I have a dual quad high rise manifold on my car. Just had the engine rebuilt to a 348 stroker.

Had it running, and noticed that the back passenger side header (#8?) was glowing, as was the second to the back (#7?).

I pulled the spark plugs from both #8 and #7 ... as well as the opposite side (#1 front drivers side).

They all look fine (if anything rich). Interestingly, the diode on the spark plugs had a smaller diameter on #8/#7 than on #1. All the plugs were the same manufacturer and part number. I went out and bought new spark plugs, compared them to #1 ... and they appeared to be the same size.

Installed them, and let the car idle to temp. I still have a glowing in #8 (#7 I don't notice anymore). The glowing in #8 is less noticeable now.

I don't understand what it could be. The glowing of header indicates it's running lean ... but the plugs indicate it's running rich.

Thoughts on fixing this? Engine guy says there might be a leak somewhere, but how can the plugs show it's running rich?

I've gone through and tightened all the bolts.

 

i'd say retarted ignition, but if it's only a single cylinder you're burning your mixture in the header exhaust instead of the chamber. maybe an exhaust valve not closing properly?
otherwise I would have said the cylinder is running lean but you should have seen that on the plug. reason for that could be a vacuum pickup in that specific intake runner

 

Yep, good call Kali. Retarded ignition, or valves need to be relashed. Something is causing the burn in the exh.

 

or maybe vac leak at the intake/head...

 

Thank you for the replies. I've set the timing twice to what the engine guy said. (34 at 3,000rpm).

Of course he also said that it couldn't be the valves (that's what I think it is) ... but he put them in, so I would guess he'd say that.

As for the vaccum leak, wouldn't this cause the cylinder to run lean? And at the spark plug, it's running okay to rich.

He tells me he's gonna come over to my house and look at it ...

 

I wonder if a vacuum leak could be disturbing the mixture by enough such that it doesn't completely burn in the cylinder, leaving enough to burn in the pipe to make it glow.

I had the same sort of thing happen (too many) years ago whan I was still working with carburetors. Exactly one pipe (#1/driver side front on a SBC) glowed quite nicely in the evening darkness. Tightening up something - I can't remember if it was one or two carb mounting bolts or a couple of manifold bolts any more - solved the problem.


Norm

 

if it were a vacuum leak on a runner you should see it as lean plugs. If I were a betting man the valves just need a bit of re-adjusting.
but nice that he's coming over. great service

 

Unless it's a 9-10,000rpm engine, it doesn't need a dual quad high rise. If it shows signs of rich it's probably because the idle is too rich, so fuel is burning in the exhaust. If the idle control sucks from too large of an intake, it's gonna need a rich mixture just to run.