Wrong : Increasing the octane will allow a slower burning flame front that will produce lower Exhaust Gas Temperatures which in turn will radiate less heat . The combustion temperature will also be reduced . Especially if the engine is close to pre-detonating .
Not on an open exhaust with good cylinder excavation, and altering boost will get a much greater impact on EGT anyway. (edit) and actually now I'm thinking about it, a higher EGT is actually desireable for lowering combustion chamber temperatures, it helps excavation quite a bit.
In my race engines raising octane didn't solve high running temperatures, I had to get the head reflowed (ports were slowing excavation at the greater cfm). Also I had to increase the radiator volume and was told my setup was oversize for the oil journal drilling of the basic block (I tried bigger sump and playing with the oiling as best I could). This was for the same engine bored/stroked but tuned to the same spec, a good parable for the DB-601E to the 605A trying to run the same tuning. Raising octane didn't help running temperatures one bit, I tried it.
Raising octane did help with the pinging I got with the bigger capacity on 105 grade (I took it up to ~120 grade for track work), but it still ran just as hot and that was killing off a ton of horsepower (~15%). In fact, and this is an entirely anecdotal statement, I swear black and blue it ran even hotter on the higher octane but did ping less (I could control this on the throttle, since I used vacuum slide valve carbs, and also by reducting intake). Proof of this was the fact I had to run cooler plugs on high octane in track tuning than I did for street cruise and pump grade (much more retard though, you're right for that). Also if it helps I used a mechanical ignition system pretty much identical to a aero magneto setup.
So as it turned out I was actually less competitive with a bigger capacity than I was at the smaller one (which had nicer harmonics at high rpm), until I solved the high running temp. Fixing that was what made all the difference, hence my view is the 605D was the proper development of the larger capacity version of the 601 and the 605A was only halfway there.
I dont understand the opens up the seals and bursts into flames bit ?
It opened all the block seals (eg. mainseal) with overheating if run at high boost settings for an extended period, spraying oil backwards over the exhaust and flaming. This is documented.
If you took comprehensive guaging of the temperatures, the oil would run high from the word go, the water would run high at normal power settings and the cylinder head/block temperature would go through the roof at high power settings. A lot of the heat problem in the cylinder is coming from the crank and pistons (not from the combustion chamber), due to inadequate oiling as a cooling effect. The journals were drilled for the 601 cfm flowing 1200-1300PS and not the 605 cfm flowing 1350-1475PS (not to mention it was always intended that it would be taken out to at least 1550PS).
I am saying categorically, a point of which to my mind there is absolutely no question. High combustion chamber temperatures in the 605A are caused by high block/piston temperatures and not high intake temperatures, poor excavation or high EGT. The fact it even flows 1475PS suggests an excellent excavation.
Hence I am equally adamant the primary difference between the 605A and 605D blocks are the oil journal drilling (water jackets are only going to help cylinder head temp, which doesn't solve our oil seals issue).
raising octane does not improve output by itself : It actually does albeit a small amount . You can lean it out and change the timing on the engine to get the most out of it .
Incorrect. Raising octane reduces output by a slight amount in point of fact. I can model this for you if you like and show you the difference in graph. All high output engines run at the lowest possible octane to get the most horsepower (race engine building 1:01 dude), but predetonation and usable/ideal ignition timing dictates the minimum octane. What raising octane allows you to do is advance the ignition more for a lower rpm torque band, but if you're already running an ideal torque band/rpm range then this is no good. It also lets you raise boost or dynamic compression for a total net gain even though the initial raising of octane actually lowers your base output.
It's like this, on a say 300hp engine you drop to 293hp raising octane but what you do is raise boost from 1 bar to 1.2 bar for a net return of 330hp.
Alternatively on an engine producing 400ft/lbs at 3000rpm but 250ft/lbs at 2500rpm you raise octane and advance timing for 385ft/lbs at 3000rpm and 300ft/lbs at 2500rpm. Much quicker in acceleration off the mark but you might lose a touch coming out of fast turns (picking it up coming out of slow turns, you get the idea).
Also you don't lean out when raising octane if you're in it for the output (you could do that for cruise efficiency, you'll get more out of a tank), what you do is advance the timing (or raise your dynamic compression).
Raising capacity doesnt mean you have more to cool .
More cfm means more heat. The easiest way to get more cfm is more cubic inches. This is a rule of thumb. Generally speaking larger capacity engines are a larger external block, so that solves the higher running temperatures with having more meat.
It becomes a problem with stroker engines, or raising swept capacity on a common block. It's elementary.