WW2 without V-1710: options for the Allies?

As a tank engine it was rated at both 2600 and 2800rpm. It NOT was a direct copy of the Merlin but then I am not so sure about it's being test and production tooling ordered in mid/late 1940. Some sources say only a 2 cylinder test rig was running in 1941.
Ford was approached about building the Merlin in summer of 1940 and given a sample engine and some blueprints, by Sept they not only backed out of the deal and Packard given the contract ( and gotten the materials for Ford) but Ford had signed up to make P&W R-2800s in a brand new Factory. It took until the summer of 1942 for the V-8 tank engine to show up. Grants had been being built with 9 cylinder radials, twin 6-71 diesels and the 30 cylinder Chrysler multi-bank with the same power units transferred over to the Sherman production. Seems like a long time if the Ford engine was really ready to go in V-12 form in 1940.

Shortround6 said:

As a tank engine it was rated at both 2600 and 2800rpm. It NOT was a direct copy of the Merlin but then I am not so sure about it's being test and production tooling ordered in mid/late 1940. Some sources say only a 2 cylinder test rig was running in 1941.
Ford was approached about building the Merlin in summer of 1940 and given a sample engine and some blueprints, by Sept they not only backed out of the deal and Packard given the contract ( and gotten the materials for Ford) but Ford had signed up to make P&W R-2800s in a brand new Factory. It took until the summer of 1942 for the V-8 tank engine to show up. Grants had been being built with 9 cylinder radials, twin 6-71 diesels and the 30 cylinder Chrysler multi-bank with the same power units transferred over to the Sherman production. Seems like a long time if the Ford engine was really ready to go in V-12 form in 1940.

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"Ready to go" was probably not accurate. While it had been dyno tested, full testing for aviation use would have most likely taken 6 months more or longer.

The Tank engine didn't show up until 1942, because Ford wasn't approached and issued contract for the engine and M4A3 tank until late 1941. The first pilot rolled out the door on May 13th 1942. The cut down V8 version of the engine was ready prior to this date. While the GAA is fairly well documented, the V1650 is very difficult to trace history. I hope to have copies of the original drawings of the aero-engine from the Henry Ford Museum in the near future. (When they find them). Next step will be to compare the aero specs to a GAC tank V-12 I'm tearing down for rebuild. (Yes, Ford built some V12sduring WWII for prototype tanks). I'll post the drawings on here when I get them.

Another view on it's history. While I know the person that researched and wrote this, I've not verified any of it.

Origins:

In late 1939 Edsel Ford made an agreement with Rolls Royce to produce their Merlin V12 Aircraft Engines in one of Ford's unused factories in Michigan. About 3/5 of the projected production was for British use, mostly for Canadian produced aircraft including; Landcasters, Mosquitoes and Hurricanes. Rolls Royce sent blueprints, tooling and parts to Ford, and it appears that Ford immediately started to redesign the Merlin, two very modified enbloc engines were built in their prototype shop.

Rolls Royce did not approve of the changes and Henry Ford's insistence that Ford only manufacture for U.S defense caused the Merlin production to be later moved to Packard, who subsequently built about 58,000 Merlin's.

The Ford V12 Aero Engine

Ford was a very successful Company with many innovative designs, a great engineering staff, especially in the area of large castings. And they had the aircraft engine designs from Rolls Royce. The Merlin is a very complicated engine with many, many parts, and the assigned Ford engineers thought they could improve it. Ford, knowing war was coming and there would soon be a large market for aircraft engines, continued development and had the tooling made to produce their design.

The result was a less involved, more durable and powerful 1650 cubic inch V12 of identical bore and stroke as the Merlin, however, that is the only similarity, the balance of the engine is completely different.

The GM Allison Engine was originally designed in 1929, the Merlin in 1933, the 1940 Ford design, was a more advanced design than either of these engines. Had it been developed to its potential, we likely would have had Ford Mustangs, (P51 Fighter Aircraft, not cars) by 1943.

