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Priority Oiling Main System - Ask Anything

The Mains Are The Priority: Priority Oiling
Mike O'Brien; via I was looking at an old issue of Car Craft and reading Jeff Smith's reply to a fellow on the LS oiling system. In the accompanying diagram, the oil system appears to furnish oil first to the valvetrain. Is there a way to make this a priority main system?

Jeff Smith: The short answer to your question, Mike, is yes, but not by modifying the existing block. It would be far too difficult and costly to convert the priority oiling of a production block over to priority main. If main bearing lubrication is a concern, the easiest solution is to purchase an aftermarket block. But before we get into that, it's worth noting that the original small-block Chevy and now the LS engine both use a similar system and neither really has a main bearing lubrication problem, even at elevated horsepower levels. For example, we ran a Horsepower! feature on a turbocharged LS engine that routinely makes more than 2,000 hp using an ERL-modified aluminum production block. Even with that kind of cylinder pressure pushing down on the main journals, the engine is happy and has no lubrication issues.

However, if priority main-style lubrication priority oiling is a necessity, you do have a couple of options. Among the iron block avenues would be the GM Performance Parts LSX Bow Tie block. This fully CNC-machined casting features much thicker cylinder walls that can accommodate up to a 4.200-inch bore, which is useful for increased airflow. The block is also machined for six head bolts per cylinder as opposed to the standard four along with a host of other features. Perhaps its biggest drawback is the weight penalty of additional iron that tags the LSX at 225 pounds, which is 20 pounds more than a production iron block (205 pounds) and roughly 125 pounds more than a production aluminum casting (100 pounds). The LSX standard deck height block is PN 19213964 and goes for $2,185.95 from Scoggin-Dickey.

RHS now offers a relatively new aluminum aftermarket LS block that is also a priority oiling main design. The RHS block is available with most of the features you would expect from a well-designed casting like this. A standard deck height block, bored and finished honed to a 4.165-inch size is PN 54902, and we found it on Summit's website at $4,615.95. Certainly, this is not cheap, but you also have, with a 4.165-inch bore and a conservative 4.00-inch stroke, a 436ci inch monster that normally aspirated has the potential to make more than 700 hp with a carburetor or fuel injection. Because airflow potential is so fantastic with the LS-series engines, you can make this power without a radical camshaft, making this engine completely streetable. Plus, you're looking at an all-aluminum block that only weighs 110 to 120 pounds (depending on configuration) and 100 pounds less than a production iron block.

More Info
GM Performance Parts

Warren, MI

Racing Head Service
Memphis, TN

Scoggin-Dickey Parts Center
Lubbock, TX

Solution For LT1 Ignition Woes
Charles Nel; George, AK: I am planning on fitting an LT1 and a six-speed to a mini-truck and gradually hot-rod it as the money allows. I see on some Internet sites that the Opti-Spark is considered unreliable. Is it possible to replace it with a "normal" distributor, and how would one go about this? Or are the sites wrong, in your valued opinion?

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