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Old 12-22-2009, 07:14 AM
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Rebuilt 350. Headers get bright orange.

I have a 350 chevy sbc on my airboat. I just rebuilt the motor. The motor has minor up grades. It has stock 192 heads, aluminum intake, edelbrock 600 carb., gear 2 gear timing, 1000-3200 RPM cam, Accel HEI distributor, and shorty block hugger headers.
The problem I'm having is that I started it for the first time and within 1-2 minutes the headers are bright orange....but the motor temp. has just barely started to warm up. I ran the motor for about 5-10 mins until the temp got to about 160 and then shut it off.
What is causing the headers to get that hot so quick? I haven't had a chance to check the timing or adjust anything on the carb, but it wasn't running bad. It never missed or sputtered. I need to run it longer to break the cam in better but the headers are concerning me. The plug wires and starter are so close to the headers.
Any suggestion on why they are getting extremely hot will be appreciated.
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Old 12-22-2009, 07:18 AM
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It is normal for headers to glow, but with your small cam they shouldn't glow that bright or that fast (though it is still possible). Check to make sure you're not running overly rich, and that you have enough timing advance, either of the two can cause unburned fuel to burn in the headers thus creating more heat in them and causing them to glow.
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Old 12-22-2009, 07:22 AM
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Quote:
Originally Posted by SthrnStyle3
Any suggestion on why they are getting extremely hot will be appreciated.
Check the timing and see what the plugs look like. It could be lean (white plug porcelain), you don't want it too lean.

Are you using a vacuum advance?
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Old 12-22-2009, 07:41 AM
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Quote:
Originally Posted by SthrnStyle3
The problem I'm having is that I started it for the first time and within 1-2 minutes the headers are bright orange....but the motor temp. has just barely started to warm up. I ran the motor for about 5-10 mins until the temp got to about 160 and then shut it off.

Any suggestion on why they are getting extremely hot will be appreciated.
The timing is very retarded or you have a major vacuum leak causing a very lean condition.

I opt for the timing first.

Hook up a timing light. Remove the vacuum advance hose from the vacuum cannister and plug it off. Start the engine. Increase the RPM to around 2500 and set the timing around 34-36 degrees. Continue the cam break-in run for about 20 minutes with the RPM varying occasionally between 2000-3000. Do NOT have the engine idle during this period.

After the cam break-in run, change the oil and filter. Re-start the engine and then you can finalize the timing for your application and after that you can adjust the carb. Trying to adjust the carb and/or final timing is somewhat futile until after the cam break-in run on a flat tappet cammed engine. This is because that combo should not be run at idle RPM until after the cam break-in.

Just FYI, if your headers are either chromed (finish will turn 'golden' in color) or coated (finish will be dull and look more like aluminum paint), the finish has been destroyed due to the excessive heat after your initial startup. If they are painted they can be redone after the burnt paint has been removed.

Last edited by Frisco; 12-22-2009 at 07:49 AM.
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Old 12-23-2009, 07:46 AM
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No I'm not using vacuum advance. Airboat company's don't recommend it. If I need more timing or a fast change in timing, to change the dist. springs and weights. I don't have any hoses, besides the fuel hose, hooked up to the carb.. All of the other ports on the carb are plugged. The timing was initially set close to TDC to get it to run. So it is possible that the timing and/or carb. is out of adjustment.
I hate running the motor as it is, in order to break the cam in. The prop's not on it, so it won't take much to over heat it and the headers get too hot. I was thinking of putting the prop on, starting it and adjusting the timing real quick and run it for a little longer (about 30 mins.). Will this be ok?
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Old 12-23-2009, 08:13 AM
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Quote:
Originally Posted by SthrnStyle3
No I'm not using vacuum advance. Airboat company's don't recommend it. If I need more timing or a fast change in timing, to change the dist. springs and weights. I don't have any hoses, besides the fuel hose, hooked up to the carb.. All of the other ports on the carb are plugged. The timing was initially set close to TDC to get it to run. So it is possible that the timing and/or carb. is out of adjustment.
I hate running the motor as it is, in order to break the cam in. The prop's not on it, so it won't take much to over heat it and the headers get too hot. I was thinking of putting the prop on, starting it and adjusting the timing real quick and run it for a little longer (about 30 mins.). Will this be ok?
Setting the initial timing for the break-in run does not require the prop to be installed. The prop would cause the engine to be "under a load".

You do not need the vacuum advance for your application. It should not be connected when checking and/or setting the timing anyway.

Carb should be adjusted after the timing has been set and after the cam break-in run.

Setting the initial timing "close to TDC to run" will not yield enough initial timing and will cause the engine to overheat quickly and can also enable the headers to "glow". Your timing needs to be advanced. See my previous post.
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