Kelly, I wouldn't hesitate to use an early 20b. The early 20b housings are plenty robust enough for a/c use. The beefier irons could be an issue if you're building a turbo race engine due to the higher loads imposed during up shifting and down shifting. We don't experience any of those loads. I'm pretty certain that my 20b is an early model and I have not experienced any issues with irons cracking around the dowels. The weakest area is along the inner walls of the o-ring grooves nearest the water jackets. If your o-rings aren't to factory specs, you run the risk of cracking an o-ring wall which ruins the housing. Been there, done that. If you treat the engine with the same care you would a certified a/c engine, then you won't have any trouble with longevity. MarkOn Fri, Feb 6, 2015 at 12:00 AM, Kelly Troyer <flyrotary@lancaironline.net> wrote: Mark Steitle or other 20B Drivers, I am looking at a 20B that looks to be an early one before they added additionalmetal in the dowel/oil passage area of the iron housings because of some that I haveread developed cracks in this area in service in the autos I presume....... Can you tell me if this a potential problem for the 20B in our aircraft use ?.......Alsocan you tell me if your 20B has the later reinforced housings ?......... -- Kelly Troyer
Mark Steitle or other 20B Drivers, I am looking at a 20B that looks to be an early one before they added additionalmetal in the dowel/oil passage area of the iron housings because of some that I haveread developed cracks in this area in service in the autos I presume....... Can you tell me if this a potential problem for the 20B in our aircraft use ?.......Alsocan you tell me if your 20B has the later reinforced housings ?......... -- Kelly Troyer