prop question

Props, Spinners and McDowell Starter issues.
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dfcpac
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prop question

Post by dfcpac » Sat Mar 03, 2012 16:55

on my 71 champ with a a65-8 i changed the prop from a 72cw44 to a 72cw42 cause it wanted more climb. there was really no change in the take off noticed about 50 more rpm's on roll out but that was about it. shouldnt it have done more than that or i'm expecting too much for a 65hp champ

thanks

dan carley
n9176l

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rkittine
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Re: prop question

Post by rkittine » Sat Mar 03, 2012 17:27

Hey Dan,

If you only got 50 more RPM, I do not think that you are getting all you should based on what you said it was turning and what others said in response to another post of yours. I remember that the 75HP modification for the A65 required a Change in Prop and also a change in the carb jetting in order to get the added fuel to the engine to allow full RPM. You might need to make that modification. The actual conversion also calls for the oil passages to be expanded. If you call me on Tuesday I will be at the airport and the guy there with the Chief that you saw when you and Pete were there, has the modification and I will ask him what RPMs he gets. He and I get his A65 Chief into the air effortlessly and he is bigger than I am.

Ciao - Robert
Robert P. Kittine, Jr.WA2YDV
West Nyack Aviation, L.L.C.
New York, New York 631-374-9652
rkittine@aol.com

dfcpac
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Re: prop question

Post by dfcpac » Sat Mar 03, 2012 17:45

rob,
one of my cyl compression is 64 the others are 78 could that be part of the problem?
dan

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rkittine
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Re: prop question

Post by rkittine » Sat Mar 03, 2012 18:22

Dan,

I was getting full RPM when one of my cylinders was 50. No change in RPM when I put a new cylinder on. How are your Mags and Ignition Wires?

According to the Continental Type Certificate on line, the A65 needs 2,300 RPM to develop 65 HP and the same displacement engine, develops 75 at 2,600. The recommended cruise was listed for the A65 as 2,150. Something is holding it back.

Caio - Robert
Robert P. Kittine, Jr.WA2YDV
West Nyack Aviation, L.L.C.
New York, New York 631-374-9652
rkittine@aol.com

Bo Grave
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Re: prop question

Post by Bo Grave » Sun Mar 04, 2012 07:20

Dan,

The next things i would check is engine timing and then you carburator. check your jets but also your venturi size is correct, 1 1/4 for an A65. also the intake spyder they should both have the same size opening. this is will limit rpm. venturi size is measured at the narrowest point in the throat. i have had that they are not what is stamped on them, so i recommend you measure it. To have good climb you want the highest static RPM that is allowed.

When i got my champ it had very poor take-off and climb. This with a low time engine 150 tsoh and great compressions. it would just make the low end of the static rpm It had a prop with 72/46 i repitched to 72/43 this gave me 75-100 rpm, A75 timing gave 75 rpm, checked the venturi found it undersize this gave a 100 rpm when correct. with all of this the static was at the top of the range. it was a big improvement. i did all this while i was waiting for lycon to overhaul a c85 for me. i now have the stroker c85 installed. i highly recommend this engine

Bo Grave
N1663E
Eugene ( Bo ) Grave
A&P, IA, R&E
CHAMP
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rkittine
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Re: prop question

Post by rkittine » Sun Mar 04, 2012 10:21

Some other great things to check, as I did not that there was different timing listed for the A75 as compared to the A65. I bought the Don's Dream Machine, C-85-12 Stroker with the 0-200 parts and agree that is a wonderful engine. I do like my C-90 in my 7CCM.

Dan, Horsepower rolls off quickly as RPM drops. An 0-200 only gets 100 HP at the very high end of the RPM curve and rolls off much quicker than some of the other engines, primarily the C-90, which is considerd a better engine than the 0-200 for most small plane applications. Just hard to find them.
Robert P. Kittine, Jr.WA2YDV
West Nyack Aviation, L.L.C.
New York, New York 631-374-9652
rkittine@aol.com

dfcpac
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Re: prop question

Post by dfcpac » Sun Mar 04, 2012 11:24

flew it again today, it must have been the poor wheather yesterday. it's working better. tried both props the 72 42 works better

dan

dfcpac
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Re: prop question

Post by dfcpac » Thu Mar 29, 2012 18:07

going with the c85-12 conversion problem solved

dan carley

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