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What makes an 8 Stack Injection spit back through the stacks at idle?
When you experience “Spit back” through the butterflies and sometimes spitting through the air vents in the nozzles – Here are some things to check.
Barrel valve is set too lean
Butterflies may be bent
Bad Valve Job on the heads
Intake valve adjusted too tight
Vacuum Leak around manifold or shafts
Timing too retarded – Generally timing should be 30-36 Degrees for unblown, injected engines except flatheads – less for them
You may be trying to idle it too slow – 1200-1600 RPM is where it will want to idle
Butterfly gap for 8 Stacks:
The larger the engine, the more generous you can set the leakdown % since it will want more fuel at idle
.002” Methanol Leakdown % 16-25
.003” E-85 Leakdown % 12-16
.004” Gasoline Leakdown % 8-12
Barrel valve is set too lean
Butterflies may be bent
Bad Valve Job on the heads
Intake valve adjusted too tight
Vacuum Leak around manifold or shafts
Timing too retarded – Generally timing should be 30-36 Degrees for unblown, injected engines except flatheads – less for them
You may be trying to idle it too slow – 1200-1600 RPM is where it will want to idle
Butterfly gap for 8 Stacks:
The larger the engine, the more generous you can set the leakdown % since it will want more fuel at idle
.002” Methanol Leakdown % 16-25
.003” E-85 Leakdown % 12-16
.004” Gasoline Leakdown % 8-12