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Has anyone used a Bugpack 4061-10 with a 34 PICT34-3 and gotten it to idle well?
We have fresh build 1641 with this combination, no other exotic stuff, and can't seem to get it to idle dependably. Idle at ~900 is very lumpy and AFR is ~ 17: 1 increasing the revs it smooths out about 1500 at or so at ~12.5: 1 AFR and runs reasonably well. Timing changes don't help. We've tried 2 other 34s and they all behave the same way. We are wondering if this combination is just too much for the idle circuit.

Cam specs @0.050" lift are:
IO 14 BTDC
IC 40 ABDC
EO 50 BBDC
EC 4 ATDC
Lobe lift 0.338"
Dur 234 degrees
I C/L 103 degrees
E C/L 113 degrees
Lobe separation 108 cam degrees
Overlap 18 degrees
Built in advance 5 degrees

Any opinions?

Weak vacuum at idle so doesn’t pull fuel from the carb.

Like Bruce said not enough vacuum at idle you need a cam with a wider LSA to help increase the idle vac.

AdminSteve

The engine will be converted to EFI but we were hoping to get it running well on the carb before commiting.

Give a bigger idle jet a shot, also make sure your throttle plate is adjusted properly and you only use the air bleed screw to adjust your idle speed. Have you tried messing with the timing when you are trying to get it to idle lower. Also double check fuel pressure and float level

V8Nate: All done.