85 pistons in a C-90
- Thread starter flynfishr
- Start date
Steve Pierce
BENEFACTOR
Graham, TX
Put the C85 cam in for more power.
redrooster
Registered User
western Washington
Jim, I was wondering where you came up with the 8.7:1 for the compression ratio--did you test/calculate from an egine you'd built, or did Klaus (O-200 Lightspeed ign dude) have this info? What is the stock compression ratio for the C85,C90, and O200? 7;1, as I recall? And you said OK for cargas-- 87 octane or 91 octane?
Steve- I'd always heard (including on this site) that the C90 cam was the right stuff. Or at least one of the C90 cams- I guess maybe there's two?
Rooster
Steve- I'd always heard (including on this site) that the C90 cam was the right stuff. Or at least one of the C90 cams- I guess maybe there's two?
Rooster
Steve Pierce
BENEFACTOR
Graham, TX
Don Swords (Don's Dream Machines) gave a talk at the Cub Club Forum at Sun & Fun. He said the C85 with the O-200 crank, rods and pistons is the best set-up. He said the cam in the C85 is the best. When I talked to Ken at Lycon he said they had been cam doctoring some cams and were trying to find the best combo. He said the higher lift cams didn't perform on the dyno like the low lift C85. Don took a legal C85/O200 cranked engine with new Millennium cylinders that were flow matched with the intake spider and after a 10 hour break in got 115 hp and 240 ft. lbs of torque at 2475 rpm. The O-200 puts out 75 hp at 2500 rpm. There was an old cam that is know illegal for the C90 that had a 35 degree duration. He said with a straight exhaust like a Luscombe it would spit fuel on the ground and burn. I understand they are like hen's teeth.
Jerry Burr
MEMBER
Sedro Woolley, Washington.
Cam
Hi Steve.
There was an old cam that is know illegal for the C90 that had a 35 degree duration.
I think what you mean is that the 35deg cam came stock in the 90 and that it is illegal (not certified) in other models. Is that correct? Jerry B.
Hi Steve.
There was an old cam that is know illegal for the C90 that had a 35 degree duration.
I think what you mean is that the 35deg cam came stock in the 90 and that it is illegal (not certified) in other models. Is that correct? Jerry B.
Rooster, I didn't calculate it -- and forget where I got it. However, based on calculating some other piston compression ratios, qualitatively it looks pretty close.
Re the weak O-200, I'm flying an O-200 powered long-wing J-3 that outruns a newly overhauled C85/200 local clipwing J-3 in level flight by quite a margin. I turn about 2640 rpm on climbout, so climb performance is reasonable as well.
JimC
Re the weak O-200, I'm flying an O-200 powered long-wing J-3 that outruns a newly overhauled C85/200 local clipwing J-3 in level flight by quite a margin. I turn about 2640 rpm on climbout, so climb performance is reasonable as well.
JimC
Steve Pierce
BENEFACTOR
Graham, TX
Jerry, The way Don said it the cam was no longer legal in the C-90 but I could be mistaken. I think he said there was a service bulletin or something like that. I will look it up.
Jim, I can never get that rpm out of an O-200. I think the lower rpm torque curves are much better on the C85/O-200 crank engines. Don was pretty excited about the high torques they were getting so they can transfer that power to more prop.
Jim, I can never get that rpm out of an O-200. I think the lower rpm torque curves are much better on the C85/O-200 crank engines. Don was pretty excited about the high torques they were getting so they can transfer that power to more prop.
bob turner
Registered User
Jin: Check the timing on that anemic C-85/O-200. The STC wants the timing retarded so the thing puts out 85 HP+/-. But there is a legal tolerance . . .
Some Cubs are just faster than others, and it is difficult to figure out why. Even the Smart Level can't tell you everything.
I hear there are C-180s that do 160 kts on 9 1/2 gph, but I could never even come close.
Some Cubs are just faster than others, and it is difficult to figure out why. Even the Smart Level can't tell you everything.
I hear there are C-180s that do 160 kts on 9 1/2 gph, but I could never even come close.
The timing's not retarded on the C85/200. It came out of Don's shop a few months ago, and he dyno'd it at 97 hp. I'm not knocking the engine -- I think its a great piece of work and have the utmost respect for Don. Steve, it's on Ed's clipwing at Colonial. The O-200 longwing J-3 we're comparing it against will turn 2950 rpm in level flight at 118 mph with two folks on board (not bad for a J-3), but the 337 limits us to 2640 rpm, so except for two short test runs early on, we don't give it full throttle. The 337 does allow us to climb out at 2640 rpm, so we do. The O-200 prop is a McCauley 1B90 CM7142. We've also tried it with a CM7441 with similar results, but that prop isn't legal on the O-200, so after that test, it was removed.
