ShinodaVette

I'm looking for some ideas here as to what is most likely causing my headers to glow bright red hot. They actually started melting a couple of my plug boots and they aren't even touching the headers.

Here's the scoop: We just fired up my engine for the first time on Sunday night. I rebuilt this engine myself with the help of some good books, videos, my neighbor, and most importantly this forum. It is a 10.5:1 compression 355 ci engine with an ~8.3:1 DCR. I have Trick Flow aluminum heads, Edelbrock Performer RPM Air Gap intake, and a Speed Demon 650 carb. Everything on the engine is brand new except the exhaust and headers.

The headers and exhaust came off my '56 Chevy Pickup and I have no idea how old the setup is. They are definitely rusty. When we started the engine a bunch of dirt and rust came flying out of the mufflers but that stopped pretty quickly. The headers smoked a lot for about 30 - 60 seconds and then that stopped too. My neighbor has been helping me a lot with questions and was over to help me get it started on Sunday. He used to build race cars and has been pretty helpful. He set the initial timing to 6* advanced and felt like that was a good "safe" number for a new engine. We then promptly took the engine to 2500 RPM for 20 minutes. The engine sounds awesome and seems very healthy. The throttle response is quick. We originally started it up with no electric fans running and then when the temp got to 180* we kicked on one of the fans. When the temp kept going up and got to around 210* - 215* we kicked on the other electric fan and lowered the RPMs a little and the temp came right back down to 180* (Dewitt radiator and dual spal fans).

Everything seemed pretty normal with the exception of the headers glowing red hot. These aren't Corvette headers but they fit fine. The only reason I mention that is because the shape of them doesn't follow a normal Corvette pattern. They pretty much come straight down in the middle of the head and then make almost a 90* turn backwards. It is mainly the two inner pipes that get red hot and I think it is the heat from those two that is heating up the other two pipes but the other two don't glow red as much. It's definitely pretty hot though.

Last night I went out and fired up the engine again and since I wasn't running it at 2500 RPM the headers didn't turn red hot but they were definitely getting pretty hot (of course). Then I decided to run the engine for a few minutes at 2500 RPM and the headers immediately started glowing again (which I expected).

So, I'm looking for ideas as to what is most likely causing this. I don't want to put my Jet Hot coated headers on the engine until I know what is causing the problem. I've been doing some reading in the archives here on the forum and I've assembled this list of possible causes:

• Timing not advanced enough. 6* may be keeping too much heat in the combustion chamber when the exhaust valve opens. I was considering going with 10 - 12*. My neighbor doesn't agree with this one at all and said more advance will just make the headers glow hotter.
• Poor flowing mufflers that may be keeping too much heat in the headers. They are old and rusty.
• Carb running too lean. My neighbor thinks the carb is actually running a little rich based on smell and the black smoke that comes out of the exhaust when you blip the throttle.
• Possibly the headers are just thin from being so old and rusty and it is the fact that they are so thin that is causing them to light up bright red hot. This was just a possible guess but I'm not so sure.

So, I was hoping you guys might share your thoughts as to what direction to go in here and what might be good to check first at this point. I don't really know how to confirm whether the carb is running too rich or too lean at this point. It is sitting on my rolling chassis so it is definitely not something that I can road test.

Sorry for the long post. If anybody has any other suggestions I'm all ears as well.

Thanks!

Durango_Boy

I would suspect a lean condition too, and you might have a problem similar to one I saw not long ago. A new engine was built, but the intake gasket didn't fit around the #4 intake runner perfectly and it was sucking air in. The cylinder wasn't firing properly, and it was way lean, yet there was a smell of unburnt fuel.

The intake got pulled off, new gaskets were bought, modified to fit around the ports better, and re-sealed. Everything was fine after that.

bashcraft

Bump the advance up to 12 and see what happens.

I've also seen pin holes in header tubes that allowed air to be sucked in and caused them to run red hot.

