendations? i'm not gonna have these heads redone again. might as well upgrade a little.
Click to expand...

Vortecs are awesome for a budget but require a new intake manifold. Which is good if you want to upgrade that too but if you already have a nice manifold its a little bit of a waste. Dont forget you can also sell your existing manifold though.

Worked Camel humps can bring almost as much power as the vortecs but the vortecs are superior in torque.

Then theres the aftermarket.
 
4x4orbust said:
that stinks, i just put these heads on when i re-did the top end last year. i checked compression in the cylinder just for laughs and it reads 110 psi.

what would cause this to happen? i want to remedy the problem before i throw another set of heads on.
Click to expand...

What were the rest of them? That's not that far out of line unless the rest are way higher.
I'm not saying you guys are all wrong, but I don't think anyone's got enough info for a solid conclusion yet. You could easily have a plug or a wire that is acting up (even if they are new) and causing an issue like this.

I'm not saying this is definitely the problem either, but worth researching before pulling a cylinder head.
 
the ONLY thing i've ever seen do that is a failed exhaust valve of some sort, whether burnt, sticking, bad seat, etc... i've NEVER seen a plug or wire do it, not that it's not possible... i'll bet that cylinders down 30, 40 psi, far more than 10%, 110 is pretty anemic...

if the heads are worthy, i say just send it out to have the seats gone over... far cheaper than changing heads...
 
i only checked the #4 cylinder at that time, and it read 110 as well. the plug looked the same as #6. i will test the other 6 cylinders tom. and see what they are reading. what is a normal compression reading? i thought the 110 was within the realm...

i was checking for a jumping spark plug wire when i found this out. i did it at night to see the sparks better, and that is the only reason i know about it. the wires and boots showed no signs of being the weak link.

the heads are nothing special, stock ones that came with the motor. i had a shop go through them when i did the top end. might be trying to find a new shop soon.
 
most motors are usually in the 130 to 150 range... 110 is usually a pretty damn tired motor... a leakdown test will pinpoint any issue...
 
thats disheartening. motor has at most 10,000 miles on it. could still see hone marks in the cylinder walls when i did the work last year. maybe theres a head gasket problem as well? (probably my fault, it was my first time getting into a motor that deep.)
 
run the compression test on all of them... make sure all your plugs are out and your throttle plate is open... if you find any down more than 10%, put some oil in em to see if they come up.. that seals off any ring issue and verifies a valve prob..

and it might be a good time to invest in the leakdown tester... it'll indicate where the cylinder is having issues, if any, rings, exhaust, intake, etc...
 
I just hate to see people jerk motors apart, buy expensive parts, etc, put it all back together to find the problem could have been solved for the price of a good tune up.

I would be interested to see the results of a full compression test and a leakdown test. The leakdown should tell the tale if it is a valve issue.
 
ryoken said:
most motors are usually in the 130 to 150 range... 110 is usually a pretty damn tired motor... a leakdown test will pinpoint any issue...
Click to expand...

Completely depends on many things: what altitude was the compression test taken at (even here at 6K feet of elevation we're ~25% less air pressure), was the car held at wide open throttle, etc.

Compression numbers themselves really don't mean much. If one number is much lower than the others, you have a problem. Otherwise, if you have 110 across the board (+/- 10 or so) there is no need to worry.
 
can also be caused by that intake runner leaking and causing that cylinder to run lean. do a wet compression test on that cylinder to see if it raises the compression.
 
There are only 2 things that will cause a header tube to glow red hot. That particular cylinder is either running rich or running lean. If it's running rich the excess fuel is burning in the header tube and not in the cylinder and if it's running lean a lean condition makes all kinds of heat which will make a header tube glow red hot. Do a compression test on ALL cylinders with all the plugs removed, carb at WOT, and engine at operating temperature. Like Chris said, the numbers really don't mean anything as long as the difference between the highest and lowest doesn't vary more than 10%. If the readings are pretty consistant across the board then you can rule out any kind of internal mechanical problem (rings, or valves). If your reading in that cylinder is alot lower than the others then you do a leakdown test to determine if it is rings, exhaust valve or intake valve giving you the low reading. Now when you take it apart you know exactly where to look for the problem.
 
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