Technical > Spud Miller's Cave
Hilborn stack idle problems
masracingtd1167:
Just a thought When you leak down your barrel valve do you have the secondary blocked off ? Don't know if this will help you but my motor is 394 cubes barrel valve leaks at 24 percent no secondary 0 1/2 pump .037 nozzle .
BK:
Usually the pressure you check at is higher than the secondary setting so you need block it off.
PSweeney:
--- Quote from: Spud Miller on September 27, 2017, 06:19:39 AM ---
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
--- End quote ---
hi there Spud. 29% wow ?, we're at 25% now and it's fat. We've very little data on the car due to bad weather. Warming in the pits we got a reading of 260F off the pipes, with cyl 2 one 60-70F higher. We looked over this cylinder, it's got good compression, no stuck valves, manifold is torqued, no discernable plug reading or colouring on the pipes and just seems as fat as the rest.
Do you think more timing would help all round at idle, ie cleaner, leaner burn at idle ? When we took shims from the idle bypass it droped the pressure from 40psi to 30psi but it made no difference to the milking
We have no quibble with how it's running, it's launching off idle great, hitting the bar nice, MPH is right up there as expected 147-148mph, it's just milking the oil and idling too high. I'm less concerned with the idle now as the convertors loose enough to cope. We knew it had more in it ie timing and nozzle but until se fix the idle don't feel the need to go after it
PSweeney:
--- Quote from: slingshot383 on September 27, 2017, 11:09:37 AM ---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.
--- End quote ---
I think there maybe something in that, maybe time to add a little more.
PSweeney:
--- Quote from: masracingtd1167 on September 27, 2017, 12:19:50 PM ---Just a thought When you leak down your barrel valve do you have the secondary blocked off ? Don't know if this will help you but my motor is 394 cubes barrel valve leaks at 24 percent no secondary 0 1/2 pump .037 nozzle .
--- End quote ---
my partner in the car tunes it and i'm pretty sure he does but will mention it.
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