MONTY THE ANSWER MAN ARCHIVE

CONTINENTAL O-300 INFO Page Four...


TROUBLESHOOTING MANIFOLD PRESSURE... (040100)
Subject: Continental O300 D Manifold Pressure
From: "Ed A. Lloyd" <edlloydaustin@juno.com>
Hi Jim, Got a question concerning manifold pressure on the O300D engine. The gauge in 56K hasn't worked since I've had it. I was told there is a restrictor fitting in the intake manifold where the manifold pressure line is attached and it could be plugged. I removed that restrictor fitting and it was not plugged. I removed the gauge and applied a vacuum source and the gauge did not move so I promptly sent off and had it repaired. I reinstalled the gauge, and much to my surprise, when the engine was cranked , the manifold pressure gauge still didn't do so much as flicker, regardless of the power setting. Now I'm being told that there should not be a restrictor fitting in the intake manifold! Any suggestions? Tomorrow, I'm going to remove the gauge and disconnect the line from the manifold and see if the line itself could be plugged. If the line is open, should I tap into the manifold with a normal AN fitting without a restriction and try that? Thanks for you help and Cheers.....Ed Lloyd

Ed,
I have not seen a restrictor fitting at the intake manifold end of an O-300 manifold pressure line. There is usually one in the guage itself. Many years ago, I had a GC-1A with a manifold pressure line plumbed into the little manifold directly below the carburetor, every so often, the gauge would partially fill with gas! I installed a restrictor fitting. The manifold pressure line on an O-300 normally goes to a 1/8" pipe nipple or inverted flare fitting on the rt. intake manifold, but it can just as well be routed to the 1/8" pipe primer port on the top of a cylinder. (some late cylinders don't have these) It seems like the gauge might flicker, but it works ok in my experience. To check out your gauge, with it removed, just stand in front of a mirror, put the AN 4 or inverted flare fitting, whatever is in your gauge, in your mouth and suck as hard as you can. You should be able to draw it down 10 inches or so. If you can't get the needle to draw down something is wrong with the gauge. With the gauge removed from the aircraft, start the engine.

It might idle petty bad. Put your finger over the end of the manifold pressure line and make sure there is suction there. If there isn't, obviously the line is blocked. -- Jim

MANIFOLD PRESSURE FIXED... (040200)
From: "Ed A. Lloyd" <edlloydaustin@juno.com>
Hi Denis, re: the comments about manifold pressure in the newsletter. It took some digging but I finally found the problem. Checked the gauge with a vacuum pump and it was ok. Disconnected the line from the manifold and it held vacuum with both ends of the line loose!!! Tried blowing compressed air through the line in both directions and it was plugged. Traced the line to where it went through the firewall and there was a firewall AN fitting. Removed the line on the firewall side and blew air through the line both ways ok. Looked at the fitting where it protruded through the firewall and there was the problem, the fitting was plugged with what appeared to be drill shavings. Blew out the remainder of the line, reassembled the system and walla, it worked as advertised. Now I've got manifold pressure. Just shows, you gotta think it through and do complete trouble shooting. Cheers....Ed

ENGINE DATA PLATES...  (050500)
From: Larry Rengstorf <swiftair@pacbell.net>
Subject: Data plates
Hello Jim - again, I have a couple more questions, this time about engines === We are not real sure what engine is in this airplane we are building up. It came out of the plane originally, and the plane came out of a trade school. The engine did not have a data plate and the school isn't any help. No log books either!!! Don asked that I talk to you and ask these questions=
1. How do you get a new data plate ? thru Continental ?? or ? Do you need the serial number to get a new data plate ??
2. How do you tell what the serial # is ?, any tell tale info. (We rebuilt it here in the Sea Fury / R-4360 engine shop in Hamilton's hangar) & could not find any serial numbers, or anything that even looked like ser #. The only numbers were cast #s on each side of the case halves.
3. How do you tell what the engine is ?, According to the info in the Continental over-haul manual, it is a 0-300-B or a C-145-2. (It has the orifice for the 2 position prop control on the lower left front of the engine.) The starter is the inline type- with the pull cable. No vacuum pump pad either. Thanks Again, Larry R.