The Ford GG Aero Engine was a dual overhead cam (4 total), 48 valve, 60 degree bank, aluminum V12. Unlike the multi-part units of the Merlin and Allison, the block was a very rigid monolithic enbloc unit, (similar to automotive V8s). Rods were stronger individual pieces-running in parallel on the crankshaft (like a standard V8 ) the crankshaft was held by 4 bolt main caps. Accessories were driven from the end opposite the propeller, induction was by a mechanical fuel injection pump. The heads were a pent roof 4valve per cylinder design, similar to the Miller/Offenhauser race engine. Spark plugs were in the top center of the heads between the valve sets, resulting in better fuel ignition and less flame travel than either the Allison, Merlin or Griffon. The cam train had no rockers, the cams drove directly onto "buckets" which pushed down on the valve stems. The jewel of the engine design was the cam drives which consisted of an assembly of helical and cone gears driving two angled shafts on the rear of each bank which simultaneously drove both intake and exhaust cams. This is far simpler than the much more involved arrangement of the Merlin or Allison.
Supercharging was by a large proprietary 2 stage Turbocharger.

The design was magnificent. Three were built; on the first test, the engine put out 1800HP! Unfortunately, the design was not ready in 1942, subsequent development was spent on Tank Engines, and the engine never flew.

There are 2 things here that might raise an eybrow or two:
1st - when the engine would be ready for production? If the answer is 'after Pearl Harbour' (or later), then it cannot fill V-1710's shoes, since it is too late.
2nd - what rpm was the engine turning and how big was the boost when engine made 1800 HP. What fuel was used? When where it did that? Was the supercharger system really a 2-stage turbo (= what abut engine stage supercharger?), or was it a turbo plus engine stage supercharger? Dimensions of superchargers?

I acknowledge that there is lot to be learned about the Ford's V-1650, however claiming performance figures without presenting sources does not look like a good research.

You are either dyno testing a full engine or you are not.

Now several other engines started as one, two or even 9 cylinder test rigs ( first R-2800 was actually a R-1400 of 9 cylinders) but plenty of V-12s started as V-2 test rigs. 6 months is a miraculously short period of time to test an aircraft engine. P&W started work on an 18 cylinder R-2600 in Aug 1936, changed to to the R-2800 March of 1937. The 9 cylinder test rig X-80 first ran in Feb 1938, By March 1939 it had run just under 700 hours. There were at least three 18 cylinder test rigs. The engine was type tested By July 1 1939 after 3300 hours of testing, all ground running. July 12, 1939 was first flight. Feb 12 saw the completion of 5000 hours of testing and a bill of materials released to production. March 25th saw the first production engine complete model test. However only 17 engines were completed in all of 1940. These are also the 1850hp two speed (or a few single speed engines?)

And the Ford engine was a very highly stressed, technically advanced engine. I am afraid ready to go in 1941 or even 1942 ( as an aircraft engine) are rather doubtful. Ford was aiming at 2000hp from 1650 cu in using standard american (not British) 100 octane fuel in 1940 which would certainly limit the boost (manifold pressure) used. Both Allison and R-R took until 1945 to get to such power levels using much better fuels. Now a much lower rated Ford engine might have made it into production sooner but Ford had a habit of promising things he could not deliver ( granted some of his factories did produce amazing quantities of war material by anybodies standard, just not near what Ford had promised to begin with).

m37b1 said:

In late 1939 Edsel Ford made an agreement with Rolls Royce to produce their Merlin V12 Aircraft Engines in one of Ford's unused factories in Michigan. About 3/5 of the projected production was for British use, mostly for Canadian produced aircraft including; Landcasters, Mosquitoes and Hurricanes. Rolls Royce sent blueprints, tooling and parts to Ford, and it appears that Ford immediately started to redesign the Merlin, two very modified enbloc engines were built in their prototype shop.

Rolls Royce did not approve of the changes and Henry Ford's insistence that Ford only manufacture for U.S defense caused the Merlin production to be later moved to Packard, who subsequently built about 58,000 Merlin's.

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Commonly accepted history is that Ford (America) was NOT asked to build the Merlin until the Spring/ early summer of 1940. The deal with Ford fell through in just a few weeks and Packard was brought in just a few days, initial talks went good but actual signing of the contract was in Sept of 1940 so the wording "caused the Merlin production to be later moved to Packard" might be technical correct but paints a rather distorted picture. It took Packard over a year to deliver more than a symbolic engine or two. Ironically ford was signing contracts to build a Factory to Build the P&W R-2800 with in a day or two of Packard signing the Merlin contracts.

The Ford V12 Aero Engine

Ford was a very successful Company with many innovative designs, a great engineering staff, especially in the area of large castings. And they had the aircraft engine designs from Rolls Royce. The Merlin is a very complicated engine with many, many parts, and the assigned Ford engineers thought they could improve it. Ford, knowing war was coming and there would soon be a large market for aircraft engines, continued development and had the tooling made to produce their design.

