Merlin and Spitfire Oil Change Answer
Thu Nov 26, 2009 11:55 am
John Dupre asked a question about Spitfire oil changes and I thought it might be of general enough interest to be its own topic.
The rule of thumb for Merlins, has been 25 hours for oil change intervals, and that pretty well was accepted whether it was a Rolls in a Spitfire, or a Packard in a Mustang. If any Allison guys or reading this, what was/is their norm?
The Merlin comes from the factory with 3 oil filters( or is it 4?). The are two in the sump that are wire mesh, not too fine, you could stick a needle through the holes. Then there is a fine mesh one on that filters the oil going into the prop. Might be another, I can't be sure as I have not change it myself in a long time. I don't think Rolls does, but at least some Packards in 51s have a Cuno (brand name?) filter also, which is I think is a stack of fine mesh metal disks.
Originally all ran on straight mineral oil, there was not an AD or ashless dispersant. Some in England still use this. You know the Brits, "Hey if it was good enough for Capt. Cook, it's good enough for me". Just teasing, guys? Do you know why the Brits put long range tanks on a Spit? So they could fly over to France and get a decent meal. They do make some beautiful airplanes and cars, and some fine pilots, and they know how to do a tennis tournament or a play. Not to mention Liz Hurley and Sir Winston, when it comes to style.
Some things are new. There is now A D oil, which resists forming ash which is a by product of combustion. The stuff more stays in suspension to be drained off at oil change or filtered out. Some old timers inaccurately refer to "detergent" oil and mineral oil. This is not correct, there has not been any detergent in aviation oil in many years. There is AD and mineral, none of it is detergent, unlike auto engines. Both types now come in single weight usually 100( 50) or 120 (60), as well as various multigrades, 20-50, 20-60, which tries to act like a 20 weight when cold and a 60 when hot. One thing is well known, if you start a Merlin that has been sitting for days, it will take some time for oil to flow up the the top to the cams and followers ( rocker arms or fingers) and wear may occur. This is bad if it is cold, at say 40degrees 120w is like honey. So if you can you preheat the plane in a nice warm hangar, or some owners like me have added a simple glue-on 120 v electric heater to the sump and oil tank, as well as a pre oil pump. I use Phillips 20w-60 oil, at home and when I can get it on the road. You can add any other type and weight ok if you need to top up enroute.
Next and of vital importance is the kit that Jack Hovey machined that adds Champion paper cartridge filters to the oil system.The Merlin pumps so much oil that you need two flters. These are very fine and really filter down to microns. Cost used to be about $2500 per kit an d worth every penny. So now there are 2 fliters to replace and 3 to clean.
So as original, 25 hours was normal to change oil and clean the screens. With the better paper filters we normally do it about 35 hours. It is important to cut open the filter to see how much and what kind of debris may be caught. A trace of iron, aluminum is normal piston and cylinder wear, BUT you do not want to see the copper alloy stuff from main bearings, and not much steel from the crankshaft, etc. That's called "making metal" and may mean an overhaul if it gets worse, or if you are Strega it might mean that "Fat Bear" is going to win that day. I also send an oil sample out to be analyzed as to amount and type of metal and dirt ( silicon) found, but often the filter inspection is more telling.
To change the oil on my plane requires removing 4 cowlings, the side ones are easy with the Brit type qiuck release fasteners. Then the air fliter box on the bottom of the engine . We change this filter at annual , and we use a Bracket oil wetted foam, they supply it cut right to size, it is cheap, and more affective than the original factory mesh type. I have never understood why an otherwise seemingly rational Mustang owner would operate an expensive plane with a rare and expensive engne without an air filter and suck dirt right into the engine, but many do. Some will tell you the only fly off paved surfaces,but there is plenty of dust in the air at Oskosh, not to even mention Madera or Leward Air Ranch or Genenseo. The Spit air fliter system is different than the 51 type, but when we didn't have a good seal in the door that closes the direct air path and puts the filter in use, I saw more silicon (dirt) in the oil analysis.
My plane holds about 12 gallons of oil, I get a chuckle when the line guy at FBO s bring out a single quart to top up.
