Swift Continental C125/C145/O-300 Operational Information

From: "Mark R. Fischer" (
Subject: Engine operations
I have recently been blessed with 80787, SN 190. She is an absolute delight to fly and look at. I have been learning as I go through reading the Swift Foundation materials and talking with folks who have flown swifts, but I have some specific concerns regarding power settings that I hope you or someone you know may help me with. I have a C-145 and a fixed pitch prop. I also have a manifold pressure gauge. From reading bits and pieces from the electronic and printed newsletters, I understand that I may need to use reduces power settings so as not to exceed certain limitations. The airplane was also marked with redlines on the tach at 2350, and on the MP gauge. I have been taking off with full power of course, and reducing to 25-25 for climb, and then pulling back to 23" for cruise. At these power settings, I am always above 2350 RPM - especially in cruise. I checked the Continental engine manual, and it indicates a redline of 2550 RPM for the engine.

Am I going to blow-up my engine operating it this way? If I pull the power back to keep the rpm below 2350 I plod along at 110 mph, and I can't believe that I should be doing partial power take offs. Any sage advise you can offer would be greatly appreciated. -- Mark Fischer

The red line for a C-145/O-300 is 2700 rpm, the C-125 red line is 2550. (that was with the "light" case, I believe with the "heavy" case it should be 2700 rpm also, but no one ever bothered to get it changed. The reduced rpm for the 145 series engines is a paperwork technicality. To get the STC with a minimum of fuss, they just de-rate the engine to 125 hp. 2700 rpm won't hurt a 145!

The only thing that will hurt these engines is excess heat. The cylinder design is not the best. The "lower end" of these engines is near "bullet proof" and is almost identical to the 210 hp IO-360.  I cruise my Swift at 24" x 2600 if I'm in a hurry. (about 80% power) that is 116 hp according to the power chart, well below 125 hp. -- Jim

Guest Answer Man Steve Wilson ( also responded to Mark's email...
With a fixed pitch prop you will never pull more than 125 hp (not even close) from your 145 hp engine. The placard is part of the STC and is required, but who ever did the math, should have made a power chart which would become part of the operator's manual and make it easier to see exactly what power you are pulling. Best advice is, "Be happy. Don't worry." Every engine has a "sweet spot" where it likes to cruise. Below that power setting, it is not making the best power and you are not getting the cruise you should. Above that power setting, it is wasting fuel and not getting a corresponding increase in airspeed. Sometimes you can see it as an increase in temps with little or no increase in airspeed. Heat is a killer on the small TCM Engines. My setup right now has a "sweet spot" at about 2475 to 2500 RPM. I am about to switch to another prop (from 59" pitch to 62" pitch). If I figured it right and encounter a little luck on the way maybe the "sweet spot" will move up about 100 RPM (which would be ideal). If it works, I should be able to move up a few knots with only a little or no increase in fuel burn. It's kinda like putting your car in overdrive. All the best with N80787. As you are finding out, there's nothing quite like a Swift!!!

O-300 CHT AND RPM...  (12399)
From: Ed Lloyd <>
Subject: O300D Operation
Got a question for you. After a recent flight in 56K, I was visiting with Duane and Dorothy Golding and just shooting the breeze. I mentioned that my CHT peaked at about 190 during a climb. After pulling power back the temp lowers maybe 10 degrees or so. They felt the gauge was in error and indicating low. I have an Alcor ET gauge also. When I am lean of peak, the CHT will rise above the 190-200 range, and then settle down to operate at just below 200 degrees on the CHT that's coupled to this engine. Can you shed any light on the CHT being low or high or ok as it is? RPM at cruise 2550. With the prop I have, at WOT, the RPM in level flight will go 2650 to 2700 RPM. This is a heavy case engine also. Thanks......Ed Lloyd

