C4 Tech/Performance L98 Corvette and LT1 Corvette Technical Info, Internal Engine, External Engine

Basic timing question

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Old Jun 27, 2007 | 10:55 PM
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Default Basic timing question

I know this will expose my ignorance but I've searched and don't see anything that answers this question:


If you want to advance the timing a bit at the track between runs to see the results.. and you are starting at the stock 6 degrees before.. are you turning the distributor clockwise ? and if you do is the timing line then going to go even more 'before' to 8, then 10 etc?


Just want to be clear on what I'm doing~

Thanks~
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Old Jun 28, 2007 | 01:08 AM
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Counter clock wise. I have a SuperRam and the distributor is VERY close to the SR. I have set the timing prior to going to the track and have made small wooden spacers that fit against the SR to set the timing at 8, 10 and 12 degrees. This way, I don't have to pull out the timing light, just loosen the distributor and turn it counter clock wise to open the gap between the SR and distributor. I then insert the spacer I want and turn the distributor until it is snug against the spacer and tighten down the distributor bolt. I do this with the engine shut off, therefore I don't have to disconect the distributor wire. It is quick and easy.
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Old Jun 28, 2007 | 11:33 AM
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Thanks John, but i'm still confused..

You said to turn it counter clockwise, then later you say you turned it counter clockwise to loosen it before putting your spacers in.. which means you'd be turning it clockwise to tighten up against the new spacer?


I'll rephrase the question...

If the car is currently at 6 BEFORE, will turning the distributor counter clockwise bring the car to 8 BEFORE, then 10 BEFORE, etc.. AND is that the right way to go??

Thanks~


ps. I made some practice launches today and ran it through 1st, 2nd, and 3rd a few times and found the car 'felt' quickest shifting right at 4500. I'm not sure what track conditions will be like tomorrow night, but I was getting really nice launches at 1700 rpms by releasing the clutch quickly (but not snapping it) and flooring the gas at the same instant. Hope it works that well tomorrow~
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Old Jun 28, 2007 | 11:46 AM
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Counter clockwise advances the timing. Clockwise retards the timing.

http://forums.corvetteforum.com/show....php?t=1403802
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Old Jun 28, 2007 | 05:51 PM
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You turn the distrubutor body opposite of the direction the distributor rotor turns to advance timing. Turn it the same direction to retard. But, if your car has a computer doesn't it adjust the timing back to where it was? I read somewhere that it does.
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Old Jun 28, 2007 | 06:41 PM
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Originally Posted by joe wilson
You turn the distrubutor body opposite of the direction the distributor rotor turns to advance timing. Turn it the same direction to retard. But, if your car has a computer doesn't it adjust the timing back to where it was? I read somewhere that it does.

On the L98's you have to disconnect the EST wire so the computer has no control. The timing is computer controled on the LTx's.
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Old Jun 28, 2007 | 07:04 PM
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Originally Posted by joe wilson
But, if your car has a computer doesn't it adjust the timing back to where it was? I read somewhere that it does.
No! The L98 doesn't have a crank shaft position sensor and therefore the ECM has no clue as to when the plug is firing. The ECM advances and retards the timing based on the input from many of the sensors, but the changes it makes are based on what it is programmed to do, with each of the changes of input. The programming is based on an initial, base timing, of 6° BTDC. When you change the base timing, you are changing the timing for every set of circumstances and for all conditions.

The best way to determine your optimum base timing, is to make 1/4 mile runs with the stock 6° base timing, to establish a baseline of performance. Then, make subsequent runs, advancing the timing by 2° for each new set of runs. Stop advancing the timing when you have reached the highest MPH from the series of runs.

RACE ON!!!
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Old Jun 28, 2007 | 11:21 PM
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SEA4,
You have it correct, turning the dist. counter clock wise will take you from 6, 8 10 and then onto 12. I turn it counter clock wise to open the gap between the SR and the distributor cap, insert the spacer and then turn the distributor clock wise against the spacer. This allows me to adjust the distributor without the car running. If I used a timing light, the car would have to be in drive with an automatic parking brake set and block the wheels and the EST wire disconnected and the timing light out trying to see the timing marks in the California bright sun.

So if you do this in advance of going to the track, it is a quick and easy way to play with the distributor setting.
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Old Jun 28, 2007 | 11:26 PM
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Thanks to all for helping out.. I'll be making several runs tomorrow night and taking notes.. I'm hoping the car will run into the 13's..

(my only real 'performance' mods are the frisbee removal, AIR pump removal and the less restrictive exhaust.. so, we'll see..)
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