Larry,
To get a data plate from TCM is a big deal. They want a letter from the FAA verifying what it is etc. A C-145-2H can be distinguished from an O-300B by several minor differences:
1. The galley plugs at the forward end of the oil galleys are bigger on the C-145 -- 1/2" pipe vs 3/8" pipe. (I think that's correct, I never could eyeball pipe sizes)
2. The splitter baffle above the carburetor is a riveted in sheet metal piece on the C-145 and cast integral on the O-300B.
3. The "C" series cylinders have bronze spark plug bushings. The O-300's have helicoils.
4. If the cylinders are removed, the C-145 cases have the cylinder base studs tapped thru and are "wet" studs - they can potentially leak oil. The O-300 studs are are "blind" - they revised the castings in 1955 so the studs aren't tapped thru.
5. Look for the casting date. Cases cast from 1948 thru 1955 are 145 cases. From 1955 to 1967 are O-300 cases.
6. Details such as carburetor and magnetos may be different but these parts are so easily changed they are not valid for identifying the engine.

Can't you just find a different data plate? If I had a C-145-2H data plate laying around I would send it to you. I have a C-125 data plate if that would do you any good. -- Jim

PS If you want that last bit of speed to beat Denis you probably need a Sensenich prop. But a McCauley can be reworked to provide virtually the same speed and it will climb better. The secret is to narrow the tips to near the repair limit and to round the tips. Sometimes it is then necessary to pitch it up a couple inches to avoid overspeeding. A McCauley with wide tips that will only turn 2500-2700 rpm WOT level will be slow.

ENGINE SWAP...  (060300)
Subj: 0300A
From: Dennis Friedrich <dennisd@crcwnet.com>
In changing from a C125-2 on my Swift to an O300A, is there anything that need to be altered to install the engine? Thanks.

Dennis,
The engine will bolt right on with no alterations required. Oh, there might be a few detail differences, like the size of the fittings in the engine case for the oil cooler and the mag. P-leads if the magnetos are different. Some of the baffleing may require trimming to fit the beefier fins of the O-300A. If you switch generators, the regulator may need to be changed to match. -- Jim

SNAP, CRACKLE, POP REVISITED...  (060300)
Subj: O-300A Questions
From: Steve Roth <stevenroth@aol.com>
My O-300A engine pops out of the exhaust at low-mid RPM (circa 1000-1500) on the ground. Also, as I throttle up it really snorts and runs slightly rough (stumbles) as I go from high idle (1000 RPM) to around 1400-1500 RPM. It acts as if I have the mixture control out and one or more cylinders are not getting enough fuel. Once above 1400-1500 it runs smooth. It always runs smooth in the air even as I come back on the throttle when landing. The engine appears strong and I have no problem getting full RPM. This characteristic has not changed over time. One source told me it is probably related to the need for the "pepper box" nozzle in the carburetor, that the old style atomizer is causing it. A carburetor source told me that no, the carburetor does not affect the mid-range. It appears to not be the accelerator pump since it snorts while at low/high idle and does not hesitate when in the air. Another source at MMI who heard it snorting says it is related to the intake valve(s) not closing complete. But, it does not backfire through the carb -- it cracks out of the exhaust. Same person said it might be related to weak valve springs, and/or cam and/or push rod(s). Okay, but it runs well in the air and easily runs up to redline (I have a climb prop - Sens DR1-59). I perform oil analysis and levels are nominal. The overhaul 500 hours ago was done with all ECI (Texas) rebuilt components. Any ideas where to start looking? I still suspect the carburator. Thanks, Steve

Steve,
I would get a new or reman. carburetor. You can get a Consolidated for about $550 or a while back Precision had no remans in stock so they were selling brand new units at their reman price, about $600. I do not think the valve springs would cause that problem at that rpm. Valve springs can cause the engine to apparently miss at full throttle, low rpm, such as climb with a fixed pitch prop. I'm not sure I agree that the accelerator pump is not at fault. Did you check which hole the link was in? I'm wondering what cam and lifters are in your engine. The C-125 lifters and the O-300 cam are not compatible, but I doubt if you have that combination because it probably wouldn't have run 500 hrs! -- Jim

