Project Low-Buck SR20DE, Part 2

In our last edition of Project Low-Buck SR20DE, we stated our goals of obtaining a decent amount of naturally aspirated horsepower and good track day driveable reliability from an underdog plain jane SR20DE-without breaking the bank. Fulfilling these goals would also create an engine with excellent street driving characteristics. Our engine work will be done on the cheap with a tight budget in mind, but with plenty of attention to minor details that can really help an engine live under the stress of track day pounding-perhaps the most abusive environment that a grassroots enthusiast will subject his engine. Unlike drag racing, a car driven on a road course is pounded to the redline for 20 to 40 minutes at a time. This requires attention to detail for the engine to survive. In our first installment we selected Eagle Rods and SR16VE pistons for our build. We modified the pistons for more piston-to-valve clearance, applied optional thermo barrier, and antiwear and antifriction skirt coating. For the budget-minded drag racers or for pure street use, the stock rods will also work pretty well, being rock-solid safe up to 8,000 rpm. To save a few bucks and still obtain respectable results, you can live without the coatings and piston machining.

Since we're retaining the standard bore with the SR16VE pistons, we avoided the expensive task of boring the SR block oversize. The SR20 block suffers from severe bore distortion when the head and transmission are bolted in place. The bore can distort as much as 0.0015 inch, an amount that can really affect ring seal or even contribute to piston scuffing. It's important to use a deck torque plate and bolt a transmission bellhousing to an SR block when it's being bored and honed to keep the bore's roundness accurate. Not too many shops in this country can do this sort of work on an SR, and packing and shipping your block to places like Jim Wolf Technology in California or Mazworks in Florida can be very expensive.

Fortunately, in most cases a stock SR exhibits very little bore wear, even in 100,000-plus mile motors. In this case our free core engine was pulled from a friend's NASA SE-R Cup car, where it was raced for two seasons. Although the rings were worn, the bore was in excellent shape. We simply used a ball hone to clean the bore up so new rings could sit easily, and we were done. The Swain coating we applied to our piston actual brought our piston-to-wall clearance in on the middle tight side of stock-perfect. Finally, Technosquare then lightly decked the block, removing about 0.003 inch of material to ensure a flat surface for the head gasket. For optimal sealing, Technosquare used very fine cuts to create a smooth surface that would be compatible with an MLS-type head gasket.

SRs are known to be hard on rod bearings. If the engine's oil is constantly monitored and maintained right at the full mark on the dipstick, no more and no less, usually the bearings are trouble free even under hard use. However, later versions of the SR20, like the SR20VE and some turbo SR20DET engines, have improved oiling for the rod bearings. This is done by adding a groove to the main bearing saddle in the block that intercepts the oil feed hole coupled with the use of SR20DET main bearings, which have additional oil feed holes in the upper bearing shell. This assures that the rod bearing feed holes in the crank receive a good supply of oil for a full 180 degrees of crank rotation.

Jim Wolf Technology performs this modification to SR20 blocks that don't have the groove from the factory using a cutoff wheel and a simple guide jig. This could be duplicated with a little skill and patience. This mod isn't absolutely needed and many a fast SR has been built without it, but it's a good detail to help engine life under hard use.