Glowing headers
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Joined: Jul 2003
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From: phila Pa
So i read up on Liars papers on timing and distributor advance. I have fast burn heads, And in the distributor paper, he says " On most GM V8 engines (not including "Fast-burn" Style heads, will produce peak torque and power at wide open trhottle with a total timing advance of 36 degrees ( Some will take 38). My question is where does that leave me? Where should i be?? THe numbers athat GM Give, are they maximum performance?? can someone explain fast burn theory, and how the heads are different.
Drifting
Joined: Nov 2002
Posts: 1,665
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From: Ontario
Originally Posted by 1971_CorVette
can someone explain fast burn theory, and how the heads are different.
For max power & efficiency you want the ignition to happen when the piston is at a certain point, around top dead center.
If the ignition happens too soon (timing too advanced) the piston is still in the compression stroke (moving up) and the engine looses power. This is where you can get 'knocking'.
If it fires too late (timing retarded) the piston is already in its power stroke (moving down) and the engine is not making as much power as it could, reducing efficiency.
The reason for having variable timing advance - as the engine RPM increases the pistons travel faster. You have to fire the spark plug sooner in order to get the ignition to happen at the ideal piston position.
Bottom line - compared to traditional heads, fast burn heads take a shorter amount of time for the compressed air/fuel mixture to ignite from the time the spark plug fires. This means you want to run with less timing advance, which makes your engine more efficient.
Compared to traditional heads, fast burn heads (using less timing) make more power, are better for fuel economy and better for emissions.
Le Mans Master
Joined: Jul 1999
Posts: 9,206
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From: Sewell NJ
GMs HT383 engine, which I believe has the same or similar heads as your engine, calls for a maximum timing of 29 degrees. But in my experience things like this are only guidelines and a lot of tweaking is required. I would advance the timing in two degree increments from 30 to 36 degrees and see what the engine likes. In the case of my engine the sweet spot was around 34 degrees. Once you have that determined you can either lower the initial by extending the limiting groove on the distributor plate or raise the initial by brazing the groove or using a limiting bushing on the pin.
Pro
Joined: May 2005
Posts: 515
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From: Grosse Pte. Mich.
[QUOTE=Boofers]Thats what you get with the hot cam. 
If your A/F mixture is too lean or too rich you can get red hot headers.
In my pre Corvette days, I had a BB Olds W-30.
When that engine went back in the car with a stronger cam,
it too displayed glowing red headers. Scared the hell
out of me. My condition was corrected with a larger carb.
750 or 800cfm if I remember correctly. Good luck.
If your A/F mixture is too lean or too rich you can get red hot headers.In my pre Corvette days, I had a BB Olds W-30.
When that engine went back in the car with a stronger cam,
it too displayed glowing red headers. Scared the hell
out of me. My condition was corrected with a larger carb.
750 or 800cfm if I remember correctly. Good luck.
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Joined: Jul 2003
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From: phila Pa
So i went ahead and set the timing Back to the 30 Deg that the tech guys told me to, and the headders are still bright orange. I just changed the carb on it and like i said It is prob pig rich. My next step is to jet the carb down. Oh and i pulled two plugs and they werent very wet, and had a fairly decent browinsh white color, did not look horribly fouled???? what is this all about?