The result was a less involved, more durable and powerful 1650 cubic inch V12 of identical bore and stroke as the Merlin, however, that is the only similarity, the balance of the engine is completely different.

The GM Allison Engine was originally designed in 1929, the Merlin in 1933, the 1940 Ford design, was a more advanced design than either of these engines. Had it been developed to its potential, we likely would have had Ford Mustangs, (P51 Fighter Aircraft, not cars) by 1943.

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Again a bit of miss direction. While the Allison started development in 1929 there were quite a few changes to the engine by 1939 let alone by 1941. The Production Merlins ( or all but a few hundred?) also had a number of changes including a different cylinder head/combustion chamber than the 1933 version. While the Ford engine was , in some ways more advanced, the likelyhood of it matching the the Merlins used in the Mustangs in 1943 are pretty slim. Ford apparently lost a lot of money tooling up for an engine they never got a contract for. BTW Ford was paid 14.3 Million just to build the R-2800 factory, that amount of money did not cover a single production engine. And Ford, for all their car manufacturing expertise simply copied the layout of the P&W East Hartford plant. Ford did make valuable contributions to the manufacturing processes of some R-2800 parts but that did not come until they had been building them awhile.

The Ford GG Aero Engine was a dual overhead cam (4 total), 48 valve, 60 degree bank, aluminum V12. Unlike the multi-part units of the Merlin and Allison, the block was a very rigid monolithic enbloc unit, (similar to automotive V8s). Rods were stronger individual pieces-running in parallel on the crankshaft (like a standard V8 ) the crankshaft was held by 4 bolt main caps. Accessories were driven from the end opposite the propeller, induction was by a mechanical fuel injection pump. The heads were a pent roof 4valve per cylinder design, similar to the Miller/Offenhauser race engine. Spark plugs were in the top center of the heads between the valve sets, resulting in better fuel ignition and less flame travel than either the Allison, Merlin or Griffon. The cam train had no rockers, the cams drove directly onto "buckets" which pushed down on the valve stems. The jewel of the engine design was the cam drives which consisted of an assembly of helical and cone gears driving two angled shafts on the rear of each bank which simultaneously drove both intake and exhaust cams. This is far simpler than the much more involved arrangement of the Merlin or Allison.
Supercharging was by a large proprietary 2 stage Turbocharger.

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The other two were 48 valve, 60 degree bank, aluminum V12s, just SOHC. As far as Rigid goes, early Merlin had to pull the cylinder block from the crankcase to do a valve job, Cylinder heads were NOT detachable from the Cylinder blocks. crank cases on Both the Merlin and Allison were beefed up a bit over the years to handle the higher power. If you use connecting rods like a car you have to stagger the cylinders. One bank is slightly forward of the other bank. The Allison and Melrin had the cylinders directly opposite. Slight difference in engine length and it may (or may not) affect vibration patterns. Allison used pent roof combustion chambers with 44 degrees between the valves. DOHC and angled valves are great for power ( if actually needed) but mean larger heavier heads.

The design was magnificent. Three were built; on the first test, the engine put out 1800HP! Unfortunately, the design was not ready in 1942, subsequent development was spent on Tank Engines, and the engine never flew.

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Well here we have a bit of conflict. First test and they were pulling 1800hp? very confident or very foolish? and design not ready until 1942? what happened to ready to go in 1940?

Please reread my second post.

I clearly stated that I had not verified the details, including the date that conflicts with my premise.

Thought it would be interesting for the folks here to read about an engine that is quite intriguing.

It is, but it was never an aero engine that flew. Interesting that it MIGHT have been a player, though.

Wish they had pursued it at LEAST to flight test.

I agree, it is intriguing. But lets look at it objectively and not like either a press agent or Ford fanatic.

4 valve pent roof combustion chambers date back to at least the 1913 Peugeot Grand Prix car if not even earlier. A number of race cars and WW I aero engines used 4 valve heads with angled chambers so it was not a "new" idea in the 1930s and any engine designer worthy of the job description was aware of them. Like many items or details they have both advantages and disadvantages.

Harry Miller designed at least two "aircraft" engines that never flew. One never made it off paper, and the other ( a straight 8 ) for use in the Tucker XP-47 ( same Tucker as the post war car) had component parts built that were used a in a few post war racers, while similar to the "normal" Miller/Offenhauser design it was different in detail and NOT just two Offenhauser engines place nose to tail.

