Merlin powered carrier fighter other than Seafire

[FLYBOYJ]

True but they had to wait till mid 1943 to get the F6F. The Sea Hurricane would have been a useful stopgap and the USN could have had them in service in mid 1942.

Although I believe the Hurricane was the better flying aircraft (I think the F4F could take more punishment and was better carrier suited), I don't believe possible unless that decision was made right after Pearl Harbor (probably sooner), and even then, would Canadian Car and Foundry (who only produced only about 1,400 units) been able to supply the US Navy enough aircraft to really make a difference? The F4F was in full production, the first production F6F was in the air by October 1942. Additionally the aircraft would have been subjected to carrier trials (which it would have easily passed).

Aside from logistics and red tape, I don't see the US Navy taking Canadian Sea Hurricanes as "value added" in the 1942 time frame, additionally you also have the reluctance of US Navy commanders placing large amounts of glycol on aircraft carriers.

 

[tomo pauk]

...

The Sea Hurricane 1 was about 20-40 mph faster than the F4F-4 under 10k ft and had a much higher climb rate:

A Sea Hurricane II would have been about as fast under 10k ft as a Sea Hurricane I but somewhat faster above that altitude, than the Sea Hurricane I. The ideal use for the Sea Hurricane would have been as a point defence fighter in lieu of the Wildcats that were kept as CAP (rather than escorts) where it's high climb rate would have allowed it to gain the altitude advantage over incoming raids and provide top cover for the Wildcat, while the Sea Hurricane I would have given USN pilots speed parity with the zero under 10k ft along with better overall manoeuvrability. The Sea Hurricane II could carry twin 45IG drop tanks and could have served as an escort fighter but without folding wings it could not be carried in the same numbers as the F4F-4.

While I agree that the Sea Hurricane would be an interesting addition for the USN carriers, the F4F-4 did not have Cyclone engine, but the 2-stage Twin wasp. The F4F-3 with same engines (lighter, non folding wings, 4 HMGs) was further 10 mph faster than the F4F-4, ie. at ~330 mph at 19-20000 ft.

 

[RCAFson]

Although I believe the Hurricane was the better flying aircraft (I think the F4F could take more punishment and was better carrier suited), I don't believe possible unless that decision was made right after Pearl Harbor (probably sooner), and even then, would Canadian Car and Foundry (who only produced only about 1,400 units) been able to supply the US Navy enough aircraft to really make a difference? The F4F was in full production, the first production F6F was in the air by October 1942. Additionally the aircraft would have been subjected to carrier trials (which it would have easily passed).

Aside from logistics and red tape, I don't see the US Navy taking Canadian Sea Hurricanes as "value added" in the 1942 time frame, additionally you also have the reluctance of US Navy commanders placing large amounts of glycol on aircraft carriers.

The USN could have borrowed a couple of Sea Hurricanes from the UK for carrier trials.
CCF's biggest obstacle was a lack of engines, but if more Packard Merlins had been allocated to CCF they could have increased production, especially if given the needed priority levels and the Hurricane was also being produced in very large numbers in the UK at this time. Even a hundred or so Sea Hurricanes allocated to the USN in 1942 would have allowed an allotment of a dozen or so per carrier. Certainly, I don't think the Sea Hurricane was the complete answer to the Zero, but it was the only fully engineered alternative to the F4F that was available and had been used, in combat, aboard RN carriers from July 1941. Converting a Hurricane to a Sea Hurricane was a relatively easy process and could even be done as a field mod, aboard a carrier. However, it would require more extensive mods to be fitted with USN avionics.

The USN did fly off a number of V-12 fighters, from their carriers in 1942, so they probably had some provision for glycol stowage.

 

[RCAFson]

While I agree that the Sea Hurricane would be an interesting addition for the USN carriers, the F4F-4 did not have Cyclone engine, but the 2-stage Twin wasp. The F4F-3 with same engines (lighter, non folding wings, 4 HMGs) was further 10 mph faster than the F4F-4, ie. at ~330 mph at 19-20000 ft.

