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Thread: Carb Temp variations in Pponk'd C180s

  1. #1
    SJ's Avatar
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    Carb Temp variations in Pponk'd C180s

    I have an EI carb temp gauge in my 55 c180 and pretty much ALWAYS winter or summer, have to have at least a little carb heat on to keep it out of the "ice zone". It has proven at night over Pennsylvania that it can make ice like a Manitowoc ice machine - in fact, enough that it won't clear all the way even with full car heat.

    The other day I flew in a gorgeous 59 c180 with a PPonk and asked the owner about his carb temps. 135 degrees and he never uses carb heat, never had ice, etc. It was about 30 degrees out that day.

    I have the "small" crossover tube on my engine which is what is prescribed to help with this problem.

    The cowling intakes are different on these two planes.

    Any ideas?

    sj
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    For the majority of the years I've owned my 180 it had a carb temp gauge in the panel. It pretty much always ran in the yellow zone. My plane doesn't make ice so I never paid attention to it and I never ran with partial carb heat. When I replaced the old panel and installed an EDM711 I added the carb temp probe so I could experiment with partial carb heat to help normalize cylinder temps, something I'd read about for years. That experiment lasted about 5 minutes and I've never looked at carb temp since. And I still don't use partial carb heat. Some 180s make ice. Some don't.

    If your friend's carb temp was 135* he's getting heat from somewhere.

    It sounds like you ought to re-plumb your carb heat source!
    Last edited by stewartb; 12-17-2016 at 09:00 AM.

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    Dave Calkins's Avatar
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    Great Subject. The "early" pre-1956 Cessna 180's with the large intake probably flow differently than the smaller intake 1959 model or even SB's late model.

    Speculation as to how and why induction icing would be more acute on the early models would be welcome.

    My 1953 requires attention to the carb temp. I have a JPI EDM 900 engine instrument cluster. I love that thing

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    Dave Calkins's Avatar
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    Steve, you mentioned "135 degrees". Can you clarify what that is about?

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    It isn't a matter of what year. Some J models make lots of ice. Mine doesn't. It's a mystery that modern science should be able to solve.

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    SJ's Avatar
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    Quote Originally Posted by Dave Calkins View Post
    Steve, you mentioned "135 degrees". Can you clarify what that is about?
    He was using the same EI carb temp probe that I do, and his reads 135 degrees of intake air and he has never had carb icing. Never uses in landing, etc. While he lives in Texas, he flys in plenty of conditions where I would need near full carb heat.

    sj
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    Steve Pierce's Avatar
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    Quote Originally Posted by Dave Calkins View Post
    Great Subject. The "early" pre-1956 Cessna 180's with the large intake probably flow differently than the smaller intake 1959 model or even SB's late model.

    Speculation as to how and why induction icing would be more acute on the early models would be welcome.

    My 1953 requires attention to the carb temp. I have a JPI EDM 900 engine instrument cluster. I love that thing
    I was curious if the larger intake scoop on the earlier models had an effect.
    Steve Pierce

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    I wonder if carb intake air pressure has some role. If my plane was an ice maker I'd make a temporary flange around the intake perimeter to make a little ram air collector to see if that helps. With the history of carb ice accidents in aviation I don't understand why more hasn't been done to study it.

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    I haven't had many carb ice issues in my 54 Pponk. Several years ago (when i still had a J engine) I was flying with another 54 (also with a J engine). His was running so rough, he thought he was going to have to put it in a field. Mine had no issues. Not sure what could have been different between the 2 planes. I don't have a carb temp gauge...seems like it would just give me something to worry about.

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    mvivion's Avatar
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    Quote Originally Posted by Skywagon View Post
    I haven't had many carb ice issues in my 54 Pponk. Several years ago (when i still had a J engine) I was flying with another 54 (also with a J engine). His was running so rough, he thought he was going to have to put it in a field. Mine had no issues. Not sure what could have been different between the 2 planes. I don't have a carb temp gauge...seems like it would just give me something to worry about.
    One possible culprit that could explain that behavior is if your airplane has an insulated induction crossover tube at the front of the engine and the other plane didn't.

    A lot of 180s won't run for beans in cold unless that crossover tube is wrapped with some pipe insulation. Without that insulation, they exhibit exactly the symptoms you describe.

