C-90 Performance Mods

Besides using C-85 pistons and the p/n 530788 35 degree overlap cam (approved cam - just hard to find) what other mods are being done to increase the power from the C-90's? Mine is a -12. I have heard that using a intake spider off an A65 and grinding it to make it flow better also helps. I do not want to do anything that has not proved reliable.

I think you answered your own question. I have heard about the A65 manifold trick. The C90 is my favorite small Cont.

c-90

the pistons will give quiet a boost also use gapless rings.

What are gapless rings? How do you get them on?

What are gapless rings? How do you get them on?

c90

Gapless rings are not really gapless. They are two piece with one thinner ring slipping on to the bottom of the other main ring. The gaps are staggered and thin ring covers the gap of the main part.
I have used them in VW aircraft engines, and seem to work ok. No better, no worse. Do not use them in both compression grooves as they may scrape too much oil off the cylinder, and the cylinder may run dryer than it should. This is caused from the thin ring causing a much higher pressure point than a thick stock ring would . The thin ring section is almost identical to an oil control ring in some engines.
Ron

Straight pipes, with no muffler (to take advantage of the cam). Port and polish all the cast intake pieces.... spider, elbows, intake side of Cylinder. Take special care to line up the intake tubes with the elbows and spider. Venturi the 65 spider. Internally balance EVERY reciprocating part, doesn't really gain anything in hp, but will make it an exceptionally smooth engine. Run a Metal prop. Nitrous?

nkh

c-90

While at it, go with a four into one tuned exhaust. Make that puppy breathe.
Ron

85 CONTINENTAL

HI I GOT J3 WITH CONT WHEN INCREASING POWER ON DEMAND
ENGINE SPUTTERS OR MISSES WAT COULD BE PROBLEM
RUNNING GOOD AT CRUISE BUT SCARY WHEN NEED TO THROTTLE
UP FAST TEMPERATURE GOOD MAGS NOT THAT OLD .

What is the difference in the C-85 pistons and the hot rod pistons Lycon is selling?

Fireball, does your carb have an accelerator pump?

Steve Pierce said:

What is the difference in the C-85 pistons and the hot rod pistons Lycon is selling?

Click to expand...

Probably spark plug clearance. I think the original C85 cylinders had the spark plug boss raised up just a bit.

Tim

What do you guys think is the best carb for the C90. Also does anyone know who makes four to one exhaust for the 90.

Thanks, Ryan

C85 pistons are flat topped, and are about 1/8" taller than O-200 (pin to top). Normal compression is about 6-1 with O200 pistons, running C85's takes it to about 7/7.5-1?....sorry I don't know the exact number. LyCon's are a domed top piston that run up to about 10-1 and take special rings.

Fireball- We need a little more info. Is it sputtering as you accelerate the throttle on take off? Through what RPM? From what I've gathered, sounds like it's coughing at about 1300-1500rpm? If so, it's getting caught where it changes from the idle jet to the high jet, and you need to en-richen the carb a little. Or change your rhythm while pushing the throttle.

Ryan- Best carb? Whats the best truck? Some people will say Stomberg, and other will say Marvel. Strombergs occasionally have a problem leaking while on the ground, but it's not a problem if you use a new steel needle and seat and lap them together. Personally I think it's what you can get your hands on.

nkh

c90

I have a Stromburg on mine, but if I had deep pockets I would go with a Marvel if for no other reason it has a mixture control that works. The accelerator pump will also stop that hesitation you have now.
Try setting the idle screw richer, as this may help with the transition when you open the throttle. Make sure you have no intake leaks before doing anything.
Check the location of the cable attachment on the carb arm. It should be as far away from the shaft as possible.
When properly set up the Stromburg will not cough on acceration, unless you are a real animal with the throttle :lol:
Ron

I have the Marvel with the accel pump. Sometimes I get a bit of stumbling/roughness and occ. rpm drops shortly after I 've gone to full throttle. My guess is that accel pump is just shooting too much up in...

What's the best fix?

85 CONTINENTAL

Is there a screw to increase mixture or a lever ,i've never worked on
one but i do see a lever tied and locked with wire. I don't know if there
is an accelerator pump . The sputter or miss is between 1200 approx
1600 and yes im pretty aggressive with throttle . do you know wat gap supposed to be on plugs .I know you check intake leak on car with
propane but how do you check on airplane any sugestions.Can i take
accelerator pump without taking all carb apart if there is one.Is there
a place were i can get break down of carb.

