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C-85 Stroker too lean on take off

D

djonesutah

Registered User
My C-85 Stroker runs too lean in this colder weather, so that it stumbles terribly when advancing the throttle slowly on T&G's. I started leaving the carb heat on when advancing the throttle, and that helps, but very little. The Wag Cuby runs cold. I don't have CHT, it really takes a long climb just to get the oil temp to 150. Field temp was in the low 30's. I know that is common.

I see that a j-3 restrictor plate is available and commonly used for winter flying. My question is, is that only for 65 hp models? Will it make my stroker run too rich by having too much restriction for an engine pullng hp somewhere in the 90's? Can I lean the carb with mixture control the right amount to compensate?

Thanks for the advice in advance.
 
sounds like the first thing you need to do is get that carb rejetted or the float reset. if you are running lean you might be shocked at how high your cht and egt temps are running and you may be very close to detonation which is going to cause a lot of cylinder replacements. get an e.i. or aerospace logic 4 cyl cht and egt. installed SOON.
gary
 
Thanks for the responses guys. I think I will try both. I'll probably want to use some other CHT gauge than the two suggested. My Cuby doesn't have a charging system, though it does have a battery and a starter so I think I better huse a non-12V powered type.

I've wanted at least a CHT gauge because I am aware of how critical maintaining low CHT's is to engine life. I was kind of under th impression though that with the open cowling of a J-3 high CHT's weren't a concern. EGT is something I hadn't considered. I've flown 150's, 152's, -18, Luscombe, all older and stock, and an experimental 701 with and O-200. None had EGT monitoring. I guess I just assumed it wasn't something to worry about much.

The baffle looks easy enough to make, but I think I'lll just buy one if I can find it.

So If I end up with a non-powered CHT or combination CHT/EGT, I think I am limted to one sensor for each. Which cylinder is likely to run the hottest, and which cylinder should I run EGT on? And can I get a bayonet type CHT for a Continental, or do I need to get the sensor type that fits under a plug?

Again, thanks in advance.
 
Thanks for the responses guys. I think I will try both. I'll probably want to use some other CHT gauge than the two suggested. My Cuby doesn't have a charging system, though it does have a battery and a starter so I think I better huse a non-12V powered type.

I've wanted at least a CHT gauge because I am aware of how critical maintaining low CHT's is to engine life. I was kind of under th impression though that with the open cowling of a J-3 high CHT's weren't a concern. EGT is something I hadn't considered. I've flown 150's, 152's, -18, Luscombe, all older and stock, and an experimental 701 with and O-200. None had EGT monitoring. I guess I just assumed it wasn't something to worry about much.

The baffle looks easy enough to make, but I think I'lll just buy one if I can find it.

So If I end up with a non-powered CHT or combination CHT/EGT, I think I am limted to one sensor for each. Which cylinder is likely to run the hottest, and which cylinder should I run EGT on? And can I get a bayonet type CHT for a Continental, or do I need to get the sensor type that fits under a plug?

Again, thanks in advance.
 
spend the extra money to get the 4 cyl. job and then you will know for sure which egt and cht is hottest, however that can change with temp and humidity.
gary
 
Longwinglover's solution from the Bower's website cured this problem on both my C-65 and C-85 hp Cubs. It took 30 minutes to build from scrap aluminum and cost nothing.

Mark
 
One additional point with reference to the OIL temperature running cool. There was a cloth insulated blanket that buttoned around the oil sump on these little engines to help keep the oil temp up in winter. Don't know where you'd find one, but you could probably make one. I also don't know how much they would help increase oil temp.

Getting the oil temperature up to ~180 plus is important in winter to cook off the moisture that inevitably builds up in the case.

MTV
 
You didn't say whether you have a Marvel carb or still have a Stromberg. Or is a Marvel part of the stroker STC?
 
Back in the eighties I bought a cover for the oil tank from Wag-Aero. I think you can also get snapon restrictors for the main cooling intakes. I wouldn't restrict until fully instrumented. Also, put a lenghtwise slit in the breather hose close to the engine. The thickness and springiness of the hose will keep it from weeping until all the moisture in your crank freezes at the lower end of the hose. Then a little weeping is better than blown seals. Don
 
puttputt said:
Back in the eighties I bought a cover for the oil tank from Wag-Aero. I think you can also get snapon restrictors for the main cooling intakes. I wouldn't restrict until fully instrumented. Also, put a lenghtwise slit in the breather hose close to the engine. The thickness and springiness of the hose will keep it from weeping until all the moisture in your crank freezes at the lower end of the hose. Then a little weeping is better than blown seals. Don
Click to expand...

Also clamp the breather tube outlet to the back of the tailpipe and the heat from the tailpipe will keep the breather tube from freezing.

Glenn
 
All good advice. Thanks.

It's a Precision (Marvel) carb. The wag is experimental. The engine builder docs say "all work done according to STC". It's not a yellow tagged engine though. I really don't think the STC specifies a carb, but I'm not sure. Engine build (carb rebuild or new) at around 40 hrs ago.

I should have mentioned too that I have a 74-37 Mac metal prop. Since receiving the links here I learned that a metal prop is partly responsible for the stumbling (the engine is more likely to stumble) because of the increased moment of inertia. Takes more to change it's speed than it would for wood. Makes sense to me.

