Engine conversion

[N95334]

If I wanted to convert my Taylorcraft to a Cont 85hp what dash number is acceptable on the STC?
Can it be upped to a C-90hp?
Also heard you might uses O-200 but with 85hp parts.

[cvavon]

Re: Engine conversion

The best thing you can do is get a hold of Terry Bowden and ask him as he owns the STC paper work you need to make it legal I used the C85-12 on a short mount check my thred on n26658 here on the site lots of photos

[Edwin Otha]

Re: Engine conversion

Dennis,
As far as Continental is concerned they only made the C85, and the dash number indicates the modification level of the series. If you need a electrical system use the -12, if not use the -8.
If you use a STC you install what the STC holder certified.
If you want 90 HP install the C90.
There is a STC to install the O200 crankshaft in the C85, but it's still a C85.
EO

[Jim Herpst]

Re: Engine conversion

use an 0-200 crank yes it is still an 85 but it has far greater HP even at a lower RPM than a stock 85 it puts out 97 hp and is a bit better than an 0-200(more hp at lower RPM) Torque helps fly planes. Just clarifying for this Gentleman who started the question. Yes reasearch all these things before you start jumping engines....

[cvavon]

Re: Engine conversion

This came from Harry Fentons web site on fly babe site about the 0200/C85 crank mod makes good sense


O-200 Cylinders on a C85
My mechanic has somehow lost the cylinders I gave him last winter to refurb, hone and re-ring (due to excessive blow by). He has a set of refurbed O-200 pistons and Cylinders that he is willing to install on my C85 (on a 1941 Piper J-5A) if I can find and procure a STC to do it. Do you know of any STC's that would cover the pistons and Cylinders only without changing the cam/crank and rods? The engine has about 800 hours on the bottom end and the oil pressure is good and no metal in the oil screen so I an trying to keep from doing a rebuild on it for 300-400 more hours, even though it was put on the airplane in 1985. If I can't find a STC we will have to find some good C-85 cylinders or see what kind of a deal the mechanic can give me on the rest of the O-200 he has in parts, assembled and installed on the J-5. He would get my C-85 for when he finds the cylinders and I would get a big bill for the exchange and an extra 15 hp. Thanks for any help you can give me.

Unfortunately, there is no STC for just O-200 cylinders. However, the basic C-85 and O-200 cylinders are nearly identical, except for valve springs and minor details. If you have a set of O-200 cylinders, you might want to see if you can have a cylinder shop convert the O-200 cylinders to a C-85 configuration. If you do this, then there are no major changes to the engine. Just bolt he cylinders onto the engine.

By the way, installing the O-200 crankshaft, rods and cylinders does not increase horsepower on a C-85. If legally installed and legally run to the limits detailed by the STC, the parts change provides no increase in engine horsepower. The increase in legal horsepower is an Internet wives tale or at least a continual re-telling of incorrect t information.

Yes, when the crank, rods, cylinders and piston are bolted the O-200 are bolted to the C-85, the C-85 becomes mechanically similar to the O-200 in crankshaft throw and displacement. However, the C-85 is legally limited to 2575 rpm whereas the O-200 is rated at 100 hp at 2750 rpm. The difference in rpm limits the modified C-85 to 85 hp. I think that most customers report that the engine runs stronger, which is probably true. But, if you think about it, the primary reason to convert to the O-200 parts is because the C-85 is runout and in need of a rebuild. Of course, once the engine is rebuilt with any sort of new parts, the previous “tired” engine is going to feel like a “new” engine with lots of power. Also, once someone has spent the money to convert their C-85, there is little chance that they will not say that the conversion yielded heaps of power.

So, it is an outright myth that a C-85 will be turned into an O-200 via the parts detailed in the STC. A C-85 remains a C-85 if the STC is accomplished in a legal manner.

