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Old 10-02-2009, 07:31 PM
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Locked timing problem

Recently, after many, many threads here, i have decided to lock out my ignition timing (mostly because of f-bird'88). Well, after removing all the mechanical advance hardware and making it so it can't move, i set the timing to 38*.

BIG PROBLEM!

When i rev up the motor, the timing retards!!

at idle - 38*, retards to 34* by 2500 or so, but didn't go much past that because i am by myself doing this an i can't be in two places at once.

Any idea as to why my timing is doing this???

327 sbc, 256/264 @.050, 105* lsa

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Old 10-02-2009, 07:58 PM
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3 possibilities.

1 your timing light sucks.

2. electronic ignition can retard 1 deg per 1000 rpm by it very nature.
(usually you don't notice this till well beyond 6000rpm)

3. most likely a slack timing chain and or worn distributor gear or both.
How does it run now otherwise?

Because you see the retard by 2500rpm I suspect #3.


Possible the vac adv / magnetic pick up mount plate is moving around too?

Last edited by F-BIRD'88; 10-02-2009 at 08:04 PM.
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Old 10-02-2009, 08:06 PM
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First off, it is an aftermarket distributor (procomp) No computer at all, just a power and tach pigtail. It is a very smooth retarding curve, but could that be due to resistace in the wires and/or plugs???

the timing light is from checker auto parts...

The gear shows almost no wear, and it was brand new when i got it 6 months ago.

seams to run good, slightly improved off-idle torque, i don't have to grind the clutch as much to get er moving.
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Old 10-02-2009, 08:10 PM
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just to specify: the timing retards with rpm, just like a normal mechanical advance curve would work. 2500 is the furthest I've been while reading the timing mark. the timing advance back to the original set point as the engine slows down. very weird.
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Old 10-02-2009, 08:25 PM
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Probabily the cheap chinesium ignition module in the pro comp distributor.
(lack of modern module design with built in electronic dwell compensation)
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Old 10-02-2009, 08:34 PM
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did you install a ignition power interupt switch to aid cranking and starting when the engine is hot?

Do you have the proper factory rear starter motor support bracket/brace installed?

Both are highly recomended when the distributor is locked out.
remeber you will have to spin up the engine to get going with this big cam.

Just as a automatic has to use a high stall converter to bypass the lowest rpm on acceleration, to get the motor rpm up where its "on the cam".
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Old 10-02-2009, 08:45 PM
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I dont have the power interrupter switch, but is has been cranking over fine so far (but i have really only started it about 15 times since my most recent delema), and i have the stater brace ordered.

So what should i do about the retarding timing???
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Old 10-02-2009, 10:12 PM
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Quote:
Originally Posted by Biscuit6447
I dont have the power interrupter switch, but is has been cranking over fine so far (but i have really only started it about 15 times since my most recent delema), and i have the stater brace ordered.

So what should i do about the retarding timing???
well I would first look at the distributor. Possibley reinspect the distributor drive gear. Maybe try a GM Delco module if this distributor is a HEI knock off.

Could be camshaft timing chain 2 deg + 2deg of distributor gear wear.
Something is up for sure.
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Old 10-02-2009, 10:33 PM
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well, a while ago, i had hypertech distributor that was used on a "stock" motor. somehow, it still sits in my garage. looking at it now, i can see that the teeth on the drive side are probably worn `.05-.1", like there is a "wear ridge" on each of the teeth of the gear.

On this current dizzy, the gears are scuffed up, but are completely intact. And the whole body of it is machined aluminum.


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