I think I've settled on the Micro 1000 EGT/CHT for AS. I can go with non-TSO'd.
 
Doug, is it running lean or are you running out of gas, now thats it's colder check your gascolator screen you have more climbing ability with the colder air and might be outclimbing your fuel supply, I also have a 85 stroker, mac 74-36 and have run both a marvel and stromberg carb down to below zero without any stumble no matter how fast I advance the throttle, I think that the baffel plate that go's in front of the aircleaner is just a bandaid for the real problem, when I'm on floats or skis I don't run a aircleaner and it never stumbles even when at 0*

Glenn
 
Cubdriver,

Thanks for taking an interest. The problem comes at a time of first TO run, TW down. Once I get past it My TW is up immediately and there isn't a hint of a miss. There isn't a problem in flight, WOT, Vx, which is much steeper AOA than the plane on the ground in 3 pt. Could it be a fuel supply issue with that being the case? I am using pressure caps.

The engine is always sensitive needing a slow throttle advance, even in the summer, it's just worsens with temperature drops.

I also notice that I have more trouble when doing T&G's than I do with the very first TO after doing runups. I have been landing with slight power on, to avoid shock cooling, but I think even with that the engine is colder than after a runup.
 
And how long do you leave carb heat ON at runup? I've had carb ice on low RPM taxi out on carbureted Continentals. In pretty wide Temperature/Dewpoint spread.

Thanks. cubscout
 
On initial runup using carb heat only about 10 - 15 seconds, enough to see that it is working, and no change during the time that it is on. On T&G's applying carbheat midfield on DW and leaving it on until stopped (or close), then, at first, taking it off then applying throttle, then on subsequent TO's, leaving it on until engine full rpm and turning it off (about the time the tail comes up). That helped a little.

Carb is a Marvel.
 
Running Lean....

Pardner,
It looks to me like you have either a really fouled up carburetor, or a major air leak in the induction system. That Marvel carb has an accelerator pump, and those pumps really work well when adding power.
I think you should do some checking before you fry your engine, or worse.

Mike
 
djonesutah said:
I should have mentioned too that I have a 74-37 Mac metal prop. Since receiving the links here I learned that a metal prop is partly responsible for the stumbling (the engine is more likely to stumble) because of the increased moment of inertia. Takes more to change it's speed than it would for wood. Makes sense to me.
Click to expand...

Actually I always found the Wooden props would stumble more and die than the metal props, Wood props are light and do not store energy like a metal prop does. I ended up on a road between some Cranberry Bogs Learning this! Anyway the Continental Baffle Was the fix and Every winter I would install it and enjoy good safe engine operation. The metal prop cubs would Stumble too But the Flywheel effect of the heavier mass metal prop would help keep her going a little longer until the Carb. caught up.
 
Is it the correct carburetor for the engine? I have found a lot of C85s with the wrong carburetor because they are so hard to find and expensive to get the Marvel Schebler modified (STC) for the C85.
 
we had a Marvel(MA3spa) on our C85 but it was the wrong part number and never ran all that great,might want to check the TCDS for the C85 and check the part numbers listed against what is on your engine.
 
Thanks!

I followed the combined advice from many who responded to my post for advice.

I bought the oil tank insulator and induction tube insulators from Wag. I found that my air box filter consisted of only screens (this plane was on floats until I purchased it....some don't use air filters when on floats?), and, I fabricated and installed the cover over the air filter like many mentioned or PM'd to me.

It worked out well for me, I flew it this weekend. It was probably in the mid-30's. I could punch the throttle rapidly and only a small hesitation could be noticed. Previously, in 60 degree weather, I had to advance it moderately to avoid a stumble. And the time I flew it in mid 20 degree weather which prompted my post, I really had to be careful in advancing the throttle. Maybe more importantly,when flying, the engine just didn't feel and sound right. Made me uncomfortable to fly so I just returned the few miles and put it away. This last weekend the engine ran very well, sounded right, etc.

Anyway, I appreciate all the advice. I contributed to this site to become a member. without this group I would have not flown the plane again until warm(er) weather. I know I couldn't have found any useful advice locally, even if I paid for it. A great group of guys (and gals?) here.
 
Great to hear the cover you made worked....!

I just got around to making one last week, haven't tried it out yet, but looking
forward to after hearing your good outcome...

Turns out you're problem was mine too. I've been following this
thread with interest. Will second your praise of the help offered here.

Kem
 
I'm glad your back flying but each aircraft must be different, I have no aircleaner, no front plate, and no problems, flew around 2 weeks ago at zero and ran fine unless I decended to long at idle but if I left the carb heat on to taxi it ran fine, I have run it without an airclearer in very heavy rain and snow without any problems, each one of these little Continentals has there own qwerks, you just need to figure yours out :D

Glenn
 
cubdriver2,
what purpose does running your engine without air cleaner serve? how much more power can there be? i'm asking because i don't know much about engines.
gary
 
Depends on the tempeture but on a 60* F day about 25 rpm static, I know not that much, but in the summer I'm on a small pond and need all the help I can get, and I'm on snow most of the rest of the year so not worried about the dirty air, seems small but I'm a performance nut 8)

Glenn
 
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