Bruce:
That is the cost of the TR5 cam, with its tight lobe centers.
Both valves are open for a significant amount of time, which allows
the intake charge to push the exhaust gases out of the cylinder. This makes
for an uncontaminated intake charge and good power, but a portion of the
intake charge gets blown out of the exhaust before the exhaust valve closes.
Hits economy pretty hard as you have seen, and emissions go through
the roof. The unburned intake charge shows up in the exhaust gasses as
hydrocarbons (HC).
Modern cams use wider lobe centers and about 10 degrees more timing
on the exhaust than the intake, which avoids these problems. The TR5 cam may
be very old school, but no one was ever disappointed with the power.
Vance
-----Original Message-----
From: 6pack-bounces@autox.team.net [mailto:6pack-bounces@autox.team.net] On
Behalf Of Bruce Simms
Sent: Monday, May 09, 2011 1:39 PM
To: 6pack@autox.team.net
Subject: [6pack] SU Needle Selection
I have TR5 280 cam, 9.5 head etc.
<snip>
Good power, but its thirsty.
Bruce Simms
73 TR6
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