Crankshaft journal and bearing adjustments
For the most part, all of the bearings looked great when we disassembled the supercharged stroker motor. There were some discolorations in the bearings, but nothing looked out of place. That's why it was a bit of a surprise when Federico (RD Sport) pulled me aside and told me Carrillo wanted to redesign the connecting rods.
After I gave RD Sport permission to redesign the rods, I left Van Dyne Engineering and went directly back to Auto Talent. I wanted to take a much closer look at the bearings and take as many pictures as possible of every connecting rod and every bearing from every possible angle. I was able to immediately see the excessive bearing wear at the joints, just as Federico had told me. And the more I looked at the bearings, the rattier they began to look to me. But I'm not the engine builder, and I have no idea what Van Dyne planned to do about it (if anything).
As you can see below, the good bearings look pretty good, and the others vary from decent to rather ratty looking. Here's a sample of the bearing pictures. The complete set of all bearing pictures can be found here, starting at the bottom of page-2
. If you click on the photos, they will expand to a full screen to get a closer look. The photos actually look much worse than the bearings look in real life. In real life, there's really nothing more than a few discolored spots on the bearings. I think the lighting has amplified the discolorations and makes it look much worse than it actually is. But the lighting also makes it real easy to see what I'm talking about.
Good bearing photos:
Ratty bearing photos:
Measuring the journals
Since BMW doesn't publish their bearing journal clearances, we measured a few crankshafts and connecting rods to figure out what those factory clearances are. Van Dyne doesn't use platigauge to measure the clearances, they measure it much more accurately and in a more sophisticated manner. Van Dyne pre-assembles and correctly torques the main and connecting rod caps. Using an expanding micrometer that can measure inside diameters of a circle, Van Dyne measures the assembled bearing size. Then using a micrometer on the crankshaft main and rod journals, those measurements are subtracted from the bearing size to calculate the bearing clearance. If Van Dyne doesn't like the clearance they measure, they will recommend to change it.
Many people might have read that and thought BMW knows best and you shouldn't make any such adjustments. But BMW doesn't publish these specs and doesn't offer any different rod bearing sizes to allow you to make adjustments. This means BMW literally has a one-size-fits-all mentality to connecting rod bearings -- even though main bearings come in three different sizes. Van Dyne isn't the type of shop that simply slaps the motor together with the parts available. Van Dyne has a very long and prestigous racing pedigree (see side-bar below). As I mentioned earlier, if they don't like the measurements, they will want to make adjustments.
For weeks we had been getting ready to assemble the bottom end. All of the parts were at Van Dyne and ready to assemble. The only remaining job was to meaure the bearings and journals. Now that everybody's schedule was in sync, Van Dyne made the measurements and wasn't satisfied. 48 hours before we were supposed to assemble the bottom end, everything came to a screeching halt. Van Dyne wasn't satisfied with the clearances and believed they were too tight; they wanted to make some adjustments. Van Dyne recommended to resize the main and rod journals to obtain the exact clearance they wanted. Using an exact journal-by-journal measurement, Van Dyne sent the crankshaft down to the machine shop for resizing, re-treating, and re-balancing. Resizing the journals cost us another two week delay. Hopefully it would be our last!
Unfortunately I don't have any pictures of the measurement process. But I do have pictures assembling the rest of the bottom end after the adjustments were made. The following pictures are just a few of the many pictures I took. To see all of the photos, please view this photo album
Who is Van Dyne Engineering?
Stewart Van Dyne was the principle engine builder for Drake Engineering (formerly Meyer/Drake Engineering). Stewart and I worked together at Drake Engineering in the early 1980's. Stewart built Mark Donahue's Indy-500 winning motor, along with motors that have won endurance races in Lemans and Sebring. Stewart's winning race motors are far too numerous to list. Drake Engineering was no lightweight racing shop. The Drake "Offy" won the Indy-500 twenty-six times of which seventeen of those wins were consecutive. During my tenure at Drake, I witnessed our engine designer, in conjunction with Stewart design and build prototype motors motors for Chrysler, Buick, Mc Laren, and Carol Shelby. When I left Drake Engineering, they were in the process of designing a five-valve OHC cylinder head for a small block Chevy. When John Drake retired, Stewart Van Dyne bought all of his engine molds and patents, thus ensuring the ability to remanufacture any of the historic Drake racing engines and other Drake racing engine parts.