190 may be a little low, my CHT runs 210 normally. Back in the "old days," before EGT, they leaned the Stratocruisers and DC-7's by CHT, and I would expect to see just what you're reporting. Your gauge may be reading a little low, but so what? Just learn what it usually indicates and don't get uptight unless it changes from what's usual. Level flight RPM of 2650 to 2700 RPM is normal, mine will go to 2800, but I have a McCauley 7359 prop. -- Jim

O-300 PERFORMANCE... (080600)
Subj: Engine RPM and performance
From: Mark Kadrich <>
Hi Monty,
I've just gotten back from the Evergreen fly-in and after doing the 1200 mile round trip a question popped into my mind: What is the maximum RPM for a Continental 0-300C with 1500 hours? The reason I ask is that I cruised at 135 indicated (sorry, no GPS yet :-) and I tach'ed 2600 RPM at 3500'. (This is my normal 'putting around the patch' altitude. We cruised between 4500 and 7500 and the view was fantastic.) My tach says that 2700 is max. Is this correct? Not that I want to stress the engine, but it is nice to know what the limits are. The manual is confusing me. It would seem that the gating factor is the manifold pressure? Thanx for the time, Mark, 3243K

The type certificate and the operators manual say 2700 rpm max. If the engine is worn, perhaps it might be prudent to baby it a little, but 2700 is the red line. If you want to be a clubhouse lawyer, you can find several references to higher rpm than 2700. The altitude performance curve in the operators manual shows manifold pressure of slightly over 28" and 2800 rpm. In prop certification, the engine can turn 110% red line rpm with the throttle closed when dived to red line airspeed. (2970 rpm) Horsepower (BMEP) is a cross section of rpm and manifold pressure. If you follow the curves on the power chart, you can determine the percentage of power you are using. With a fixed pitch prop, you are somewhat limited in the combinations of rpm and manifold pressure you can obtain, but by observing what comes up for different throttle settings, you can determine the percentage of power you are using. The O-300 is what might be called a "48" engine. In other words, a combination of rpm and manifold pressure that equals 48 is 75% power. For example, 24" mp x 24(00) rpm = 75%. Other 75% settings might be 23" x 2500, 22" x 2600 or 21 x 2700 rpm. Other power settings can be determined by consulting the chart.  --  Jim

RED LINE??? WHAT RED LINE... (090100)
Subj: Max RPM
From: Tom Taylor <>
Just out of curiosity.... In looking over the reply you gave Mark Kadrich about the max rpm to be turned by an O-300 Swift, I noticed you made reference to the RPM limitations in the type certificate (engine, I presume) and operator's manual. However, doesn't the Swift STC for the O-300 limit RPM to 2270 (sea level) and 125 HP? Of course, everybody ignores this (I'm not admitting anything!), so that on a practical level, I think your advice was quite correct for the O-300 engine... but, isn't it true that the tach should carry a redline for 125 HP? Or, are some of the other O-300 STC's more liberal than the ones I have seen? -- TAT

The Swift Association STC (old Piedmont) limits the engine to 125 hp. (Most others do also) 125 hp is 86% power for a 145 hp engine. Whoever wrote up the STC should have written it that way, but they didn't. Instead, they simply said, "Do not exceed 2270 rpm at any time". What they left unsaid was, "at full throttle at sea level manifold pressure". There are plenty of alternate power settings for 125 hp. For instance, 2700 rpm and 25" = 125 hp. 2600 rpm and 26" = 125 hp. 2500 rpm and 27" = 125 hp. 2400 rpm and 28" =125 hp. 2300 rpm and 29" = 125 hp and yes, 2270 rpm and full throttle, at sea level manifold pressure = 125 hp. (this assumes a little over 29" HG @ sea level.) The STC requires a placard, "do not exceed 2270 rpm at any time", but the tach should be red lined at 2700 rpm. I have applied for an STC to use the Sensenich 74DR prop on the Swift and have worded it accordingly. I wouldn't get caught up in legalese interpreting wording on that old STC.

