# Packard vs Rolls-Royce Merlins



## wuzak (Oct 23, 2013)

What are the differences?

My understanding is that the initial production of Packard single stage engines differed from the equivalent Rolls-Royce engines in minor details only. Such as the sealing between the head and the block. Which was changed to match the Rolls-Royce engines later.

The two stage engines differed in having a Wright designed epicyclic supercharger drive system, as opposed to the Rolls-Royce Farman type.

Packard engines going to the USAAF had SAE splined prop shafts, those going to the UK/Commonwealth had SBAC shafts.

From another thread:



> Packard Merlins were built to Rolls-Royce specs and standards.





> No, they were not. There were built to more stringent standards.



Packard Merlins were surely built to Rolls-Royce drawings, even if they had to be redrawn for American conventions. So I can't see why Packard Merlins were "built to more stringent standards".




> Parts built by Packard were interchangeable with parts made by Rolls-Royce and Ford UK.





> Not all parts in all equivalent engines. R-R still had many hand fit parts and much "File to fit" in their engines.



Apart from the eronious term "file to fit", did Rolls-Royce production Merlins (as opposed to those built in the experimental shop) have parts individually fitted? I have my doubts, especially for engines built by Ford UK.


Now, the Packard Merlins all had equivalent Rolls-Royce engines, and were rated according to the Rolls-Royce ratings.

V-1650-1 = Merlin 28
V-1650-3, -5, -7 were 60 series engines.
V-1650-9 and later were 100 series engines - with strengthened components.

An example of the supposed superiority of the Packard built engine was the V-1650-9. With water injection and +30psi boost the -9 delivered just over 2200hp.

The equivalent Rolls-Royce engine (RM.16SM) was not fitted with water injection, and was limited to +25psi boost and just over 2000hp. With ADI the other 100 series Merlins could, surely, match the 2200hp of the -9?

Just how much engine development did Packard do on the Merlin?


Finally, the RM.17SM was cleared for flight at 2380hp with +30psi boost @ 3300rpm (I assume with ADI). It was to be rated at 2200hp @ 2000ft MS gear and 2100hp @ 15,000ft FS gear. I believe both were at +30psi and 3000rpm.

And the RM.17SM was tested for 15 minutes at 2620hp, +36psi boost, 3150rpm with ADI.


----------



## pattle (Oct 23, 2013)

You can have a black cat but there is always someone who claims that their cat is blacker.

Reactions: Agree Agree:
1 | Like List reactions


----------



## Shortround6 (Oct 23, 2013)

I think the "file to fit" was pretty much done away with the British Ford involvement. There may have been a lot less "file to fit" than measuring parts and selecting the best fit. As in measuring the bores of the cylinders and picking the pistons that fit the bores best even if not all pistons would fit all cylinders rather than 'filing' the pistons. 

There were four UK sources and Packard. The UK sources provided over 100,000 engines

There were Six UK and RAF overseas repair facilities. The UK based repair facilities repaired/overhauled 50,000 engines. The number repaired/overhauled in the overseas facilities is unknown. 

That is a _LOT_ of "filing and fitting". 

According to one source not a _single_ engine from the Ford Tafford works failed or had to be torn down and rebuilt for failure to meet specified performance on test.

Reactions: Like Like:
2 | Like List reactions


----------



## michaelmaltby (Oct 23, 2013)

".... No, they were not. There were built to more stringent standards."

They most surely were built to _different _standards ..... BSI for the UK builds and American Standard for Packard builds (and De Havilland and AV Roe employment in Canada for Mossies and Lancs).


----------



## wuzak (Oct 23, 2013)

michaelmaltby said:


> ".... No, they were not. There were built to more stringent standards."
> 
> They most surely were built to _different _standards ..... BSI for the UK builds and American Standard for Packard builds (and De Havilland and AV Roe employment in Canada for Mossies and Lancs).



In what way?

If Packards were built to American Standards they would have been fitted in UNC and UNF threads - they, in fact, used BSW and BSF threads.

BSI and American Standards may have had different tolerances - but the Packard engines would have used the tolerances specified on the drawings. Doubtful that they would have changed them.