    MTV

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    SJ's Avatar
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    Quote Originally Posted by mvivion View Post
    One possible culprit that could explain that behavior is if your airplane has an insulated induction crossover tube at the front of the engine and the other plane didn't.

    A lot of 180s won't run for beans in cold unless that crossover tube is wrapped with some pipe insulation. Without that insulation, they exhibit exactly the symptoms you describe.

    MTV
    Interesting. I don't understand why that crossover makes such a big difference.

    sj
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    Fuel condenses in the foward induction area. That has nothing to do with carb ice.

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    Quote Originally Posted by Skywagon View Post
    I haven't had many carb ice issues in my 54 Pponk. Several years ago (when i still had a J engine) I was flying with another 54 (also with a J engine). His was running so rough, he thought he was going to have to put it in a field. Mine had no issues. Not sure what could have been different between the 2 planes. I don't have a carb temp gauge...seems like it would just give me something to worry about.
    It's obvious that the carb temp probe causes carb ice

    Glenn
    "Optimism is going after Moby Dick in a rowboat and taking the tartar sauce with you!"

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    Dave Calkins's Avatar
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    Quote Originally Posted by cubdriver2 View Post
    It's obvious that the carb temp probe causes carb ice

    Glenn
    except on the buddy of SJ's 180 and also SB's 180

    To add to this, plenty of SuperCubs i have flown didnt make ice and a few of em really did!??

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    mvivion's Avatar
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    Quote Originally Posted by stewartb View Post
    Fuel condenses in the foward induction area. That has nothing to do with carb ice.
    Stewart

    Correct, but it could be precisely what the difference was between the two planes he described. It's possible this was carb ice related, but I'll guarantee that a lot of 180s will run really rough and almost seem like they're going to die in cold weather without that balance tube insulated.

    MTV

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    mvivion's Avatar
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    Quote Originally Posted by Dave Calkins View Post
    except on the buddy of SJ's 180 and also SB's 180

    To add to this, plenty of SuperCubs i have flown didnt make ice and a few of em really did!??
    Exactly. I put quite a few hours on a SC in Kodiak, where icing is common. Never made much ice till the engine was swapped for new. I don't know what else was. changed, but that plane REALLY made carb ice after the new engine. I figured the air box or ??? was rebuilt during the engine change.....maybe.

    MTV

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    Quote Originally Posted by mvivion View Post
    Stewart

    Correct, but it could be precisely what the difference was between the two planes he described. It's possible this was carb ice related, but I'll guarantee that a lot of 180s will run really rough and almost seem like they're going to die in cold weather without that balance tube insulated.

    MTV
    My comment was in reply to SJ. I remember my 180 with an uninsulated balance tube. The front cylinders don't run well with condensed fuel making them excessively rich. It does feel a bit like carb ice except carb heat doesn't fix it. Hmm, a little heat from the get-go might reduce it, though. Perhaps that is what SJ is describing?

  18. #18
    mvivion's Avatar
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    In my experience, carb heat doesn't help an uninsulated balance tube much, but it really depends on how cold it is I reckon.

    MTV

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    Quote Originally Posted by mvivion View Post
    ...A lot of 180s won't run for beans in cold unless that crossover tube is wrapped with some pipe insulation. Without that insulation, they exhibit exactly the symptoms you describe. MTV
    It was cold around here (Puget Sound) last week-- nothing like what some of you guys experience, but lows in the low-to-mid 20's & highs ranging from 31 to 36 or so. I was flying home on one of the colder days, after leaving my airplane to sit on a cold ramp for a couple hours, and I pulled the carb heat on briefly (as is my habit) a few minutes after takeoff. Only this time the engine ran like crap, just like when you have carb ice and the engine ingests a bunch of water after carb heat melts it off.
    But it didn't clear up after a few seconds, just kept running like crap. Ran OK without carb heat, cruise power mag check was fine.
    Is this something that might be crossover tube related? I have a 53 180 with a K engine, not sure what size crossover tube it has but it's not insulated.
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    Quote Originally Posted by hotrod180 View Post
    It was cold around here (Puget Sound) last week-- nothing like what some of you guys experience, but lows in the low-to-mid 20's & highs ranging from 31 to 36 or so. I was flying home on one of the colder days, after leaving my airplane to sit on a cold ramp for a couple hours, and I pulled the carb heat on briefly (as is my habit) a few minutes after takeoff. Only this time the engine ran like crap, just like when you have carb ice and the engine ingests a bunch of water after carb heat melts it off.
    But it didn't clear up after a few seconds, just kept running like crap. Ran OK without carb heat, cruise power mag check was fine.
    Is this something that might be crossover tube related? I have a 53 180 with a K engine, not sure what size crossover tube it has but it's not insulated.
    Could there have been any ice in the scat tubes? IF water gets into your scat tube and freezes, the carb will be flooded with moisture with carb heat on.