The 150 Lycoming engine installation in a Swift has a similar 125 hp restriction. The placard requirement is much more sensible: PLACARD FOR LYCOMING O-320 ENGINE : "To avoid exceeding the 125 hp limitation of the Lycoming O-320 engine at 2700 rpm A straight line variation of manifold pressure from 25" HG at sea level to 23" HG at 5,000 feet altitude must be observed". (I don't think this placard is quite right either, but it is on the right track.) At any altitude 24" x 2700 rpm should equal about 125 hp. (the O-320 has a slightly different characteristic than the O-300, due to a slightly higher compression ratio. Remember I said an O-300 is a "48" engine? (rpm x mp = 48 = 75% power) The 150 Lycoming is a "47" engine. -- Jim

O300-A TEMPS... (090200)
Subj: Cooling
From: Dennis Friedrich <>
Just got my 300A installed and took it up for the first time today. The temp is running 375 degrees or so. Never over 400 however. Is that the normal temp? Looks like certain portions of the cylinder get hotter than others as indicated by the discolored paint. Just want to make certain that it is cooling fine. Don't want to crack a new mil. cylinder. Also am told that I should run it at 2600 for a few hours. What about the mixture while breaking in the new TOP overhaul? Thanks.

375 is fine! Redline is 525. Don't lean the mixture while running in an engine. 2,600 will probably be OK, as long as the manifold pressure is not too high. I say probably because I don't know how your cylinder walls were prepared. If the cylinders were finished to an RMS of 35 to 45 (factory spec) 2,600 rpm will be OK, if the cylinders are rougher than that it may be necessary to "slow time" the engine to avoid wearing out rings in just a few hours. -- Jim

Subj: General
From: Robert Carver <>
If I'm looking at a Swift that is powered by a 145, what kind of cruise speed and fuel burn would it have? Also, if adding a fuselage fuel tank of 10 gal. for additional range, would it be necessary or even a good idea to get the weight increase? Adding more fuel will cut down the passenger + baggage that can be carried, which seems to be defeating the purpose of using the a/c for cross country flights without landing every hour and a half for gas. What have most folks done to make their Swifts so powered to be a better x-c plane? Maybe they fly their 182's when they go somewhere? Thanks for the answer, if there is one. Although I'm not presently an owner, I enjoy your "answerman" input in the weekly email. Bob

For many years I flew a 145 Swift with no aux. fuel and very rarely thought I needed any. I planned x-c flights for 3 hours, burning 7 - 8 gph and a fill usually took 21 - 25 gallons. My par speed for a 10 year period was 125 mph when throttled back and leaned out, 140 mph average and 150 mph when I was in a hurry. With a tailwind, I would throttle back and burn about 6 gph. At 6 gph, 28 gallons (which a Swift actually holds, despite the 26 gal. capacity marked on the fuel cap) is good for 4 hours plus reserve. At 150 mph consumption is 9.5 gph so I planned on 2 1/2 hour legs. The Swift I have now holds 37 gallons and is good for more endurance than I am! Due to health problems I no longer fly cross country. It seems everyone needs 50 gallons of fuel these days. A Swift flys a lot nicer when the empty weight is below 1200 pounds and of course the normal gross weight is 1710 pounds. Mark Holliday flys his 210 hp Swift to California and Florida and points between with standard fuel. -- Jim

Subj: Max RPM
From: Bob Price <>
Jim: During the runup yesterday the engine checked out great at 50 RPM Mag Drop both L and R... After warmup I set the brakes and ran the engine up to max RPM and could only get 2150... Is this normal? I have a McCauley Prop DM7357... Thanks Jim......... Bob >>

If you look at the Swift Type Certificate, (available for viewing on the Swift site) you will see the static rpm limits are not over 2050 not under 1950. So you are actually a little high! Now don't worry about it, your tach may be off a little and the wind may have contributed to what you saw. Also, a 73x55 prop allows static rpm up, to 2180 which does not make much sense to me but that is what it says. -- Jim

