Packard vs Rolls-Royce Merlins

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Its logical to me SR all piston aviation engines were high performance and comparatively large piston diameter. Making a diameter/ ovality tolerance becomes harder as it increases. In any case I would prefer to burn oil than have a seizure. The point I was making was that RR engines burned oil when others didn't, RR cars burned oil as normal from new into the 1970s.
 
If Packard's tolerance were the same as Rolls Royce, then the Rolls engines would be very interchangeable. The fact that they aren't from batch to batch while the Packards are gives the notion of the same tolerances the boot. Either that or Rolls wasn't following them. I doubt that in the extreme. More likely Rolls had some tolerance from the manfucatured part dimension and Packard had an absolute tolerance with the same limits. The two situations do not give rise to identical parts.

I have no dog in this hunt, but I DO know a number of Merlin owners who can tell you that they aren't the same, but it also isn't the case that one is better than the other ... they are the same basic design and have similar power outputs, but aren't necessarily interchangeable, regardlsess of any claims to the contrary.

Experience with the real engines trumps paper knowledge every time.

Ask anyoine who flew a Brewster-built Corsair after a unit built by Vought. They feel lucky to have gotten down in one piece!
 
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Did the Merlin actually use oil at a much different rate than other aircraft engines of it's time?

Some of the published "book" figures for aircraft engines range from around 0.015-0.025lb of oil per HP hour. These may very well be advertising brochure figures and not real world. What is interesting is that Allison was saying 0.025lb of oil per HP hour and RR was saying 0.022 for most Merlins. Which company was more accurate (or honest) I don't know. Bristol was saying 0.018 for ALL of their radials, poppet valve and sleeve valve and Wright was saying 0.020lb/hp/hr for four different engines.

These are all cruising consumptions, full power may vary (and leave the company an out?) but basically ALL high powered aircraft engines used oil at rate that is hard to grasp by modern car owners. A B-26 bomber held over 40 gallons (US) for each engine which is much higher than most fighters using the R-2800 engine. The JU-88 had an auxiliary long range oil tank in the port wing to be filled when on longer missions as examples.

Cruising at just 500hp an engine that uses 0.020LB/HP/Hr will use 10lb of oil an hour.
 
Spot on Milosh. In the 1960's in the middle of the supercar era, they didn't burn a lot of oil unless you were up in the higher rpm bands. I was there a lot at the time, so they used oil. My 426 Hemi burned it when turning more than 5,000 rpm. The Chevy 396 did, too. Ditto the Chevy 427, Ford 427 / 428 / 429. So does a Chevy 454. ... had a 1970 Chevelle SS 454 LS7. It could pass up everything but a gas station, an auto parts store, a tire store, or an insurance company.

Stay slow and they are fine, push the rpm and you use oil ... but it DID protect the internals! All were almost bulletproof if operated within specs.
 

If a car engine wasnt burning oil before the 1970s it was about to seize

The RR inline 6 Inlet Over Exhaust engines were oil burners they went through more oil than a Oil Tanker on the rocks but the 410 V8s werent too bad by the blue hazy standards of the day.
 

The point I was making was that by the 70s RR competitors like Mercedes were producing engines that didn't burn oil. I drove big American Cars and Vans in Saudi Arabia the 80s. It was fun but I am glad I wasn't paying the petrol bills in Europe. My Dodge had a range of 120 miles on a full tank we burned all the valves out on a dash from Yanbu to Dammam. Its all to do with production engineering.

It may be more cost effective to match barrels to pistons when you produce 1000 units a year it isn't when you are making 100,000.
 
The story goes that when Ford of England was brought in to produce Merlins they looked at the original drawings and tolerances and claimed they could NOT build the required number of Merlins IF they stuck to the Rolls-Royce tolerances. When somebady at Rolls asked if they (Ford) couldn't build to R-R standards the Ford guy said, no, they couldn't mass produce engines with such loose tolerances as R-R used. When making cheap Fords with low cost labor they needed tight tolerances to reduce the amount of hand fitting, not that R-R filed parts to fit but rather measured and selected available parts in the bins to get the required fit or balance.
For instance on early Merlin engines the allowed weight variation of pistons in ONE engine was 1/2 ounce. The allowed weight difference for each pair of connecting rods, pistons, rings, pins was one ounce. That does not mean that pistons or paired connecting rod assemblies were interchangeable between engines and that is where the problems in production come in. One engine could be using all "heavy" pistons and connecting rods and the next engine all "light" ones.
Ford of England (and other shadow factories?) and Packard spent the time and money on tooling to produce large numbers of parts to tight tolerances to reduce the amount of hand selecting of parts needed to assemble an engine to the desired tolerances. Once a Derby engine was assembled it's Piston to bore fit and bearing clearances and such were the same as another Merlin.
 
I've flown Betty Jane about 15 hours in the last 10 days and it hasn't burned through any oil...still read 9 1/2 this morning. Most of the engine builders are using new connecting rods and pistons...even newer parts are on the way

Jim
 
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fastmongrel said:
If a car engine wasnt burning oil before the 1970s it was about to seize
Click to expand...
My 1962 Chevy Nova has a 250 cid (4.1L) L-6 that never leaked nor burnt oil. The same can be said for my 1966 Ford Mustang, which also has a straight-6 (200 cid/3.2L) with quite a bit of mileage on it. Doesn't burn oil although it likes to piddle a little bit of oil at the back of the valve cover once in a while.

