[DeTomaso] Initial Timming

[Göran Malmberg]

19 and 41 dgr, thats is some unusual but very okay numbers. What I see
as unusual is the odd numbers, moost of the time there are only 34-36-38
steps for some strange reason. I have been wondering why?
Goran


Paul,

I have another data point for you.  I'm running 22 degrees of advance with
19 initial and 41 total on closed chamber iron 351C heads with 353 cu-in
displacement.  It starts fine when hot and doesn't ping on 92 pump premium
as long as I run a half bottle of 104+ "Super" octane boost (not the
standard cheaper 104+) plus 4oz of Bardahl Instead-O-Lead to keep those
valve seats happy.  This amount of advance was arrived at on the dyno where
it made 444 HP through long tube (70 Mustang) headers.  A change to Mind
Train headers dropped the dyno HP to 415.  I'm using an Edelbrock F351-4V
dual plane intake, large Holley Carb, MSD-6AL, and Autolite #25 plugs.

Hey Jack, aren't your heads aluminum?  Maybe the iron heads need far more
advance than aluminum heads or maybe it's just the difference between our
cams

Doug Braun


-----Original Message-----
From: detomaso-bounces at realbig.com
[mailto:detomaso-bounces at realbig.com]On Behalf Of JDeRyke at aol.com
Sent: Sunday, April 26, 2009 9:58 PM
To: rimov at charter.net; deTomaso at realbig.com
Subject: Re: [DeTomaso] Initial Timming


In a message dated 4/26/09 7:36:46 PM, rimov at charter.net writes:
snip....
> .... Chevy or Ford have their timing around 18 degrees BTC and run around
> 42 degrees total advance by 4200 rpm. Does this sound about right for a
> mildly build 351c......
>
IMHO, way too much total OR initial timing, especially on todays gasoline,
for a normal pushrod V-8 except during light-load cruise. I run 10-12
degrees initial and 22 degrees centrifugal in our 351C for a total of 34,
with no
vaccum advance at all. Makes starting the engine easier, too. The Cleveland
closed-combustion chamber is very efficient and only needs about 34-36
degrees of total ignition lead. Very late Chev LS-2, -3 and -6 engines also
only
need about the same. F-1 engines with extremely efficient combustion
chambers currently run around 18 degrees TOTAL ignition lead.   Only old
open
chamber heads such as early '60s Hemis and flathead Fords actually run very
well
under load with that much lead. And many of those are set for drag racing.
Are you referring to a DOHC Ford? I'd expect those to not need such timing
either. Last engine I worked on that needed that much initial lead was a
turbo
Corvair, and it had centrifugal RETARD to keep the pistons in the
block..... My 2¢- J Deryke



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