    Keeping induction air warm would easily effect the ability of the air to bring atomized fuel into the cylinders. Maybe many of the issues experienced in the past is more of a fuel atomizing issue, not a carb ice issue.

    Consider once carb heat is on you warm the carb, with warm air which will also warm the entire induction system. Carb heat goes off and you again get cold air, which after a few minutes will cool the induction system.

    If the temps needed to keep fuel atomized are not sustained, the plane will begin dropping out fuel in the inductions, and running rough.


    Any thoughts?
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    mvivion's Avatar
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    Quote Originally Posted by hotrod180 View Post
    It was cold around here (Puget Sound) last week-- nothing like what some of you guys experience, but lows in the low-to-mid 20's & highs ranging from 31 to 36 or so. I was flying home on one of the colder days, after leaving my airplane to sit on a cold ramp for a couple hours, and I pulled the carb heat on briefly (as is my habit) a few minutes after takeoff. Only this time the engine ran like crap, just like when you have carb ice and the engine ingests a bunch of water after carb heat melts it off.
    But it didn't clear up after a few seconds, just kept running like crap. Ran OK without carb heat, cruise power mag check was fine.
    Is this something that might be crossover tube related? I have a 53 180 with a K engine, not sure what size crossover tube it has but it's not insulated.
    I kind of doubt it. That said, no down side to installing some foam pipe insulation (the split stuff) and zip tying it in place.

    How long did you leave the carb heat on when applied? May not have had time to comepletely remove all the ice?

    MTV

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    www.SkupTech.com mike mcs repair's Avatar
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    Quote Originally Posted by hotrod180 View Post
    ...kept running like crap. Ran OK without carb heat, ....
    does that one get its carb heat from muffler shroud??? if so, the muffler may be broken under shroud on carb heat side

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    www.SkupTech.com mike mcs repair's Avatar
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    Quote Originally Posted by 18180 View Post
    but have yet to pull carb heat....
    thats scary operations!

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    Quote Originally Posted by mvivion View Post
    I kind of doubt it. That said, no down side to installing some foam pipe insulation (the split stuff) and zip tying it in place.

    How long did you leave the carb heat on when applied? May not have had time to comepletely remove all the ice?

    MTV
    But that would necessitate SJ to remove the cowling, he hates that task.
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    Quote Originally Posted by Steve Pierce View Post
    But that would necessitate SJ to remove the cowling, he hates that task.
    And a true PIA that is by oneself...
    Last edited by OLDCROWE; 12-21-2016 at 09:42 AM.
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    Quote Originally Posted by hotrod180 View Post
    It was cold around here (Puget Sound) last week-- nothing like what some of you guys experience, but lows in the low-to-mid 20's & highs ranging from 31 to 36 or so. I was flying home on one of the colder days, after leaving my airplane to sit on a cold ramp for a couple hours, and I pulled the carb heat on briefly (as is my habit) a few minutes after takeoff. Only this time the engine ran like crap, just like when you have carb ice and the engine ingests a bunch of water after carb heat melts it off.
    But it didn't clear up after a few seconds, just kept running like crap. Ran OK without carb heat, cruise power mag check was fine.
    Is this something that might be crossover tube related? I have a 53 180 with a K engine, not sure what size crossover tube it has but it's not insulated.
    Did you lean the mixture to smooth it out? If you're cruising rich of peak and pull carb heat it should run like crap until you make adjustments. And yes, the balance tube may play a role in it.

