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 advanced LT1 opti spark timing by oblonging mount holes

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sdowney717



Posts : 40
Join date : 2017-01-01

PostSubject: advanced LT1 opti spark timing by oblonging mount holes   Sun Jan 08, 2017 10:45 am

Was wondering if anyone else had done that.
Engine ran more powerfully after the timing advanced.
Simply I filled sideways the 3 bolt bolts so the distributor would twist a little more against the direction of rotation of the crankshaft.
About 1/8-3/16 inch wider holes so go figure a little more advance.

I had a friend with another 94 wagon and his engine always felt as if it had more power than mine.
Since I advanced the timing, mine is like his. And it does not ping on regular.
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jayoldschool

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Posts : 2481
Join date : 2009-06-14

PostSubject: Re: advanced LT1 opti spark timing by oblonging mount holes   Sun Jan 08, 2017 11:43 am

Why bother rednecking it when you can do it correctly, and accurately by altering the programming?
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jasonlachapelle

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Join date : 2011-01-24
Age : 34
Location : CFB Bagotville, QC.

PostSubject: Re: advanced LT1 opti spark timing by oblonging mount holes   Sun Jan 08, 2017 12:24 pm

I have never heard of anyone doing that. I did advance my timing in the PCM though. Some guys use cam bushings to change the timing by a few degrees.

I have too much work to look into it, but if the dowel pin from the camshaft is seated in the opti properly, I'm not even sure rotating the unit would change anything.
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sdowney717



Posts : 40
Join date : 2017-01-01

PostSubject: Re: advanced LT1 opti spark timing by oblonging mount holes   Sun Jan 08, 2017 2:12 pm

I am pretty sure it worked doing that.
I always wanted to do it, so when I had to change the waterpump I did.
Reason was it is very easy to do versus I have no idea about PCM mods.

MSD sells an expensive optispark with an adjustment that can make timing changes, so by twisting the housing,  gave me the idea.

[You must be registered and logged in to see this link.] "The MSD Distributor can alter the timing +/-7°"

"Once installed, you have the ability to adjust the ignition timing – the only distributor that offers timing adjustability! An adjustment screw allows the timing to be tweaked up to +/-5°. The distributor is equipped with a fresh air vent and has an extra thick mounting surface for the cap to eliminate leaks. "
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MalibuSSwagon



Posts : 577
Join date : 2014-01-12
Location : NH

PostSubject: Re: advanced LT1 opti spark timing by oblonging mount holes   Mon Jan 09, 2017 10:37 am

With GM EFI systems, the distributor is locked in place at 0 degrees and the ECM does all the ignition advance. By doing this I would theorize that you are throwing off the whole spark map.

It's simple to program the LT1 PCM yourself. Don't sit there and say you have no idea how that works, google it.
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Andebe

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Join date : 2013-02-20
Age : 49
Location : Marion,NC

PostSubject: Re: advanced LT1 opti spark timing by oblonging mount holes   Mon Jan 09, 2017 11:01 am

Eric,this comes from experience? No tone implied,just curious.
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MalibuSSwagon



Posts : 577
Join date : 2014-01-12
Location : NH

PostSubject: Re: advanced LT1 opti spark timing by oblonging mount holes   Mon Jan 09, 2017 1:45 pm

Yes I have installed a TPI setup in my C10 years ago, an important point of early GM EFI is setting the distributor at 0 degrees because the ECM does ALL of the spark advance including at startup. If you set the distributor at 4 degrees static for example, with no programming changes then the ECM is going to assume that is 0 degrees and advance from there. So you'll be off by 4 over the whole map. The ECM has no clue what you've done, it's a computer following a pre-programmed set of instructions, unless you go in there and change those instructions.

Also as far as I know there is no timing tabs on a stock LT1. So no way to know what advance you've set. On the TBI engines there was a connector to disconnect so the ECM would revert to base timing and make no changes while you were setting the timing. I don't think LT1 have that connector. Sure you could hack it and all, the seat of your pants feel good, etc. But engine damage is very possible, crappy fuel mileage, etc.

Oh and just because an aftermarket company put out a part for your car, doesn't mean it's good. OEMs sink millions upon millions into R&D to make sure they put a good reliable product out there. Aftermarket companies pump out parts as fast as possible to make money, they aren't on the hook for lemon laws, NHTSA safety recalls, and so on. So shop with care.
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