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

Setting Timing on L98

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Old May 22, 2025 | 09:06 AM
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Default Setting Timing on L98

Since I haven’t gotten it to fire up yet, should I disconnect the EST before I try again? Reverifying that I stabbed the dizzy right and the plug wires are correct. If it is out 180°, it will backfire through the intake, correct? Also, can a DUI cap be used on a stock dizzy? Thanks.
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Old May 28, 2025 | 07:54 AM
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I would leave the EST plugged in to ensure you get the L98 running and up to temperature to begin with. This will confirm you have the correct TDC. Then, turn engine off, unhook EST connector by the brake booster and start the car to time the engine. I timed my distributer to 6 degrees then re-connect EST.
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Old May 28, 2025 | 11:05 PM
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Originally Posted by Brandon Iron Smithe
Since I haven’t gotten it to fire up yet, should I disconnect the EST before I try again? Reverifying that I stabbed the dizzy right and the plug wires are correct. If it is out 180°, it will backfire through the intake, correct? Also, can a DUI cap be used on a stock dizzy? Thanks.
Pull the #1 spark plug. Put your finger over the hole while you have someone turn the engine over by hand. Feel for compression as the timing marks come to TDC. If you don't feel compression it means you're on the exhaust stroke. Keep rotating the crank until you're on the compression stroke at TDC. Then remove the distributor cap and verify the rotor is pointing at #1 plug wire position.

If that all checks out, verify that you have spark by grounding a plug to the block and cranking the engine over.

What's a "DUI cap"?
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Old May 29, 2025 | 01:07 AM
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Originally Posted by Brandon Iron Smithe
Since I haven’t gotten it to fire up yet, should I disconnect the EST before I try again? Reverifying that I stabbed the dizzy right and the plug wires are correct. If it is out 180°, it will backfire through the intake, correct? Also, can a DUI cap be used on a stock dizzy? Thanks.
I use a DUI cap and coil, and their fancy red sleeved plug wires in my '89. Good stuff.
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