Throwing a 95mm stroke Eagle crank into the mix is as simple as grabbing one from stock and fitting it with some .137” (longer-than-stock) Eagle rods and a set of our pistons with the pin raised .250”. It’s terribly tempting, but we’ve yet to see a B series engine make as much power as one of our two liters. Granted, they will handily belt out 180+ ftlbs of torque…..and at reasonably low rpm too, but the LR ratio is close to awful at 1.47-1 and I figure that the combination will wear itself out just as quickly as spinning a two liter two thousand RPM higher for grunt. But damn, that torque is tempting.

The combination that we’re going with is pretty well set now. The block is the poorest of five used CRV blocks that we have left here. Frankly, this one’s a mess. It was originally bored and honed by a local machine shop here in Ft. Worth that “specializes” in import engine machining. Their machine work was an abomination, with the cylinder bores as much as .0016” out of round, with lots of taper to the cylinders from top to bottom. Clearances for the experimental strutted pistons the block was originally sized for range from .0012” to .0029”, which is simply unacceptable by any standards in this day and time. This block also suffered the ill effects of an acid bath (busted battery) in the CRV’s wreck that liberated the engine. I spent about three hours six or seven months ago with all sorts of solutions to neutralize the acid and finally cartridge rolls and a grinder in an attempt to stop the acid’s attack of the block’s exterior.

Now it’s just got a strange look to it, as it’s fairly shiny in places, but it’s heavily pitted everywhere. Even with all the block’s problems, I’m looking to turn this turd into a rose by the time all’s finished

In inspecting the block for structural integrity, the first thing I look for on a B20 is the quality if the aluminum casting that surrounds the 4-in-1 cylinder sleeves. Viewing the block’s deck, there should be no areas where the aluminum wasn’t absolutely flush with the bore casting, especially in the fillets between the adjoining cylinders. All B20 blocks are not created equally in this important area, and if the block isn’t “perfect”, broken cylinders are a certainty.

The cylinder casting that Honda uses in these B20’s is extremely brittle when compared to more resilient “round” individual bore liners. This is simply the nature of a casting such as this where sectional thickness varies so significantly. These cylinders are easily cracked if there’s just a hint of detonation and all it takes to break one of the blocks with the small casting flaws is about 220 HP, so they can certainly be a liability.

The second thing I look for in a block are main bores that are straight and true. I always spin the crank in the blocks when I disassemble a shortblock. If the crank isn’t “free”, the block’s got a problem.

Inspect the main bearings that come from the block as well. Abnormal bearing wear is also a clue that the mains aren’t as straight as we’d like to see.

This particular block has excellent casting integrity around the cylinder casting and the mains are in good shape, so we’ll set it aside for the time being.

I’ve made up my mind that the stroke I’ll use is 89.0mm, so a B18 / B20 crankshaft will be the pick. Once again, I have several cranks here to choose from, but I’ll pick one based on it’s main journal diameters, so overall main bearing thickness will be in the middle of the color chart after the block’s fully machined and ready to assemble.

Since as noted above, these blocks are a bit on the fragile side, I’ll use the old NASCAR trick of “posting” to improve its survival rate. BTW, as a point of interest, there are all sorts of clowns in the import industry claiming to have invented “posting”, but if they weren’t old enough to be building engines in the late 60’s, they’re liars because “posting” had it origins with attempts to strengthen Ford blocks and heads back then. Hell, after looking at some of the hand-built race blocks from the first half of the 20th century, “posting” probably began much earlier than that.

The posting process involves machining and tapping holes in the thrust sides of the block and torquing in threaded aluminum “posts” that physically “connect” the outer part of the cylinder with the outside (peripheral) walls of the block. With these “posts” installed, if the cylinder walls are going to move, they have to move the outside walls of the block too, so they add a tremendous amount of strength, making the block capable of withstanding a lot of abuse. This modification also has no ill effect on cylinder cooling, which is something I’m big on these days.

Since the block is going to run some old 84.5mm development pistons that are unfit for anything except conversation pieces, the next step is to size the cylinders.

The boring and honing process is one that should be accomplished by someone who does little other than cylinder wall preparation. Good boring and honing is an art form / science, and while good equipment is essential, a machinist who has a lifetime of experience (and who charges by the hour rather than having a set price for the operation) is the only way to go, as the right clearances and a good ring seal are all-important to making power. If the rings don’t seal, all the other modifications in the world won’t do you any good, as the power will go right past them.

We bore and hone the block to the same specs we provide our piston customers. All boring and honing operations are referenced from then main bearing bores of the block, so the cylinders will be absolutely perpendicular to the crankshaft. We don’t ever use the engine’s deck surface as a reference point.

The honing process must be performed using Sunnen equipment, such as a CK-10 (or newer) automatic honing machine. BTW, the “automatic” part is a joke, as it still takes a machinist with lots of experience to do it “right”. Right in this case would normally be a clearance of exactly .0028” (to the tenth), with no more than .0001” taper, or out-of-roundness. Our honing expert (who does cylinder wall preparation of winning domestic Pro Stock engines) is also giving the cylinder walls “teeth”, for an even greater effective ring seal. These “teeth” cause the bores to be smooth when you run a finger down the bore, but extremely “rough” when you pull the finger “up” the bore. This texturing is just one of the many “tricks” necessary when competing in a class where all 16 qualifiers are within .02 second on elapsed time! Loose effective ring seal on one of these 500 cubic inch normally aspirated gas-burning engines and you’ll lose a hundred horsepower!

It takes 3 hours of “finesse” time to hone our awful cylinders and before we’re able to get the bores straight and true, we’re looking at .0039” piston to wall clearance….which is “real loose”. We will shrink that clearance to the more desired dimension, however, with some very creative work on the pistons, as you’ll see later on.