41 Super Chief A-65-8 with new slick mags and low power

Pre-War Aeroncas
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skookum
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41 Super Chief A-65-8 with new slick mags and low power

Post by skookum » Sun Jun 03, 2012 20:35

Well in the fall of 2011 during the annual, I had new Slick magnetos installed. Replaced the original Eisemann's. Prior to replacement, my 41 Aeronca Super Chief did not want to tach over 1900 rpm and it was blamed on magnetos. The new Slick Magnetos are installed, along with new shielded wiring harnesses, plugs and cowl bumps. Timing was set at 30 TBDC (so stated in A&P's notes) which is standard for this A-65-8, or at least it is so stated in the MS894-D manual that is what it should be.

First time up (solo) and on climb out performance was poor, or so I thought - about peak was 1900 RPM's. Using 100LL and some non-alcohol car gas (STC certified), about 1/2 each. On run - up magnetos were very even little no RPM drop on individual mags) I never saw any RPM over 2100, at full power during climb out or at cruise. Could not get the engine over 2100 ever. Used to get 2300 all the time, when needed and could cruise at 90 easily. Cruise on this first flight with new magnetos was never over 85, straight and level. Compression is great on all cylinders (high 70's and high 80's). Flew it at 3/4 to full throttle for about 1 hour. There was little or no difference between 3/4 throttle and full throttle during normal flight as regards engine performance, so I left it at 3/4 throttle for the majority of the flight. Tach stayed at about 2000 to 2100 during this 1 hour of flight.

I noticed what I thought to be a BIG difference with a lot less power with the lower RPM during take off and when flying doing a climb from 3000 to 4000 feet at full throttle the engine seemed to run rough but when leveled out and the throttle brought back to 3/4 it ran smooth.

I have posted several articles on the timing issue with my plane and the old Eisemann magnetos, that I have now replaced at the A&P recommendations.

Any one have any thoughts on this, as I need the power on take off for a short grass strip with obstacles at the ends. That being said, I am a low time new pilot, have a pretty good knowledge of mechanics and engines. I have very little experience with pre-war Aeroncas, except mine, and trying my best to understand what should be the RPM to expect on full power takeoff roll with say no wind or low wind (4 MPH headwind) on smooth ground.

I would like to get all I can out of this 65 HP engine and it does not feel like it is giving me that now like it did in the past when flying with a CFI during training in this plane.

FYI, I called the A&P who did the Slick install and set this up before I fly again, but am searching for information from you experienced pilots and plane owners.

Thanks,

Any thoughts on this topic would be very much appreciated.

David - aka Skookum

skookum
Posts: 41
Joined: Mon Nov 09, 2009 18:08
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Re: 41 Super Chief A-65-8 with new slick mags and low power

Post by skookum » Mon Jun 04, 2012 07:13

The A & P who installed the Slick Magnetos just responded and said that all the ignition system is brand new and it is timed correctly, so he thinks that the carb is the problem.

Any thoughts out there as to what in the carb might be causing this problem? This carb has no internal plates for leaning it out - they were removed when it was last rebuilt 2 years ago.

Paul Agaliotis
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Location: San Martin, California
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Re: 41 Super Chief A-65-8 with new slick mags and low power

Post by Paul Agaliotis » Mon Jun 04, 2012 16:21

David,
What prop are you running? Try a flatter pitch to get the RPM. Unless you really have something wrong with the Carb and Mags, changing them won't help. Make sure the carb heat is all the way off and you have a good air cleaner. Check the throttle control to make sure you're full open. They can slip on the clamp welded to the mount and change the adjustment.
Paul
Mailing Adress : Paul Agaliotis 2060 E. San Martin, San Martin,Calif. 95046

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