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Old 04-29-2008, 01:57 PM
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Getting the timing right on a 383 with Vortec heads

Hey everyone. I'm getting ready to fire my new 383 up. I have a comp 268XE cam and vortec heads. I believe compression will be about 9.7 to 1, and I'll be pumping 93 premium. I wanted to ask what base timing numbers should I be setting it to, intial? advanced? The more I look, the more confused I make myself. Thanks!

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Old 04-29-2008, 02:31 PM
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There's no golden rule that if you have this you must use this timing, it's more of a trial and error. Adjust to what your engine likes, play around with it. My 383 with TFS 195 heads and about 9.6:1 CR likes 17 initial 35 total. But you will probably see all kinds of figures if everyone just started posting their ignition timing.
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Old 04-29-2008, 02:37 PM
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Vortec chambers are very efficient and will probably require less timing than conventional designs. Start at 32* initial/centrifugal.
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Old 04-29-2008, 03:49 PM
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Something between 12 and 16 initial is good. Something between 31 and 36 is good for a total mechanical. I found very little difference between 32 and 36deg.
On my vortec motor. The initial timing (separate from the total) has more effect on performance. (ET on a drag strip pass)
The total timing can be determined by watching the MPH on a drag pass.
If /when you find that 32 to 36 don't change the MPH much, use the lesser.
Improper carb jetting or lack of top end fuel volume {fuel starvation} (way too rich or way too lean will want more timing that expected normal(s).
Something around 10 to 15deg of additional vacuum advance for P/T hiway cruise is good. You have to dial in the advance rate (slope) for whats best.
It's up to you to experiment within these parameters to fine the sweet spot.
I found Champion RS9YC RS10YC or RS12YC spark plugs work very well in vortec motors.

Last edited by F-BIRD'88; 04-29-2008 at 03:57 PM.
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