----------



## Aozora (Oct 24, 2013)

wuzak said:


> Packard Merlins were surely built to Rolls-Royce drawings, even if they had to be redrawn for American conventions. So I can't see why Packard Merlins were "built to more stringent standards".
> 
> Apart from the eronious term "file to fit", did Rolls-Royce production Merlins (as opposed to those built in the experimental shop) have parts individually fitted? I have my doubts, especially for engines built by Ford UK.



Here is an analysis of the Packard Merlin's construction; it should help answer several questions:

View attachment PackardMerlin.pdf


According to this, Rolls-Royce continually modified the Merlin to make it easier to build on both sides of the Atlantic; Packard helped contribute innovations to the overall design, as well as developing features unique to their version of the Merlin:



> During the life of the Merlin almost 1,000 modifications were issued by Rolls-Royce to increase reliability or simplify manufacture. Packard initiated some of these as well as a number which applied only to Packard-built engines....A few of the more significant changes contributed by Packard were: Introduction of the two-piece cylinder block; introduction of a new design water pump with sealed ball bearings; use of a continuously variable ratio supercharger drive....Although it has been reported in some prior publications that the design of the Packard epicyclic two-speed supercharger drive was one derived from on in use by Wright Aeronautical, that is not the case...(page 7)



Also attached is a description of how R-R analysed early Merlin performance.

Reactions: Like Like:
1 | Like List reactions


----------



## wuzak (Oct 24, 2013)

Aozora said:


> Here is an analysis of the Packard Merlin's construction; it should help answer several questions:
> 
> View attachment 246126
> 
> ...



Thanks for those files Aozora.

A couple of things I would take issue with:



> Introduction of the two-piece cylinder block



That's all good, but they didn't design or develop the 2 piece cylinder block. Rolls-Royce did, and the only reason RR didn't introduce it earlier was because they were busy building engines for the war effort. RR waited until they started 60-series production before they went to the two piece block.



> use of a continuously variable ratio supercharger drive



Packard Merlins did not have a continuously variable supercharger drive. They had two distinct ratios.


----------



## GregP (Oct 24, 2013)

I believe there were some "fitted" parts in British Merlins that ran just fine but were not interchangeable. The Packard Merlins were interchangeable throughout.

I have not heard that Packard or Rolls-Royce Merlins had significantly different time-between-overhaul if operated in similar climatic conditions.

I HAVE heard the quality of the Packard Merlins surprised the British, who expected they would not be "good," but found out they ran just fine. That is no knock on the British at all. It is rather a natural expectation ... expect the worst and be happy if you are incorrect. At that time, the British had not had a lot of recent things to be "happy" about, and lower than the highest expectations seems quite natural. Hopefully they were pleasantly surprised. 

I wonder how many Rolls-Royce Merlins versus Packard Merlins are running today but really have no idea myself. It isn't a subject that matters a great deal either. Whoever has a running Merlin is probably happy with it if he or she can find parts at all, regardless of the source. Whoever has a FLYING Merlin these days is largely happy to just keep it running well, and hopes the next parts he of she gets won't be even MORE expensive ... but they probably will be.

Reactions: Like Like:
1 | Like List reactions


----------



## Aozora (Oct 24, 2013)

wuzak said:


> Thanks for those files Aozora.
> 
> A couple of things I would take issue with:
> 
> ...they didn't design or develop the 2 piece cylinder block. Rolls-Royce did, and the only reason RR didn't introduce it earlier was because they were busy building engines for the war effort. RR waited until they started 60-series production before they went to the two piece block.



This is explained in the article (page 4):



> On 2 August 1940 three representatives from Rolls-Royce came to talk to Vincent about the engine and "almost immediately after their arrival they raised the question as to what type of engine block we were prepared to tool up for. Up to that time we had never heard of the two piece block....They showed us drawings of the two-piece cylinder block and stated that in their opinion we should tool up for this improved two-piece construction....(Actually the two-piece cylinder design was modified by Packard to facilitate manufacture and was used only in engines made by Packard. Rolls-Royce continued to use single-piece construction for some time before they were able to switch...when they finally did it was one designed by themselves and somewhat different from Packard's. For the sake of uniformity Packard switched to the Rolls-Royce design at that point.)



Packard started Merlin construction from the outset using their own version of two-piece cylinder block, before switching to the R-R version once R-R had changed to two-piece construction with the introduction of the 61 (from memory the 60 still used single-piece blocks?).



wuzak said:


> Packard Merlins did not have a continuously variable supercharger drive. They had two distinct ratios.