Harry

[Jim Herpst]

Re: Engine conversion

This came from Harry Fentons web site on fly babe site about the 0200/C85 crank mod makes good sense


O-200 Cylinders on a C85
My mechanic has somehow lost the cylinders I gave him last winter to refurb, hone and re-ring (due to excessive blow by). He has a set of refurbed O-200 pistons and Cylinders that he is willing to install on my C85 (on a 1941 Piper J-5A) if I can find and procure a STC to do it. Do you know of any STC's that would cover the pistons and Cylinders only without changing the cam/crank and rods? The engine has about 800 hours on the bottom end and the oil pressure is good and no metal in the oil screen so I an trying to keep from doing a rebuild on it for 300-400 more hours, even though it was put on the airplane in 1985. If I can't find a STC we will have to find some good C-85 cylinders or see what kind of a deal the mechanic can give me on the rest of the O-200 he has in parts, assembled and installed on the J-5. He would get my C-85 for when he finds the cylinders and I would get a big bill for the exchange and an extra 15 hp. Thanks for any help you can give me.

Unfortunately, there is no STC for just O-200 cylinders. However, the basic C-85 and O-200 cylinders are nearly identical, except for valve springs and minor details. If you have a set of O-200 cylinders, you might want to see if you can have a cylinder shop convert the O-200 cylinders to a C-85 configuration. If you do this, then there are no major changes to the engine. Just bolt he cylinders onto the engine.

By the way, installing the O-200 crankshaft, rods and cylinders does not increase horsepower on a C-85. If legally installed and legally run to the limits detailed by the STC, the parts change provides no increase in engine horsepower. The increase in legal horsepower is an Internet wives tale or at least a continual re-telling of incorrect t information.

Yes, when the crank, rods, cylinders and piston are bolted the O-200 are bolted to the C-85, the C-85 becomes mechanically similar to the O-200 in crankshaft throw and displacement. However, the C-85 is legally limited to 2575 rpm whereas the O-200 is rated at 100 hp at 2750 rpm. The difference in rpm limits the modified C-85 to 85 hp. I think that most customers report that the engine runs stronger, which is probably true. But, if you think about it, the primary reason to convert to the O-200 parts is because the C-85 is runout and in need of a rebuild. Of course, once the engine is rebuilt with any sort of new parts, the previous “tired” engine is going to feel like a “new” engine with lots of power. Also, once someone has spent the money to convert their C-85, there is little chance that they will not say that the conversion yielded heaps of power.

So, it is an outright myth that a C-85 will be turned into an O-200 via the parts detailed in the STC. A C-85 remains a C-85 if the STC is accomplished in a legal manner.

Harry

Huh ?? I suggest the mechanic that "lost" the C-85 cylinders then the same mechanic offers to give him 0-200 cylinders explain to that mechanic that he find him suitable cylinders that are re-buildable for his c- 85 and then he find another mechanic. Second If one installs the 0-200 crank (after the case is midified to accept it ) and retains the c-85 cylinders (AS PER THE STC) one wil achieve the 97 HP at the stated redline (2575) and not need to spin up to 2750 to get the hp. It is called "stroking" and hot rodders have done it for years. The 0-200 engine is not as strong on takeoff as a stroked 85. Why? because it does not develope the hp at the lower RPM needed forr climb. Also to assist in this there are big differences in the cam between the 85 and the 0-200. The cam is also one of the keys in yeilding the better power curve at the lower end . The C-90 cam or the C-85 cam is critical to be retained in fact for the conversion to get claimed hp....again at a lower RPM than the 0-200. My opinion is to suggest Harry Fenton look at actual Dyno Data. Dont believe every thing you read either.

[jim cooper]

Re: Engine conversion

Are you saying that Don Swords conversion does NOT increase the 85 horsepower by a significant amount? That makes no sense at all. I agree with Jim...,hot rodders have been doing mods like this for YEARS! The guy who " lost" the 85 cylinders? Did they fall out of his pocket? They probably ended up on someone else's converted 85-200 cont. Get rid of him for sure! The mod sure made sense to me when Don swords explained it to me on the phone. Bill pancake says it the way to go.....good enough for me. The conversion makes a whole different airplane out of the Taylorcraft, much more fun to fly! With this conversion, a lot more off airport and short field takeoffs are accessible where before they were not. You can easily get a 65 HP Taylorcraft into a strip you can't get it out of on a hot day or for that matter any day. JC

