Technical > Spud Miller's Cave
Hilborn stack idle problems
BK:
Secondary bypass is OPEN from idle to about 20 deg. of opening. You primary bypass and idle will generally be the same. Containing a spring loaded check for idle pressure and your main bypass jet or pill. The secondary should by a spring check set significantly higher than your idle check maybe 25 lbs or so.
retroboy:
I've come across this high idle but otherwise runs fine before and it was simply the popett and spring weren't sitting correctly in the pill holder. Drop in type pills. Cheers
PSweeney:
so we've put a few more runs on the cars, changing oil every run. The idle is still high and we popped the idle bypass, Which had the poppet, spring and 3 shims. We took 2 shims out and saw no difference in the idle or oil milking. BV is still at 25% or so. Is there a recommended ratio between BV and Idle leakdown % ?
Spud Miller:
For methanol, I always use 7% of the engine size for an initial leakdown number. That's assuming a 1-2 PSI main check valve.
So, for you: 420 x .07 = 29
29% should be really close...within a flat or three...tweak from there for idle EGT of 350-450F and good throttle response when you whack it from an idle.
Do you have any idle temperature information? Hand-held temp gun shooting the pipes?
Spud
slingshot383:
Running that low of timing in a SBC, I bet your main is fat. That motor would be happier in the 36* - 40* of timing and leaned out main.
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