Not sure what the author was referring to, unless he was describing the Simmonds automatic supercharger control; he was also incorrect in implying that the British 60/70 series all used manual supercharger controls - most also had automatic, barometrically controlled clutches.


----------



## michaelmaltby (Oct 24, 2013)

".... BSI and American Standards may have had different tolerances - but the Packard engines would have used the tolerances specified on the drawings.

You are correct. I misspoke.

"An often asked question is; “did Packard replicate the British thread system when they built Rolls-Royce Merlins under license during World War II?” The answer is yes; all threads that were used on the Merlin were accurately replicated by Packard. This would include BSW (British Standard Whitworth), BSF (British Standard Fine), BSP (British Standard Pipe) and BA (British Association). Having said that, however, Packard Merlins> used U.S. built Bendix injection carburetors; PD-16 for single stage engines and PD-18 for two stage engines, both of which used U.S. Unified threads. British built Merlins employed S.U. carburetors using Whitworth threads. The job facing Packard when they undertook manufacture of the Merlin was daunting to say the least. It’s bad enough having to build a complex product like the Merlin but exacerbating the situation was the fact no tool maker in the U.S. made Whitworth taps or dies. Therefore, Packard were forced into making their own. Although this created a significant hurdle to overcome, the effort was well worth it, Packard and Rolls-Royce components were interchangeable.

[Source]


----------



## fastmongrel (Oct 24, 2013)

My Dad was an instrument fitter on a Coastal Command squadron post war in Malta. They operated Lancaster mkIIIs which originally came with Packards. By 1946 the Packards where in short supply in Malta so RRs were fitted in there place apparently they slotted into place just fine and aircrew could never tell which engine was fited. 

Also time expired Merlins were broken for parts for Meteor tank engines when there was a shortage of crankshafts and Packard and RR parts were used interchangeablely without any problem.

Reactions: Like Like:
1 | Like List reactions


----------



## beitou (Oct 24, 2013)

Did they sound any different or would that be a product of their mountings and exhaust systems?


----------



## GregP (Oct 24, 2013)

V-12's with similar firing orders have very similar sounds, but the actual sound depends on the exhaust stack fitted. A P-40 exhaust stack sounds different from a P-38 or P-39 (all Allison) and the stacks used on several British planes using Merlins are different-souding from one another, but the basic firing sound and frequency is the same. One particularly noticeable different sound with the Griffon is a normal Griffon Spitfire compared with a Griffon Firefly that has the nigh-fiighter shelves over the stack. It deflects the sound outward and the Firefly with these is VERY loud to an observed compared with a Griffon Spitfire.


----------



## Aozora (Oct 24, 2013)

beitou said:


> Did they sound any different or would that be a product of their mountings and exhaust systems?



Youl'd be hard pressed to tell the difference between the _engine_ sounds but there were differences depending on the aircraft they were in

_View: https://www.youtube.com/watch?v=a3eBD6tLVOQ_

The P-51D had a distinct whistle, almost a howl...


_View: https://www.youtube.com/watch?v=HPTIe30hr1E_

The Griffon was altogether gruntier...


_View: https://www.youtube.com/watch?v=3EcCYA68m_w_

and the Allison V-1710 was smoother, more mellow than either the Merlin or Griffon...


_View: https://www.youtube.com/watch?v=CjZoWU5R9dA_

according to pilots who flew both the Allison engined and Packard Merlin P-51s the Allison was a smoother engine, particularly at lower cruising revs and it could be leaned out more.


----------



## OldSkeptic (Oct 24, 2013)

wuzak said:


> Thanks for those files Aozora.
> 
> That's all good, but they didn't design or develop the 2 piece cylinder block. Rolls-Royce did, and the only reason RR didn't introduce it earlier was because they were busy building engines for the war effort. RR waited until they started 60-series production before they went to the two piece block.



No the 2 piece clock was introduced in the XX series (2 speed, single stage) engines. Later versions of the 45 (Spit 5, single speed, single stage) had it to.

The Merlin 60 (prototype 2 speed, 2 stage) had a single block but all the production 60 series engines were 2 piece blocks.

