Glowing Exhaust Manifolds

[Kaweh]

Hello, I've read a lot of posts here over the past 4 months and so I thought I'd chime in for some possible RVer insight. I drive a 34' Winnebago Elante year 1992 with a 7.4L Chevy. Five months ago I had a backfire that was caused by the injector wire grounding out to the throttle body. Ever since that was fixed I've noticed the exhaust manifolds glow under a load. Lots of testing led me to learn that the manifold vacuum was not steady and so I even went as far as rebuilding the engine. I left the camshaft alone but changed the lifters even though they were fine. The previous exhaust manifolds were cracked so I put on new ones and the heads were sent to the machine shop and came back looking brand new. Other things that were changed are the MAP sensor, O2 sensor, engine coolant sensor, water pump, timing chain, of course a full tune up and initially we thought the catalytic converter was clogged, which it wasn't so i put a new one in and checked the muffler too. So now it's rebuilt with a new computer, the right injectors and a new higher performance fuel pump.

The fuel pressure now reads 12 psi. All cylinders were tested and show 150 psi, the fuel pressure regulator was rebuilt as well, The car fires right up and has great power in the city or straight a ways. The timing is advanced 12 degrees and I've ran it at 4 whites factory spec and at 6 degrees advanced and no matter what I've tried and tested it still makes the exhaust manifolds glow ridiculously red when i'm going up a hill. Giving it more gas just makes them glow more. So bad that at night you can see the both manifolds glow all the way past the Y pipe. Its scary!!!

I've replaced all vacuum lines, tested for vacuum leaks (none found). Its bizarre, I've met some amazing mechanics over this past 6 months and they are all stomped!

So i read a lot on here about how some folks put on headers and I know that this year 454 was prone to exhaust leaks, restrictions and manifold cracks. So I wonder did ya'll have this happen to you too or do you think it's normal for the manifolds to glow like crazy when on a hill? Is it somewhat normal for them to glow? If so to what degree? Cause this is scary bright red and even though i've had people say it's normal.... you're putting a lot of strain on this engine and 16,000 pounds blah blah blah, I don't buy it and here is why....... Some wise guy who owned it before me had put on air horns. Well the compressor for the horns was all the way in the back of the coach and the holding tank in the front by the radiator! Dumb design! nonetheless, i have owned this RV for six years and we went to Burning Man in it all six years and before this happened my air horn worked. It turns out when the manifolds started to glow, it cracked and melted the air line. the line was going along the frame and past the right exhaust manifold. And so if they were glowing before like this, the air horn air line would have bursted before. So that's how I know this is not normal.

Any thoughts are appreciated. I'm considering changing the exhaust to duels and a chip upgrade from tbichips.com but the car has been fine since 1992 and I don't think i should have to upgrade stuff to stop it from burning up the exhaust manifolds.

Ok, thats it for meow. Thanks for reading!

Kaweh
www.kaweh.com
Spanish Guitarist San Francisco Bay Area.

[rcmiller32]

Having worked on both the 427 and 454 GM V-8 engines in fire equipment over the years. Both will get glowing red hot exhaust manifolds when they are being worked hard. Have scene some get the exhaust red hot all the way down to the muffler.

The one poster about the harmonic balancer is correct. They fail making it very hard to set the correct timing.

[rgatijnet1]

Have you checked your ignition timing through the entire RPM range? Even though your ignition was set to factory specs at idle, the is timing is supposed to change as the RPM's increase.

[Camreal]

454s are also famous for cracking the exhaust manifolds too.

[Bumpyroad]

SCVJeff wrote:
I have no idea what has or hasn't happened since the backfire, but 454's are famous for glowing manifolds, you probably just didn't notice it till now. I have a pretty good hill to climb to get home so mine was nice n' pretty when we got home at night.

yep, chevy added some metal baffles on the P-30/32 chassis to try to duct some more air around them and at one time CW sold add on baffles.
if the OPs lack the baffles, see if you can get some.
bumpy

[SCVJeff]

I have no idea what has or hasn't happened since the backfire, but 454's are famous for glowing manifolds, you probably just didn't notice it till now. I have a pretty good hill to climb to get home so mine was nice n' pretty when we got home at night.

[Kaweh]

Rickieblue wrote:
I would say the timing marks you are using have changed and you are running the engine timing retarded. Chev harmonic balancers are known to shift due to 2 piece construction with the rubber between them deteriorating. I would advance the timing until it pings under heavy load and back it off a touch or put it on a chassis dyno and adjust it to get max horsepower. Just my 2 cents worth........

Thank you for that info. Remember this was happening before the rebuild and still. Also, I did just that. It is now at its maximum advanced timing before pinging.

[PaulJ2]

I would thoroughly check out the ignition timing system. Late timing for the various speeds the engine is running is the usual cause of this. A too lean fuel mixture is another cause. I know you have tried advancing the timing etc, but is the spark timing advancing properly with engine speed? Is the spout connecter wire ( disconnected for setting base timing ) connected back up properly? This is where i would look first.

[Rickieblue]

I would say the timing marks you are using have changed and you are running the engine timing retarded. Chev harmonic balancers are known to shift due to 2 piece construction with the rubber between them deteriorating. I would advance the timing until it pings under heavy load and back it off a touch or put it on a chassis dyno and adjust it to get max horsepower. Just my 2 cents worth........

[Golden_HVAC]

HI,

I put a Banks stainless steel exhaust system on my nearly new 1997 Bounder motorhome with a 460" V8 Ford chassis, just because Banks said it would make more power, and the factory manifolds tend to crack and leak. I did not want a 1,000F exhaust leak near the wood frame that is close to the engine!

So far my stainless steel exhaust has held up well, no leaks in about 50,000 miles. I gave the old system to my mechanic, who had a 65 Econoline pickup with a 460" engine in it.

I would highly recommend the Banks system, even though it is probably more expensive than a equally good working header by another manufacture, such as Gibson or perhaps Edelbrock?

Good luck on your project. I was going to recommend looking for a vacuum leak, but I guess rebuilding the engine would have solved any prior intake manifold leaks?

You might also check out the distributor. I had one rebuilt for my 75 F-350 and it ran like a champ once rebuilt. Clutches Unlimited in Midway City, CA did the work.

Fred.