Recommended BBC timing - Chevelle Tech
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post #1 of 10 (permalink) Old Feb 13th, 11, 9:25 PM Thread Starter
Javier
 
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Recommended BBC timing

Hi, I'm new to the forum. Would like to know the recommended initial and total timing on a ZZ502. Running a big moth a thumpr comp cam, strip dominator single plane intake and a race demon 850. thanks
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post #2 of 10 (permalink) Old Feb 14th, 11, 12:15 AM
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Re: Recommended BBC timing

Here's a PDF you migh find interesting...

http://www.gmperformanceparts.com/_r...ngine_Base.pdf

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post #3 of 10 (permalink) Old Feb 14th, 11, 11:15 AM
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Bob
 
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Re: Recommended BBC timing

Hello,

I'd start out about 32* TOTAL; then advance it 2* at a time until it drops in power on a dyno, OR loses MPH in the quarter. Once you see a loss, back-off the previous setting. BB's I have played with tend to go between 32-40* TOTAL; see what YOUR engine likes.

Good luck,

Bob
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post #4 of 10 (permalink) Old Feb 14th, 11, 4:34 PM
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Re: Recommended BBC timing

This may give you some insight on the timing that BBC's often like.

For 540ci BBC Street/Strip motors, 37* total is fairly common. That's what mine likes, and so do quite a few others that I'm familiar with. These motors run solid roller cams with around 265* to 275* duration at .050, and around 11 to 1 compression. They also generally like about as much initial timing as your distributor can muster. Mine is very happy with 30* initial, then another 7* centrifugal, for that total of 37*. With that tune-up, it starts immediately, the throttle response is surprisingly crisp and quick for a big motor, and it made 710 ft lbs and 781 hp on the dyno. Less initial can make these big motors a bit lazy with throttle response.

A note on not using too much initial:
As I said above, my motor and others tend to like a lot of initial timing. But you can end up with too much of a good thing as well. If I give mine too much more than 30* initial, it will on occasion, if conditions are just right, think about kicking back. It hasn't quite kicked back yet, but it will out of the blue try to turn over slow like it has way higher compression. And this is with a good Optima battery and a good high torque mini starter. As long as I keep it to no more than 30* initial, then its always as happy as a clam.
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post #5 of 10 (permalink) Old Feb 14th, 11, 9:34 PM Thread Starter
Javier
 
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Re: Recommended BBC timing

Thanks for all the replies guys. Will start playing with it. I think right now it's set up at 12 initial and 36 total. It's runnin really strong and pretty perfect, but will diesel after shutoff every once in a while.
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post #6 of 10 (permalink) Old Feb 14th, 11, 9:37 PM
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Re: Recommended BBC timing

The dieseling may be your idle is set too high. Back it off a little at a time and see if that doesn't fix it.
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post #7 of 10 (permalink) Old Feb 14th, 11, 9:46 PM Thread Starter
Javier
 
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Re: Recommended BBC timing

The idle is set at 750, any other suggestions?
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post #8 of 10 (permalink) Old Feb 14th, 11, 11:32 PM
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Re: Recommended BBC timing

Pull motor and send it to me, J/K Mine seems to like 38* total by 3000 MSD distributer.

New Best!! All Motor 1969 Chevelle
ZZ502 Stock Crate Motor
Turbo 400 4.10 Rear Gears
Car weight 3625
Car & Driver 3905
Best Numbers Ran:
60' 1.449
330 4.465
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Mph 96.53
1000 9.240
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post #9 of 10 (permalink) Old Feb 15th, 11, 12:07 AM
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Re: Recommended BBC timing

This may be too obvious, but is that 750 rpm idle in gear, or in park? If it's in gear, your idle at park may be too high. There should be only a couple of hundred more rpm's in park, but some set ups have a wider gap.
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post #10 of 10 (permalink) Old Feb 15th, 11, 6:47 AM
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Re: Recommended BBC timing

If you wind the initial up from 12 to 18 or more (and still keep 36 total mechanical) and put on manifold vacume advance, you can close the throttle blades and still keep the same idle speed. That should reduce or eliminate runon.
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