The two stage engine didn't help performance at lower altitude where most naval air combat took place and even though it was lighter the F4F-3's performance was only marginally better than the F4F-4 which, in turn, had about the same performance as the F4F-4B under 15000ft. The Sea Hurricane II would have been at least as fast as the F4F-3 (and I have commented in the past that the SAC data for the F4F-3/4 is somewhat optimistic) but it's combat climb rate would have been far higher.

 

[Glider]

I think its worth considering the aircrafts footprint. The Wildcat was a very small aircraft and the Hurricane was a lot bigger and while the Hurricane may have a small advantage in the air you could probably fit five Wildcat F4F-4 into the space of two Hurricanes. Now that is an advantage worth having.

 

[tomo pauk]

The SAC data is realistic. The British ADS (available here, scroll down) are in good agreement with SAC tables. What is not realistic is picking out an almost heaviest F4F, that has the weakest engine installed, and then claim that version is the F4F-4.
The 2-stage engines was also offering almost 100 HP more than single stage, or Cyclone, at altitudes between 10 kft and 15000 kft.

 

[FLYBOYJ]

The USN could have borrowed a couple of Sea Hurricanes from the UK for carrier trials.

Again, time frame. If this was to happen you're still talking time to get the aircraft to North America and testing set up. Say at least two months there and another month for carrier trials, at least!

CCF's biggest obstacle was a lack of engines, but if more Packard Merlins had been allocated to CCF they could have increased production, especially if given the needed priority levels and the Hurricane was also being produced in very large numbers in the UK at this time.

Agree but again who would allocate those engines? The first Packard Merlin was produced in 1941. How could this procurement been supported in the allocated time frame? How would this get slipped in for P-40 Packards?

Even a hundred or so Sea Hurricanes allocated to the USN in 1942 would have allowed an allotment of a dozen or so per carrier.

With the issues just described with the Packard Merlin, do you really think the USN "would have" seen a hundred or so Sea Hurricanes anytime in 1942? Would the UK in early really 1942 even consider cutting loose a hundred Hurricanes? If anything they probably would have wanted someone giving them a hundred aircraft of any type!

Certainly, I don't think the Sea Hurricane was the complete answer to the Zero, but it was the only fully engineered alternative to the F4F that was available and had been used, in combat, aboard RN carriers from July 1941. Converting a Hurricane to a Sea Hurricane was a relatively easy process and could even be done as a field mod, aboard a carrier. However, it would require more extensive mods to be fitted with USN avionics.

Yes, and at the time of Pearl Harbor there were already quite a few F4Fs operational and many more being produced in an area far from the war zone.

The USN did fly off a number of V-12 fighters, from their carriers in 1942, so they probably had some provision for glycol stowage.

They did, and those operations were limited, so would be the supply for glycol.

Unless someone had a crystal ball and there were people within the USN brass that really had a liking for the Sea Hurricane, the only way this was going to happen if the planning and contract were signed before Pearl Harbor - not saying it's a bad idea, just saying even under the best circumstances, not worth the effort for the little extra performance.

 

[tomo pauk]

In case USN really wants another fighter really bad and fast, and will be satisfied with non-folding wings, then why not a 'hooked' P-40?

 

[RCAFson]

The SAC data is realistic. The British ADS (available here, scroll down) are in good agreement with SAC tables. What is not realistic is picking out an almost heaviest F4F, that has the weakest engine installed, and then claim that version is the F4F-4.
The 2-stage engines was also offering almost 100 HP more than single stage, or Cyclone, at altitudes between 10 kft and 15000 kft.

We've gone through this before. The SAC data on the F4F-3/4 is somewhat optimistic when it comes to climb rates and moderately optimistic when it comes to max speeds. UK and USN trials of actual aircraft show much lower climb rates and lower max speeds than the SAC data, which is inline with actual pilot comments regarding performance of the F4F-3/4.

