Tampa Racing - Tech: Honda Tuner Engine Balancing

When I first found this article, before I read it, I thought it would be a lame article about some fag who runs all motor and almost into the 9's or something gay like that... however, after reading a few lines I realized this was a pretty damned interesting article and goes into pretty good detail on how to balance an engine.... Some assembly required. ;)

The Straight Story Pt.3
Honda Tuning demystifies the effort and expense that go into creating a competitive all-motor drag car by building our own CRX racer.

By Bob Hernandez
Photography: Bob Hernandez

In this third part of a continuing piece, Editor Bob takes notes as all-motor guru Erick Aguilar blueprints and balances the internals of our GS-R powerplant.

[1] Our B18C1, fresh from a Golden Eagle sleeve job and ready to be built - or so we thought. Shortly after we deliver the engine to Erick's Racing, Aguilar schools us on the intricacies of building a near zero-tolerance engine and points out some flaws in our progress.
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We're big boys. We can take a little constructive criticism, especially from a guy on the verge of a 9-second, naturally aspirated run. Aguilar begins by setting our engine up for blueprinting, a process that involves hand-finishing engine parts to their most ideal specs within production tolerances. Aguilar will also balance statically and dynamically every engine part that rotates and reciprocates. Both blueprinting and balancing seek to reduce friction, wear and vibration, and increase horsepower and reliability.

[2-3] Aguilar starts off by checking piston-to-wall clearances. P-to-W clearances are typically included on the piston spec sheet and usually range between 0.003 and 0.005 of an inch. Before he begins, he sets the bore gauge to match the piston diameter. He does this by measuring one of the JE pistons with a micrometer and transferring that length to the bore gauge, thus establishing a zero point.
[3]
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[4] Using the zeroed-out bore gauge, Aguilar measures each individual cylinder at several different points. Turns out a couple of our cylinders were slightly oval by a couple thousandths of an inch.

May not seem like a lot, but Aguilar likes to keep his P-to-W tolerances within 0.002 of spec. "The cylinder wall is all one sleeve," he says. "The straighter it is, the closer it is to spec and the better the engine is going to perform."

Before continuing, Aguilar sent the block to one of his contacts to get it dialed in to his specs. Note that forced induction motors tend to have looser tolerances because they generate more heat. With more heat comes greater expansion, thereby needing more play.

[5] Next, Aguilar measures deck height variations with a deck bridge. The sleeves in our block stick out about 0.002, which we expected because of Golden Eagle's step-deck process. This works fine for our application.

[6-7] Aguilar balances the Eagle conrods, JE pistons and wrist pins next. First, he weighs each individual component on a postal scale to determine which is lightest of the bunch. This becomes the point of reference. The part is then moved to the balancing scale and measured against a set of counterweights equal to the point of reference. This gives Aguilar an idea in grams how much over the component weighs.

[7]

[8-9] Both the big and small ends of the conrods should be measured, and Aguilar labels each one with the amount over that it is. Two of our rods were dead on, but the big ends from the other two were about a gram over, so Aguilar took them to the bench grinder to remove some material.

[9]

[10] Before balancing the pistons, Aguilar notices a bunch of sharp edges on the piston crowns and decides to round them off with a burr and cartridge roll. He says these sharp edges could easily create hot spots and cause detonation in the cylinder.

[11] Aguilar sets the slugs back on the scale and a couple of them still need some weight shaving. Grinding out material from the inner surfaces of the piston should do the trick.

[12-13] Before balancing the crankshaft, Aguilar gets micrometer measurements of the rod journals and main journals and records each one in a notebook.

[13]

[14] The main journal dimensions are for main bearing clearances, but we'll hold off on checking those until we install the main caps during the actual engine assembly. For now, Aguilar inspects rod-to-crankshaft clearances by taking the rod journal numbers, comparing them to bore gauge readings from the rods' big ends, and seeing if the difference falls within Honda spec. They do.

[15-16] Balancing the crankshaft requires that it spin on a horizontal cradle balancer, a machine that measures static and dynamic balance (sort of like the way tires are spun during a wheel-balancing). When the crank is spun, the amount of "unbalance" registered on the machine's meter indicates how much adjustment the crank requires. A strobe light helps identify from what areas we'll need to remove weight.

[16]

[17-18] Aguilar determines the crank is 8 grams off, so he removes material from the hardened counterweights by drilling into them. That's it for the rotating assembly. From here, all of the balanced goods get one more washing before installation.

[18]

[19] Upon its return from Aguilar's re-bore and honing, the block receives a thorough cleaning from Aguilar's assistant Oscar Castillo. Castillo sprays brake cleaner into every water jacket and oil gallery, forcing out all the gunk with compressed air.

[20] Before Aguilar sends the block back to the parts washer for one final cleansing, he runs sandpaper over the deck to eliminate any high spots and edges.

Source: http://www.hondatuningmagazine.com/t..._part3stright/