The same can be said for the 1953 Pontiac Catalina Starliner I owned several years ago. It had it's original, unrebuilt inline 8 (268 cid/4.3L) with well over 100,000 miles on it. Didn't burn oil and it didn't leak any, either.
 
Hello guys,

First time poster--I have been lurking for awhile and learning a lot. I didn't have anything useful to post so I have not.... until now.

GregP... I had a 70 SS 454 Chevelle with the LS6 and 4 speed. Your assessment was spot on.
Fastmongrel... I note you are from the UK. If your experience is limited to British engines, your experience is valid... even through today. Land Rovers for instance, right up until BMW made the engine were notorious for eating/leaking oil regardless of age or use. It's just sort of ubiquitous to the brand much like the saying: "Lucas Electronics... the original inventors of darkness". No offense is meant.

Oil burning, or lack thereof, has much to do with designs, materials, tolerances and use. There are two ways to encourage oil burning. The first is by poor design (I mentioned Rover earlier) or loose tolerances (through build or excessive wear). The second has to do with internal crankcase pressures. Every engine has a certain amount of blow by from the rings. This increases with cylinder pressures (like high compression ratios or high amounts of boost). As the amount of blow by increases, an engines ability to evacuate that crankcase pressure is critical. Oil as much as gases can be passed through the blow-by tube when it reaches a certain level. With engines having an EGR (exhaust gas recirculation system) that oil can be then burned in the cylinder. High RPMs can definitely contribute to this; however, it is less about the speed of the internals than it is in order to get there, one is usually pushing high HP and thus high cylinder pressures.

GrauGeist: Your examples make perfect sense as they are all low compression (relative sense) engines; however, I am surprised they don't leak more oil as old time seals are usually not all that great over time. I think Land Rover is still trying to figure that out. Sorry LR fans... I get to say that as I've had a few Range Rovers over the years and have first hand experience

I have a diesel that went 135,000 miles without burning a drop of oil. That was at a 305 HP rating. Now that it'll push over 900 HP, well, oil everywhere. Same internals.

Hope that contributes something.
 
Hi soulezoo my jokey remark was just that a joke i know not every car was a mobile oil slick. Its a fact though that large parts of the British Midlands and Detroit are wasteland because the Japanese and the Germans built cars and engines that didnt use oil and throw a wobbly every time you needed some electrons. If all US and UK motors had been such oil tight reliable paragons then I wouldnt be working as shop foreman in a garage that specialises in Mercedes and Lexus cars. 😉
 

Is there a source for this story? Just wondering - there are lots of nice urban myths out there and I'd like to know whether or not this is a documented event.
 
Well, it is related in Stanley Hooker's Autobiography "Not much of an Engineer" on pages 58-59.

" ...A number of Ford engineers arrived at Derby, and spent some months examining and familiarizing themselves with the drawings and manufacturing methods. One day their Chief Engineer appeared in Lovesey's office, which I was then sharing and said " You know, we can't make the Merlin to these drawings"
I replied loftily " I suppose that is because the drawing tolerances are too difficult for you, and you can't achieve the accuracy".
' On the contrary', he replied, ' the tolerances are far too wide for us. We make motor cars far more accurately than this. Every part on our car engines has to be interchangeable with the same part on any other engine, and hence all parts have to be made with extreme accuracy, far closer than you use. That is the only way we can achieve mass production'.
Lovesey joined in, "Well, what do you propose now?"
The reply was that Ford would have to redraw all the Merlin drawings to their own standards, and this they did. It took a year or so, but this was an enormous success, because, once the great Ford factory at Manchester started production, Merlins came out like shelling peas at a rate of 400 per week. And very good engines they were too,....."

Now wither anybody actually wrote the conversation down and dated it I don't know but you have one of the "claimed" participants telling the story in his autobiography
 
Soulezoo, welcome to the forum!

Also, yes, the Pontiac engine is lower compression, as was the Ford L-6. The Chevy L-6 on the otherhand, has stock 8.5:1 compression, which was higher than most stock V-8s of the day. Alot has to do with the design of the engine both internal and external, like the headbolt placement (and torque application), oilpan bolt placement (and gasket design) and in the case of the Chevy L-6, had 7 mains so it seemed to suffer a slower degredation of the journals than other manufacturer's L-6s.

Then again, I had a 1979 BMW 320i (E21) with the M10 2.0L and it was a screamer and a joy to drive BUT, it burnt oil.
 
Re post #56. That's good enough for me! Thanks SR. Appreciate the sourcing info.

I'm still struggling to understand how the RAF dealt with the supply/maintenance challenges of such variable tolerances. Manufacturing is one thing but maintaining engines at the squadron or MU level would be almost impossible if the units had to factor in, for example, engines with "all heavy" pistons and "all light" pistons (and, presumably, "all points in between" pistons!).
 
I wonder if Ford being a US based company did its drawings to a different standard to the RR drawings. Dont know which projection RR used but I believe the US standard was different to British and someone used to 1st angle would struggle with a 3rd angle blueprint and vice versa.
 

I imagine that since it was Ford UK and they would have used mostly British workers, that the drawings were to British standards.

Packard spent some time converting to US standards, which probably wouldn't have been required if Ford UK had done theirs to US standards.
 
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