While intriguing they were of no practical value.

I am not anti-Ford. The tales of the Continental IV-1430 and the Lycoming O-1230 (both chronically under funded for much of their lives) should also point out the problems with thinking you can design, develop and build aircraft engines in months instead of years. If you could bring an new engine from drawing board to production in 3 years or under you were doing a great job. It often took longer and that is by aircraft engine companies with experience in aircraft engine design. I would note that both Continental and Lycoming not only built small aircraft engines but built car, bus, truck and marine power plants for a variety of customers in the 1930s. They were not small shops specializing in one or two low production engines. They were smart enough not to sink too much company money into the US Army designed "hyper" engines though. I would note again that the proposed power output of the Ford engine was well into the hyper range.

m37b1 said:

Another view on it's history. While I know the person that researched and wrote this, I've not verified any of it.

Origins:

In late 1939 Edsel Ford made an agreement with Rolls Royce to produce their Merlin V12 Aircraft Engines in one of Ford's unused factories in Michigan. About 3/5 of the projected production was for British use, mostly for Canadian produced aircraft including; Landcasters, Mosquitoes and Hurricanes. Rolls Royce sent blueprints, tooling and parts to Ford, and it appears that Ford immediately started to redesign the Merlin, two very modified enbloc engines were built in their prototype shop.

Rolls Royce did not approve of the changes and Henry Ford's insistence that Ford only manufacture for U.S defense caused the Merlin production to be later moved to Packard, who subsequently built about 58,000 Merlin's.

The Ford V12 Aero Engine

Ford was a very successful Company with many innovative designs, a great engineering staff, especially in the area of large castings. And they had the aircraft engine designs from Rolls Royce. The Merlin is a very complicated engine with many, many parts, and the assigned Ford engineers thought they could improve it. Ford, knowing war was coming and there would soon be a large market for aircraft engines, continued development and had the tooling made to produce their design.

The result was a less involved, more durable and powerful 1650 cubic inch V12 of identical bore and stroke as the Merlin, however, that is the only similarity, the balance of the engine is completely different.

The GM Allison Engine was originally designed in 1929, the Merlin in 1933, the 1940 Ford design, was a more advanced design than either of these engines. Had it been developed to its potential, we likely would have had Ford Mustangs, (P51 Fighter Aircraft, not cars) by 1943.

The Ford GG Aero Engine was a dual overhead cam (4 total), 48 valve, 60 degree bank, aluminum V12. Unlike the multi-part units of the Merlin and Allison, the block was a very rigid monolithic enbloc unit, (similar to automotive V8s). Rods were stronger individual pieces-running in parallel on the crankshaft (like a standard V8 ) the crankshaft was held by 4 bolt main caps. Accessories were driven from the end opposite the propeller, induction was by a mechanical fuel injection pump. The heads were a pent roof 4valve per cylinder design, similar to the Miller/Offenhauser race engine. Spark plugs were in the top center of the heads between the valve sets, resulting in better fuel ignition and less flame travel than either the Allison, Merlin or Griffon. The cam train had no rockers, the cams drove directly onto "buckets" which pushed down on the valve stems. The jewel of the engine design was the cam drives which consisted of an assembly of helical and cone gears driving two angled shafts on the rear of each bank which simultaneously drove both intake and exhaust cams. This is far simpler than the much more involved arrangement of the Merlin or Allison.
Supercharging was by a large proprietary 2 stage Turbocharger.

The design was magnificent. Three were built; on the first test, the engine put out 1800HP! Unfortunately, the design was not ready in 1942, subsequent development was spent on Tank Engines, and the engine never flew.

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Obviously Canada was not contemplating building Lancs and Mosquitos in 1939, but there was a very large investment into the CanCar Hurricane plant which was effectively crippled by Henry Ford's treachery and it lay nearly idle for lack of engines. If Ford hadn't reneged on the deal, Cdn Hurricane production would have peaked 6-12 months sooner than historically with hundreds of additional Hurricanes available to the Commonwealth prior to Pearl Harbor - just when they were needed most in North Africa, Malta, and Singapore.

I am afraid this argument doesn't hold up very well either.

Unless someone can up with real evidence of talks starting in 1939 the time line looks like it started in the Spring of 1940, according to Danial Whitney "Vees for Victory".