The Merlin 28 (Packard version of the RR XX) used their own 2 piece construction, from the Merlin 33 (Packard version of the RR 23) onwards they used the British 2 piece construction.


----------



## wuzak (Oct 25, 2013)

OldSkeptic said:


> No the 2 piece clock was introduced in the XX series (2 speed, single stage) engines. Later versions of the 45 (Spit 5, single speed, single stage) had it to.



If that were the case then the 2 piece block would have been in production in the UK from 1940. Which predates Packard's use of a 2 piece design.

I am sure that early XXs used the 1 piece block, while later ones got the 2 piece design - around the time they were stting up 60-series production.


----------



## OldSkeptic (Oct 25, 2013)

True the XX (and 21) were 1 piece blocks. All the later were 2 piece. That's why I said XX series, should have made myself more clear.


----------



## wuzak (Oct 25, 2013)

OldSkeptic said:


> True the XX (and 21) were 1 piece blocks. All the later were 2 piece. That's why I said XX series, should have made myself more clear.



According to Lumsden the 22 and 23 were also single piece block engines, while the 22A and 23A had 2 piece blocks, but were otherwise the same as the 22 and 23.


----------



## OldSkeptic (Oct 25, 2013)

According to RR the 22 was a 2 piece block and the 22A a XX conversion. The 23 was reversed cooling for the Mosquito and was 2 piece, the 22A was a 21 conversion.
The conversions were to a 2 piece block.


----------



## asma18 (Jul 23, 2014)

1. The Merlins and Packards differed little, Magnetos, supercharger drive and in fact the Bendix Carb was on the Merlin before Packard
2. It took Packard 12 monthes to convert the Rolls drawings to American convention
3. Two piece cylinder heads suggested by Packard manufactured by Rolls and were fitted to both
4. Rolls/Royce tolerances and specifications were followed to the letter by Packard. Spurious statements have been made that Packard had closer tolerances.
5. Someone has said the Packard engine achieved over 2000 hp ,from Rolls Royce Merlin Variants V-1650-9 1710 hp combat. And that was the most horsepower from a Packard in WW2
6. 1 to 4 from Rolls Royce Heritage Trust Derby U.K.


----------



## GregP (Jul 25, 2014)

Someone said there was a Merlin with a continuously-variable supercharger drive ... and someone said there wasn't.

Actually there was.

It was a Packard V-1650-19 of which 2 were built. They had a SUndstrand vartiable speed supercharger drive with automatic speed controller. It was 1,170 lbs net dry weight, and made 2,200 HP @ 3,000 rpm WER at sea level, and 1,875 HPP @ 3,000 rpm at 17,000 feet. Takeoff power was 1,700 HP and cruise was 2,700 rpm at 8 lbs boost.

Yes it was an experimental engine but they DID, in fact, built two of these beasts as the big pistons were just about to go extinct. Had pistons hung around a bit, they might have built it for production ... in an alternate reality.


----------



## wuzak (Jul 25, 2014)

GregP said:


> Someone said there was a Merlin with a continuously-variable supercharger drive ... and someone said there wasn't.
> 
> Actually there was.
> 
> ...



I had never heard of that until someone mentioned it in another thread.

I think, perhaps, you have mistyped the weight of the engine, since single speed, single stage early Merlins were about 1350-1400lb.


----------



## Shortround6 (Jul 25, 2014)

1770lbs?

http://www.enginehistory.org/ModDesig/I2 5.tif

These charts are not 100% reliable but the weight fits.


----------



## GregP (Jul 25, 2014)

No, I have not mistyped the weight.

Packard V-S Drive


----------



## wuzak (Jul 25, 2014)

GregP said:


> No, I have not mistyped the weight.
> 
> Packard V-S Drive



1,770lbs it is.

(You did have 1,170lbs.)


----------



## wuzak (Jul 26, 2014)

Thanks for the link Greg.

It seems that the variable speed drive worked on teh same principle as the V-1710's 2 stage drive - ie, the auxiliary stage was driven by the VSD, while the main/engine stage was driven by the normal gearing. The difference being that there was the two speed drive for the main/engine stage impeller.


----------



## GregP (Jul 26, 2014)

Well hell, I DID mistype ... didn't I? Jeez, that's never happened before!

Next time you visit, slap me, please.