SOMETIMES IT IS THE SIMPLE THINGS... (060400)
From: Stephen James Martin <stevmart@pottsville.infi.net>
Subject: Re: June #3 GTS Internet Update
Re: The Snap, Crackle, Pop Question in the last update:
I had the same problem with my Luscombe and chased all the same suggestions listed in the E-Messages. I finally found that it was a simple vacuum leak in the intake runner for No. 1 cylinder. Check all the intake fittings/gaskets etc. before springing for a carb. Can't hurt and doesn't cost anything (except maybe gaskets). -- Steve Martin

ANOTHER VOTE FOR "INTAKE LEAK"... (060400)
From: Bob Webster <bob-jewell@wk.net>
Subject: Rough Engine
Dear Denis,  I goofed and deleted the last newsletter that was sent so I don't have the E-dress, but if you have it with the one where the guy had the engine that was popping and banging at low RPM, but would smooth out and be fine after he was up above 1000 or 1200 RPM tell him instead of doing all the mag work and all that to first check for an intake leak. This is apparently pretty common on the 125/O-300 engine and all it takes is replacing the paper intake gasket. My neighbor has a 145 Swift and he had the problem and I had it on a Lyc O-360. It runs rough at low RPM because it is sucking AND blowing due to valve overlap, but at higher RPM it is just sucking and seems to run fine, but there is probably a lean cylinder now. I am not an expert, but my guru that lives down the street (Charlie Cummins ) said to pass the word on before the guy spent some big money for no results. And Charlie knows! Hope it works. -- Bob Webster

MONTY AGREES THAT STEVE ROTH'S ENGINE WOES COULD BE AN INTAKE LEAK...  (060500)
Steve,  I see in the GTS Internet update several guys are telling you that you might have an intake leak. They may be right. I presume you have a manifold pressure gauge. Is the reading steady? What does it read at idle? What does it do when the engine is "stumbling"? All O-300 cams are p/n 530803, but they changed them many times. The early cams are "pointies" (more pointed lobes) and the later cams are "roundies" (more rounded lobes) The early cams idle at 10 -12 inches of manifold pressure. The later cams idle at 15 -16 inches of manifold pressure. (more overlap) If you have a higher reading than 16", you have a leak. Also, if the needle jumps around, you have a leak or a broken valve spring. Try and inspect the gaskets at the intake elbows. (not real easy sometimes) You might try removing the intake manifolds and the intake elbows and replacing the intake elbow gaskets. -- Jim

STEVE SAYS THANKS...  (060500)
Subj: Re: O-300 running
From: Steve Roth <stevenroth@aol.com>
Unfortunately, I do not have a manifold pressure gauge installed. Nevertheless, I am now convinced an intake leak is the prime candidate. It is time for annual anyway and I need to replace the rubber intake hoses so I will have them pull the manifolds and check the gaskets. I will have the man pressure gauge installed at the same time. I appreciate everyone's help on this irritating problem. Thanks - REGARDS, Steve

Steve,
I really believe in a MP gauge - I don't understand how anyone can run an engine without it. It also can be a handy trouble shooting tool - like in this instance. When flying a Swift, I just never exceed 24" continuously. RPM like 2600 never bothered me. If your prop for instance, turned 2300 RPM at 24 or 25 inches it would not be pitched right. My prop for instance, turns 2600 RPM at 24" and 2500 RPM at 23", which I think is just right. -- Jim

"BEEFIER" CRANKSHAFT FLANGE...  (060500)
From: Bob Sandberg <swifter@bellsouth.net>
Hey guy, I appreciate all the information I get from you on the Swift! I need to know what model # of the O-300 has the beefier crankshaft flange. Is there an STC for the 0-300D? I also need the 3 pieces of metal that the rear glass sits in on the GC1-A (just fwd. of top turtle deck). I have the pattern but not the tool to run the bead the glass sits in. -- Bob Sandberg

