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3200cc/3187ccNeither Bob Sutcliffe or Garth Wilson can figure out why the author calls this a 3200cc (or 3187cc) engine. The displacement with 94 mm cylinders is 3105cc (189.75 CID). There must have been a communication breakdown somewhere... CreditsMr. Sommer didn't give complete contact information for the two vendors featured in the article. They are: Bob Sutcliffe Garth Wilson Sand dune usageKeep in mind that this article is aimed at people building VW-based sand dune vehicles. They need to reverse the rotation of the Corvair engine. They also are focused on an off-road, very high-performance application. "Streetability" is not a concern. You can read more about this genre at the Hot VWs web site. Rod journal holesBob Sutcliffe does not recommend welding the holes and redrilling them for reverse rotation (e.g., sand dune) applications. He does recommend chamfering the existing holes, however. He does this on all of the big-bore engines he builds, mainly due to the severe service they often see in dune buggies and race applications. John Barnes (Seattle machinist who built my engine with Linn Richardson) has never done this and doesn't see the need (expense) for a street engine. Woodruff keysNot to be too picky, but only one key is used, not "a set". Bob Sutcliffe does recommend doweling the hub in place, as shown in the photo. (He built a jig to facilitate the procedure.) John agrees that the dowels are a good idea--he just hasn't tried it yet. Flywheel bolt holesMr. Sommer appears to be in error here. Both Bob and John say that 7/16" is too big for these holes. John leaves them the stock size (11/32") while Bob sometimes bores them out to 3/8". Wrist pinsBob uses stock-sized full-floating VW wrist pins (±22 mm / .866"). John has not tried this yet--he has been using Corvair wrist pins. Bob's approach requires boring out the rod a bit but potentially gives better performance. Cylinder comparisonYou may wonder what the heck type of cylinder is shown on the right side of the comparison photo--it definitely doesn't look like a stock Corvair component. It's a Corvair cylinder with a "power sleeve". A power sleeve is a "straight jacket" put on the cylinder to hold it together in very high-HP applications (e.g., turbocharged sand dune engines with nitrous oxide). Rod comparisonWe had a difficult time seeing any difference in the two rods shown. The one on the left may have had a small amount of material removed from the crank end, which is necessary to do to clear the piston skirt on the opposite side. Order of assemblyJohn pointed out that you can't hang the rods on the crank unless you're using full-floating wrist pins. Piston skirt notchNeither Bob or John recommends grinding this notch on a grinder as shown in the photo--it's too hard to get a straight edge. They both use a mill. Exhaust tubesIt is not mandatory to increase the exhaust tube diameter in a street engine. My Stage I engine had stock exhaust tubes and good performance. Changing the tubes means you won't be able to run stock exhaust manifolds. Rod cap clearanceSimilar to the piston skirts, neither Bob or John recommends using a grinder for this operation. Bob uses a mill; John uses a flat carbide file. Case studsWhile certainly nice to do, case studs are not required for a street engine and may be overkill. Most street engines do not see the kind of torque that can pull a case apart. |
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