May 28th 1940
"Henry" Ford Announces that the Ford motor company stood ready to "Swing into production of a thousand airplanes of standard design a day."
Same day William Knudsen is appointed Commissioner of Industrial production.
Edsel Ford travels to Washington to discuss production programs.
British have been looking to source 6000 Merlin engines.
Edsel Ford announces the Merlin deal.
3 days later Henry reneges on the deal, claiming he will not build war material for foreign powers (although a number of Ford overseas plants are already doing so).
Knudsen flies to Detroit to talk to Ford, to no avail.
Meanwhile the US army is concerned that they only have one supplier of v-12 liquid cooled engines and while plant expansion is going well Allison has actually delivered only 35 engine in 1940 by the end of May.
June 17th 1940 sees General Arnold calling for co-operation with the British in manufacture of the Merlin engine provided the US can get 3000 engines over an above the 6000 engine British requirement.
June 24th 1940 sees Knudsen meeting with Packard Motors ( who had previously inquired about getting back into aircraft engine work) and initial agreements were quickly reached so that Packard started work on June 27 1940 using Drawings that had previously been shown to Ford.
Final contracts are not sighed with Packard until Sept 13 1940.
Aug 20th, 1940 Ford enters talks with Knudsen about building aircraft engines. Sept 17th 1940 sees Ford Break ground on a New plant to build the R-2800. Aug 23 1941 sees the First production roll of the line and Ford did NOT have to convert every single drawing/blue print from 3rd order projection to 1st order ( or the other way around, I can't remember at the moment) nor did Ford have to come up with taps, dies and gauges for a variety of British thread sizes/standards. Aid from P&W did not have to come from across the ocean to help Ford.

Fords flip-flop, despicable as it may have been and politically motivated, did not delay Merlin Production by more than a month or so.

By your own dates, Ford's treachery cost a 3 1/2 month delay - but this assumes that Ford and Packard had identical design and production facilities, when Ford had by far the greater resources(and their subsidiary in the UK was already building Merlins!) so we have to add the additional time that it took Packard to bring the Merlin into production, and I think that an additional 3 to 9 months is probable, so that means 6 to 12 months of lost production, even assuming that Ford would not have had greater productive capacity and output.

Shortround6 said:

Fords flip-flop, despicable as it may have been and politically motivated, did not delay Merlin Production by more than a month or so.

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Henry Ford might have been playing politics but he was a business man way before he was a patriot. In mid 1940 who are you going to hitch your wagon to, the Germans who have won stunning victories or the British who are down and taking the count according to bootlegger Kennedy. If Ford backs Britain and Germany wins he loses all his factories in Europe and is left with a useless factory tooled up for a design the USA probably wont buy. If he backs Germany he gets to keep his factories in Europe and possibly the Germans take over the British contract.

Please look at it again. Ford had NO existing facilities for aircraft engine production. You do NOT build aluminium 1650 cu in V-12s that weigh 1300lbs in plants that built 221-239 cubic in cast iron V-8s that weighed 400-500lbs.
Ford of England was building Merlin's using the standard British projection drawings which would have to be redone for Ford of America just like Packard had to redo them. ( Changing the order of projection used in the drawings confuses and causes mistakes in already trained machinists). Ford of England is either already using or or has ready access to Whitworth taps, dies and gauges, British fine thread taps, dies and gauges, British course thread and British pipe thread. Unless England sends tons of tooling to America Ford of America is going to have to either make this stuff themselves or find subcontractors to make it just like Packard did.
Packard started work in less than 30 days after Fords initial agreement. Where does the 3 1/2 month delay come from?
Please look again. It took Ford just about 14 months to build a New facility and deliver more than few engines. It took Packard about 18 months to do the same thing with much less help. ( R-R did send two engineers, one if not both who died after several years of exhausting work). Ford could rely on P&W for much more support, and a much easier time of getting subcontractors to supply small parts to normal american standards.
Ford may have had more workers, more engineers and more money than Packard but Ford had NO experience in building aircraft engines. Packards was about 10 years old. Packard was tooling up to build 2500 cu in V-12 torpedo boat engines ( based on their last aircraft engine). Packard went on to be ranked 14th out of all American companies in value of war production so it wasn't exactly a small job shop.

To build aircraft engines you also need test cells. Rooms were each and every production engine is run for several hours to check performance and do initial break in before being torn down, inspected and reassembled. Which means every test cell needs test instruments, dynamometers, cooling systems or fans for air-cooled engines.

In 1942 Packard built more engines that Ford did (by about 850 engines) but Fords engines( being larger and with more cylinders) had more total HP.

