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Old 04-19-2013, 02:24 PM
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Lean/Bog when initially stepping on gas

Hi,

I have a bog (A/F gauge shows very lean) condition when first step on the gas then all is fine all the way to WOT.
I especially notice this when leaving a stop sign/light or cruising at 30 mph in the city and touching the pedal to maintain speed. Only happens in the first touch of the pedal then gone (approx 300 rpm of travel)

Everything else works fine; just this part.

* SBC 350, cam is 450 lift, 224 duration
* Initial timing set to 20 with mechanical timing set to limit to 36.
* Quickfuel 680vs carb with idle air bleeds set to 74 and mixture screws set to maximum vacuum.
* tslots set at 0.040
* Dual plan intake (edelbrock)
* checked for a vacuum leak and nothing

I'm thinking I need to either increase the shooter or get a different profile shooter cam?

Thoughts
Thanks for any assistance.
Gary

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Old 04-19-2013, 02:31 PM
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Idle air bleeds are probabily too big.
Reset both the primary and sec throttles idle position.
You probabily got the pri side too far open.
Connect vac adv to ported vacuum. and reset the idle.
Check the function of the accelerator pump linkage and immediate shot when thottle moves.
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Old 04-19-2013, 02:32 PM
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If this a 106 LSA cam?

you posted about this same engine before. Start by correctly tuning the idle air bleeds.
Solder up the (removable) idle air bleeds and drill with a 1/16" .062" drill bit. They will now be slightly too small.
hand hone to correct size with the drill bit as required.
This engine will need 24-26deg initial base timing at idle. (a 10deg mech adv curve) Do not connect the vaccum advance to full manifold vacuum. Use PORTED VACUUM.
The increased idle timing will correct the burn at idle and allow correct T slot position at idle.
Custom tuning the idle air bleeds will correct the idle and off idle transition.
ALL this needs to be done.

Last edited by F-BIRD'88; 04-19-2013 at 02:44 PM.
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Old 04-22-2013, 07:59 PM
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bog

Hello F-Bird'88,

Yes it is the 106 LSA,

I will get the Quick Fuel Air Bleed Assortment Kits (0.065 - 0.075) and experiment with that. much more precise then me trying to hand hone with my shaky hands.

primary and secondary throttle idle positions were set initially to 0.040" and not changed at all since carb was put back in so they will still be at 0.040".
Accelerator works instantly as soon as throttle is touched.
Timing is set to 20 degrees initial with 16 degrees mechanical advance. Why not connect to full manifold vacuum? that gives me 32 degrees at idle with vacuum attached, she idles great this way. I cannot change the timing as the pertronix distributor was custom setup with the 16 degree mechanical advance from the engine shop I bought it from. As a last resort I can take it back and have the regrind the mech advance but want to leave that for last resort. Setting timing at 24 degrees with the older MSD 8365 distributor caused backfiring.

I'll experiment and get back to y'all.

Thanks for the continued help!
G
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Old 04-26-2013, 11:23 PM
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Resolved

Issue resolved,

I increased the primary t-slot by 0.015 and decreased secondary by same and now all is working as expected.

Cheers

Gary
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