 

[RCAFson]

In case USN really wants another fighter really bad and fast, and will be satisfied with non-folding wings, then why not a 'hooked' P-40?

The P-40 would probably have pretty poor landing and TO characteristics because of it's high wing loading.

 

[tomo pauk]

Once the P-40 uses up its hefty load of fuel, the wing loading will go down substantially. The P-40s with belly tanks were flown off the carriers.

SAC data for the F4F-4 gives 320 mph at 18800 ft, 310 mph at ~11500 ft, 285 mph at SL. For F4F-3, the SAC gives 329 mph at 21100 ft, 316 at 11500 ft, 290 mph at SL.
British ADS (Wildcat V, 4 HMGs, 2 stage engine, here) gives 332 mph at 21000 ft, 313 mph at 13000 ft, 292 mph at 3250 ft. The tests found at Williams' site give similar numbers.

I agree that SAC gives rather optimistic RoC figures.

 

[RCAFson]

Again, time frame. If this was to happen you're still talking time to get the aircraft to North America and testing set up. Say at least two months there and another month for carrier trials, at least!

Hurricanes were available in North America, in some numbers prior to Dec 1941 so one or more of these could have been converted to a Sea Hurricane for deck landing trials.

Agree but again who would allocate those engines? The first Packard Merlin was produced in 1941. How could this procurement been supported in the allocated time frame? How would this get slipped in for P-40 Packards?
With the issues just described with the Packard Merlin, do you really think the USN "would have" seen a hundred or so Sea Hurricanes anytime in 1942? Would the UK in early really 1942 even consider cutting loose a hundred Hurricanes? If anything they probably would have wanted someone giving them a hundred aircraft of any type!

The P-40 was already engineered for the Allison, so a hundred or so more Allison engined P-40s and a hundred or so fewer P40Fs. The UK had a relative abundance of Hurricanes in late 1941/early 1942 so much so that Hurricane production actually began to taper off in mid 1942. There was actually lots of aircraft in the UK waiting for "export" to other markets such as the USSR and North Africa.

Yes, and at the time of Pearl Harbor there were already quite a few F4Fs operational and many more being produced in an area far from the war zone.

Actually, not that many (a couple hundred maybe) and the F4F-F didn't begin production till Jan 1942, IIRC.

They did, and those operations were limited, so would be the supply for glycol.

We're talking maybe a dozen HSHs per CV, and I think the USN was resourceful enough to tackle that problem.

Unless someone had a crystal ball and there were people within the USN brass that really had a liking for the Sea Hurricane, the only way this was going to happen if the planning and contract were signed before Pearl Harbor - not saying it's a bad idea, just saying even under the best circumstances, not worth the effort for the little extra performance.

It wouldn't have taken a whole lot of clairvoyance in mid 1941 to see that the FAA was short of fighters, and that the USN would be too in a shooting war, so a joint Cdn/USA project to produce Sea Hurricanes would have made some sense, especially as the conversion kit had already been engineered in the UK and the Hurricane was in production in Canada (albeit in small number prior to large scale Packard production). Not a completely likely scenario, but not completely implausible either.

The ideal fighter might have been a Sea Hurricane II with 4 x .5in with 350rpg (or 8 x .3in with 500rpg) and a couple of 15g internal wing tanks in lieu of the outer guns on the Mk IIB wing. This would have given the FAA and USN a useful addition to the F4F that was carrier ready and also well suited to base defence.

 

[RCAFson]

Once the P-40 uses up its hefty load of fuel, the wing loading will go down substantially. The P-40s with belly tanks were flown off the carriers.

I'm pretty sure those aircraft were launched via catapult. No way a P-40 with belly tank can get off a carrier otherwise.