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    hotrod180's Avatar
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    Quote Originally Posted by stewartb View Post
    Did you lean the mixture to smooth it out? If you're cruising rich of peak and pull carb heat it should run like crap until you make adjustments. And yes, the balance tube may play a role in it.
    No, didn't mess with the mixture.
    Yes (to an earlier question), left the carb heat on long enough to melt any ice--
    the temperature / dewpoint spread was wide enough where I shouldn't have had any icing anyway.

    FWIW I flew the airplane again two days ago, after the cold snap was over,
    and it ran just fine-- including with carb heat pulled.
    Just one of those things I guess.
    Cessna Skywagon-- accept no substitute!

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    SJ's Avatar
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    Quote Originally Posted by Steve Pierce View Post
    But that would necessitate SJ to remove the cowling, he hates that task.
    Actually I don't mind removing the cowling at all - it is putting it back that I hate!

    sj
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    With a seaplane exhaust extension the bottom cowl won't easily fall off with gravity and is much easier to install solo.

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    Maybe I am wrong, but I always either had full carb heat or no carb heat never partial, just cause temp gauge says its cold enough for ice means very little in my opinion

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    mvivion's Avatar
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    Quote Originally Posted by dryfarmer View Post
    Maybe I am wrong, but I always either had full carb heat or no carb heat never partial, just cause temp gauge says its cold enough for ice means very little in my opinion
    That is the most common advice, probably because carb air temperature gauges aren't that common in most airplanes.

    They are fairly common in Cessna 180/182s, at least the older ones. That is because those airplanes do tend to make ice a bit more than other airplanes. If it is equipped with a carb temperature gauge, there's no problem running partial carb heat. Only down side is you're feeding unfiltered air into the engine, but at altitude that shouldn't be an issue.

    Fly a Beaver sometime.....the POH calls for carb heat any time they're in the right conditions. POH says run sufficient carb heat to keep carb inlet temp at or above + 4 C (or was that +7C? Been a while.). Pull on full carb heat and it'll sound like the engine is dying...great way to scare passengers.

    MTV
    Last edited by mvivion; 12-22-2016 at 09:25 PM.

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    Dave Calkins's Avatar
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    4 deg C for the Beav.

    One operator I flew for didnt train for maintaining it as I recall about carb air temp or carb heat settings in the Beav other than it being in the TO and landing checklist for "cold". As I recall.


    A different operator I flew for last season had a very specific regimen for setting carb air temp and maintaining 4 C per DeHavilland specs with partial carb heat.

    I also run partial carb heat on my 180 every flight it seems. That had been normal 180 ops for me before flying Beavers.
    Last edited by Dave Calkins; 12-22-2016 at 02:32 PM.

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    The big reason for maintaining the Beaver carb temp above +4C is for proper atomization of fuel according to the POH I read some time ago.

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    I had a P-Ponk 180. Had a big variation with the EGT's front to back. Turns out there are three sizes of crossover tubes, I had the "medium". When I changed to the "large", they got closer but I still had to run partial carb heat to get them within a reasonable range. (And no, I did not have an induction leak.) I have heard of others going to the smaller tube with like results. YMMV

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    The best thing I ever did to level EGTs and CHTs was to increase the fuel flow. I can still lean it to the flow rate I used to have but temps are definitely better now. It may not make perfect sense but it's true. My engine has always been a little leaner than I'd like. Not any more. Take off fuel flow in a Pponk engine should in the into the 20-something gph. Any less and it won't have enough fuel flow for cold weather. That's when I used to see my greatest temp spreads.
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    mvivion's Avatar
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    Quote Originally Posted by Randyk View Post
    The big reason for maintaining the Beaver carb temp above +4C is for proper atomization of fuel according to the POH I read some time ago.
    Now that you mention it, I recall that advice as well. When I was getting checked out Jerry Lawhorne told me "when that check pilot gets done checking you out in your airplane, you come talk to me, and I'll tell you how you're gonna run MY engine." Jerry was our Chief of Maintenance and he knew more about 985s than just about anyone I ever met.

    MTV

  37. #37
    CenterHillAg's Avatar
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    Is that carb heat reccomendation specific to the Beaver, or do the 985's tend to make ice in general?