Check for leaks physically and visually, make sure all the hose clamps are tight and the rubber tubing (inner and outer) are in good shape....i.e. no cracking, splitting, etc. Don't know about using propane, hell I've never even heard of it.

The lever you see tied off is the mixture control. And it's really not much of one, called a "Back Suction Mixture" Best to just leave that alone.

Your problem with the sputtering is mainly with the advancing speed of the throttle. Slow it down to about a 3 count....ooooone tttwo thrrrrree, stop to stop. REMEMBER airplane engines aren't built like cars! You've got to be easy on them if you want it to last.

There's a knob on the back side, I think, of the carb, thats gonna be your idle mixture. Screw it out a little at a time to en-richen the idle mixture, only if you still have hesitation problems with the slower throttle speed.

Spark gap 18/22 go/no-go

nkh

JP, I've got about "0" experience working on small Marvels, most is on the Stromberg. :roll: But I bet Ron will be able to give you some idea's.

nkh

C90 Mods

Thanks for the replies. I am most likely going to run a 76-AK-2 Sensenich prop pitched pretty low (43) as well. Performance Propellers out of Arizona makes a wood prop that all the acro guys are crazy about- it is supposed to be as good or better than a metal prop. I guess I would have to fly one to believe it.

I have been struggling trying to decide between the 0-320 and a little C90 with some performance mods. The airplane is a 750 pound clipped wing Tcraft. The addition of the 0-320 adds so much cost and weight- more fuel, more structure, better brakes, electrical system etc. I think the C90 is my best bet in keeping it simple and light.

For an exhaust I use a simple 2 into 1 Luscombe 8E set up, no muffler.

Thanks for the replies again. BTW- I build all wood clipped Tcraft wings- if anyone wants a set for a CWC project let me know- I will be glad to share my jigs and drawings. Mine come out at 55 pounds per side, for reference a stock wing is 80-85 lbs so you eliminate alot of weight. I am currently designing a set for a J-3 with an 0-200 and Tcraft wings.

Nathan K. Hammond said:

JP, I've got about "0" experience working on small Marvels, most is on the Stromberg. :roll: But I bet Ron will be able to give you some idea's.

nkh

Click to expand...

Gosh, I hope so. I'm sort of mystified. She runs a bit rough and drops off on rpm about 60 seconds or so after full throttle is applied. Doesn't matter how fast or slow I apply. It only happens at 2250 and above. The engine also has a hard time sometimes getting to full rpm (2525) and will lag and then surge. I've seen how much fuel an accel pump can squrt and the duration for which it does it, so that' what I suspect. I hope Ron let's me know what he thinks.

I've also discovered that the C-90 carbs can ice in a hearbeat.

What sorts of props and model number stroms and marvels is everyone using on a C-90?

Jeff-

The correct stromberg is on the c-90 TCDS.

http://www.cub-club.com/tc/Continental/E-252, C90 &O200.pdf


Can anybody give the comparisons between the stromberg and marvel carbs? The C90 I have for the J-5 has a stromberg on it. I can get a marvel if I want one. Thanks

Tim

eric, 750# WOW thats gonna be a hoot to fly! If I was in your shoes, I'd most likely stick with the C90. If you do all the tip and tricks, getting 120hp out of it with good reliability isn't a problem. I didn't think about it before, but an Aeromatic prop would be a REAL BIG advantage. It's basically a constant speed prop without the need for any controls. Great thing about them is you get full RPM for T/O and can get a good cruise too. Had a guy tell me about a Clip Wing Cub with a C90 and an Aeromatic.... he swore he could get off the ground in 50 ft. and out cruise a Citabria! DANG! There pricey at around $4200 but for what you get, it's worth it. www.aeromatic.com

JP, in the case of the Stromberg, it's a NA-S3A1. But that carb is the same for A65's up through O-200's, what changes is the ventrui. Example: the A65 setup may have a 1 1/8" diameter venturi, and a C90 may have a 1 7/8" diameter venturi. (THESE NUMBERS ARE NOT CORRECT, JUST AN EXAMPLE).

nkh

At 750#s empty wt. I would stick with the Cont. too. Sounds like a fun aircraft. I have ridden in a Swick with O-320 and it went well despite my lard in the right seat, about like a Decathalon.

