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RickR
06-15-2004, 08:08 AM
I need second opinions before I start drilling holes :boggled:

Holley 800 (4150) HP 500 carb, mechanical secondaries, choke removed, idle mixture screws on primaries only.

HP 500
9.4/1 compression
Cam retarded 3 degrees
Gil Mag Choice
MSD

Very little response to idle mixture screws

New engine, idle is VERY GOOD when the engine is at normal operating temp

But when engine is below normal operating temp it's loading up at idle and off idle.

At OE setting the primary transition slots are NOT exposed BUT the secondary slots are exposed about 1/16"
I tried closing idle setting on secondaries (1 full turn so slots not exposed) but to get an idle I had to open primaries to the point that primary transition slots are exposed At that setting the primary idle mixture screws worked.

Should I drill holes in the butterflies? What size?

THANKS!

Forrest
06-15-2004, 09:38 AM
How much manifold vacuum do you have at idle?

Rootsy
06-15-2004, 09:45 AM
your primary butterlfies probably need to be cracked a little more... 20 thou or so of the transition slot should be uncovered.. open the secondaries just enough to let enough air in to make her run.. and run as MUCH initial timing as you can and still get her to start easily...

i have an over rich condition on the idle circuits of my demon.. #1 i have a bit too much carb and that does not help... jim and i've discussed it and i have conversed a couple of itmes with the head of BG's tech support... they both feel the idle bleeds need to be opened up to gain more control of the idle circuit, essentially bleeding off some manifold vacuum and allowing for more use of the needles...

with my divorced runner dual plane it is collllld blooded until i get heat into the runners also... the idle will be erratic sometimes... and difficult to adjust precisely. hell last night it owuld not idle at all after running 3500 rpm... i had an idle bleed plugged with somthing.. oil from the pcv maybe... had to run it on transition or higher otherwise it'd flood the hell out... #^^(#$^(%*^#*$(#& :mad: and embarrassing...

RickR
06-15-2004, 11:13 AM
Forrest
18# at idle (6.5 powervalve in primary is good/ no powervalve in secondaries)

Rootsy
Timing at idle is 16 BTDC
From what I understand the 4150 Holleys require the butterflys to be closed enough to cover the transition slots at idle to prevent the transition circuit from introducing too much fuel?
On the 4150s the idle circuit port is about 3/16 below the transition slot.