For the last 20 years or so when I built an engine, I always used good German stock 69mm cranks. I send down to Rimco in Santa Ana those that mic’ed out near std/std, and had them counterweighted and drilled for 8 dowels. The work cost around $200.
In recent months I have found it harder to get good used stock German cranks. I did some research and found many suppliers selling Chinese cranks std/std with glowing reports on the quality of the Chinese cranks. As usual, this was not the way things actually are from the after-market suppliers. These Chinese cranks are just the usual low quality knockoffs. I will not risk using these inferior quality cranks, especially since the engines I build are an investment of upwards of $2500 in parts.
Look at picture #1 and you will see the difference between the Chinese crap crank and the used stock German crank.
This picture clearly shows the chamfer is merely an afterthought. Comparing the chamfer, the German crank has a long tapered chamfer that allows plenty of oil to enter the main oil galley. The Chinese crank barely has any chamfer, and I have seen some that are actually off center from the oil galley hole. The regular oil galley holes for the rods themselves show poor workmanship as well. The Chinese oil galley oil holes are not chamfered at all in comparison to the stock German crank.
Picture 2 shows the difference between the main bearing oil galley grooves.
There is zero chamfer on the oil pick up holes for the rods on the Chinese crank.
The chamfer is evident on the stock German crank.
The aftermarket suppliers are going the cheapest way they can find. The quality of the parts are not as important as their profit margin. They leave us to deal with the junk after it has been installed for customers or our own projects… it’s never the supplier’s fault. They say that they will accept bad parts back with an RMA number, but that doesn’t take into account the tear down of the engine, nor the pissed off folks left holding the bag for downtime and shipping.
Always ask for Country of Origin when ordering parts. That way, at least you know going into your project just what to expect …..junk!