The Allison is a much tougher engine than the Merlin. Today, racing "Merlins" mostly use Allison rods because they are stronger.
I would check out that statement very carefully. Pent roof and hemispherical combustion chambers are NOT the same. The hemispherical combustion chamber dates back to at least 1913 in Peugeot Grand Prix car and pent roof chambers (or at least angle valve heads) were used in several WW I aircraft engines. A 4 valve head using angled valves was used in the Mercedes 18/100 4.5 liter 1914 Grand Prix engine and was not the first 4 valve automotive engine.and had pent-roof/hemispherical combustion chambers before that became common even high performance automotive engines.
There is a lot of truth in that, however, the devil is in the detail, and the pent roof 16valve head only REALLY started to work properly once the ports were sorted to get tumble and the piston>chamber geometry was sorted to get the squish working. I`ve never seen any car cylinder head get all those details right until the Cosworth DFV, although I "believe" that it was probably managed first in 1950`s motorcycles, the V-1710 almost got it but I think the squish zones were far too small, and the squish gap too big to hit the money. Squish gap is one of those things where "nearly right" is worse than none at all in many cases.I would check out that statement very carefully. Pent roof and hemispherical combustion chambers are NOT the same. The hemispherical combustion chamber dates back to at least 1913 in Peugeot Grand Prix car and pent roof chambers (or at least angle valve heads) were used in several WW I aircraft engines. A 4 valve head using angled valves was used in the Mercedes 18/100 4.5 liter 1914 Grand Prix engine and was not the first 4 valve automotive engine.
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There are a lot of websites and magazine articles and books that claim that post WW II advances in auto engines were a result of work done in WW II. Most are bullsh*t.
Most think that the Ford flat head was the height of automotive technology until the early 1950s.
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Hi Callum. OK, I can rephrase that.You might consider rephrasing that as:
"Racing Merlin's often use Allison rods because the Allison rods are stronger"
... because I`ve never heard of a single other V-1710 part being used in any racing Merlin.
Dam phone..As far as I am aware, no V-1710-93 was ever fitted to the P-38.
Also as far as I am aware, no war-time V-1710 fitted to the P-38 was ever operationally rated over 1600 BHP at 3000 rpm at 60"Hg - WER or otherwise - using 130 grade fuel.
The -93 was fitted to the P-63A/C but was never operationally rated at 1800 BHP and 75"Hg.
Even post-war, the V-1710-140 series (~improved -93) fitted to the F-82E/F/G - with 115/145 grade fuel - had to use ADI to achieve 74"Hg in WER. They tried higher ratings than 3200 rpm at 65"Hg without ADI but the engines kept blowing their intake manifolds off and/or destroying pistons & rods.
F-82E restrictions - maneuver, loads, and engine using 115/145 grade fuel - from 1948
A Merlin has something like 13,500 parts. A large number of those parts are nuts, washers, and bolts. An Allison has about 7,000 parts. So, working on an Allison results in torquing a LOT less bolts.
Those parts were required for the proper installation of the Flying Lady.I`ve heard this many times, and I`m afraid I dont believe it, and I have never once seen any evidence for either figure (I`m sure the 7000 is true, but I dont think
any supercharged aero V12 will have a parts count varying by more than about 25% to any other, what on earth could they be ?, surely this is
something like one person counting each carburettor jet and magneto winding wire, and the other person ignoring all the ancillaries)
Even if each bolt had an extra lock pin and washer it would not amount to more than a few hundred bits.
Until someone takes both engines to bits and films it, and counts the bits - this one is firmly in the "myths" basket for me. I dont know, maybe if you
picked a fuel injected two-stage 1946 Merlin-100 and the very first V-1710 ever made in 1930... but like-for-like, no way.
Documents show 65" Hg. MAP was established for 8th AF P-38's while operating with 150 octane fuel.ThomasP
I also have not come across any reports of P-38 engines being operated at greater than 60" of MP, but on page 72 of the P-38 pilot manual, there is a graph that shows 62" of MP at 3000 rpm
Pilots Manual Lockheed P-38 Lightning Pilot Training Manual (3).pdf
The attached chart shows the speed of a P-38L-5 at 64" MP. (note, weight and rpm not given) Now, if these MP's were used operationally or not, I do not know. I have read of pilots on pre P-38J models running their engines above the maximum MP's given in the manuals.
These documents show the modifications needed for P-38's to operate at the higher MAPs allowed with 150 grade fuel.The only Allisons in WWII that I have run across that might have been operationally cleared for more than 60"Hg are the F21R/M and F3R/M when using 150 grade fuel, as mentioned in a Bristol document dated Jan'45. They are listed as F/T (full throttle), but I have no idea what full throttle would be for them. The document has the note that full throttle is only allowed if "Allison engines cleared for 150 grade operation provided Thornton induction straightener or American equivalent is fitted" - I have not been able to locate any info on the "Thornton induction straightener".
The same Bristol document mentions that "American Army Order TMI 01-75FF-13 clears the P-38 installation." but does not list the MAP allowed or any additional details..