Bob,
I was trying to reply about what you wrote Bob Runge re: wing fittings. Bob got his copy ok, but the copy I sent to you came back. I wouldn't say any model O-300 has a "beefier" crankshaft flange, but the O-300A & B have the bigger (8 bolt) flange and the O-300C & D have a smaller (6 bolt) flange. The O-300D is not STC'ed. Many have been installed using the O-300A STC with a field approval for the different prop. Sorry, I can't help you on the 3 pieces for the 3 windows. Some metal wizards like Mark Holliday and Duane Golding have fabricated the parts, but I don't have that capability. -- Jim

OIL DRAIN PLUG SIZE... (080500)
Subj: Oil Drain Plug
From: Richard Aaron <raaron@pica.army.mil>
Jim,
I just got a quick drain plug for my oil sump, which has a 1-18 thread. I was just curious how come all the catalogs list this thread for the C145 but not the C125? Also, there's no lug on the sump for attaching a safety wire. I've been tying it off to spot on the rear baffling; there seems to be no other choice. How come such an obvious thing was omitted? Do you have any other recommendation? Regards, Dick, N2405B

Dick,
The original 125 sumps had a smaller size drain plug. If you have a drain plug the same size as a 145, your sump has probably been replaced. I safety mine to the engine mount. -- Jim

WHEN PUSH COMES TO SHOVE (PUSHRODS)... (090300)
Subj: Pushrods
From: tom@electrodesign.to (Tom Numelin)
Jim, I pulled a cylinder off to fix an oil leak and I forgot to label the pushrods so I couldn't tell which one was for the intake valve and which one was for the exhaust. When I stood them up one was clearly longer than the other by maybe 15 thousands. I thought they were all the same and interchangeable. Does it matter which one goes where/ My mechanic said he thought it didn't matter since they are hydraulic lifters. Tom Numelin

Tom,
The pushrods are the same, BUT, there are two lengths of pushrods listed in the parts manual, standard and P.030. (plus thirty thousandths) When setting up the engine at overhaul and with the lifters bled down, (no oil), the rocker clearance should be .030 to .110. If the clearance is over .110, say .125, a longer pushrod must be installed. The rocker arms are not adjustable, so the only way to change the clearance is to grind the valve face, or grind the valve seat, or to install a longer pushrod to decrease the clearance. Or grind the valve stem or rocker arm to increase the clearance. I also have seen P.070 pushrods listed but I don't know if they are genuine TCM parts. Once the engine is run, the lifters pump up and are filled with oil, the clearance can no longer be checked. The only way to check the clearance is to remove the cylinder and pull the guts out of each lifter and wash all the oil out and reassemble without oil. BTW - pulling the pushrods out can be hazardous on an early engine - the lifters have no circlips and the pushrod cup can come out part way with the pushrod, then get cocked in there and break the lifter when the engine is rotated. If the cylinder is removed it's no problem because the parts can be easily reassembled while the cylinder is off. Did you grind the valves or valve seats? If so, you probably can reinstall standard pushrods. It sounds like you have one P.030 pushrod. If the clearance is below .030 the valve will remain open and will leak. If the clearance is over .110 the engine will clatter from the excess valve clearance. I would install two standard pushrods. If, after an hour or so of running, there is any rocker clearance, install the P.030 pushrod. There should be "0" clearance after the engine is run and the lifters pump up. Standard pushrods are easily obtained from any engine overhauler. I have hundreds of them in my shop, left over from overhauls where P.030 pushrods were installed. It's the P.030 pushrods that are valuable. -- Jim

CONSIDERING O-300...(120200)
Subject: Re: O-300A
From: Larry LaForce <LaForce55@aol.com>
Hello Jim... I read all you had to say about the O-300A engines in the archives. It seems to be your favorite which is the main reason I'm considering one. I have located a fairly low time O-300A minus the carburetor. I noticed one archive article where someone was running a C-125 carb on their O-300A. Will the O-300 perform OK with the C-125 carb? The reason I ask is I have a C-125 carb that I could use. Thanks...... Larry LaForce N80844

