The RV Journal N399SB Gets a Fresh Enginepage
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(5/23/00) The fresh engine parts are starting to arrive in the shop. A few days ago a shipment came in from Rick Romans in Tulsa, Oklahoma (crank, lifters, and other steel parts), and the new Millennium cylinders have been on hand for several days. The crankcase is due any day along with new bearings, gaskets, rod bolts, and cam. Just in case this overhaul business is vague to you, here are some photos to give you an idea of what you can expect to see when your reconditioned engine components have had several hundred dollars thrown at them. The key to a certificated rebuild is having all components either replaced or attached to yellow tags. The yellow tag certifies that the FAA-blessed repair station has guaranteed the parts to be in serviceable condition. If any components are found to be beyond hope, they suffer the indignity of a red tag and you can throw them in the scrap heap. (Note: Unless...........you want to use them anyway. Since we are building an engine for an experimental aircraft, we can put any kind of part in the motor we wish. Matter of fact, there is a thriving business of building airboat engines out of rejected aircraft components, and some of these engines end up on experimental aircraft. While it is legal to put such an engine in our experimental craft, you have to weigh whether the cost savings is worth the additional risk. For me, it isn't. I am going to have a "yellow-tagged" engine which will make me feel much better as I wing over inhospitable terrain around the country.....not to mention the $$ value added to the aircraft.)
Here is the heart of a good bottom end overhaul, a yellow-tagged crankshaft. The main journals were ground .006" undersize, and the standard-sized rod journals only required polishing. Remember the evidence of movement we saw on the backside of the main bearings? That is probably why the mains required grinding. The hollow crank AD was complied with, and the prop flange replated. Also part of the rebuild is putting the crank through a two-stage magnafluxing procedure which reveals any subsurface cracks; presence of cracks will present the crank with a red tag. Seeing the crank with a yellow tag is a major financial hurdle behind us! A new crank will put a $5000+ dent in your wallet...
The fresh crankshaft needs good connecting rods to complete the package. The rods in our engine were checked for proper balance, alignment (to make sure the piston pin journal and crank journal were perfectly parallel), the small ends were rebushed, and all rods were magnafluxed.
It's just like Christmas! Boxes full of shiny, clean, magnafluxed Lycoming innards. Here are the oil pump gears, and the crankshaft gear. We are in compliance with the oil pump AD which requires replacement of sintered iron gears.
Here are the lifters. Two of our lifters were DOA, and they have been replaced with reground units. All the original lifters were magnafluxed, plated, and reground, which reconditions the bearing faces.
This is an expensive contribution to the scrap pile. As expected, the cam was rejected and will be replaced with a new cam. The yellow arrow indicates the destroyed lobe.
You can see the reason for the tag of death. Compare the profile of the arrowed lobe with the lobes adjacent to it. The good lobes have a "pointed" end, and the bad one is very rounded. I measured 0.090" difference in the heights of the lobes. Most likely I was flying with two cylinders that yielded less than full power.
(5/31/00)
The UPS truck has delivered the remaining bits and pieces for our engine! The largest box contained the crankcase which has been refaced, line-bored and finished in some sort of alodine. A set of bearings, gaskets, and various mandantory replacement parts are on hand, so........let the games begin.
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Please submit all questions and comments to sbuc@hiwaay.net
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