[Roadsters] Maximum Advance and Octane -- how far can I go?

[jover4x4 at aol.com]

Nathanial,

I had my Solex U20 on a dyno at 5000ft with regular gas and saw no appreciable hp difference between static timing settings of 15 and 20 DBTC.

Octane boost will allow more compression without detonation?however I don't believe it will?allow you much more power with just a timing change.? 

I.e. If you advance the timing too far you get into timing related pre-ignition not detonation.? I think the octane boost only helps on the latter.

I am looking for others to chime in here to confirm my thoughts, or to shoot me down if I need corrected.

John Over
Denver, CO


-----Original Message-----
From: Nathaniel Leeds <nmleeds at mindspring.com>
To: datsun-roadsters at autox.team.net
Sent: Wed, 20 Aug 2008 11:19 am
Subject: [Roadsters] Maximum Advance and Octane -- how far can I go?



Still tuning,

And now I'm starting to have evil urges. There's a little devil sitting on
my shoulder which wants me to buy a crate of octane boost and crank out my
advance (20+ degrees on my SU carb, Solex cam, U20). What is people's
experiance in this regard. How much maximum advance (mechanical + vacume)
can the U20 take on 91 octane, and then how much more can it take with a
little street-legal octane booster. I know there are standard formulas
depending on the engine, I just don't know what they are.

Also, does someone know where I can find the advance charts for the U20
distributors (plural because I know there are a couple of available curves,
and I don't yet know which mine is). I'd like to get a feeling for what my
maximum theoretical advance is without pissing off the neighbors by running
my engine at 6000 rpms.

Nathaniel Leeds
'69 2000 U20
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