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    Quote Originally Posted by stewartb View Post
    The best thing I ever did to level EGTs and CHTs was to increase the fuel flow. I can still lean it to the flow rate I used to have but temps are definitely better now. It may not make perfect sense but it's true. My engine has always been a little leaner than I'd like. Not any more. Take off fuel flow in a Pponk engine should in the into the 20-something gph. Any less and it won't have enough fuel flow for cold weather. That's when I used to see my greatest temp spreads.
    Further, if you have less than 20+ fuel flow on takeoff it might mean the carb was not jetted right - and you will burn up exhaust valves - which I know from experience.

    sj
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    Steve Pierce's Avatar
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    Quote Originally Posted by Randyk View Post
    I had a P-Ponk 180. Had a big variation with the EGT's front to back. Turns out there are three sizes of crossover tubes, I had the "medium". When I changed to the "large", they got closer but I still had to run partial carb heat to get them within a reasonable range. (And no, I did not have an induction leak.) I have heard of others going to the smaller tube with like results. YMMV
    I was thinking Steve Knopp told me to use the smallest balance tube.

    I ran a 53 model 180 up on a cool day and saw frost form on the induction Y. Cool day in Texas is about 60 degrees.
    Steve Pierce

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    P.Ponk 180 Ice

    Quote Originally Posted by SJ View Post
    I have an EI carb temp gauge in my 55 c180 and pretty much ALWAYS winter or summer, have to have at least a little carb heat on to keep it out of the "ice zone". It has proven at night over Pennsylvania that it can make ice like a Manitowoc ice machine - in fact, enough that it won't clear all the way even with full car heat.

    The other day I flew in a gorgeous 59 c180 with a PPonk and asked the owner about his carb temps. 135 degrees and he never uses carb heat, never had ice, etc. It was about 30 degrees out that day.

    I have the "small" crossover tube on my engine which is what is prescribed to help with this problem.

    The cowling intakes are different on these two planes.

    Any ideas?

    sj
    I own and fly a 1954 Cessna 180 that currently has an P.Ponk engine. I have owned the airplane since 1982. I have had 3 different engines in this plane, the original o-470-J, an o-470-R and now the o-470-50. The O-470-50 is an original io-520-D with the original high compression pistons (by field approval). Back in the day I remember thinking how "ice free" the old J beater was. I think the only time I ever had to use carb heat in cruise was flying low level over Lake Iliamna during a rain storm. The aircraft was equipped with the factory original carb heat gauge and probe. Those early carb temp setup's were not very accurate as the probe was in the air box, not the carburetor throat. I think it was only telling you the temperature of the air BEFORE it enters the carburetor. When I installed the o-470-R I discovered why the J beater almost never produced ice, the rubber seal in the air box valve was all but gone. Having a temperature probe forward of the carburetor and an almost non-existent seal in my air box, I had been unknowingly running around with partial carburetor heat for years. I then replaced the rubber seal and installed a cheap Westach gauge and probe. At least the probe was now located in the carburetor. I did experience the cross over tube icing condition with the O-470-R once while crossing the Alaska Range during the winter. For whatever the reason the rough running engine could not be smoothed out with carb heat or mixture adjustment. What was funny is that it occurred during a climb at about 7000 feet (an altitude way over my usual 1000 feet). If I stopped the climb and descended to 6800 the roughness stopped. If I started the climb again the engine would run rough again right at 7000. I just stayed at 6800. Talking with Alaskan Aircraft Engines they told we to switch to the bigger cross over tube and insulate it. I have done that and never experienced that problem again. I now have the P.Ponk engine with an EDM-900. If you want to get overloaded with data get an EDM-900, one could spend a life time trying to decipher what is causing a multitude of engine parameters you were totally unaware of before the EDM's install. I know now my carb box valve seals well so there is little to no heated air leaking into the carb with the carb heat in the cold position. I would say the o-470-50 is an ice maker. Partial carb heat is required to operate on most Alaskan summer days. If not used you will constantly see a slow decrees in manifold pressure. The accuracy of the EDM allows partial cab heat to maintain a temp just above freezing. Set it and forget it. But I'm thinking just get rid of the carburetor and install RSA fuel Injection. Working to get that done now.
    Thanks Steve Pierce thanked for this post

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