changing hp on a a 65a

[dfcpac]

how would you change a a65a to 75 hp is there a noticable diffrence? would it be worth the trouble?

thank you
dan carley

[Senior]

legally probably very hard

but I hear a jet & ventura change along with a prop repitch gives a great boost

[james gevay]

A copy of Continental Service Bulletin M47-16 will tell you which engines are able to be converted from one model to another. Not all models can be converted, but you can do a A65-8 to a A75-8. I did mine about 20 years ago.
Also, I think you need to either follow an STC, which is SA3-435, or copy someones 337, which is what I did. The STC requires you to do some cowling modifications which I didn't want to do.

I can't remember all the parts to change, I know you need drilled rods and maybe valves and springs. Other than than that, you need a cutdown and repitched prop, a new red line on the tach at 2600 rpm's and a data plate. Oh, on the data plate, to legally do that, you need a letter from the feds allowing you to remove the data plate and send it in to Continental for a new one, about $10.00.

Is there a big difference, hard to tell by just the seat of your pants, probable as good as a strong A65.
Your prop is probably less valuable because you can't use it on a stock Champ anymore.
Would I do it again, probably not.
Those are some of the basics.

[Paul Agaliotis]

Dan,
It's really not worth the trouble getting the 75HP. By the time you get a prop small enough for rated RPM it's too small to pull the airplane. Most people do the 75 mods as reliability upgrades. If you want more power put in the C85.
Paul

[Champ Dreamer]

As far as gietting a new data plate from Continental goes...GOOD LUCK ! I called them when converting my C-75 to a C85 and was told to get a letter from the feds, then send them $100 (not $10) and they would get me a new data plate in about 10 days. I got the letter, called them (continental) back, and the guy seemed suprised that I had obtained a letter. He him-hawed and passed me on to another guy, who did not answer his extension, and did not return 5 or 6 voice mails. Called the first guy back, and he said that only the second guy could do it,,,keep trying. I gave up (which is what I suspect they were hoping) and bought a really nice data plate from Don Jones. My IA and I figured we had a letter from the FAA, and we were okay. Got the local trophy shop to engrave it, and it looks great.

Brian Walker
NC1197E '46 7AC

[skyking3286]

The old time way to do a A-75 conversion was to log an overhaul and simply put in the logbooks all the part #s and the procedures that made it a A-75. No need to change the dataplate in those days. It was just an overhaul done with a SB in mind.

[Griphos]

My Chief has the upgrade to 75 horses, and even though I can't really get the full 2600 rpm with my prop, it's nice to be able to cruise at 2300 if I want to. Where I really see the difference is in climb. My Chief climbs great! The other day, 100 degrees outside, density alt at least 3000 ft, full gas and a passenger and we climbed out about the same as usual. Don't have a VSI, so don't know the actual figure, but it was a lot better than the A65 Champ I've flown at the same field. On cooler days, I'm almost at 500 ft above the runway by the end of the runway at KILE where I sometimes fly. Course, that's a 5500 ft runway.

Isn't faster in cruise, I don't think, but it's much better in climb performance. Everyone comments on that.

[flyboy1964]

Phil, What size prop do you have? I have the 75 conversion and don't have real great climb. Maybe I am just expecting to much. my prop is 70x42

[Griphos]

Prop is 73x42. Doesn't get up to full rpm, but the plane was based in Denver before I bought it, so I think they put this one one for climb performance. And you understand I mean great performance for an Airknocker. I'm not saying it's like a Kitfox. But it does get up well enough that people watching frequently comment. And I've always been quite happy with its performance.

Is your prop a McCauley?

[flyboy1964]

I believe so, now you've got me thinking I will have to make sure when I get home.

[Senior]

My experiences from real world practice.
With a simple ventura & jet change (& yes drilled caps)
my 65hp went from struggling to pull 2150 on climb out to 2450 with the same prop!
I can not be anything but more hp or tq to spin the same prop (74-42) faster.
I then went to a 72-42(now at 2500rpm) & the climb diff is huge from stock to finished!