SIXFOOTER

Its lean and/or late timing, bump the timing up and make sure the fuel mix is right.
If it has an intake leak it will show up on a Vac Gauge as a rapidly fluxuating needle

Matt Gruber

try 16 base, 36 total + 10-15 or so from vac. advance.
u do have vac adv to manifold?

moosie982

I think its a three way tie between timing , fuel mixture and old thin headers, Good luck Peace,,,Moosie

DRIVESHAFT

Tell your neighbor he is wrong.
When you dont have enough timing advance, the fuel is still burning when it gets into the exhaust.
Thats why glowing tubes can be caused by insufficient advance.

WillEE

Although he sounds very helpful and friendly, I must say that it's a little concerning that your neighbor who built race engines thinks 6* is on target with your parts combo so definitely keep an open mind and establish your own knowledge about this aspect - which you are obvioulsy doing so that's good. I would agree somewhere between 12 - 15 would be where most engines similar to yours perform and run well (w/32 - 36+ total). How 'bout valve/rocker arm adjustement - what procedure did you use and do you feel confident you got them adjusted properly?

jdmick

Advance the timing. Been there, done that.

69427

gkull

I vote for two things. Over rich carb in the idle circuit which demons are known for out of the box and not enough timing. both cause fuel burning in the primary pipes.

I operate a dyno and I've been making changes and get to see the results. Lean fuel mixtures raise the temp in the combustion chamber.

pws69

"DRIVESHAFT" made an excellent point about the fuel still burning in the exhaust. I had the exact same thing happen to me with a 350 I put an old Tri-power intake on. Turns out it was much TOO RICH causing the glowing headers.

So, the recommendations here are all good ones - you certainly need to bump that timing up significantly - 12 initial at least, but also check fuel for too lean OR too rich.

gkull

Actually to set timing it doesn't matter what the initial timing is, because you can't change it with out recurving the distributor.

You alway set your timing with the motor turned up to 3500+ rpm with all the mechanical advance in and vacuum disconnected. Old iron heads seem to put out the most at @ 38 degrees and modern fast burns @32 degrees + or - a couple of degrees with special racing heads as low as 28 degrees

ShinodaVette

He's been super helpful but I'm definitely keeping my eyes open and trying to learn as much about this stuff as I can from all the sources that are available to me.

I've got 93 octane in the tank and don't think I'll have any detonation issues at 12* advanced so I'll probably give that a try tonight.

So far as valve/rocker arm adjustment, I'm running Comp Cams full roller rockers, 1.52 ratio, and I tightened the nut just to where I could feel the tension on the pushrod, then another half turn of the wrench and locked them down.

I can't be positive that I did it right but from what I've read it should be.

Thanks.

Matt Gruber

is vac. advance connected to manifold?

Vette79C3

Just went through this during my break-in. Timing was retarded! Adjust timing...

ShinodaVette

I really appreciate all these replies. I am running an MSD pro billet distributor and the new MSD 6AL-2 ignition. It says that it is throwing spark for a full 20* of crankshaft rotation so with having only 6* advance right now that is probably making the problem even worse.

I'll start with 12* initial and then check the full timing and see where the initial ends up. I haven't connected the vacuum advance yet. I'm currently running the two heavy silver springs in the distributor so I don't think the timing is all in until around 4000 RPM.

Then I just have to figure out how to check the carb for a rich condition. Hopefully it will be in the instructions.

Thanks!

DRIVESHAFT

Connecting the vacuum advance would be a big help, too.

ShinodaVette

That makes sense. I'll connect it up after I set the timing and then see how it acts. I'm not looking at the instructions right now but I believe that will add more advance based on how much vacuum is being pulled right?

Should I bother with changing out the distributor springs yet to try and have the advance all in by an earlier RPM? Say 3000 RPM?

69427

Given the rich exhaust smell, I suggest you check your timing first for inadequate advance.