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Priority Oiling Main System - Ask Anything

Jeff Smith: The LT1 engine is considered the Gen II small-block Chevy with quite a few differences between it and its older Gen I cousin. The most significant difference is the Opti-Spark ignition system. While this ignition is much maligned, there are several ways to address its shortcomings. GM engineers relocated the distributor from the back of the engine to underneath the water pump to drive it directly off the front of the camshaft. It appears that crossfiring and misfires are the most common problem and are attributed to moisture trapped inside the distributor housing. There were actually two versions of the Opti-Spark, with the early '92 to '94 version having the most difficulties. This is partly due to the lack of ventilation that allowed moisture to collect inside the cap area and also that the system wasn't sealed properly with an electrical connection located on the top that allowed dirt, oil, and moisture to enter the cap area. The optical sensor system used to trigger the ignition is actually quite accurate, with a 360-tooth wheel that doesn't suffer from issues such as cam walk and the tolerance stack-up that results from driving a rear-mounted distributor. One of the Opti-Spark's biggest problems is access, as the cap and rotor are buried behind the water pump, requiring removal of the pump and a portion of the front accessory drive. In essence, most of the problems associated with the Opti-Spark system can be traced back to the presence of high-voltage arcing within the distributor body. So it would stand to reason that any upgrade that would remove the high voltage would dramatically increase ignition system durability.

We priced a stock replacement cap and rotor for a '94 LT1 at Rock Auto and were surprised to find the least expensive kit was $189.00; a second kit from a different manufacturer was $257.00. Then we priced an MSD replacement cap-and-rotor kit from Summit Racing and discovered that both the early design ('93 to '94, PN 8481) and the later model ('94 to '97, PN 84811) were priced at $144.95. Not only are the MSD caps better, but they're less expensive, too. MSD also makes a complete Pro Billet replacement distributor (early PN 8381 and late 83811-both at under $500.00, Summit Racing). While pricey, this distributor offers a billet aluminum body, improvements on the optical encoder, and a different optical pickup compared with OE models. Perhaps its best feature is its ability to manually adjust ignition timing plus or minus 6 degrees with a small adjustment screw on the distributor. There is also another company, Dynaspark, building a replacement distributor that costs $599.00.

Rather than convert to a rear-mounted distributor, which would require a different intake manifold, we've been investigating a far more creative way to eliminate the LT1's Achilles heel. There are a couple of companies that have taken innovative approaches to converting to a distributorless ignition system (DIS). The first from Bailey Engineering retains the original LT1 distributor and optical sensor. This sends a mere trigger signal to a microprocessor and wiring harness setup. The system connects to a set of LS coil packs that you adapt either to the valve covers, like an LS1 or relocate to a remote location and run slightly longer plug wires. The Bailey LTC-1 sells for $399.00 and includes both a rev limiter and an adjustable timing retard. While the system does not employ a cam sensor, the 720-degree system (a 360-tooth wheel turning at half engine speed) can extrapolate proper engine position so that all eight individual coils fire sequentially, just like on a stock LS1 ignition.

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