Initial Timing 489 CI
Thread Starter
Drifting
Joined: Jun 2007
Posts: 1,552
Likes: 99
From: Lake Villa Illinois
St. Jude Donor '14
Initial Timing 489 CI
I have the MSD Atomic EFI on my engine which allows me to change timing and AFRs by pressing a few buttons.
The engine is a 489 with Brodix race rite rec port heads at about 10.3:1
Factory '66 L72 aluminum rec port intake manifold.
Factory '66 exhaust manifolds feeding 2-3/8" flow path side pipes.
Tremec 5 speed.
Hydraulic roller cam. 224/234, .578 lift 109 sep.
850 rpm idle.
15" vacuum at idle.
AFRs set to 14.5
Right now I am running with 26 degrees initial with about 12 degrees of vacuum advance. With the computer controlling the vacuum advance, the idle timing is about 35 degrees. Total advance is 37 all in at 1800 rpm.
My question is, why is this working for me when the consensus is 18-20 initial? Balancer is new and lines up properly with the timing marks.
Thanks
Gerry
The engine is a 489 with Brodix race rite rec port heads at about 10.3:1
Factory '66 L72 aluminum rec port intake manifold.
Factory '66 exhaust manifolds feeding 2-3/8" flow path side pipes.
Tremec 5 speed.
Hydraulic roller cam. 224/234, .578 lift 109 sep.
850 rpm idle.
15" vacuum at idle.
AFRs set to 14.5
Right now I am running with 26 degrees initial with about 12 degrees of vacuum advance. With the computer controlling the vacuum advance, the idle timing is about 35 degrees. Total advance is 37 all in at 1800 rpm.
My question is, why is this working for me when the consensus is 18-20 initial? Balancer is new and lines up properly with the timing marks.
Thanks
Gerry
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It's not unusual. Think about all the folks who run around on the street with timing locked at 36-38*? I haven't played with the MSD system...I'm assuming it has a cranking retard feature maybe that is helping it crank?
I like all the initial it will stand..sure makes it responsive!
JIM
I like all the initial it will stand..sure makes it responsive!
JIM
Thread Starter
Drifting
Joined: Jun 2007
Posts: 1,552
Likes: 99
From: Lake Villa Illinois
St. Jude Donor '14
It's not unusual. Think about all the folks who run around on the street with timing locked at 36-38*? I haven't played with the MSD system...I'm assuming it has a cranking retard feature maybe that is helping it crank?
I like all the initial it will stand..sure makes it responsive!
JIM
I like all the initial it will stand..sure makes it responsive!
JIM
No cranking retard, although you can set the timing curve starting at 500 rpm. That lets you use a lower advance at cranking rpm, and still bring the timing up aggressively to be all in at 1500 rpm at the earliest. I don't do that though, and I have no problems with hot starts at 26*. Maybe I can use more?
What determines all the initial it will stand? Bucking against the starter on hot starts?
Thanks,
Gerry
Race Director
Joined: May 2006
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My guess you are getting away with 26 due to the characteristics of the camshaft. Not knowing what the intent of your car is, isn't the all in by 1,800 low for anything other than drag racing, more typical would be all in by 2,800 to 3,000.
Thread Starter
Drifting
Joined: Jun 2007
Posts: 1,552
Likes: 99
From: Lake Villa Illinois
St. Jude Donor '14
Gerry