SAC data for the F4F-4 gives 320 mph at 18800 ft, 310 mph at ~11500 ft, 285 mph at SL. For F4F-3, the SAC gives 329 mph at 21100 ft, 316 at 11500 ft, 290 mph at SL.
British ADS (Wildcat V, 4 HMGs, 2 stage engine, here) gives 332 mph at 21000 ft, 313 mph at 13000 ft, 292 mph at 3250 ft. The tests found at Williams' site give similar numbers.

I agree that SAC gives rather optimistic RoC figures.

Actual performance tests of the F4F-4 (in 1942) at reduced weights (~200lb less than the SAC F4F-3 figures), can't match the F4F-3 SAC Vmax figures:
http://www.wwiiaircraftperformance.org/f4f/f4f-4-5262.pdf
http://www.wwiiaircraftperformance.org/f4f/f4f-4-4058-performance.jpg

I suspect that the Martlet V data is taken right from Grumman, and not from an actual flight test, but the data is from Nov 1944 so that aircraft may have more a efficient prop and/or other changes to increase Vmax.

 

[tomo pauk]

I'm pretty sure those aircraft were launched via catapult. No way a P-40 with belly tank can get off a carrier otherwise.

Spitfire Vs were capable to take off from a fleet carrier with 200 imp gals (170 + 29 actually; or 240 US gals = 1440 lbs plus empty tank weight) extra, during Malta reinforcement operation. The belly tank fuel for the P-40 weighted 450 lbs for 75 US gals, plus empty tank. From mid 1942, the V-1710F offered 1325 HP for take off, prior that 1150 HP, Packard Merlin offered 1300 HP, Merlin 45 1185 HP.

Actual performance tests of the F4F-4 (in 1942) at reduced weights (~200lb less than the SAC F4F-3 figures), can't match the F4F-3 SAC Vmax figures:
http://www.wwiiaircraftperformance.org/f4f/f4f-4-5262.pdf
http://www.wwiiaircraftperformance.org/f4f/f4f-4-4058-performance.jpg

The military power of the F4F-4 (2-stage R-1830-86) was 1050 HP. Rated power, or max continuous power, like the one in the graph, was 1000 HP. Extending the speed graph until 1050 HP value, we have 325 mph for the, still heavy, F4F-4 with 4 guns.

I suspect that the Martlet V data is taken right from Grumman, and not from an actual flight test, but the data is from Nov 1944 so that aircraft may have more a efficient prop and/or other changes to increase Vmax.

The Martlet II (single stage R-1830, 1050 HP at 13100 ft, no ram) does 317 mph at 14000 ft; British ADS. Wildcat III (F4F-3A, same engine) does 307 mph at 14000 ft; ADS.

 

[RCAFson]

Spitfire Vs were capable to take off from a fleet carrier with 200 imp gals (170 + 29 actually; or 240 US gals = 1440 lbs plus empty tank weight) extra, during Malta reinforcement operation. The belly tank fuel for the P-40 weighted 450 lbs for 75 US gals, plus empty tank. From mid 1942, the V-1710F offered 1325 HP for take off, prior that 1150 HP, Packard Merlin offered 1300 HP, Merlin 45 1185 HP.

The 170IG tank was designed for direct flight from Gibralter to Malta. TO from carriers was with the 90IG tank and standard internal fuel (85IG).
Max boost of the Merlin 45 was 16lb from Dec 1941 and so TO HP was about 1450hp; a Spitfire V with a 90 IG tank had more power than the P-40 and weighed about 1500lb less.

The military power of the F4F-4 (2-stage R-1830-86) was 1050 HP. Rated power, or max continuous power, like the one in the graph, was 1000 HP. Extending the speed graph until 1050 HP value, we have 325 mph for the, still heavy, F4F-4 with 4 guns.

According to the SAC chart military power is ineffective above 14000ft which is in agreement with this test:
http://www.wwiiaircraftperformance.org/f4f/f4f-4-02135-performance.jpg

The Martlet II (single stage R-1830, 1050 HP at 13100 ft, no ram) does 317 mph at 14000 ft; British ADS. Wildcat III (F4F-3A, same engine) does 307 mph at 14000 ft; ADS.

