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Our pistons came with JE's straight wall pins and ring set. For moderate boost, we prefer a straight wall piston pin. It is less likely to bow and grab the rod small end bushing and spin it like a super light taper wall tool steel pin. We might use such a pin in a high revving NA motor. On a high boost turbo motor, we would prefer a thick wall piston pin for the high loads imposed by a lot of cylinder pressure. JE's rings are narrow with low tension to reduce friction. The top compression ring is chrome plated for long wear while the second compression ring is ductile iron with a scraping Napier profile. Napier rings are good for reducing oil consumption and rapidly breaking in to give a good seal. The oil ring is narrow with low tension for friction reduction and has two scrapers with a separator rail.
For rods, we didn't have much choice because not too many people make the oddball rod that the FA20 requires. Fortunately, Brian Crower is one of these companies. To get access to tighten or loosen the rod bolts in the tight confines of the boxer engine, the rod must have an odd offset cap like you can see in these photos.Brian Crower or BC makes the FA20 rod in both H beam and I beam configuration. Both styles have identical power handling capabilities and weights so we choose the I-beam parts just because we usually run BC's H-beams! We opted for the standard rod instead of the extra heavy duty Extreme rod. Not to worry though, the standard rods are rated for 200 hp per cylinder which is more than enough for our application!
The BC rods are made of vacuum degassed 4340 steel from blank near net shape forgings. This gives proper grain alignment, especially around the cap for great strength and fatigue resistance. 4340 is a high nickel and manganese steel alloy that is exceptionally tough and ductile. These properties are great for handling the cyclic impact loads that connecting rods are subjected to. BC standard rods use high-quality ARP 2000 bolts which have a yield strength of 220,000 psi. This is plenty for what we want to do. BC's Extreme rod have ARP 625+ custom age steel bolts which are even stronger at 285,000 psi! We figured that this was overkill for our application.
The BC rods are shotpeened which results in a layer of compressive stress on the surface of the part and leaves tough fine-grained forged like skin that is about 0.005″ deep. It is very hard for cracks to start in this layer. Shotpeening can thus increase the fatigue strength of a part by at least 100%.The small end of the rod has an aluminum-silicon-bronze bushing with an oil retention groove in the middle. The bushings are machined from one piece bronze billets and are available separately as a service part.
We reused the stock crank, we just balanced it, checked it for straightness and polished the journals.
The stock crank has extensive chamfering at the oil holes which is a nice touch. Normally, we have to do this ourselves. The stock crank is plenty strong, machined from a forging, having decent journal overlap and rolled fillets. It can hold the power we want to make and more.
