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Crankshaft Knowledge » Gene Berg Forged Cranks
The following information is the description of how our cranks have been manufactured in the past. The last paragraph pertains to our new stroker cranks which will be available in late 1999.

The ultimate in VW crankshafts. Berg cranks are a true fully forged crankshaft as are the VW factory crankshaft and the Okrassa. All other aftermarket crankshafts are hammered to outside shape without proper grain orientation. Ours are done in the original VW forging dies that we had modified for additional cheek width, stroke length, plus we have added the maximum counterweight which will fit in the case. We increased #2 main bearing size to the 411 bearing diameter, to increase cross section strength and rigidity. This is a simple installation with the use of Berg's special adapter bearing (GB 157 through GB 157C) for a standard case. (See bearing section on using the standard #2 bearing in the #3 location).

All main bearing journals can be made to the 411 diameter for those that are using new aluminum cases bored out to use all 411 bearings. We can even install a 411-flywheel bolt pattern if you so desire when using the crank in the Waterboxer engine. Our forgings allow from 69mm through 92mm stroke. We only stock the most popular strokes which are: 78mm with the VW rod and 82mm through 86mm in Porsche or Capri rod size and journal width. The reason we only make the longer strokes with the Porsche and Capri journal is because it provides a thicker cheek cross section and increases the strength proportionally to the added stroke length.

Shorter and longer strokes are special order. Typical delivery on special orders is approximately 14 to 18 weeks. Special orders require full payment in advance. No exceptions! No refund once the work is started. (See special order section of catalog).

Berg crankshafts are fully forged to journal configuration providing proper grain orientation and are forged from the same chrome alloy steel used in Porsche 911 crankshafts. Forging, heat treat and X-ray are done by the original supplier to VW, Porsche, BMW, etc. in Sweden. Forging the journals close to the size and stroke provides a strength superior to all other VW crankshaft suppliers. Grain flow follows the forged shape. It is also interrupted by this method so each grain line is not carried straight through to the next journal (see photo of all other crank grain structure).

Our commitment is to make every crank as strong as possible. Other VW aftermarket suppliers have hammer forged their cranks without grain flow as the journal is not forged to size which is far cheaper (90% less) to do. When they cut the rod journal, regardless of stroke, it cuts straight through the grain structure under each journal, drastically weakening the part. Even a crankshaft cut from a solid billet suffers from this weakening effect of cutting straight through the grain structure.

Many have reduced the cheek thickness between each journal so it is thinner and weaker than a stock crankshaft, which reduces the rigidity of the crankshaft even more. The longer the stroke the more flex the crankshaft has. This often causes blow-by and wrist pins to come out from side loading the piston and pin every time the piston reaches top or bottom dead center.

Porsche and Capri type Carrillo or Bugpack Porsche size rods do not have an offset. When we make our Berg forged cranks using those types of rods, we move the journal location for proper centering of the rod in the piston. This means that we increase the cheek thickness from journal to journal more than 2mm than that of the stock VW width. The cheek/main bearing structure is strengthened by about 30%. Rod journals are cross-drilled to the proper size to maintain oil flow and pressure for up to 10,500 RPM. Main bearing oil holes have leading grooves (scoops) for maximum oil pressure to the rods.

This is what is called "hydro-dynamic" oiling of the rod journal. It actually increases the pressure at the rod journal. They are not cut out on the backside of the grooves or have a groove around the crankshaft that allows oil to get away from the oil hole that oils the rod journal, and reduces the rod bearing oil pressure

We drill and tap the oil galleries so you can thoroughly clean each one before assembly. You install the furnished set screws with a drop of Loctite to seal the passages. We have seen many drive in aluminum plugs come loose, causing needless rod bearing loss. The bad part is when people fix a burnt journal on a crankshaft with a drive in plug usually it fails almost immediately as the plug still leaks.

After machining, we stress relieve to stop stress cracks caused by machining, grind these stress cracks out leaving the journals 0.015" above size, install the oil holes, re-stress relieve, and finish grind the rod journals with the proper radii. We then set up and grind every surface on the main line in one setting, again with the proper radii. This requires 5 different dial gauges (at a cost of over $1000 each) which provides a perfectly true centerline on the flywheel, pulley, and crank gears in relationship to the main journals. Next, the crankshaft is Nitrided (surface hardened) for maximum life, shot peened, micro-polished, and dynamically balanced.

We precision match dowel your (or one you purchase from us) flywheel with the standard 11/32" offset pattern to the crank, at no extra charge at this time. Again, as mentioned before, this is to assure proper fit from the crank, dowels, and flywheel. (See doweling information). Wedgemated crankshafts include GB 084-O flywheel and are precision balanced. We are confident this is the best crankshaft money can buy for a VW, yet it is competitively priced. Forged in Sweden, made in USA by Gene Berg Ent., Originated by Gene Berg in 1978.

Note: Some of our competitors use Berg cranks in their race cars, even though they may recommend or sell a different type to their customers.

Now that our connection in Sweden has past, we have sought out a new source for crank forgings. We found a forging company in the USA that can do the job. We have redesigned our crank to be stronger than before. We have found that the forging itself was excellent, however, the Nitriding process of the crank created sort of an eggshell effect. The Nitriding was done to help with wear resistance on the journals themselves not necessarily for the strength of the crank. This problem showed itself with the cranks getting a crack in the journal radius and eventually would work itself into the center of the forging.

The first time the crank bent it would crack -- not good. So, after some research we found that by bringing up the core Rockwell and eliminating the nitride we got the best of both worlds; not a soft core with a hard shell covering it, but a harder core with enough hardness to prevent premature wear on the journals. This took some researching to get the right core strength without making the forging brittle, however, the wearability on the journals suffered slightly. Now, after 100,000 miles the journals will probably need regrinding unlike in the past where most of the time it just needed a polish.


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