Again these tests appear to be based upon Grumman data, as they do not correspond to any actual test data that I can find and are at considerable variance to actual flight tests of the folding wing Martlet II and IV.

 

[GregP]

When I look up Spitfires in US service, I see they accounted for an entire 15 victories in the ETO and 364 in the MTO where they were the equipment available to us at the time along with some P-40's and P-38's.

The P-40's recorded 592 victories in the MTO and the P-38's recorded 1,431 in the MTO, telling us exactly how widespread they were in US service ... not very. The three British aircraft use by the USAAF were the Spitfire, the Beaufighter and the Mosquito. Among all three types together, they accounted for a Total of 411 victories out of 25,486, or 1.6% of US air-to-air victories.

Like I said, we didn't use them much except as expedient and as available. Nothing whatsoever wrong with them, just the attitudes of the time by the brass who, after all, made the decisions for the men in the services.

 

[tomo pauk]

The 170IG tank was designed for direct flight from Gibralter to Malta. TO from carriers was with the 90IG tank and standard internal fuel (85IG).

You are probably right. On 90 + 84 gals, the range was 1035 miles, going by Morgan Shacklady.

Max boost of the Merlin 45 was 16lb from Dec 1941 and so TO HP was about 1450hp; a Spitfire V with a 90 IG tank had more power than the P-40 and weighed about 1500lb less.

Let's not confuse boost allowed with plenty of ram and at mid altitudes, with almost no ram and at sea level (or near to it). The single speed S/C engines, tailored for altitudes of 10-20000 ft (ie. Merlin III or 45, V-1710s with 9:60:1 S/C) were not comparable with two-speed S/C engines (Merlin X, 20 series, Jumo-211), or dedicated low level engines (V-1710s for A-36) when it comes down to take off power.
Merlin 45 was rated for +12 lbs boost for take off in 1943:

...where it gave 1185 HP; the engines with 'M' suffix (S/C diameter of 9.50in) were making a bit more, due to smaller S/C doing less mixture heating, ie. greater mass of air for same boost pressure:

According to the SAC chart military power is ineffective above 14000ft which is in agreement with this test:
http://www.wwiiaircraftperformance.org/f4f/f4f-4-02135-performance.jpg

Military power is ineffective above 14000 ft, according to SAC chart??? Where is that chart? And then you present a graph where military power is 1100 HP at 17200 ft*. Please, don't let your credibility to hit rock bottom.
The 2-stage R-1830 was making 1050 HP at 19-20000 ft*, and there is at least 5 documents at Williams' site that say so. Including USAF and RAF documents.

* = no ram

Again these tests appear to be based upon Grumman data, as they do not correspond to any actual test data that I can find and are at considerable variance to actual flight tests of the folding wing Martlet II and IV.

RAF sheets give better values than Grumman data.
Every aircraft have had variances. We can find a Mustang I barely making 360 mph clean, a P-47 barely making 420 mph clean, Spitfire V doing 360 mph etc, P-40 making 330 mph. Should we now use only the worst test data and claim that all produced A/C were equally bad, while putting aside the better test results?
The 'appears' and 'I cannot find' weight far, far less than actual historic documents.

 

[RCAFson]

Let's not confuse boost allowed with plenty of ram and at mid altitudes, with almost no ram and at sea level (or near to it). The single speed S/C engines, tailored for altitudes of 10-20000 ft (ie. Merlin III or 45, V-1710s with 9:60:1 S/C) were not comparable with two-speed S/C engines (Merlin X, 20 series, Jumo-211), or dedicated low level engines (V-1710s for A-36) when it comes down to take off power.
Merlin 45 was rated for +12 lbs boost for take off in 1943:

...where it gave 1185 HP; the engines with 'M' suffix (S/C diameter of 9.50in) were making a bit more, due to smaller S/C doing less mixture heating, ie. greater mass of air for same boost pressure:

Do you really believe that a Spitfire V pilot trying a one time take off from a carrier while loaded with a 90 IG DT is going to limit TO boost to 12lb? Pilot's Notes weren't written for that scenario, and I'm sure that there are similar entries in the P-40 manual.

