MONTY THE ANSWER MAN ARCHIVE

CONTINENTAL O-300 INFO Page Three...

BAFFLING QUESTION...  (12399)
Subject: Re: engine baffles
From:Don Cumpston <don@penn.com>
Monty:
I am currently rebaffling my c-145 with thick silicone baffle material and would like to know the best way to seal the back of the engine against the block. Should you cut the material to the contour of the block or go to the block and fold 90 deg and lay against it? With so many curves on the block, folding the material like the old stuff was does not seem to seal very good. Your input would be appreciated. Thanks Don

Don,
Joe has the original baffle material and he can send the original size seals. When I changed my engine a couple of years ago I bought this baffle kit from Joe and although I didn't use every piece, I found it useful for patterns. I believe you have a downdraft cowl. Many pieces of the baffleing are the same. I used the original type stuff next to the case and sealed it to the case with oil resistant RTV and laced the baffle with safety wire where appropriate. -- Jim

TIME TO ROCK AND ROLL... (100600)
Swifter Larry Owen emailed to tell us that he has been in touch with US-Airparts <www.us-airparts.com> regarding their ad in Trade-A-Plane offering roller rocker arms for the Continental C-145 and O-300 engines. Paul Preibus of US-Airparts, (email: usap@mindspring.com), emailed Larry to tell him that the price for an O-300 would be $1050. They are currently out of stock but they should have some in stock in about a month. Quantity pricing is available if others might be interested (Swift Parts are you listening???). In any event, Paul suggested that anyone interested could email him at the above address if he could be of any service or if there are any questions. Thanks to Larry for passing along the information.

ENGINE MOUNT... (020100)
Subject: Re: engine mounts
From: Lee Davis <80730@aol.com>
Is there any difference between the 125 engine mount and the mount when you install a 145 or a O300 ... just wondering. -- Lee Davis

Lee,
No, you use the same mount. -- Jim

CASE BY CASE... (020100)
Subject: C125
From: Lee Davis <N80730@aol.com>
How can you tell between a C125 light case and a C125 heavy case and is there any other little tidbits of info or hints that can be helpful ?

Lee,
The C-125 and C-145 cases made before about 1950 were "light cases". The 125 has no AD notes, but it will crack if operated with a metal prop (as opposed to an Aeromatic), or with extended running over 2550 rpm. The 145 has a different harmonic and it will crack, period. Continental corrected the problem by going to the heavy case and in the 145, using harmonic dampers on the crankshaft. The last few 125's had the heavy case in production, but most we see today are C-145 and O-300 cases. There are several p/n's which can be called "heavy cases". To identify a heavy case, the easiest thing to look for are 3 thru studs in the vicinity of the fuel pump. (or the lack of them on a light case) The light case will have nuts on the left side only, the area near the fuel pump will be lacking any 7/16" studs protruding and no nuts, of course. The heavy case has 2 thru studs for every cylinder, but you can't tell if a stud in the middle of the engine is a thru stud unless you put a wrench on it and turn it, then (maybe) the nut on the opposite side will turn.

The C-125-2 or C-145-2 has no significance re: the type of case or crankshaft. The cases made after about 1956 are better, they have a revised casting and the non-thru studs are tapped into blind holes, so they have fewer oil leaks. The earlier cases were tapped into the inside of the case and had engine oil splashing on the stud, which tended to seep oil to the outside of the engine eventually. If you are building up an engine, the best case to use is from an O-300A or O-300B.

Other C-125 notes: The "C" series cylinders tend to crack, they are not worth spending the money for changing all the guides and seats. The original magnetos, the SF-6-12's, have no AD notes, but they are not worth spending the money for a complete overhaul. The fuel pump has an AD calling for inspection at annual, it's the same p/n fuel pump as an O-300, which has no AD note. Further comment on request! An O-300C or D case can be used on any earlier engine, C-125, C-145 or O-300A or B. The "C" can be used if the "C" starter pivot is used. The "D" can be used if either a "C" starter pivot or a B&C starter is used. There is an oil passage to the starter bushing in the O-300D which may need to be blocked off if using the B&C starter. -- Jim

SNAP, CRACKLE, POP... (040100)
Subject: Re: O-300 Carb/Mags
From: Steve Roth <stevenroth@aol.com>
Monty: I have an O-300A with old Scintilla "Lunch box" mags. The engine runs fine (except for problem described below) with minimal mag drop. Carb appears to work correctly (RPM peaks when mixture pulled to cut-off). The engine starts easily and idles nice. With full rich mixture, as I increase the RPM for taxi, especially using my vernier throttle (say, to 1100-1400 RPM), it crackles and pops out of straight pipe. If I "clear" the throttle with a burst of higher RPM, it will settle down. Runs fine in the air in cruise rpm (2200-2700). It does not hesitate when I push the throttle in. It does not crackle when pulling throttle for landing. I can't recall if it does this only when it is cold or if it does it all the time.

This situation reminds me of when I have the mixture out for ground operations (taxi, etc.) and try to give it throttle which requires more fuel. It snorts and crackles then also, but I have experienced that in my C-172 with O-300A so kinda know that is normal. It has had this condition since I had it. My mechanic at last annual was not worried about above condition since engine ran so smooth other than a narrow band in middle of RPM range. Other aspects of engine are excellent (compression, plugs, etc.). Can you shed any light on this? I am thinking carb. Thanks, Steve Roth & N2397B

Steve,
I suspect that when transitioning from the idle circuit to the main fuel delivery nozzle there is a moment of too lean fuel delivery. To correct this you might need a new accelerator pump. A simple fix might just be to put the link for the accelerator pump discharge in a hole which will discharge more fuel. Since your airplane has always been in a warm climate, maybe the link in the "minimum" hole. Try one of the other two holes. If you have a C-125 carburetor, I would suggest you get a new or reman. carb. for an O-300. The 125 carb is a 10-2848. They will take the 125 carb in as a core now. -- Jim

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