Larry,
The 125 Carburetor, a 10-2848 will work just fine on an O-300. Actually, the Swift Association STC says, "Install the O-300A engine using same.....carburetor...no modifications necessary. The 125 has 18 fewer cubic inches of displacement and the manual says there are "different carburetor metering parts". I wondered about that one day so I dismantled a 125 carb and a 145 carb at my workbench. The jets were all the same, at least on these two carburetors. The 172's that most O-300's came in were meant to be flown by low time pilots, so as a precaution, Cessna may have jetted the O-300 slightly rich to provide more cooling. The 125 (10-2848) nozzle is p/n A47-652 and the 145 (10-3237) is p/n A47-702, but that's the only difference I have found. I have several hundred hours behind an O-300 with a 125 carburetor and never had any negative experience that might indicate too lean operation. -- Jim

MORE O-300A...(120200)
Subject: Re: O-300A
From: Larry LaForce <LaForce55@aol.com>
Jim... A few more questions about the O-300A's. What were the production years and are they all the same? Is one year preferred over the others? Thanks.... Larry

Larry,
I think the one I have now was made in 1959. They should all be pretty much the same. The crankcases were revised from the C-145-2 so the studs are "blind" - they changed the castings so the back side of the studs is not exposed to engine oil - and possible oil leaks. The later camshafts are possibly better - but many camshafts have been replaced in the 40 some intervening years. All camshafts are p/n 530803, but the later ones have a suffix, such as 530803-AN or AT or AU.

The part number can be found near one of the aft lobes and if it goes around the cam, it is a late part and if it is longitudinal it is an early part. The early cams are "pointies" and the later cams are "roundies". (The shape of the lobes; as you know, a racing cam is more rounded) You can identify which cam you have simply by running the engine if you have a manifold pressure gauge. At idle, if the manifold pressure if at the bottom of the scale it is an early cam. If it idles at 16" MP, it is a late cam. (more overlap) The early cams do have their backers, some claim the shorter timing brings the useable rpm down into the range where the prop does its best work. Regardless - there isn't much difference - TCM never changed the horsepower rating of the engine, altho I suspect the later cam is good for a few more hp at a few more rpm. The O-300A's were made from about 1955 to 1961. --- Jim

MONTY DOESN'T WANT TO BE A LAWYER. AND WE'RE ALL GLAD FOR THAT...(120300)
Subj: O-300-A STC
From: Wes Knettel <wsknettl@centuryinter.net>
Jim,
I was reading the Dec #2 update. You mention the use of the 125 carb. My experience with STC's for engine changes indicates you must either supply a O-300-A IAW it's TCDS or you must also have an approved STC for engine alterations. Since the carb, starter and etc are part of it's TCDS. I am not familiar with this STC. Is there in fact 2 seperate STC's for the switch to the O-300-A? One for the airframe and one for the engine. Just curious, Wes K

Wes,
Only one STC is involved, SA1-326, the "A" standing for Airplane (or Airframe?) An engine STC would be "SE". I would not want to be a lawyer interpreting the STC. I will quote Step 2.

Step 2. Install Continental O-300A engine using same or identical motor mount, bolts, baffles, exhaust system, wiring, plumbing, fuel pump, carburetor, and cabin heater systems; and oil cooler and lines, no modification necessary.

I would not make too much out of the interpretation of that statement. Yes, you are correct in what you say, but there are many loopholes. A 125 carburetor might be considered a minor alteration. The engine is rated at 125hp. -- Jim

NUTS ABOUT D/G AND A/I...(010401)
Subj: Vacuum pump on C-125
From: Michael Ward <millerk@gte.net>
Jim,
I read your response to a question concerning the lack of vacuum pumps on C-125 and C-145 engines due to the stock cowl not having enough room for a belt driven pump. If I was still NUTS enough to want a D/G and an A/I, what would be your best suggestion. Buy electric instruments or by a different cowl? Do you have an idea of the expense, and where could I find the proper cowl? Regards, Michael Ward