Military power is ineffective above 14000 ft, according to SAC chart??? Where is that chart? And then you present a graph where military power is 1100 HP at 17200 ft*. Please, don't let your credibility to hit rock bottom.
The 2-stage R-1830 was making 1050 HP at 19-20000 ft*, and there is at least 5 documents at Williams' site that say so. Including USAF and RAF documents.

* = no ram

See: http://www.wwiiaircraftperformance.org/f4f/f4f-4.pdf
page 5, line 1 shows the effects of military power and how it is ineffective above 14000ft.

RAF sheets give better values than Grumman data.
Every aircraft have had variances. We can find a Mustang I barely making 360 mph clean, a P-47 barely making 420 mph clean, Spitfire V doing 360 mph etc, P-40 making 330 mph. Should we now use only the worst test data and claim that all produced A/C were equally bad, while putting aside the better test results?
The 'appears' and 'I cannot find' weight far, far less than actual historic documents.

FAA Data sheets are only as accurate as the tests they are derived from. Actual testing of individual aircraft by the FAA and USN shows Martlet and Wildcat performance that is somewhat less than the SAC data and FAA Data sheets that appear to be drawn from Grumman test data.

 

[tomo pauk]

Do you really believe that a Spitfire V pilot trying a one time take off from a carrier while loaded with a 90 IG DT is going to limit TO boost to 12lb? Pilot's Notes weren't written for that scenario, and I'm sure that there are similar entries in the P-40 manual.

Of course he is going to limit his boost to what the manual says - he is about to make a 1000+ miles journey, and an engine that quits 300 or 500 miles ahead will likely kill him. Plus, he, or some other pilot will actually use that A/C once it arrives to the destination. An unexpected or unforeseen use of engine does not make it stronger, so it can use greater boost.
The Spitfire V (with Merlin 45) has about equal wing and power loading as the Wildcat anyway. It does not matter if I (or anyone else) agree or disagree with what was written in the manual for that matter.
There is no other take off rating for the V-1710s and V-1650-1s than a 'regular' power setting. It took engine modifications strengthening to increase take off rating for the V-1710 from 1040 (1940) hp to 1150 HP (early 1941), and then to 1325 (Spring of 1942); all for single stage engines. The engines, with somewhat up-rated power above ~14000 ft, have had only 1200 HP for take off; available from mid 1942.

See: http://www.wwiiaircraftperformance.org/f4f/f4f-4.pdf
page 5, line 1 shows the effects of military power and how it is ineffective above 14000ft.

Thanks for pointing me to that graph. Seems like the military power was used only in S/C operating in 'neutral' and 'low' position, but not in 'high'? At any rate, that document puts the F4F-4 at 320 mph at 18800 ft and at 310 mph at -11500 ft.

FAA Data sheets are only as accurate as the tests they are derived from. Actual testing of individual aircraft by the FAA and USN shows Martlet and Wildcat performance that is somewhat less than the SAC data and FAA Data sheets that appear to be drawn from Grumman test data.

The SAC gives 329 mph at 21100 for the F4F-3 (2-stage engine), USN test give 330 or 331 mph at 21100ft, depending on weight here (pdf). This is in agreement with Grumman and British data. Seems like Grumman company was true to their word.

The F4F-4, but with only 4 guns, was good for ~324 mph on 1050 HP at 19000 ft (http://www.wwiiaircraftperformance.org/f4f/f4f-4-4058.pdf). Other USN tests, but for 'regular' 6 gun F4F-4, give 318 or 319 mph at altitude (pdf). This test gives 316 mph for 'regular' F4F-4, but at 17200 ft.