As part of the oil change, Ray checks the top end, he removes the cam covers and looks for cam wear. The Merln Fingers with the carbide wear surface are an imrovement over the factory followers. Just goes to show that those Canucks are pretty smart when sober, even when not on hockey skates. He also checks head torque. We have never found any problem there, the bolts always seem to stay as set. I have heard 51 mechanincs say they find loose bolts and sometimes a broken one. I do not know why my engine should be better in this regard than the Packards. Is there some design difference, or is it because normal Spifire takeoff power is 44 in vs perhaps 55 to 61 inches in the P-51? Or do all those 51 wheel landings shake the bolts loose? Who knows, it just seems to be?
So there is a fair amount of work in normal oil change and inspection on a Merlin. It may be one guy for 2 or 3 days or 2 guys for a day or 2. Perhaps $2000 and relative piece of mind for another perhaps 6 months. remember in combat the ground crews use to take a look at the engne between each mission, even if not an oil change. Some might think that this level of service is too much trouble for the priviledge to getting to fly behind a Merlin. For these folks, there are lot's of ordinary airplanes that don't ask for as much.
The rule of thumb for Merlins, has been 25 hours for oil change intervals, and that pretty well was accepted whether it was a Rolls in a Spitfire, or a Packard in a Mustang. If any Allison guys or reading this, what was/is their norm?
The Merlin comes from the factory with 3 oil filters( or is it 4?). The are two in the sump that are wire mesh, not too fine, you could stick a needle through the holes. Then there is a fine mesh one on that filters the oil going into the prop. Might be another, I can't be sure as I have not change it myself in a long time. I don't think Rolls does, but at least some Packards in 51s have a Cuno (brand name?) filter also, which is I think is a stack of fine mesh metal disks.
Originally all ran on straight mineral oil, there was not an AD or ashless dispersant. Some in England still use this. You know the Brits, "Hey if it was good enough for Capt. Cook, it's good enough for me". Just teasing, guys? Do you know why the Brits put long range tanks on a Spit? So they could fly over to France and get a decent meal. They do make some beautiful airplanes and cars, and some fine pilots, and they know how to do a tennis tournament or a play. Not to mention Liz Hurley and Sir Winston, when it comes to style.
Some things are new. There is now A D oil, which resists forming ash which is a by product of combustion. The stuff more stays in suspension to be drained off at oil change or filtered out. Some old timers inaccurately refer to "detergent" oil and mineral oil. This is not correct, there has not been any detergent in aviation oil in many years. There is AD and mineral, none of it is detergent, unlike auto engines. Both types now come in single weight usually 100( 50) or 120 (60), as well as various multigrades, 20-50, 20-60, which tries to act like a 20 weight when cold and a 60 when hot. One thing is well known, if you start a Merlin that has been sitting for days, it will take some time for oil to flow up the the top to the cams and followers ( rocker arms or fingers) and wear may occur. This is bad if it is cold, at say 40degrees 120w is like honey. So if you can you preheat the plane in a nice warm hangar, or some owners like me have added a simple glue-on 120 v electric heater to the sump and oil tank, as well as a pre oil pump. I use Phillips 20w-60 oil, at home and when I can get it on the road. You can add any other type and weight ok if you need to top up enroute.
Next and of vital importance is the kit that Jack Hovey machined that adds Champion paper cartridge filters to the oil system.The Merlin pumps so much oil that you need two flters. These are very fine and really filter down to microns. Cost used to be about $2500 per kit an d worth every penny. So now there are 2 fliters to replace and 3 to clean.
So as original, 25 hours was normal to change oil and clean the screens. With the better paper filters we normally do it about 35 hours. It is important to cut open the filter to see how much and what kind of debris may be caught. A trace of iron, aluminum is normal piston and cylinder wear, BUT you do not want to see the copper alloy stuff from main bearings, and not much steel from the crankshaft, etc. That's called "making metal" and may mean an overhaul if it gets worse, or if you are Strega it might mean that "Fat Bear" is going to win that day. I also send an oil sample out to be analyzed as to amount and type of metal and dirt ( silicon) found, but often the filter inspection is more telling.
