Modern Engine Blueprinting Techniques. Mike Mavrigian
accurized. The lifter bores should be oversized using the theoretical (correct) bore centerline to correct any centerline off-center and/or lifter bore off-angles. The lifter bores must be in the correct plane to the camshaft. OEM lifter bores are usually held to within .010 inch or so of plane, but this can be corrected by realigning, using specialty fixtures or on a CNC machine. The bores are then fitted with bronze bushings and honed to size to achieve the oil clearance needed for the lifters.
Also pay attention to the lifter bore finish. If the block was shot peened, the lifter bores may have been peened-over. The resulting “dimples” reduce oil clearance. Honing the bores with a rigid hone allows you to control material removal. A brush-type hone skips over the dimples and doesn’t solve the issue.
As with the main bore, the crankshaft bores must be accurately aligned to prevent camshaft bind and isolated camshaft bearing wear. Another aspect relates to crank-to-cam bore centerline distance and parallelism. Quality aftermarket performance blocks are CNC machined to accurately locate both centerlines, but OEM blocks may often have centerlines that are a bit off, or have a slight non-parallelism between the main bore tunnel and the cam bore tunnel. This aspect relates to the blueprinting/accurizing concern.
Lifter bore correction and/or reconditioning involves overboring the lifter bores using a precision reamer, followed by installing bronze sleeves that are then honed to size. For blueprinting purposes, the overboring is best accomplished by using a specialty lifter-bore accurizing fixture (such as one from BHJ) or by CNC machining. Either approach allows the machinist to correctly place lifter bores at the designed on-center axis and correct for any factory deviations in lifter bore angle.
Before installing bronze lifter bore inserts, oil feed holes must be drilled into the inserts (inserts are also available predrilled). Depending on the type of block involved, it is common to use a smaller oil feed hole to improve oil delivery to the main bearings. The example seen here is a Pontiac 455, where the excessively large lifter bore oil feed holes are reduced to about .040 inch.
If a cam tunnel centerline is incorrect, or if the cam bore locations are not aligned, it can be corrected by centerline align-honing the cam tunnel in relation to the main bore. Since (in an overhead-valve engine design) there are no camshaft caps to shorten in order to recreate the original bore diameter, the cam bores can be bored or honed oversize, requiring oversize-OD cam bearings (thicker shells to accommodate the original cam-journal diameter).
Your engine must provide a strong and steady supply of oil to all critical components. In essence the engine must deliver the correct volume of oil under a certain pressure to reach all the critical components during operation. If this does not happen, the engine experiences oil starvation and this obviously degrades performance. The engine’s vital components are also damaged, and this could lead to outright engine failure. In this chapter, I cover specific considerations for retaining and optimizing a stock-type wet sump oiling system and also the benefits of upgrading to a dry sump oiling system.
A “wet sump” system supplies pressurized oil to the engine’s rotating and reciprocating assemblies. Engine oil is stored in the big reservoir section of the oil pan. A mechanically driven oil pump picks up the oil, which obtains the sump’s oil via a submerged oil pickup. Depending on engine design, an intermediate shaft connecting the distributor shaft to the oil pump may drive the wet sump oil pump, or the crankshaft snout may drive a crank-mounted gerotor-style oil pump.
High-performance engines often benefit from a large-capacity custom oil pan. This oversize pan is installed on a Dart Big-M block fitted with a 4.750-inch stroker crank.
GM LS engines, as one example, have a crank-driven pump. Pressurized oil is distributed from this main source throughout the engine through the oil passages in the block, crank journals, main bearings, rod bearings, and eventually to the valvetrain. This system delivers oil to all required areas. In addition, the oil must be pushed through all of these passages to eventually route to the upper end of the engine. The oil is then free to drain back to the sump, with delivery and drainback serving as an ongoing cycle during engine operation.
In a wet sump design, the pump’s “pickup” is immersed in oil at all times and has a filtering screen. Depending on pump, engine, and oil pan design, the pickup has a short or long pickup tube that connects the pump to the pickup. If the oil pump is located directly over or very close to the oil pan’s sump, the tube length is short. If the pump is located at one end of the block but the sump is located at the opposite end, a longer tube is needed to locate the pickup deep inside the sump.
In-pan or wet sump oil pumps include (or require separately) a pickup assembly designed to be submerged in the sump reservoir. The distributor drives the pump, which is driven at half of crankshaft speed. In some cases, such as the old flathead Ford, the pump is driven by gears that engage with the camshaft gear.
Front-mounted crankshaft-driven oil pumps are commonly used on engines with distributorless ignition, and are driven at crank speed.
When fitting the pickup to the pump, test fit to make sure that the pickup is located close to the floor of the pan sump. Clearance should be approximately 5/16 inch or so between the pickup and sump floor. If the oil pump design has a press-fit pickup tube, press the tube into the pump using a pickup tube installer tool. This has a crescent-shaped head that allows you to capture the tube’s swedged end. With the pump mounted to the block, use this tool and a clean hammer to install the tube to the pump. Measure the distance from the oil pan rail to the sump floor. Then adjust the clock position of the tube at the pump to place the bottom of the pickup close to the pan’s sump floor. It measures from the block’s pan rail to the bottom of the pickup. With the pickup adjusted, use a marker to