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Engine basics => Engine set up tips => Topic started by: Terry Caron on October 08, 2015, 10:09:02 AM
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I got this on a Sterling P-40 and, looking through AMEE to determine what it is (apparently '60s .15X), I saw that the head has the bands or ribs of the .15XXX, not a plain casting.
Were the heads available separately and is there any internal/performance difference from the other .15 heads?
Thanks.
Terry
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Terry,
The important part of the modified Fox Heads is the internals.
I have a speed prepared Fox 15XX and I'm not sure if the head came the way I got it or a modifier got busy with it. But the area around the plug is opened up, to a kind of squish area even though the piston baffle clearance is still there.
There are no lateral "fins" cast into the head. Not that the head is round now, it's sides have been narrowed, and most of the cooling fins removed.
Again as I said I'm not sure if it Left Fox like that.
The important thing is - how does it run?
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I'll say about average Greg: 8-4 prop @ 12.8ish K, same as my '58 Rocket.
Since posting this I've been told that in fact some standard 15Xs heads also have the ribs (not really fins) at the base.
Terry
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A real .15XX or XXX should be a screamer and not happy with an 8-4 prop. You might try both on the same fuel, and a 7-4 prop and see if they still run the same rpm. If the suspected XXX is the real deal, it will be much happier than the steel fin. Actually, I'd expect there would be some visible clues, at least if you take the backplate off and peer inside for some modifications by the factory. However, the reports on the .15X were that it liked smaller props than the steel sleeve Rocket .15s like I had. And rather liked, considering the $6.95 price! D>K Steve
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AMEE says the XXX had a machined, red anodized rod among other mods - mine is standard aluminum rod, no XXX on lugs.
My curiosity was aroused when the seller said it was a "hemi-head" .15, which I'd never heard of, but I thought just maybe he misspoke and it was an XX or XXX.
Never hurts to hope, right? ;D
But I'll try a smaller prop anyhoo Steve, see what it does.
Terry
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I ran it same fuel w/a 7-4 MAS: 14.8K rpm, so again about average.
No hot rod, just a normal .15X.
Oh, well.
Terry
(No - I won't hurl it!) n1
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I ran the engine again, same fuel/prop, after sealing some line leaks and, while it turns the 8-4 maybe a couple hundred rpm faster, the 7-4 cranked to 17.4K, a considerable jump.
Is that above average for .15Xs?
Terry