[ihc] RE: Motoring along with Tom

["Jim Grammer" <jgrammer@xxxxxxxxxx>]

>Date: Thu, 22 Jul 2004 17:10:48 -0600
>From: Tom Mandera <tsm1@domain.elided>
>Subject: [ihc] Ignition - timing vs CR vs quench, Taurus fans

<great thwacking snip>
>This should result in a .038 or .042 quench distance comprised entirely
>of the head gasket.  Per a few websites that speak about this stuff,
>.040 is ideal.

>The theory is that .040 quench will let you run more advance/more
>compression on less octane w/o pinging.  Supposedly running a little
>less compression, but .060 quench might ping, while more CR and .040
>quench won't.

Great results on 85 octane, very impressive! I have long suspected that the
'E' motors are hobbled up in this regard, presumably to lower HC emissions,
NOX, or both. 'Twould be interesting to see how a fresh early 'swirl
chamber' 392 responded to a little CR bump for comparison.

>The GOOD news is that with this ~9.5:1 engine I'm running a points
>distributor with a Pertronix Ignitor, and I set the static timing at
>12deg BTDC before I left.  It seemed a little much to me, but I thought
>I'd try it and back it off if I had problems.

More pertinent to this discussion, IMO, is the total timing @ 3000-3500RPM.
Got any idea?

>90+degF ambient temp, with "hot air intake" stock filter assembly under
>the hood.

You, more than most of us, could *really* use a cool air intake! Keep the
TAC for winter-friendlyness, but maybe whack off the end of the horn and
plumb some fresh air from ????

>This is @406cid, polished chamber, ported n' polished heads (exhaust and
>chamber only), Isky 256/262 grind (12" of vacuum at idle.. <VBG>),
>headers, 1405 carb w/ LPG intake gaskets, dual Turbos.

That's a lower idle vac than I'd have expected. Is that grind adding a fair
amount of valve overlap? Any thoughts on whether blocking off the exhaust
crossover helps or hurts at this point(cooler charge temp vs. even
distribution)?

>Preliminary mileage figures fluctuate from 5mpg to 9mpg..

Ouch.

Jim