To change the oil on my plane requires removing 4 cowlings, the side ones are easy with the Brit type qiuck release fasteners. Then the air fliter box on the bottom of the engine . We change this filter at annual , and we use a Bracket oil wetted foam, they supply it cut right to size, it is cheap, and more affective than the original factory mesh type. I have never understood why an otherwise seemingly rational Mustang owner would operate an expensive plane with a rare and expensive engne without an air filter and suck dirt right into the engine, but many do. Some will tell you the only fly off paved surfaces,but there is plenty of dust in the air at Oskosh, not to even mention Madera or Leward Air Ranch or Genenseo. The Spit air fliter system is different than the 51 type, but when we didn't have a good seal in the door that closes the direct air path and puts the filter in use, I saw more silicon (dirt) in the oil analysis.
My plane holds about 12 gallons of oil, I get a chuckle when the line guy at FBO s bring out a single quart to top up.
As part of the oil change, Ray checks the top end, he removes the cam covers and looks for cam wear. The Merln Fingers with the carbide wear surface are an imrovement over the factory followers. Just goes to show that those Canucks are pretty smart when sober, even when not on hockey skates. He also checks head torque. We have never found any problem there, the bolts always seem to stay as set. I have heard 51 mechanincs say they find loose bolts and sometimes a broken one. I do not know why my engine should be better in this regard than the Packards. Is there some design difference, or is it because normal Spifire takeoff power is 44 in vs perhaps 55 to 61 inches in the P-51? Or do all those 51 wheel landings shake the bolts loose? Who knows, it just seems to be?
So there is a fair amount of work in normal oil change and inspection on a Merlin. It may be one guy for 2 or 3 days or 2 guys for a day or 2. Perhaps $2000 and relative piece of mind for another perhaps 6 months. remember in combat the ground crews use to take a look at the engne between each mission, even if not an oil change. Some might think that this level of service is too much trouble for the priviledge to getting to fly behind a Merlin. For these folks, there are lot's of ordinary airplanes that don't ask for as much.
Last edited by Bill Greenwood on Thu Nov 26, 2009 2:59 pm, edited 3 times in total.
Re: Merlin and Spitfire Oil Change Answer
Thu Nov 26, 2009 1:59 pm
Bill Greenwood wrote:Next and of vital importance is the kit that Jack Hovey machined that adds Champion paper cartridge filters to the oil system.The Merlin pumps so much oil that you need two flters. These are very fine and really filter down to microns. Cost used to be about $2500 per kit an d worth every penny.
I'm pretty sure that adaptor that holds the two filters is a Caterpillar part, it sure as heck looks like it.
Re: Merlin and Spitfire Oil Change Answer
Thu Nov 26, 2009 2:23 pm
ZRX61 wrote:Bill Greenwood wrote:Next and of vital importance is the kit that Jack Hovey machined that adds Champion paper cartridge filters to the oil system.The Merlin pumps so much oil that you need two flters. These are very fine and really filter down to microns. Cost used to be about $2500 per kit an d worth every penny.
I'm pretty sure that adaptor that holds the two filters is a Caterpillar part, it sure as heck looks like it.
Custom made by Hovey products but sold through Stallion 51 IIRC. Comes with all the paperwork to submit a 337 for a field approval if used on a limited cat A/C.
Roush is using modern filters that have a re-cleanable screen element inside a housing that screw on the same as the Champion filters.
Rich
Re: Merlin and Spitfire Oil Change Answer
Thu Nov 26, 2009 2:28 pm
51fixer wrote:Custom made by Hovey products but sold through Stallion 51 IIRC. Comes with all the paperwork to submit a 337 for a field approval if used on a limited cat A/C.
Roush is using modern filters that have a re-cleanable screen element inside a housing that screw on the same as the Champion filters.
Rich
Okee doke, there isn't really much difference you could design into the look of something that holds 2 oil filters, I guess they all look pretty much the same. (I have one on my Dually)
Trying to remember who's name was on the large bracket/adaptor I saw on a T6 recently. Single filter design, but quite a fat filter, probably an inch or more bigger than the Champion filters used on the twin adapotors.
Re: Merlin and Spitfire Oil Change Answer
Thu Nov 26, 2009 3:23 pm
I have not heard anything about a Caterpillar part, but I doubt it that is correct in this case. I have never flown one, looks like the wing loading might be a little high.
The kit may have been developed together by Jack Hovey, Hovey Machine Products, with the Lauderbacks, Stallion 51. They probably sell to the 51 guys, we got our kit from Jack.
There is more to the kit than just the one adapter, there are hoses, and I assume some sort of one way valve to keep the flow correct. Above all it needs to be safe. Ray had to do some adapting to use this on the Spitfire as it is slighlty different than the 51.
