[Roadsters] Compression vers Octane

[gregs672liter at netzero.net]

My current engine is 11.7 to 1 with Arias forged pistons, ported head, good
streetable cam a bit more lift and duration than Solex 1, GB dizzy running 28
degrees total advance (starting at 20), 45mm Dellorto carbs with 37 chokes
with cold air intake, Jacobs pro-street ignition, header, 2.5 inch exhaust.
In hot weather it can knock a bit if I get on it hard with 92 gas at lower
rpms.  I have a few gallons of Moroso octane boost (can't get it anymore, but
a friend had access) that mixed as suggested will take care of it.  Outside
temp has a lot to do with it in my opinion.
Greg Burrows
67 2000
Bonney Lake, WA

-- Jerry Krakauer <jsk977 at optonline.net> wrote:
Al,

My experiences, FWIW, from way back. My first BSR U20 engine rebuild used
1600 domed pistons fly cut for valve clearance, +.040 bore and the head was
cut .0005, resulting in a compression ratio of around 12.5:1.  The only way
to avoid knocking/detonation was with Sunoco 260, which if I remember
correctly was 103 octane(RON), with an occasional shot of 100/145 avgas.
With today's R+M/2 octane method that would be about 96 -97 or unobtainable.

My second BSR rebuild went back to +.040 U20 flat top pistons and some
additional head milling, resulting in 36.5cc combustion chamber volume plus
10cc for head gasket and piston to deck area, which computes to 11.7:1.
This engine would run on any brand premium, which if I recall averaged
around 97 - 98 octane(RON) or 93 - 94 today. So with the range your talking
about, I don't think it should be a problem.


Jerry Krakauer
SRL311 00099





----- Original Message -----
From: "Al Boettcher" <roadsters311 at rogers.com>
To: <datsun-roadsters at autox.team.net>
Sent: Monday, July 14, 2008 4:01 PM
Subject: [Roadsters] Compression vers Octane


>I would like to know from you racers or owners out there with high
>compression
> engines
> as to how high can you go on the street with 94 octane gas . Down the road
> I
> am going
> to build a motor and concidering upgrading the compression to 10:1 or 11:1
> compression
> for more torque . Any thoughts would be apprieciated.
> Happy motoring
> Al Boetther 68 solex.
> Ottawa Ontario.

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