TEMPS... (DEC 03)
Subj: Cyl head/oil temps
From: Harry Fenton <>
Hi Jim,
I'm kind of curious about the engine temperatures that I'm seeing. The CHT is running about 485-500F with our ambient winter temps of 25-30F and the oil temp is running about 120-130F. I felt that the oil temp was a bit low and I blocked off the air intake to the oil cooler and it now runs about 165F. I've been messing around with baffling, but the CHT consistently runs on the high side. I've checked the oil temp probe for accuracy and it is pretty close. I've used an infrared thermometer to compare cylinder surface temps with the CHT gauge and they are pretty close, too. I don't have much experience with the C125 engines, so I'm not sure if the numbers above are within reason, but the cylinder temp just seems to be about 50F on the high side. What do you think? -- Harry

What kind of cyl head temp gauge are you using? The cheap guages don't read right at low ambient temps. 500 F is too hot! As I recall, N78267 had a lot of old military surplus instrumentation, maybe the guage is just old and tired! 500 F = 260 C. I have an O-300A and never read over 210 C. Do you have the thermocouple on the top or bottom plug? I believe Continental calls for the thermocouple to be on the downstream plug, which is the upper plug on an updraft cooling system. . -- Jim

Subj: Cyl head/oil temps
From: Harry Fenton <>
The temp indications have been kind of a puzzler. I would think that if the CHT's were at 500 or 550F that the oil temp would also go off scale, but the oil temp has been running no higher than 165. Oil pressure is also very good. When I topped the cylinders the bores were perfectly shiny like a mirror but the rings and pistons did not show any heat stress. The previous owner ran the engine on the ground for 20 minutes every couple of three weeks for three years so I kind of wrote off the glazing due to this unwise operating practice. Now I'm thinking that the high CHT may be a contributor. Baffling-wise, the installation is dead stock, and while the flexible sealing material is old, it doesn't seem to be sealing all that bad. The upper seal that runs along the edge of the cowling split is the worst , but there are only a couple of areas where is not riding sealing completely. During the summer I used duct tape to seal up the gap between the top baffling and the cowling, but the temps stayed about the same, indicating about 280-290C(535 to 550F). The indicated temps were right at redline, but did not go any higher. I've also checked the mag timing, but the temps ran the same with the old SF series mags as with the new Slick 6364 mags. The gauge in question is a stand alone dual CHT gauge of late 40's or 50's vintage. I boiled some water and the gauge read accurate to that temp. After a flight, I used an infrared surface temp gauge, bouncing a signal off of the cylinder- the IR gauge indicated a temp in line with the cockpit gauge The senders connect at a spark plug gasket, which means that the temp reference is probably about 50F lower than a bayonet probe would see. The temps are nearly dead even from top to bottom. The top sender is connected to the rear left cylinder and the bottom is connected to the bottom right rear cylinder. I haven't been able to double check the high end temps, but all of my double checks from about 350F and lower seem to be linear to the cockpit gauge. A reasonable extrapolation would be that the gauge seems to be accurate. Overall, it looks like my CHT is too high, which may have contributed to the glazing condition. So, I'm going to re-do the baffle seal to see if this makes a change. The gauge is also suspect, so I'm going to rig up another gauge to see if the numbers fall into the same range. I don't want to pull the cylinders off again! The biggest puzzler to me is the high CHT vs low oil temp. High oil temps and low CHT would make sense, but I've almost always seen high oil temps along with high CHT. Anyway, I'll let you know what I find. It will probably just boil down to a baffling issue. -- Harry


One thing that has always puzzled me, why is the C-125 cyl head limit higher (550 vs 525) than the O-300? If your cylinders have lasted for over 50 years the temp must not be a problem! You might switch the thermocouple to the top side. -- Jim