Now, in case you can point me to other tests that give top speeds, at respective best altitudes, of under 325 mph for the F4F-3 and under 315 mph for the F4F-3 (both with 2-stage engines), I'd be grateful.

 

[RCAFson]

Of course he is going to limit his boost to what the manual says - he is about to make a 1000+ miles journey, and an engine that quits 300 or 500 miles ahead will likely kill him. Plus, he, or some other pilot will actually use that A/C once it arrives to the destination. An unexpected or unforeseen use of engine does not make it stronger, so it can use greater boost.
The Spitfire V (with Merlin 45) has about equal wing and power loading as the Wildcat anyway. It does not matter if I (or anyone else) agree or disagree with what was written in the manual for that matter.
There is no other take off rating for the V-1710s and V-1650-1s than a 'regular' power setting. It took engine modifications strengthening to increase take off rating for the V-1710 from 1040 (1940) hp to 1150 HP (early 1941), and then to 1325 (Spring of 1942); all for single stage engines. The engines, with somewhat up-rated power above ~14000 ft, have had only 1200 HP for take off; available from mid 1942.

The Spitfire V with a 90IG drop tank has about the same wing loading as an F4F-4 with fuel internal fuel, but considerably less than a P-40E/F

The Merlin boost override can be engaged at any altitude to be used as the pilot saw fit. In any event, a P40 with 45IG drop tank weighs about 8900lb versus ~7700lb for a Spitfire V with a 90IG drop tank.

Thanks for pointing me to that graph. Seems like the military power was used only in S/C operating in 'neutral' and 'low' position, but not in 'high'? At any rate, that document puts the F4F-4 at 320 mph at 18800 ft and at 310 mph at -11500 ft.




The SAC gives 329 mph at 21100 for the F4F-3 (2-stage engine), USN test give 330 or 331 mph at 21100ft, depending on weight here (pdf). This is in agreement with Grumman and British data. Seems like Grumman company was true to their word.

The F4F-4, but with only 4 guns, was good for ~324 mph on 1050 HP at 19000 ft (http://www.wwiiaircraftperformance.org/f4f/f4f-4-4058.pdf). Other USN tests, but for 'regular' 6 gun F4F-4, give 318 or 319 mph at altitude (pdf). This test gives 316 mph for 'regular' F4F-4, but at 17200 ft.

Now, in case you can point me to other tests that give top speeds, at respective best altitudes, of under 325 mph for the F4F-3 and under 315 mph for the F4F-3 (both with 2-stage engines), I'd be grateful.

The F4F-4 was test flown against the Zero. USA Flight testing gave the following speeds for the same Zero:
SL/270mph (F4F-4 SAC data = 285
5000ft/287 (F4F-4 SAC data = 290
10000ft/305 (F4F-4 SAC data = 305)
16000ft 326
20000ft 321.5
25000ft 315
30000ft 306

and the results of actual flight testing:

Again, these actual flight tests show the F4F-4 to be somewhat slower at lower altitude than the SAC data - again in line with F4F-3/4 pilot comments regarding their experiences with the Zero in actual combat:

8. COMMENTS AND RECOMMENDATIONS:

(a) As evidenced by statements of pilots who flew them in actual combat, the performance of the F2A-3 and F4F-3 types of airplanes is markedly inferior to that of the Japanese 00 1 Sento KI Fighter in speed, maneuverability, and rate of climb. The fact that Marine Fighting Squadron 221 gave such an excellent account of itself should not be allowed to becloud this fact, but is directly attributable largely to an exceptionally fine organization of fighting pilot personnel and apparent great vulnerability of enemy bombers. In view of the foregoing it is recommended that F2A-3 and F4F-3 type airplanes be not assigned as equipment for use in combat, but be retained for use at training centers only.
Midway 1942 : Documents : Commanding Officer Marine Aircraft Group TWENTY-TWO. Action report. June 7, 1942.