JimC
JimC
bob turner
Registered User
Well, I heard the STC was for C-90/O-200 pistons, so if you are running the O-200 crank with the C-85 pistons, you are by definition experimental, and can burn anything you want.
My STC says , I think, 26 degrees BTC, which is pretty much retarded. I didn't pull it out of the file cabinet, so I could be off by a degree.
My STC says , I think, 26 degrees BTC, which is pretty much retarded. I didn't pull it out of the file cabinet, so I could be off by a degree.
Roger Peterson
Registered User
Sweeny, Texas
The C90 cam you are talking about is the 530788 cam. I am running it in my 0-200 with 4 into 1 exhaust. Found 2 NOS cams and have one in my plane and can have copies made of the other one. Really makes a performer out of a 0-200 but you should port the cylinders.
behindpropellers
Registered User
NE Ohio
Steve Pierce said:
Are we talking experimental or certified here?
I notice that I can spin an extra 1000 rpm with a C-85, same prop as I would use with the C-90.
If I was the guy selling the C-85/0-200 STC I would be boasting high HP numbers too, just something to think about. Did Don say what timing he was using?
Tim
Steve Pierce
BENEFACTOR
Graham, TX
Possible pair of projects in the works so I have been doing a lot of research. Ken at Lycon is getting a couple more hp out of the C85/O200 cranked engine. Those numbers are on a certified engine so I assume the timing is stock. The C85 cam appears to be the key here. It has a flat spot around 1800-2100 rpm but creates power the rest of the way up the power curve where the O-200 falls off abruptly. C85 pistons will up the compression ratio from 7:1 to 9:1 but give you about 4 more hp from what Don told me. He also said the 35 degree duration C90 cam has to have a free flow no muffle exhaust system to work. No back pressure.
behindpropellers
Registered User
NE Ohio
Interesting.
Going to a C-85-12 would save me from writing one more 337 here. I just found a C-85 (guy is not sure if it is a -12 or -8) so I could build that up instead of the C-90. My TCDS lets me spin a C85 with a 74" prop at 2430 or spin a 74" prop @ 2250 with the C90.
Tim
Going to a C-85-12 would save me from writing one more 337 here. I just found a C-85 (guy is not sure if it is a -12 or -8) so I could build that up instead of the C-90. My TCDS lets me spin a C85 with a 74" prop at 2430 or spin a 74" prop @ 2250 with the C90.
Tim
Stock 85's have 6.3:1 compression ratio, so increasing an unstroked 85 to 9:1 will add 12.2% more thermodynamic power, bringing them up to 95.4 hp at rated rpm.
85's stroked to 90's while retaining the 85 pistons will (if the 9 estimate is correct and ignoring the difference in 0.382" vs. 0.41" valve lift) add 8.1% more power than a stock 90, bringing the stroked 85 up to 97.3 hp at rated rpm.
So stroking an 85 and bringing the compression up to 9:1 will give (97.3-95.4)=1.9 hp more than just putting 9:1 pistons in an unstroked 85.
Using 9.5 pistons would make the numbers at rated rpm:
C-85 C-90 O-200
stock 85 90 100
9.5:1 96.8 98.7 109.7
85's stroked to 90's while retaining the 85 pistons will (if the 9 estimate is correct and ignoring the difference in 0.382" vs. 0.41" valve lift) add 8.1% more power than a stock 90, bringing the stroked 85 up to 97.3 hp at rated rpm.
So stroking an 85 and bringing the compression up to 9:1 will give (97.3-95.4)=1.9 hp more than just putting 9:1 pistons in an unstroked 85.
Using 9.5 pistons would make the numbers at rated rpm:
C-85 C-90 O-200
stock 85 90 100
9.5:1 96.8 98.7 109.7
behindpropellers
Registered User
NE Ohio
JimC said:
What RPM are we talking for max power?
Steve Pierce
BENEFACTOR
Graham, TX
Don says he gets more hp and torque out of the C85/O200 cranked engine than the C-90. I asked this question specifically because I have a C90 and a PA18-90. If I didn't have to be legal I could use a c-85 cam and lifters and have the same thing as the O-200 cranked C-85. Will be talking to Ken at Lycon in the next few days and will put the same questions to him.
