I've been completing the tuning of my engine and am noticing a problem I
think I've seen discussed before so I'm looking for advice from the list.
I'm running a TR8, Offy/JWR Dual Port manifold, Isky mild cam, Silv-o-lite
+.040, 9.5:1 pistons, headers, Mallory Unilite w/10 degrees static advance
and 24 degrees centrifugal-only advance. I'm using the Holley 390 for
carburetion with primary jets two sizes up from stock, and the
non-adjustable secondaries. Generally use 93 octane premium from one of the
"name brand" stations.
My problem is that on WOT acceleration in 3rd and higher gears I start to
get heavy pinging starting at about 3500 rpm and continuing to redline. I
don't get knock anywhere else or under part throttle acceleration. My first
impulse was to retard the timing a bit, but I'm not pinging under light
throttle accel's which is were I've generally found pinging to first occur
if timing is too advanced. This made me wonder whether I'm not getting a
lean mixture from the secondaries since they would be opening up and adding
significantly to A/F ratio under these conditions. I've heard that you
"MUST" convert the 390 to the adjustable metering plates (4150?), is this
why?
Any and all advice appreciated.
Thanks,
Ben Zwissler
1980 TR8
1966 TR4A IRS
zwissler@hsonline.net
Columbus IN
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