Warner 145hp Engine Tips
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These tips were gathered from various folks who are knowledgeable about antique radials in general and Warners in particular.  I make no guarantees for correctness, having not yet flown behind a 145HP Warner myself.

Check out the Warner SS50A manual for the factory instructions on how to fly and maintain the engine.

Here's some more tips on the 145 engine by Dick Martin.

Even though antique engines can be a lot more work than a generic Lycoming O-320, there's nothing like the satisfaction of hearing the distinctive sound of a radial in a beautifully restored antique airplane.

Radial Oil Hygiene

If you've never worked with radials before, there are few things about oil that you should know.

First, radials leak oil.  Usually quite a lot of oil.  They leak from case seams, they blow oil out the exhaust stacks and all over the airplane on startup.  A Warner 145 not only will leak oil, it will leak grease from the rocker arm covers.  The jokes go something like "radials are externally lubricated" and "if it stops leaking oil then you know something is wrong."  So if you're not prepared to get greasy then a radial is probably not the right engine for you.

Unlike the traditional spam can engine where the cylinders are horizontally opposed, the radial engine configuration has half the cylinders pointed downward.  Gravity being what it is, the oil which normally splashes around inside of the crankcase during operation will tend to collect in the downward-pointing cylinders when the engine is shut down.  Not only will stray crankcase splash oil collect there, but radials also have external oil tanks that are located above the level of the engine.  These tanks are usually measured in gallons of oil.  The oil in the oil tank will often tend to leak out of the engine reservoir into the engine crankcase itself after shutdown.

The net of all this is that oil will end up pooling in the downward pointing cylinders of the engine.  The oil will leak past the piston rings into the cylinder combustion chambers.  Ok, what's the problem?

Piston engines work by using a piston to compress a gaseous fuel/air mix in the combustion chamber before igniting the mixture.  That works fine when the compressed mixture is a gas.  Unfortunately liquids like oil are not compressible.  Oil is so incompressible that if you try to compress it by starting the engine and thus moving the pistons into a combustion chamber that's full of oil, some other part of the engine connected to that piston such as the piston link rod will give way first.  The metal in the part will be overstressed.  Once that happens, it is usually a short time before the overstressed rod cracks and ultimately breaks.  Bad things happen when a rod breaks, and the engine stops running in short order.

The condition of a cylinder combustion chamber full of oil is called "hydraulic lock".  The lock term comes from the inability to turn over the engine because the oil in the cylinders cannot be compressed.  Hydraulic lock is an inherent danger in radials and you should always check for it.

The check is simple.  Before starting the engine, check switches off, cut the fuel selector off, and then pull the propeller through by hand in the forward direction.  I count 14 blades to be satisfied.  If there is any significant resistance, you may have a hydraulic lock condition.  Ask your mechanic to show you what is standard compression resistance to help calibrate your arm.

Usually a small amount of accumulated oil will drain out the exhaust valves and out the exhaust stack.  It will start to dribble all over the ramp.  If you're pulling the prop through outdoors be sure to park the plane so that it faces into the wind, otherwise the oil dribble will probably end up on your leg and shoes.

If you do feel any significant resistance, or if the propeller doesn't move at all, absolutely do not attempt to force the propeller through.  Propellers are long lever arms and you can develop a huge amount of force and stress on the engine internals.  If you feel resistance, stop turning and start removing the spark plugs on the lower cylinders.  Start at the bottom-most cylinders and work your way upwards on both sides of the engine until you find dry cylinders.  You should get a flood of oil from one or more of the bottom cylinders.

Do not turn the propeller backwards to try to "clear" any oil accumulations.  This technique may seem to work, but all it is really doing is moving the oil back into the intake manifold pipes.  When the engine does start, this oil will get sucked right back into the cylinder, which is now running at idling speeds.  Lots of damage potential.  The only solution to get rid of accumulated oil in the cylinders is to remove spark plugs.

Rocker Arms

The rocker arms and valves in the SS50A are not oil lubricated and require manual lubrication with grease.

Grease the rocker arms at least every 5 hours of operation.  A recommended grease that is still available today is Texaco Marfak.  This is a soap-based grease that will melt and slop around when hot.

Every 20 hours of operation, flush and re-lubricate the top end.  This involves:

  • Scooping out accumulated grease with a coffee stir stick
  • Washing out the rocker box with liberal usage of a mixture of 1/3 Marvel Mystery Oil, 1/3 30 weight engine oil, and 1/3 castor oil.  Work this mixture into the rocker arm roller and valve springs.  The castor oil forms a varnish that helps prevent corrosion, because the rocker boxes will get a lot of condensation.
  • The Warner manual recommends applying light machine oil to the rollers and the exhaust valve stems.  Flushing with the mixture above should satisfy this requirement.
  • The Warner manual recommends applying grease to pushrod tube ends every 20 hours.

While the top end is open, also check the valve clearance.  Set the valve clearance approximately 0.002" loose.  The valve clearance check procedure is described in the Warner manual.


Mixing in Marvel Mystery Oil for top-end lube is recommended, or even required depending on who you ask.

Modern rebuilds should have steel exhaust valve seats, which are ok for use with 100LL avgas.  Burning a gas with less lead, such as 80 octane avgas, or autogas with no alcohol content is recommended.

If 80 octane avgas is not available, mixing autogas and 100LL avgas about three parts autogas to one part 100LL will result in a mixture with a lead content close to that of 80 octane avgas.

