Dart B-series Engine Block Build - Pound For Pound

Last month we proposed building a 150 horsepower-per-liter B-series normally aspirated engine that had to run on pump gas and propel a full-dress Honda chassis, including a kid seat or two. There are no restrictions on engine size or parts, but because it must use pump gas and be a true daily driver, the build will not be as easy as a drunk sorority pledge during Rush week (regrettably our gas is only 91 octane, unlike most of the country, which gets 93). It also needs to be an engine that will last many thousands of miles, not just a winter. All these things make the job a challenge.

We chose a Dart B20-style block for the project. It boasts an 84.5mm bore, the tall deck option for longer rods, a Crower 92mm stroker crank pushing and pulling custom Crower rods, a GSR head and lots of Endyn components, like pistons, cams, valvetrain, and intake manifold. The combo yields 2.06 liters or 126 cubes. Take out your calculator and you get a target horsepower of 309. That's pretty damn high for a normally aspirated engine, but we are talking about crank horsepower, not wheel horsepower. We'll use an engine dyno for putting this engine to its final test.

Like last time, the owner of Endyn, Larry Widmer, is going to tell the story. Larry is a genuine Texas character and has worked for the likes of Ford, Toyota, Roger Penske, General Dynamics, and MSD. His engines have won an Indy 500, a NASCAR title, and multiple Pro Stock titles. Herewith is how Endyn assembles a short block in detail, with some of Widmer's best secrets. Next time we'll uncover Larry's true specialty, the head.

Honda Tuning: Ok, we got the Dart block for its rigidity. You said it's strong and really supports the crank and mains at high RPMs in a way a stock block can't. It also overcomes the shortcomings associated with sleeving a stock block. What's next? Is it ready for assembly of out the box?
Larry Widmer: We can start at the top. The water passages in the block aren't exactly where we'd like them to be relative to the headgasket and the head. It's very important that we get efficient cooling in an engine, especially one that's running on marginal fuel. We weld certain areas and then open them so the passages align perfectly. Also, in two of the oil drain-back areas, we add some aluminum to the deck because it's just a little short. If we didn't, there might be oil seepage. It basically extends the surface to get a perfect gasket seal.

HT: You mean the edges are too short? Are Honda blocks the same way?
LW: No, Honda blocks have enough material there, but the Darts need just a bit more so there's no chance of seepage.

HT: The top side is ready-what now?
LW: Honda blocks are die cast, whereas Dart blocks are sand-cast. Look at a Honda block and you'll notice how smooth it is relative to an aftermarket version. Internally and externally the Dart block is much rougher, which is why we spend about a half-day going through it to get rid of the coarseness and porosity. This helps oil drain back to the pan faster. We also open up all those passages and polish them for even greater efficiency. Honda heads need lots of oil to ensure valvetrain longevity, so we want to get the oil back to the pan fast to get it circulating.

HT: You also modify the oil pump for greater flow.
LW: Right, but we start with the Dart's main oil passage. As delivered from Dart, the passage isn't large enough for use with our modified pump, so we drill it out so that it kind of acts as an oil "plenum." This lets us put a whole lot more oil on that side of the block. We also clean, smooth, and radius the little passages that feed the main bearings. We want to make sure there are no small edges to interfere with oil flow, or any little bits of metal that could break off and cause a problem.

HT: So the Dart block is a good foundation, but needs some prep.
LW: They do a rough machine on the deck, align bore, and align hone the bottom, but that's about it. [Endyn] blueprints an engine of this performance level. Everything has to be to a precise spec so that we can use all Honda bearings. I can't emphasize enough the importance of using Honda bearings and its system. If you use an aftermarket bearing, it's a one bearing size fits all. Bearing fitment is one reason Honda engines are as dependable as they are, especially when you're going to increase power.

HT: Aren't Honda bearings so awesome that NASCAR teams use them?
LW: NASCAR engine builders have cranks made that can accept standard Honda bearing diameters. Because there are so many different sizes of bearings, the engine builder can have exactly the same clearance on every journal. That's exactly what we're going to do here.

For whatever reason, the Dart...        read full caption For whatever reason, the Dart block is a little short on the front side. To assure a complete seal, Endyn adds some aluminum. The water ports don't match exactly to the head gasket, so these are also welded and slightly modified for a perfect fit.	Once the block is decked to...        read full caption Once the block is decked to make it perfectly flat and set piston height, all the added material is gone and a perfect gasket seal is assured.	As cast, the water pump housing...        read full caption As cast, the water pump housing is fairly small and very rough.
Here's what Endyn does to...        read full caption Here's what Endyn does to it. Things are much smoother and the inlet to the right is vastly opened up.	This is an ITR oil pump. A...        read full caption This is an ITR oil pump. A GSR or Si will work fine, too. Endyn believes since about 2000 they were standardized. Endyn doesn't change the gears but they do open up the inlet on the block considerably and set the pump case to minimum spec. That means less oil gets past the gears, which gets you more pressure and volume. They also use their own spec bypass spring.	A great deal of work also...        read full caption A great deal of work also goes into cleaning up the bottom end as well. Because the sand casting process leaves things very rough, there are a lot of rough surfaces and casting flash that can trap or impede the flow of oil.
The arrows show a chamfer...        read full caption The arrows show a chamfer that is added to all the oil passages so that oil flow is not interrupted by a hard intersect as originally cast and machined. The upper arrow is an oil return and the lower feeds the bearings.	According to Endyn, forged...        read full caption According to Endyn, forged pistons can take a great deal more heat than OEM cast pistons, and since this is a street engine the oil squirters just "get oil everywhere," so they are capped off. Genuine Honda bearings are put in along with lube and it's time for the Crower crank.	These are both Crower rods,...        read full caption These are both Crower rods, but one is a stock LS length and the other is our custom extended length rod. Because we chose the tall block option we can put in a longer rod, which gives us a better rod ratio and less piston speed, friction, and side loading.