Whether this is on a 51 or a T-6, this is nothing to short cut or have doubts about the installation as you are dealing with the lifeblood of the engine.
The kit may have been developed together by Jack Hovey, Hovey Machine Products, with the Lauderbacks, Stallion 51. They probably sell to the 51 guys, we got our kit from Jack.
There is more to the kit than just the one adapter, there are hoses, and I assume some sort of one way valve to keep the flow correct. Above all it needs to be safe. Ray had to do some adapting to use this on the Spitfire as it is slighlty different than the 51.
Whether this is on a 51 or a T-6, this is nothing to short cut or have doubts about the installation as you are dealing with the lifeblood of the engine.
Re: Merlin and Spitfire Oil Change Answer
Thu Nov 26, 2009 3:39 pm
ZRX61 wrote:Trying to remember who's name was on the large bracket/adaptor I saw on a T6 recently. Single filter design, but quite a fat filter, probably an inch or more bigger than the Champion filters used on the twin adapotors.
Was it from here? http://www.airwolf.com/
Evan's dad Tim
Re: Merlin and Spitfire Oil Change Answer
Thu Nov 26, 2009 4:03 pm
Bill Greenwood wrote:I have not heard anything about a Caterpillar part, but I doubt it that is correct in this case. I have never flown one, looks like the wing loading might be a little high.
LOL somewhat
Altho I have come across a coupe of Merlins painted Case tractor yellow which just looks odd.Bill Greenwood wrote:Whether this is on a 51 or a T-6, this is nothing to short cut or have doubts about the installation as you are dealing with the lifeblood of the engine.
No kidding, I've come across a couple of horror installations over the years that needed to be completely reworked/replaced etc to make safe/effective. Finding an original 1940's oil line on a T6 got my attention a few years back. So rotten it had turned white.. & it had just flown from Tx to Ca..
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One of the Mustangs I work on has this set up, which I think may be a Hovey deal:
Re: Merlin and Spitfire Oil Change Answer
Thu Nov 26, 2009 4:13 pm
evanflys wrote:ZRX61 wrote:Trying to remember who's name was on the large bracket/adaptor I saw on a T6 recently. Single filter design, but quite a fat filter, probably an inch or more bigger than the Champion filters used on the twin adapotors.
Was it from here? http://www.airwolf.com/
Evan's dad Tim
No, thats not it. This filter was about 6in dia & the part # on it cross ref'd to a Wix (no pun intended) filter for race use on auto's. The bracket bolted to the engine mount to the right of the oil cooler on the T6. The top part of it was machined in such a way that it could be mounted 90deg either way. I assume depending on which part of the engine mount it was attached to. I'm looking for a pic of it.
Re: Merlin and Spitfire Oil Change Answer
Thu Nov 26, 2009 6:55 pm
Thanks Bill, great information as usual.
Re: Merlin and Spitfire Oil Change Answer
Thu Nov 26, 2009 7:10 pm
evanflys wrote:ZRX61 wrote:Trying to remember who's name was on the large bracket/adaptor I saw on a T6 recently. Single filter design, but quite a fat filter, probably an inch or more bigger than the Champion filters used on the twin adapotors.
Was it from here? http://www.airwolf.com/
Evan's dad Tim
I recently put an Airwolf kit on a T-6. Looks a bit nicer than the Skytractor unit but both are good products. Specifies a Fram Racing or equivalent filter so that may be the wix filter mentioned.
As good as the modern twin spin on filter set up for a Merlin is I personally don't believe it is much better, if at all, than the original Packard Cuno. Many of the RR built Merlins as well as all the Griffons don't have a filter, just screens which really only catch chunks. They are not meant to filter, just indicate something bad is already happening. On the Griffon they did put a filter on the inlet oil to the Prop Gov so you will maintain prop control as long as possible. Even the Packard Cuno, as well as the Hovey filter, are in the oil out line of the Pressure Oil Pump as it heads into the engine. Nothing is filtered as it leaves the engine or before it goes through the oil pump entering the engine.
The best place to filter is leaving the engine before it heads to the oil cooler and oil tank.
The Hinz filter is a step towards improving this.
I found a really good Cuno type screen/housing on the Shakleton QEC we got from Gary Austin. It is made by Dunlop and I would like to get a couple more and the technical specs for it.