Magneto Lubrication

The Warner 145 and 165 HP engines use Bendix Scintilla VMN7DF magnetos.  These are old but well-built magnetos and they will serve you well if you maintain them.

The key maintenance activity is oiling the magneto distributor rotor bearing.  If you do not oil your magneto every 25 hours the bearing will overheat and melt the magneto resulting in failure of the distributor rotor and potentially distributor gear.  Needless to say this won't be a pleasant experience.

The VMN7DF magnetos have three bearings to worry about:  two ball bearings at the front and rear of the case for the main rotor shaft, and one plain bearing for the distributor gear/rotor assembly.  As designed, the VMN7DF magnetos had two oil cups to lubricate all of these bearings, one cup on the rear case cover for the rear main shaft ball bearing, and one on the front (or engine drive end) that lubricated the front main rotor shaft ball bearing and the distributor plain bearing.  Passages within the magneto case connect the oil cups to the bearings.

Based on a service bulletin issued in 1955, the mags are modified to use packed grease lubrication for the main rotor shaft ball bearings, because the oil cups were providing too much lube to the main rotor ball bearings.  This modification calls for plugging the oil passages from the external oil cups to the main rotor bearings.

It is important to note, however, that even with this modification you must still lubricate the distributor shaft plain bearing using the front oil cup.  Don't be shy with the oil as you cannot over-oil this bearing.  The excess oil will simply drain out of the magneto case.  The Warner manual recommended oil intervals are 5 to 8 drops of 30 weight mineral oil every 25 hours, and 20 to 30 drops every 50 hours.  Do not go past 25 hours between adding oil to the front cup or you risk distributor failure.

The rear oil cup only feeds the rear main rotor shaft ball bearing, and if the magneto has been modified this oil cup is plugged off.  If not modified then the Warner manual recommends 5 to 8 drops every 50 hours in the rear cup.  If your magneto has been modified then it won't hurt to put oil in the rear cup other than potentially making a mess, so better safe than sorry if you don't know for sure.

If you haven't run your engine for a long time, say at the beginning of the flying season or any kind of long storage, make sure you oil the magnetos before starting.

If you are in doubt about your magneto's modification state, I heartily recommending sending them to Sierra Magneto Service in Grass Valley, California.  The folks at Savage really know these mags and vintage magnetos of all types and they will treat you right.

Ignition Timing Retard

Since aviation engines spend most of their life running at 60% to 75% power, the ignition systems are generally fixed at a fully advanced timing position, such as 22 degrees before top dead center, in order to make full power at cruise RPMs.  Fully advanced timing is great for cruise but terrible for starting because the advanced firing of the spark is timed for when the crankshaft (and hence the piston) is moving quickly rather than moving slowly as at starter speeds.  With full advance but slow RPMs the early firing will work against you for firing the engine because the cylinder charge burn can complete while the piston is still on the upstroke.  In extreme cases the engine will "kick back" or violently turn backwards for a blade or two.  This can really run your day if you're hand propping an engine, which is why you never wrap your fingertips around a prop edge when propping.

To work around this problem and make starting easier, most flat-engine magnetos use a spring-and-cam device called an impulse coupling.  The impulse couplings wind up over several starter rotations and then "snap" to spin the magneto quickly for several rotations generating a hotter spark.

Unlike flat-engine magnetos, the Bendix Scintilla VMN7DF magnetos on all the Warners I've seen do not have impulse couplings to help with starting (there is at least one engine floating around with an impulse coupling according to Savage Magneto folks, but I've never seen one).  Instead the Scintilla mags have an ignition retard lever.  This unique automotive-like feature retards the ignition timing based on a lever so that the engine will run easier at low starting RPMs.

The efficacy of the retard lever is debated.  Many folks use a booster coil on the magnetos for starting, which is supposed to work well.  Regardless of whether you have a booster coil, if there's no retard lever hooked up then safety wire the retard level into the full advance (with the lever at the 10 o'clock position in most installations while looking down at the rear cover).

If you do use the retard lever, it should only be used for starting.  I find it most effective to pull out or retard the timing about 1/2" before engaging the starter.  While cranking, slowly advance the timing by pushing in the lever.  If the engine doesn't start it is probably because you retarded the timing too far, and depending on your magneto this can dramatically weaken the spark.  If the retard lever isn't pulled back far enough then the engine will kick back.

In all cases, after the engine catches make sure that you push the retard lever full in, or to the full advance position.  If you don't do this then the engine will run ok but will not develop full power.

Cylinder Heads

There are two styles of Warner 145 HP cylinders heads, the heavy and light head.  You can determine the difference by looking at the exhaust port.  On the light head, the exhaust port boss is oval shaped.

Light head cylinder diagram

On the heavy head there is a rectangular area of additional metal around the exhaust port.

Heavy head cylinder diagram

Warner cylinders have a tendency to crack around the exhaust port, so this area should be inspected closely at regular intervals.  The heavy heads are desired because the reinforcements help prevent cracks.


A good source of parts for Warner engines is Harman Dickerson.  He can be contacted at 573-449-6428 or by email at hdaircraft@cs.com.


There aren't many people who do Warner overhauls.  Forrest Lovely, in Jordan MN comes up as a good source.  Radial Engines Ltd in Oklahoma does the occasional Warner.