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[Jonnyu1]

I note that the Mk III had an angled firewall, and I believe re-designed and enlarged fuel tanks with the Merlin XX installation, and with the later Merlin 60 series installation.

I believe that the Merlin Mk VII/VIII - and from those, the Mk XIV and later with the Griffon - were derived from the Mk III, but whilst the Mk XIV also had an angled firewall (same or different I don't know), the Mk VIII, with a Merlin, reverted to a vertical firewall, like the I/II/V/IX/XVI series.

Why? Seems odd!

I can't see any mention of this in the limited information on the Mk III I can find on the web.

I have the Harleyford book on the Spitfire, but not the Morgan and Shacklady book which seems to be definitive.

References to changes to engine, cowlings, intakes, radiators, wing, ailerons, undercarriage, windscreen, tailwheel etc. developments - all can be found in these sources. But not the angled firewall...

Anyone have any ideas or references I can follow up?


Many thanks

John

[Sopwith]

That's a very interesting post John, sorry I can't help, perhaps Edgar will know. If not Mark12 on the Flypast historic forum will be your man.
Incidentally welcome to the forum

[Jonnyu1]

Good tip! 

The Key Forum - Mark 12 amongst them - suggests that the oil tank was moved to the fuel bay, which was the method later adopted for Griffon versions, but presumably thought to be an unnecessary production change for later, longer Merlin 60 variants.

Many thanks

John

[Sopwith]

I saw your query on the Flypast forum and all the replies that you had. Very pleased that you had a good result and it worked.
All the best.