Rich
Re: Merlin and Spitfire Oil Change Answer
Thu Nov 26, 2009 7:48 pm
51fixer wrote:I found a really good Cuno type screen/housing on the Shakleton QEC we got from Gary Austin. It is made by Dunlop and I would like to get a couple more and the technical specs for it.
Rich
Now those are great filters!
Re: Merlin and Spitfire Oil Change Answer
Thu Nov 26, 2009 10:05 pm
My Rolls as I said has a filter at the prop gov and it is pretty fine screen, I guess it is on the inlet side. Yes that photo of the dual filter setup on the Mustang looks like the Hovey one that we have as far as I can remember.
I do believe that the modern paper cartridge filters are better than the old Cuno type biscuit filters. After all they came from the Hovey and Lauderback partnership and those are Mustang and Packard guys. They probably would not have gone to all the trouble to do this kit and addition if it was not better than the Cuno. And if any owner really wants to evaluate the effectiveness of their oil filter and air filter( or not), they can do an oil analysis and see what particles are in the oil, how much and what kind. I don't know any 51 guys who do this, but I'll bet there are, probably the Stallion 51 guys.
I have seen the filter Jack Roush uses, it seems similar in design to the Cuno, but probaby is superior in filtration. I think it uses metal disks or cartridge. They do such a nice job of making things, probably what Rolls might be doing if still in that business.
If you read much of the info on filters, one point of some doubt is how small do you have to filter the particles to be effective. Is there a point where it is small enough and protects as well as needed?
One other point, the oil change is important to also remove acids, which are corosive, as well as dirt or any fine metal.
I do believe that the modern paper cartridge filters are better than the old Cuno type biscuit filters. After all they came from the Hovey and Lauderback partnership and those are Mustang and Packard guys. They probably would not have gone to all the trouble to do this kit and addition if it was not better than the Cuno. And if any owner really wants to evaluate the effectiveness of their oil filter and air filter( or not), they can do an oil analysis and see what particles are in the oil, how much and what kind. I don't know any 51 guys who do this, but I'll bet there are, probably the Stallion 51 guys.
I have seen the filter Jack Roush uses, it seems similar in design to the Cuno, but probaby is superior in filtration. I think it uses metal disks or cartridge. They do such a nice job of making things, probably what Rolls might be doing if still in that business.
If you read much of the info on filters, one point of some doubt is how small do you have to filter the particles to be effective. Is there a point where it is small enough and protects as well as needed?
One other point, the oil change is important to also remove acids, which are corosive, as well as dirt or any fine metal.
Last edited by Bill Greenwood on Thu Nov 26, 2009 11:58 pm, edited 1 time in total.
Re: Merlin and Spitfire Oil Change Answer
Thu Nov 26, 2009 11:42 pm
Bill Greenwood wrote:And if any owner really wants to evaluate the effectiveness of their oil filter and air filter( or not), they can do an oil analysis and see what particles are in the oil, how much and what kind. I don't know any 51 guys who do this, but I'll bet there are, probably the Stallion 51 guys.
I know we do it on some of the P51's, but can't say for sure if we do it on all of them. Flying Dutchman definitely gets it done, as do a couple of the others. I'm not always right there when the oil gets dumped & thats why I'm unsure about the others.
Bill Greenwood wrote:I have seen the filter Jack Roush uses, it seems similar in design to the Cuno, but probaby is superior in filtration. I think it uses metal disks or cartridge. They do such a nice job of making things, probably what Rolls might be doing if still in business.
*ahem*...Rolls IS still in business
Re: Merlin and Spitfire Oil Change Answer
Fri Nov 27, 2009 10:07 am
ZRX61 wrote: *ahem*...Rolls IS still in business
They went bankrupt in the 1970's. Another company with the same name took over their assets.
Re: Merlin and Spitfire Oil Change Answer
Fri Nov 27, 2009 11:54 am
Fouga23 wrote:ZRX61 wrote: *ahem*...Rolls IS still in business
They went bankrupt in the 1970's. Another company with the same name took over their assets.
I think you'l find it was a Govt bail out deal, altho there has been 2 RR's for quite a while. The aviation side & the auto one now owned by BMW
edit....
Here ya go:
http://en.wikipedia.org/wiki/Rolls-Royce_Limited