29 Mar 2024, 08:52 [ UTC - 5; DST ]
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Post subject: Re: Slowest 56 C172 with AVCON Conversion HELP Posted: 17 Jul 2019, 21:59 |
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Joined: 04/18/10 Posts: 304 Post Likes: +242
Aircraft: bonanza 35j
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I have a 68 avcon conversion that does 125kts/145mph at 23/2300 at 6500 ft. A friend had a fast back 175 with avcon that was much slower. I do remember the engine mounts on mine were unusual in that the diagonal were the same, but top mounts were different and bottom were different, ie x y on top and y x on bottom. I assume you have the constant speed prop. I added the power flow as well which increased gas consumption and climb, little or no effect on speed. 68 was the first year of lycoming from the factory and required new engine mounts for the conversion.
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Post subject: Re: Slowest 56 C172 with AVCON Conversion HELP Posted: 17 Jul 2019, 22:00 |
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Joined: 05/08/09 Posts: 6994 Post Likes: +4280 Location: Stuart, FL (KSUA)
Aircraft: 1967 Bonanza V35
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I was thinking it was fixed pitch. Hmmmm what else could it be....?
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Post subject: Re: Slowest 56 C172 with AVCON Conversion HELP Posted: 17 Jul 2019, 22:02 |
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Joined: 12/28/17 Posts: 769 Post Likes: +368 Company: Bellanca Aircraft Location: Washington, OK
Aircraft: 17-30A
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Username Protected wrote: It is the AVCON Conversion. 180 Hp with a Hartzel Constant Speed. I have varied the RPM's from 2500 to 2200 at 24" MP and the speed only changed a couple MPH. I can make 2650 RPM on take off at 18.5 GPH. It climbs like a home sick angel. We maintained 1200 fpm to 2000 agl at 75 MPH Whats static rpm? Sounds like you may have a climb prop on it. I have a bit of time in a 1960 172 that we did an avcon install on, and I don't remember it really being much faster than stock, just climbed a whole lot better than the anemic continental.
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Post subject: Re: Slowest 56 C172 with AVCON Conversion HELP Posted: 18 Jul 2019, 11:37 |
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Joined: 01/04/17 Posts: 107 Post Likes: +35
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I believe engine mounts are typically rigged about two degrees in yaw to account for P factor. You indicated that your is straight at 90 degrees to the firewall.
Do you need rudder trim in level flight?
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Post subject: Re: Slowest 56 C172 with AVCON Conversion HELP Posted: 18 Jul 2019, 12:12 |
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Joined: 12/26/16 Posts: 110 Post Likes: +63 Location: Hernando, Ms
Aircraft: 7ECA, B19
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Username Protected wrote: I don't have the exploded view diagrams from the original installation that may show washers in different locations or the mounts as referred to. From Drawing 17200 AN970-716 washers used between engine & Lord mount on lower mount only. AN7-36A bolt (2) lower. Doubt it will affect speed though. Sully
_________________ Sully
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Post subject: Re: Slowest 56 C172 with AVCON Conversion HELP Posted: 18 Jul 2019, 15:38 |
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Joined: 04/18/10 Posts: 304 Post Likes: +242
Aircraft: bonanza 35j
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As I recall, the Avcon conversions on older 172 required a blister over the #1 valve cover in most installations, my 68 got by without it but had to use a lower profile valve cover to keep the cowl from cracking in that location. Air plains in Wellington ks. has a lot of knowledge in this area and said they dropped the CSP in that it was not worth the trouble modifying the cowling. I stopped by and they gave me several hints (i.e. Another Valve cover) to correct the problems of the lyc 360 with CSP.
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