Outer Limits 4x4 Board

Hey

While my carby for my tb42 was off i was playing around with it to see how it works.

I noticed their are two butterflies. A primary and a secondary. The primary opens on normal operation where the throttle cable attaches. But the secondary only moves slightly on full throttle.

Question is how does the secondary butterfly open does it run off a vacum from the actuator which it is attached to, or has it been setup wrong?

here is a pic



Cheers

Andrew

The secondaries are vaccum operated, and to be honest are absolute crap, i noticed mine would close off as i lost engine speed, was shit house up hill.

When i had my carbi rebuilt i had the vaccum secondaries removed and had them upgraded to mechanical. From Idle to 3/4 throttle the primaries worked. when you pushed ya foot down again (you can feel in the throttle it gets hard then you push it again and it goes further) i had it setup that the secondaries would open at 3/4 to full throttle, this made going up hills alot better, in fact it gave the 4.2 a new lease on life with power, it would out run injected 4.2's and even beat 4.5's

sweet, thats what i wanted to hear im pretty sure i can convert it to a mech one with a few simple mods

MyGQ wrote:The secondaries are vaccum operated, and to be honest are absolute crap, i noticed mine would close off as i lost engine speed, was shit house up hill.

When i had my carbi rebuilt i had the vaccum secondaries removed and had them upgraded to mechanical. From Idle to 3/4 throttle the primaries worked. when you pushed ya foot down again (you can feel in the throttle it gets hard then you push it again and it goes further) i had it setup that the secondaries would open at 3/4 to full throttle, this made going up hills alot better, in fact it gave the 4.2 a new lease on life with power, it would out run injected 4.2's and even beat 4.5's

I'm interested in this mod, how does is the driveability from idle to WOT, any flat spot? I get a flat spot when the pedal is mashed in mine now and can't work it out, I've messed with secondary diaphragm spring rate and even machined a holley style ball and seat in the orifice of the housing (to slow the opening speed). Not too concerned as I can get 330k's out of 55 litres on a good day anyway.