[n6346m]

Re: Engine conversion

I have converted my L2-B to a C90 and I am thrilled with it. I consider the C-90 the best engine for several reasons. First, the C-90 is rated at 90 HP maximum continuous. According to the TCDS the C90 is rated at 95 HP for 5 minutes for take-off and climb. As noted in other replies to your inquiry, the C90's horsepower is accomplished at a lower RPM than the O-200 making it better for short-field and float operation. The C90 has legal wood propellers available for it, which is important to me for winter operations as I have explained on this forum before. The O-200 has no wood props legal for it, and I don't know if any wood props are authorized for the C85 conversions using O-200 parts. Finally, the cost. If you already have a C85 and want to "soup" it up, it will cost you the price of the STC itself and the cost of the parts for the conversion. If you are upgrading from an A65 you will have to have a core engine to purchase as well. I believe that finding a running C90 from a wrecked airplane like I did, or buying a core C-90 to rebuild would probably be a lot cheaper in the long run.

[cvavon]

Re: Engine conversion

First where would the large claims of increase in hp come from 12 cubic inches, when you could get more HP by using high compression pistons in the stock engine. Also there is no difference in C85 cylinders and 0200 cylinders, they're a bolt on and the part number is legal. Pistons are different on 0200 they're higher compression, also there is only a very small difference in the cams except the 0200 is much different, and it is not on the STC. Put 7.5/1 pistons and change the mag timing to 28deg and 32 deg and throw away Taylorcraft exhaust and do Luscombe, and put a prop on it that will let it turn up and make HP, then put the money you save buying a 0200 crank in the fuel tank and have fun.

[Pearson]

Re: Engine conversion

DANG CHUCK! I can usually figure out what you mean when you mispell words but leaving out the periods and commas makes it really hard to follow your thoughts. I agree with what I think you are saying. Increasing compression would give more horsepower, but it also reduces engine life and reliability. Also I am not sure about the legality of of installing higher compression pistons unless they were listed on the TCDS, which I don't think any were for the C85.

I was searching for a C90 to put on my project for the same reasons as Bob Picard mentions. But I came across a good deal on an airplane with a C85, so that is what I will use. I am not a fan of the STC using an O200 crank in a C85. Stroking an engine moves the torque curve to a higher RPM. Higher RPM equals higher fuel consumpion and more stress on the engine. Granted, it also means more horsepower, but I like the idea of getting my ponies at the lowest rpm possible. I wish someone would certify a "high performance" cam for the A65, C85, & C90. To me, that would be the best way to get more power out of these engines without increasing RPM. I wonder if anyone has experimented with retarding the cam timing on these engines. It is a good way to move the torque curve toward the lower RPM range. I know it used to do wonders for a Ford FE engine I used to have.

[cvavon]

Re: Engine conversion

Rich we fixed the punctuation, the best Horse power gain is a prop with the right pitch. You need to turn these small engines up to get HP.

[senior]

Re: Engine conversion

I second cvavon.
Granted my plane is in a category that doesn't require all the paper work, but I can verify that high comp pistons work very well. Increase is rated at 9.8% so add that to 85hp & you get something like 93hp at the lower rpm rating. It is something I would definitely suggest looking into if your paperwork can support it.
As for the " reduces engine life and reliability", I'm not swallowing that, were not talking 13-1 comp here, even high comp 85 pistons are low comp in the rest of the world.
I can verify a very aggressive climb rate in a 750lb T with a 72-42 spinning 2500rpm

[Jim Herpst]

Re: Engine conversion

High comp pistons cheap fix . Not legal in cert plane. Correct still "low comp" when looking at the "rest of the world" Still not proven however for TBO long term reliability etc. That is why there are STC s and certifications. Not knocking or wanting flames just the facts being stated.

[N95334]

Re: Engine conversion

How do you get a hold of Terry Bowden?

[cvavon]

Re: Engine conversion

Certified aeronautical products is Terrys business the web site is www.dc65stc.blogspot.com and phone #257 715 4773