I would also note that Ford while building 4 engine bombers instead of single engine fighters just barley managed 600 planes a Month for a few months in 1944 and not the 1000 planes a day (30,000 planes a month?) he claimed he could make

I would also note that at some point in 1940 Allison was short about 800 machine tools to fill just completed factory space despite having an A1A priority rating. Structural steel was being rationed in 1940. There may have been limits as to how fast some facotires could be built and equipped no matter how large the parent organization.

12 months lost production is totally ridiculous. It would mean a NEW factory hitting Spring of 1942 production levels in the Spring of 1941, 6-9 months after breaking ground or signing the deal. NOBODY was anywhere near that fast.

Please see : http://www.enginehistory.org/References/WWII Eng Production.pdf

What this article does not say is how big some of these factories were or how much they were expanded. The Ford R-2800 plant was tripled in size by mid 1944 from the original plant that started making engines in late 1941.

fastmongrel said:

Henry Ford might have been playing politics but he was a business man way before he was a patriot. In mid 1940 who are you going to hitch your wagon to, the Germans who have won stunning victories or the British who are down and taking the count according to bootlegger Kennedy. If Ford backs Britain and Germany wins he loses all his factories in Europe and is left with a useless factory tooled up for a design the USA probably wont buy. If he backs Germany he gets to keep his factories in Europe and possibly the Germans take over the British contract.

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One story has it that he hated FDR and when told the Merlin deal pleased FDR that was enough to kill it.

On the taps and dies it is often mentioned as a big problem but surely manufacture is just a case of altering the machinery that cuts and grinds the taps and dies. Whitworth threads arent so far off Unified threads as many mechanics have found to there cost.

Slightly off topic but relevant I hope. Years ago I was researching the Comet tank and the gun on it for a book I wrote. (Sadly tanks are another love of mine). What was interesting was the politics, business and lies that were involved in the production of this vehicle - Stalling, contract awarding, friends being involved in production, cronyism with awards and inaccuracies produced as facts to justify favoritism. In the case with the Comet it was stated that the tank couldn't fit the 17pdr gun so the pocket 77 was developed and used instead - it was complete bullshit. It was all about contracts and friends.

The point I am making is, its hard to tell sometimes what the real story was in politics and business during the war in relation to development and procurement.

Interesting about the Comet - what's the name of your book? We do have the General ww2 sub-forum, so if you feel posting there ...

It is not a huge problem but taps and dies have to manufactured out of high grade steel and heat treated, a large factory will have many sets distributed in numerous tool cribs. They do wear out and/or break with time so replacements are needed. Standard taps and dies can be ordered off the shelf from sub-contractors, no need to make in house or special order from suppliers. Nuts and bolts can be purchased from suppliers with little difficulty IF they are a national standard. If they are NOT the national standard ( British threads) then arrangements have to made to build in house or have suppliers make them special in batches. The XYZ bolt company is NOT going leave a number of machines set up to make British thread bolts sitting idle while they wait for the next order. Bolts and screws can be made on lathes without a lot of difficulty but it is a slow process compared to specialized screw machines. Specialized screw machines can take lengths of bar stock and turn them into finished screws/bolts that drop down into hoppers at high rates of production. If you are trying to make hundreds of engines a month each requiring hundreds of bolts/screws you do not what your machinists trying to make screws/bolts one a time on lathes.

Aircraft grade bolts are different than car or general hardware bolts. There only a certain amount of permanent stretch allowed when torqued to a given amount. Some car or general hardware suppliers could NOT supply aircraft grade hardware.

ALL this stuff can be worked out and was worked out but it wasn't worked out in a couple weeks.

As a further note on the Merlin, the Ford was noted as having 4 bolt main caps on the crank which is an impressive feature to may hot rodders and car enthusiast. No mention of the number of bolts was made for the Merlin or Allison.

Picture of Merlin:



Please note the row of pair bolts above the sump joint. ( I know it's a dry sump) The Merlin had a crankcase that extended well below the center line of the Crankshaft the main bearing caps/blocks had two bolts that went in from the bottom but the blocks/caps fit between webs/cheeks in crankcase and were also held in place by the pairs of bolts going in each side making 6 bolts holding each block/cap in place.

It would take a good engineer with knowledge of the different bolt sizes, materials, sizes of mating surfaces, thickness of webs/cheeks and a whole lot more to figure out which is actually better.