Michael,
If you want to install a fiberglass cowl, you might try advertising in the various publications that you will trade. The stock cowls are highly sought after these days, so you shouldn't have any problem there. Alterair makes the fiberglass Swift cowling. I have no idea of the availability, they have a link with phone numbers off the Swift site. I don't know the current price of their cowl new. Having said that, I would change the engine to an O-300D if I wanted a vacuum pump. I must tell you, I had an O-300D in my Swift until a couple of years ago. I had the vacuum pump drive blanked off! An electric turn and bank gives me the ability to make a 180 degree turn, which is all the instrument capability I feel I want or need. -- Jim

(Editor says... My Swift has an O-300-B so that means no vacuum pump of course. The previous owner installed a full gyro panel with all electric gyros. This is fine for that urgent situation where one must give serious consideration to the chance that one must abandon mother nature's horizon to complete one's flight. With all electric "tilts and spins" you are creating a situation when all your gyroscopic eggs are in one basket. Not recommended for routine IFR ops. The standard set up in most IFR light aircraft, as you know, has at least one instrument, usually the attitude indicator, being vacuum driven. In many applications, like Cessna for example, both the A/I and heading indicator are air driven. The wisdom of splitting your power sources is obvious.)

LOCK JAW...(030101)
Subj: O-300-B
From: Denis Arbeau <arbeau@napanet.net>
Jim,
Occasionally, after flying and I shut down my O-300-B engine, the engine is hard to turn by hand with the prop. For example, I shut down and the prop stops about 10-20 degrees away from horizontal. When I push the airplane into the hangar I like to make the prop horizontal. Sometimes when I go to put the prop to horizontal it is very hard to move. If I move it back the other way it frees-up. Just a couple of minutes later everything is just fine the prop moves completely freely. It doesn't do this every flight. Maybe 50% of the time. I'm wondering what I have going on here... Denis

Denis
I have noticed that phenomenon before with various engines, not just O-300's. I think it has to do with the heat expansion of the piston/rings in the cylinder. The rings may have a carbon build up behind them in the ring groove and cause a lot of ring drag when the engine is at certain stages of heating/cooling. A "bad" thing which is possible is, the piston pin plugs are wearing. Have you noticed shiny aluminum in the oil? O-300's have been known for this. Sometimes, they go all the way to TBO and if the oil is analyzed, it will show excess wear on the piston pin plugs noted because of aluminum particles in the oil. If the exhaust valves are on the verge of sticking, the carbon on carbon could cause drag also. I would rule out a cause such as a generator bearing because it doesn't seem to be getting any worse. So what to do? Keep doing regular compression checks and oil changes. Use Marvel Mystery oil. Avoid 100 LL if possible, always use TCP with 100 LL. -- Jim

O-300 PARTS CONCERNS...(030501)
Subj: O300B Overhaul
From: Brian Ulmer <bkulmer@c2i2.com>
Hello Monty, got your name from the swift guys and if I may bother you with a question, I have one. Recently I called El Reno for an overhaul list for my O-300-B to see what the prices were. Anyway, they said the mains for the -B were not made anymore. Are you aware of this or ? ... I love this engine and appreciate your passing around what you know about it. Best regards, Brian Ulmer

Brian,
The only bearing that is different in an O-300B is the front main. It has oil holes and a groove for the oil controlled prop. You might try Fresno Airparts in Fresno, CA for the O-300B bearing set. If you have no intention of using a controllable prop, an O-300A, C, or D bearing will work just fine. When the engine is disassembled, a good machinist could transfer the oil holes and groove to an O-300A type bearing and using the "B" bearing as a pattern, make a "B" type front main bearing. Also, the front main bearings seldom show wear, so the front main could simply be used over. WagAero had some surplus C-125 and O-300 front main bearings some years ago, I wonder if they have any left? A phone call might locate some front main bearings. The O-300B and C-145-2H front main is p/n 530516. The C-125 and all the other O-300's take a 36170. -- Jim


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