Steve, Don dyno'd Ed's C85/200 at 97 hp, vs. the 88.2 hp that I calculated for that combination from the thermodynamic efficiency (which leads me to think that he may have turned more than the rated 2575 rpm on the dyno). If you turn the 90 up to 2575, you'll get power similar to the C85/200. Since I've run the O-200 side by side with the C85/200 and I have to throttle back substantially for him to stay with me, I think I'll stick with the O-200. That said, Ed's engine will blow the socks off a stock C85.
JimC
JimC
C-85 to 0-200
Guys I don`t have any specific numbers but I just finished my champ and built the C-85-8 that was in it used 0-200 crank, rods and pistons ( domes ceramic coated and skirts moly coated) with a C-85 cam. I didn`t touch the cylinders except for chroming them up to Std. I have found that a slightly smaller port size will give a higher velocity to the fuel/air charge thus better cylinder filling capacity and more bottom end torque. Hanlon Wilson exhausts that were coated by Jet Hot. This engine will run rings around what it was before ,more bottom end pull and much shorter t/o. If I had it to do again I wouldn`t hesitate to go the same route. Skip
Guys I don`t have any specific numbers but I just finished my champ and built the C-85-8 that was in it used 0-200 crank, rods and pistons ( domes ceramic coated and skirts moly coated) with a C-85 cam. I didn`t touch the cylinders except for chroming them up to Std. I have found that a slightly smaller port size will give a higher velocity to the fuel/air charge thus better cylinder filling capacity and more bottom end torque. Hanlon Wilson exhausts that were coated by Jet Hot. This engine will run rings around what it was before ,more bottom end pull and much shorter t/o. If I had it to do again I wouldn`t hesitate to go the same route. Skip
Here is a chart of sea level torque at 29" MP for C-85, C-90, O-200, 9.5 O-200, and 10.5 O-200 for varying rpm. Stock O-200 is in red and stock C-90 is in blue. Stock C-85 is yellow. Note the bad Continental data point for the C-90 at 2350 rpm, and note the similarity in shape of the curve between the C-85 and O-200.
Also, a chart of C-90 vs O-200 horsepower at 2750 rpm and varying manifold pressure. The crossover point is 21" Hg (about 9500 feet pressure altitude).
As an aside, based on piston pin height, C-85 pistons in an 85 stroker or O-200 will give a compression ratio of 8.68:1. Caution -- unchamphered 85 pistons will strike the heads in some older cylinders. I prefer the NFS 9.5's from Lycon, but Lycon tells me they sell more NFS 9.0's.
Edit - I know of one guy who ground the O-200 heads back to clear the top of the 85 pistons (had head strikes on 2 of 4 cylinders and evidence of the top rings topping the steel barrels. After the head work, he had a top ring overtop the barrel and hang between it and the head. Said he had a heckuva time getting the piston out of the cylinder.
Also, a chart of C-90 vs O-200 horsepower at 2750 rpm and varying manifold pressure. The crossover point is 21" Hg (about 9500 feet pressure altitude).
As an aside, based on piston pin height, C-85 pistons in an 85 stroker or O-200 will give a compression ratio of 8.68:1. Caution -- unchamphered 85 pistons will strike the heads in some older cylinders. I prefer the NFS 9.5's from Lycon, but Lycon tells me they sell more NFS 9.0's.
Edit - I know of one guy who ground the O-200 heads back to clear the top of the 85 pistons (had head strikes on 2 of 4 cylinders and evidence of the top rings topping the steel barrels. After the head work, he had a top ring overtop the barrel and hang between it and the head. Said he had a heckuva time getting the piston out of the cylinder.
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cubdriver2
FRIEND
upstate NY
JimC has helped a lot of us get a little more out of the little C engines, he knows his sh!t. I didn't champher the pistons. The top hits the spark plug casting bulge where the threaded brass insert is,(ECI) I radiused the bulbed casting to match the rest of the of the combustion chamber and left the C85 pistons alone. Always clay to check clearances.
Glenn
Glenn
Ron Graham
Registered User
Skip,
I have found that a slightly smaller port size will give a higher velocity to the fuel/air charge thus better cylinder filling capacity and more bottom end torque.
What is smaller porting?
FM4
I have found that a slightly smaller port size will give a higher velocity to the fuel/air charge thus better cylinder filling capacity and more bottom end torque.
What is smaller porting?
FM4
duckhunter10
Registered User
any pireps on don's dream machines
cubdriver2
FRIEND
