February 1999 - American Bonanza Society

A CASE STUDYThe cost of converti ng froman IO-470-C to an IO-S20-BABY STEVEN W OXMAN, Annapolis, MarylandOnVening a 1959 Bonanza K35 from ils original Continental10-470-C 10 a larger Continental [0-520-BA(powerplant is a larger lask than mighl meel Ihe eye atfirsl blush. In Ihis Iwo-pan series, I will provide a 101 of Ihedelails of my experiences.[n Ihi s firsl anicle, [will provide background fOrlhis projecI10 assisl Ihe reader wilh underslanding Ihe reasons and mOlivalionsfor whal was done. The second article will provide Ihefinancial delails of the projecI, information Ihat will undoubledlysurprise many readers.Background for this project[purchased my K35 approximalely Ihree years ago. The planehad approximately 2900 hours IOlal lime on Ihe airframe andapproximalely 1,000 hours since the lasl major overhaul on theoriginal engine. No work had been done on Ihe propeller in Ihelasl 10 years, which equaled 10 aboul 1,000 hours. The airframewas and is in good condilion. The engine seemed OK when Ipurchased Ihe airplane. It should be nOled Ihal Ihis was the firslairplane [ had ever purchased (and will mOSI likely be Ihe onlyplane I buy- I hope il will oUlli ve me). AI Ihe lime of Ihis purchase,I did nOI know whal 10 look for and I did nOl reali ze Ihisplane was going 10 require a 101 of work shortly afler ils purchase.My pre-purchase mechanic said nOlhing 10 me aboul Iheengine and propeller needing work in Ihe near fUlure.[ flew Ihe plane for a while and il seemed 10 fly fine. Thenthe engine started to give me some minor, but consistent, problems.Wilh each problem. I had my mechanic fix Ibe engine.Wilh each incident, I did more and more research on enginework and/or replacement. One day, while flying wilh my familyfrom Lee Airport, a 2,500-foot paved slrip in Annapoli s,Maryland, Ihe engine went from 26 inches 10 23 inches justafter rolalion and from 2,675 rpm 10 2,100 rpm wilhout melOuching anYlhing! My venical rale decreased quickly. I flew alight pallern and returned 10 Ihe field. ThaI day I declared IhalIhe engine was 10 be replaced.My mechanic found Ihree fouled injeclors. Wilh Ihese cleanedOUI, Ihe engine again ran fine. I continued 10 fly it. Bul I put myengine change projecl in mOlion.Decisions. Decisions.Whal 10 do? Local engine overhaul or an overhaul by oneof Ihe big guys (my mechanic likes Matlaluck)? Overhaul byone of Ihe advenisers in this magazine or overhaul by the manufacrurer?Faclory reman by the manufacturer? All of these seemedPage 557210 be valid ahemalives. However, [found little interest by the vendorsin working wilh my 1959 10-470-C engine. All the vendorsseemed 10 be imeresled in 10-470-Ns, [0-520s and [0-550s.The faclory did nOl even offer a faclory reman 0Plion for myengine. They did offer a faclory rebuild 0Plion. Wilh Ihe age ofmy engine, I decided Ihal Ihe overhaul 0Plion was nOI a COSIeffecliveoption. For one Ihing, many of the bids were openended(e.g., if Ihe crankshaft does not meel specs, Ihe cost willgo up by X dollars).OK, now thaI I had decided Ihal I was nOl going 10 overhaulmy engine, whal oplions were left Ihat [ knew aboul? A newengine or a faclOry reman engine from the factory was nOl anoption (Ihe 10-470-C was nOl available and the faclory had noSTCs for Ihe larger engi nes). To gel a faclOry reman or a newengine, I needed an STC. For cost reasons. 1 quickly removednew engines from consideralion. Therefore, I made Ihe decisionto purchase a larger, newer factory reman engine with alegal STC Ihrough a Ihird pany.Slill relatively new 10 Ihe Bonanza world, Ihe only option Jcame up wilh was a Continental (TCM) faclory reman with IheSTC from Beryl D'Shannon.Beryl offered me a small STC price break if [ ordered Iheengine through Ihem, which [did. 1 looked al Ihe 10-470-N, Ihe10-520-BA. the 10-520-BB and Ihe 10-550. [quickly removedIhe [0-470-N from consideration because il did nOI providemuch of a difference in horsepower.[ also quickly deleled Ihe 10-550 from my Iisl of choicesbecause I did nOl wish 10 modify Ihe front of my plane for Ihecanl requirement nor I did nOI want 10 li ve wilh Ihe power setlinglimilalion al lakeoff. Therefore, I was 10 purchase an [0-520. BUI which one, Ihe BA or Ihe BB? I was told Ihal the BBhad many posilive fealures like a heavy case and a VAR crank.and thaI I should spend Ihe difference in money 10 gel Ihesefearures. However, when I spoke wilh TCM people al Ihe ABSConvention, Ihey IOld me Ihal Ihe fealures [ was interesled inwould be on a BA engine, and Iherefore, save the money on Ihemodel. So that's whal I did.The add-ons and accessoriesTo gel Ihe STC from Beryl, [ also had to purchase a bafflekit. Allhough not a requirement of Ihe STC, I also needed 10purchase Ihe electrical upgrade kil and a hose kit. And since myold engine made a mess of Ihe underside, I purchased a Berylairfoil separalor. I also had to purchase a few new accessoriesIhal do nOI come wilh Ihe new engine, like the propeller gover-ABS February 1999