SO, what's it gonna cost?

[PhilP]

Hey All!
I've been doing a fair bit of research on converting the A65 to an A75.

However, I was wondering if a couple folks here could spit out the cost to do it(excluding the prop). Lets assume nothing has been done yet...

New exhaust valves, new wrist pins, piston pins, the carb mod, drilling the rod, avg Labor costs...


Anyone care to give a breakdown of the total costs one may see at the end of the tunnel? Much appreciated!!

-Philip

[astjp2]

Re: SO, what's it gonna cost?

My parts manual says that the carb remains the same, the wrist pins are the same, most rods are already drilled from previous overhauls, the valves can be the same, turn up the rpm's and change the timing (can get the same results from a 65), and a stamping on the data plate. I got my manual from Fresno, its a good reprint but dated from like 1948, so people that have newer revisions, The A-65 will have upgraded parts, Stellite valves, drilled rods, etc.

The carb is EXACTLY the same per the TCDS for both engines, if you change the venturi, then you change the Jets per the stromberg manual.

Aircraft have flown with the 65 by bumping the timing and spin it up to 2650! to get 75 hp.

If you were to do it officially, you will need to get the correct pistons and rings, (100.00 each) top end gasket sets (25.00 per cylinder), verify valve part numbers, 5-6 hours labor (75-100 shop rate in some areas), get an STC because its over the 10% unless you are lucky enough to get it field approved

An A-65 prop repitched to about 43" will get the RPM. (M74CK-0-46) repitched to (M74ck-0-43). Read the interchange manual, by part number, you can see how similar the engines are.....Tim

http://www.bowersflybaby.com/tech/Continental%20Parts%20Catalogue.doc

[crispy critter]

Re: SO, what's it gonna cost?

Hey All!
I've been doing a fair bit of research on converting the A65 to an A75.

However, I was wondering if a couple folks here could spit out the cost to do it(excluding the prop). Lets assume nothing has been done yet...

New exhaust valves, new wrist pins, piston pins, the carb mod, drilling the rod, avg Labor costs...


Anyone care to give a breakdown of the total costs one may see at the end of the tunnel? Much appreciated!!

-Philip

Find you a C-85 ,bring it to me, and for a substantial sum of money I'll do the complete 85hp conversion. 1280lbs gross with all the mods and still be LSA legal......Ooorrr just check the rods,valves,etc.... repitch the prop and make that little A65 scream!

[d.grimm]

Re: SO, what's it gonna cost?

Once you turn it into a A-75 you will NOT be able to use any of the new A-65 cylinders because they didn't include the A-75 in the FAA paperwork. Now you are limited to old cylinders. Not sure about a T-Craft, but a J-3 requires a 2in shorter prop that gives less static thrust. IMHO I wouldn't do it.

[ClipWing_T]

Re: SO, what's it gonna cost?

If money is not much of a problem do it ! :-). We had 2 fresh rebuilt
J-3's here and one had a 65 and one had a A-75 and the 75 would out climb
and was faster than the 65 hp Cub. The 65 might have had an edge on
getting off the ground quicker but after that the 75 hp Cub was a better
performer. And it did have a smalle diameter prop too.....This subject has
been hashed a gazillion times but I would go the 75 hp ! .......Don't worry
about the RPM too much , I had a buddy one time who had a Cassut Racer
with an A-65 and he ran that thing up to 3000+ RPM ..........He go through
a time or two ! ! OOOOPS ! lol.........A LIGHT Taylorcraft with a 65 is a
VERY good performer in most cases for us guys close to sea level and you
gonna burn less of that liquid gold too. :-)..........Mike

[astjp2]

Re: SO, what's it gonna cost?

I have a copy of a 337 somewhere that uses the M74ck prop on a C-85/O-200, and It sure can make a difference on climb, or there would be no Borer Props out there. Tim

[Ragwing nut]

Re: SO, what's it gonna cost?

You have to run a shorter prop to get the rpms to get the 75hp. None of the internal changes makes the hp increase, it just allows the motors not to fail at the higher rpms. You may already have the drilled rod caps, wrist pins are the same on A series engines. the different sizes are on the C series engines. I wouldn;t go through the trouble unless you already have to spend the money. It would be cheaper to go buy the A-75 Marty has for sale in the classifieds.

Mike

[astjp2]

Re: SO, what's it gonna cost?

Well my O-200-8 gets 2750+ with the 74" prop. It still cruises at 90 kts @ 2150 rpm. and I am considering getting an M76AK prop. Tim

[VictorBravo]

Re: SO, what's it gonna cost?

Sorry in advance for this, but ...