----------



## wuzak (Jul 26, 2014)

I certainly will!

btw, good to hear that you have found a new job. Hope it is interesting and pays decently well.

And doesn't cut into your time down at the museum.


----------



## GregP (Jul 26, 2014)

I have Saturdays off ... but woirking on airplanes 6 days a week may prove less than fun. The good thing about Saturdays at the Museum is I don't really HAVE to get anything done on a schedule. We DO make progress, but now I am doing every other weekend on the B-17 and the O-47 projects.

We'll see ... at SOME point.


----------



## Shortround6 (Jul 26, 2014)

GregP said:


> Well hell, I DID mistype ... didn't I? Jeez, that's never happened before!




I personally have only done it one or two......................................hundred times 


after spell check and edit


----------



## GregP (Jul 26, 2014)

Me too, Shortround. 

I am probably the worst offender in here for mistyping. You're WAY up on the list ahead of me in typing accuracy.


----------



## pbehn (Jul 28, 2014)

Much of the discussion here is about production engineering. When the merlin was first designed the projected orders would be in the order of thousands I doubt if anyone ever thought that production would run to 150,000. Companies employ different designs and methods when they produce 1000 units per year as opposed to 30,000. Long before the war started the replacements for the merlin were on the drawing board but development of the merlin meant they never really made it.


----------



## The Bigfella (Aug 11, 2014)

My understanding, based on what my uncle wrote in his autobiography (which I loaned out and haven't got back yet)... he was a Beaufighter / Mosquito pilot - and he did a course at RR as he was being proposed for test flying duties prior to being invalided out with TB.... was that the Rolls engines were built in batches, with a set number of critical spares, eg crankshafts, specific to that batch of engines. The next batch wasn't interchangeable. Packard made everything interchangeable.... need a spare crank... here, have one.


----------



## fastmongrel (Aug 11, 2014)

The Bigfella said:


> My understanding, based on what my uncle wrote in his autobiography (which I loaned out and haven't got back yet)... he was a Beaufighter / Mosquito pilot - and he did a course at RR as he was being proposed for test flying duties prior to being invalided out with TB.... was that the Rolls engines were built in batches, with a set number of critical spares, eg crankshafts, specific to that batch of engines. The next batch wasn't interchangeable. Packard made everything interchangeable.... need a spare crank... here, have one.



Thats not true RR and Packard Merlins were practically interchangeable apart from some specials and the early hand built alphabet series. A lot of time expired Merlins were broken up to provide parts for Meteor Tank engines particulary crankshafts, camshaft drives and conrods. RR and Packard engines were broken indiscriminately and all the parts had the same Rover part number no matter whether they came from the 4 RR factories at Derby, Glasgow, Crewe or the Ford factory at Manchester or Packards in Detroit.


----------



## Shortround6 (Aug 11, 2014)

They also broke up hundreds of RR built Merlins to provide spare parts for the Packard built Merlins in P-40s in North Africa. 

These stories may well have been what was being told to troops (pilots and ground crew) in the field who were _not_ doing the over-hauls. Goodness knows there were enough other rumors, legends and tall tales floating around in the absence (or even in the presence) of "official" documents. 

ALL Japanese troops wore glasses right?

Reactions: Like Like:
1 | Like List reactions


----------



## GregP (Aug 11, 2014)

From the Merlin owners I know, which number about 15, the Packard and Rolls engines are not interchangeable in a meaningful way. Some things interchange but aren't normal wear and tear items. You can interchange valve covers, but they don't often fail on their own, so it doesn't help that they interchange. Ditto for parts that bolt on like intake manifolds, oil pans, etc. Packard's tolerances on crankshafts were very tight, so a Rolls crank might or might not fit. Conversely, if a batch of Rolls engine blocks had shorter crank journals than Packard's specs, the Packard crank would not fit in the Rolls.

I understand that neither was particularly "better" than the other, but I know too many people that own one who tell me that the important parts are not all that often interchangeable for me not to believe it. If a guy's P-51 is down and he wants to fly, and has (or can get) a Rolls part, I think he'd use it if he could ... and vice versa if he has a Spitfire, Hurricane, etc. or anything with a Rolls Merlin and he has (or can get) a Packard part.


----------



## wuzak (Aug 11, 2014)

GregP said:


> Packard's tolerances on crankshafts were very tight, so a Rolls crank might or might not fit.



