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  B55 Delco Alternator Watch Outs


Baron B55's fitted with the ubiquitous IO470-L engine have been known to have a fair amount of vibration issues. Ever seen a 40-50 year old B55 air box? Well then you know what I mean.


During my 2016 annual, I discovered a failed Delco alternator bracket in my 1965 B55. My IA has repaired it by welding it back together, however, I'm going to go with the new design and sell the original repaired bracket on eBay. Give this area a good look during your annual inspections if you suspect you have the earlier bracket design. Oh yeah, you will get to find an engine hoist to lift the engine up enough to remove the rear motor mount to remove the bracket for repair or replacement .


Below is the alternator mount IPC extract. Click the image for the IPC page extract. Here are some tips on how I dealt with extracting that rod and the #15, #16 and #11 pieces of this bracketry. It is really a PITA to disassemble and reassemble, especially with the very tight space between the airbox and the tubular engine mount !


The threaded rod has to go in from the forward facing end (and also has to be extracted forward as well) of the bracket and the inner bracket rubber (#15) and washer have to be put in place (washer gets slipped in after alternator ear is in place). Then the forward rubber isolator (also #15) and the metal bushing (#16) go in AFTER the rod is slid in through the whole thing. You then place the nut on the aft end of the threaded rod and begin tightening. I tightened this down to the end of the threads without the rod slipping, then I put the forward washer and nut on and tightened it up. The rubber isolators #15 and #11 are very important pieces as well as the bushing #16.




See image below of the early un-reinforced bracket design, which is Item #4 in the above IPC:




Below is the same bracket 10 years and about 1100-1200 hours prior in pristine condition.






Fortunately, I was able to source a replacement for my early Delco alternator bracket from ENPARTS in Dallas, with what appears to be a later design with gusseted reinforcing members. Beech must have learned that this area was prone to vibration fatigue and implemented a redesign of the bracket. The reinforced bracket is shown below:




According to an excellent starter and alternator rebuilder, Modified Aircraft Accessories, another watch out for those of us B55 owners with engines fitted with Delco alternators is the fact that brushes are NLA (No Longer Available) for these alternators, so we are SOL on overhauling these units if you need brushes. If you have a Delco Alternator, HERE is a repair work order which lists all the parts for a Delco Alternator rebuild, if you can find them .


These are the Delco PNs affected:


CMC 631111


Delco-Remy 1100685


Delco-Remy 1100718


Delco-Remy 1100747


However, Modified advises that a replacement option that will fit into the existing bracketry is out there in the form of the Cessna 310 Alternator, Ford DOFF-10300B, a 60 Amp unit (which is a nice performance boost). The Cessna 310 used the same IO470 engine for quite some time as well as the Baron B55.


Big thanks to Jimmy at Modified for bringing this alternative solution to our attention. Of course you're on your own for the paperwork on doing this. You can spend your way out of the problem by changing to a Prestolite bracket and sourcing that alternator, but that will require sourcing the bracket, lifting the engine and removing the motor mount support in front of the bracket. If you're going to go through all of that you may as well change at least your rear engine mounts. Here are some of the Prestolite PNs that I think are applicable to the B55 w/IO470L engine (check the TCDS and your IPC to be sure):


Prestolite ALT-8403

Prestolite ALT-8407

Prestolite ALT-8420


Or you can spend mega bucks and go with a Plane Power conversion. You and your mechanic make the choices here.


Good Luck in whatever way you choose to deal with the Delco alternator obsolescence.



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