Well for that matter, just put a small model airplane propeller on your 65, run it up to about 4300 RPM and you'll get a little more than 75 HP. Heck we used to do it all the time in the F-1 Reno racers. Never mind that the excess RPM cut our overhaul time down to about 5 hours. Never mind 600+ CHT and 260 oil temp. Never mind that we were flying over long runways at all times, and the airplanes went to and from the race on trailers. Never mind that the medevac helicopter blades were turning while we were racing.

If you're going to run the engine harder and faster, no problem... just make sure you are always over safely land-able farm fields, and have the guys from Sacramento Sky Ranch driving underneath you with their parts truck.

OTHERWISE, how's about keeping a 60 year old engine a little happier, keeping your kids' Daddy around a little longer, running it at a more sedate RPM and temperatures, and either doing the proper 75HP or 85HP conversion or learning how to make the best out of what you have until you can upgrade the engine safely?

I screw around with stuff on my airplane as much or more than anyone else here, but there are some hard limits I observe and several things are just plain off-limits. For $695 or whatever, you can put the little VG's on your airplane and get an improved rate of climb, without giving up any reliability. A few hours of dual instruction with Forrest Barber would probably yield a noticeable improvement in your airplane's performance - through better piloting technique (I need to do that one myself). Reducing weight of the airplane will make a striking difference... how much does your interior upholstery, aluminum glareshield, carpet, five-day supply of beef and beer, 50 amp/hour battery weigh?

[crispy critter]

Re: SO, what's it gonna cost?

Now wait a gosh darn minute here Bill......you said get some dual from Forest and cut down on weight. I'm sorry but you can't have your cake and eat it too....and Forest looks as if he eats plenty of cake,lol. Sorry Bill and Forest but I just had to pick on you guys a little bit. I'd fly with Forest any day if we can get both our butts in the airplane together.

[Garry Crookham]

Re: SO, what's it gonna cost?

To convert from an A-65 to an A-75 the following are needed:

p/n 21479 stellite exhaust valves, current price from Fresno $57.50 each
p/n 40577 A-75 piston, current price $77.50
these pistons require the small (.859 dia.) piston pins $47.50 each
Your A-65 could have either the large or small diameter piston pins,
depending on the p/n of the piston that is currently installed.
If you have the p/n 40731 piston installed which takes the large
(.9215 dia.) pin, your rods will need to be rebushed for the small
pins, and drilled if not already done. Most aviation machine shops
charge approximately $40 to rework a connecting rod.

The tachometer will need to be remarked for the A-75 operating range.
The engine conversion can be accomplished with a logbook entry but
installation in the airframe will require a field approval, stc, etc. If you can
locate an A-75 powered Taylorcraft that was converted prior to Oct 1, 1955, that form 337 can be used as approved data.


Garry Crookham
N5112M
Tulsa

[PhilP]

Re: SO, what's it gonna cost?

Thanks all for the Info and Gary, thanks a lot, thats exactly the kind of thing I was looking for, a complete cost breakdown. More opinions would be appreicated. How about the parts and cost for the carb mods?

I've flown behind champs, chiefs cubs etc.. with both the A65 and A75 and to me the 10 horsepower made a world of difference, other than nostalgia's sake, I don't see why you'd keep a 65 a 65 during an overhaul. Not to metion, the planes just seem to have that little bit of extra energy left over that keeps giving where the 65's tell you it's time to push the nose over....for a while.

Thanks guys!

[lfries]

Re: SO, what's it gonna cost?

I'm on a search for that, hoped to be somewhere, 337 dated before 55.
If I find one I'll keep you posted. Currrently sending letters to BC12-D owners listed on the FAA registry with an A-75.

[Garry Crookham]

Re: SO, what's it gonna cost?

Phil

No carb mod needed for the A-75 (talking Stromberg carb). The A-50 through the A-80 engines use the same NA-S3A1 carb, Continental p/n 3628, Stromberg p/n A-18033B-4.
One other item that could be a big expense is the crankshaft. If your crankshaft has 1 3/16 crankpin lightening holes it isn't eligible for a horsepower upgrade. I think most of those cranks have been replaced by now but it would be a good idea to check and see what diameter the lightening holes are.

Garry Crookham
N5112M
Tulsa

[stormman]

Re: SO, what's it gonna cost?

As everyone has more or less said "not worth the trouble" smaller wrist pins, round pstons that burn more oil and more piston slap
As one who did it I feel its a waste of money and oil.
Repitch the prop to get more RpM and more horsepower. Or get a C85 as someone suggested
I bet Forrest is biting his tounge on this one