c-90

fireball111: I assume the main problem is hesitation when advancing the throttle? This is cause from a lean condition from either an intake leak, or insufficiant fuel mixture. Late ignition timing will cause this symptom also.
The propane is a good check normally, but too much of a prop hazard and too windy to be successful with an aircraft engine. Do a check on the intake rubbers for no splits and the clamps tight. Check the intake elbows at each head. Make sure the carb is tight on the spider. Everything must be perfect for the Stromberg to work with-out hesitation.
If all this checks out several things with the carb may cause this hesitation. The mixture control should be wired full rich, cause the damn things never worked right anyway. The fix was to leave them wired rich.
The big screw at the back of the carb is the idle mixture screw. Open it 1/2 turn at a time while checking throttle response. The engine will still idle reasonably smoothly with just a slight touch of richness. It will run lumpy with black smoke puffing out the pipes if you go too far. Idle speed should not be below 600 rpm when hot. Lower than that , you may be looking for trouble, especially when cold weather comes. (ice) Mine is set for 700 rpm hot, and cold start it runs around 500 rpm.
If that doesn't do it , the float level may be too low, which has the effect of having to draw fuel from a lower , further point, which will make all rpm ranges leaner.
The overall condition of the carb will have major effects on things. If the throttle shaft bushings are too loose, vacuum needed to draw fuel will be lost, again causing it to lean out, especially at lower rpms. The carb may have dirt in the idle jet not allowing sufficiant fuel to be delivered. If turning the idle mixture screw out has not effect, this may be the culprit.
It's hard to fix the problem with a key-board, but this would be where I would be looking for the problem. Good luck.
Ron

C-90

jrussell: See fireball111 post for some ideas. The fact it is losing full rpm is a bit of a concern. Pull carb heat at full throttle and see what happens. If you get a drop ok , but if it stays the same or increases back to where it started before dropping, you are really lean. First thing I would do is make sure fuel flow is what it should be. Sounds like you just have enough to keep it running, but no extra at full throttle. Don't rule out a sticking valve. Probably would have some clattering happening at full throttle if it is. If it's a Marvel with a two piece venturi, this could be causing some of the problem. Not familiar with it that much, so hopefully others could chime in and explain the symptoms of these venturis. I'm quite sure you only have one problem causing the stumbling and power loss. Unless you have a leaking primer I don't think too rich is the problem, as the accelerator pump fuel delivered will burn up is a second or so and have no further effect on the overall mixture. If however, you can see black smoke pouring out of the pipes at full throttle, I will update the info to suit that problem.
Ron
Ron

CONTINENTAL 85 HP

Thanks ron and guys i will check all these things starting with leaks on
intake and throttle shaft
then spark plug gap ,mixtures .Just one more thing no sure about.
The accelerator pump does it have one and is there some kind of
carb cleaner i can run true without damaging the engine.I don't think
i was in the right topic but wasn't sure how to do that sorry for interruption
on mods .witch were by the way very interesting.going to work on that this weekend hopefully if it don't snow to mutch.

gas filter

any gas filters somewer on system i haven't seen one

timming

Do i check timing with timing light hows that done were the timing marks and how many degrees adv is it supposed to be at

C-90

Fireball111: No accelerator pump on a Stromberg. Normally there are two fuel filters. One is the gaskolator and the other is in the carb. It is behind that big brass nut on the side. Make sure you install the screen in the carb with the open end in toward the carb. If the engine runs fine at full throttle, neither of these are causing your problem, but they should be looked at from time to time anyway. You need a mag syncro- timer to do the job accurately. Don't have the degree settings for c90 , but sure some-one will post it.
Ron

C90

I have owned a 180 Hp Clipwing Tcraft and a 0-200 powered clipwing T. like Cubs the lighter you can keep them the better they fly. The 180 did good but it was really heavy(1100 empty) The 0-200 powered plane was around 750.
My engine is a C90-12. I have C85 pistons that have been chamfered and will re-work the A65 intake. I finally found the good cam and will use it along with a 2 into 1 exhaust. I plan to balance everything so it doesn't eat itself. Basically - if I can get a reliable 105-110hp I am happy. Oh yaeh- I will use the MA3-SPA carb until I can find a reliable inverted f/o system for the little continental. The 0-320 A2A ia a good engine it is just much heavier than the C90- by the time I add electrical and all the structural mods I had an additional 150-200 pounds. I would have to build the plane much heavier as well. I think I will stick with the little C90 and have a really fun aerobatic sport plane keep the hard acro for the 180hp Pitts.

If anyone notices any items that are proven that I missed please let me know. Happy flying-