Packard used the same tolerances as Rolls-Royce and Ford UK.


----------



## pbehn (Aug 12, 2014)

I don't know what a tight tolerance is with a RR engine. The Merlin consumed prodigious amounts of oil, even their car engines burned oil from new.


----------



## fastmongrel (Aug 12, 2014)

Not surprising 70 year old parts dont fit, it would be amazing if they did fit perfectly. Whats important is that they were interchangeable and the 5 different production units all worked to the same standards something thats not always a given even nowadays.


----------



## Shortround6 (Aug 12, 2014)

pbehn said:


> The Merlin consumed prodigious amounts of oil, even their car engines burned oil from new.



ALL aviation engines of the time used oil, burned, leaked or out through the breathers. That is why most or all planes fitted with long range fuel tanks had bigger oil tanks or oil tanks had two fill marks, one for normal use and one for long range. 
Most specification for aircraft engines not only gave fuel consumption figures in pounds of fuel per hp hour ( or equivalent) but gave oil consumption figures too.


----------



## pbehn (Aug 12, 2014)

Shortround6 said:


> ALL aviation engines of the time used oil, burned, leaked or out through the breathers. That is why most or all planes fitted with long range fuel tanks had bigger oil tanks or oil tanks had two fill marks, one for normal use and one for long range.
> Most specification for aircraft engines not only gave fuel consumption figures in pounds of fuel per hp hour ( or equivalent) but gave oil consumption figures too.



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.


----------



## GregP (Aug 12, 2014)

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!


----------



## Shortround6 (Aug 12, 2014)

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.


----------



## GregP (Aug 12, 2014)

Next weekend I'll ask what the Merlins in our collection burn in flight ... SOMEONE should know.


----------



## Milosh (Aug 12, 2014)

pbehn said:


> RR cars burned oil as normal from new into the 1970s.



Guess you never drove American cars into the '70s. Don't know about cars in other countries. There was a reason why the oil level was checked when the fuel tank was filled.

Reactions: Like Like:
1 | Like List reactions


----------



## GregP (Aug 12, 2014)

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.


----------



## fastmongrel (Aug 13, 2014)

pbehn said:


> 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 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.


----------



## pbehn (Aug 13, 2014)

fastmongrel said:


> 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.


----------



## Shortround6 (Aug 13, 2014)

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.

Reactions: Like Like:
1 | Like List reactions


----------



## Milosh (Aug 14, 2014)

All engines burn oil, especially during break-in.


----------



## jimh (Aug 20, 2014)

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


----------



## GrauGeist (Aug 20, 2014)

fastmongrel said:


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


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.


----------



## soulezoo (Aug 20, 2014)

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.


----------



## fastmongrel (Aug 21, 2014)

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. &#128521;


----------



## buffnut453 (Aug 21, 2014)

Shortround6 said:


> 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.



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.


----------



## Shortround6 (Aug 21, 2014)

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


----------



## GrauGeist (Aug 21, 2014)

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.


----------



## buffnut453 (Aug 21, 2014)

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!).


----------



## fastmongrel (Aug 21, 2014)

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.


----------



## wuzak (Aug 21, 2014)

fastmongrel said:


> 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.

Reactions: Agree Agree:
1 | Like List reactions


----------



## wuzak (Aug 21, 2014)

buffnut453 said:


> 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 think the point that SR is making is that all production facilities making the Merlin - be they in the US or in the UK - worked to the same tolerances. That a piston from any one of these factories were to the same standard and would be interchangeable with one from another factory.


----------



## yulzari (Aug 21, 2014)

The proper comparison is between the Shadow (eg Ford) Merlins and Packard Merlins. The earlier Rolls Royce made ones were made for production order of few hundreds. The later vast factories were pushing them out by the thousands. Rolls Royce early production methods were appropriate to the investment for those low numbers. Had they invested at the beginning in the machinery that the huge factories used then Rolls Royce would have been bankrupt long before the war. The original Rolls Royce tolerances and the later shadow/Packard tolerances were both the right answers. But to different questions. Much as the Meteor was developed in a very different direction to the Merlin but was the right answer to the question of a powerful, reliable petrol tank engine at the time.

Reactions: Like Like:
1 | Like List reactions


----------

