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SJSS 08-16-2012 10:12 PM

idle gremlins
 
First off, thanks to all that helped me with the WOT bog issue shes cured of that issue, now on to the next one :smash:

After curing the bog issue she ran out of gas, I fueled up her up with 93 and she'd start, but not idle where I had her previously set (750-8) if I didnt keep the rpms up it would die. When I set the idle to around 1000-1100 it would run on its own, but do this annoying wandering idle... it would go from 1100 down to 600ish and bounce around then eventually die.

When it was running I was getting about 6-7psi for fuel, I charged the battery with my truck just in case and changed the fuel filter (smaller inlet so fuel dropped to about 5psi with new filter) and it didn't change anything.

here are the specs and some vid's I dont know where else to turn (everything is new or rebuilt)

350 4 bolt main
4 relief flat tops
eddy air gap
holley 750 vac sec
lunati 60103 (Advertised Duration (Int/Exh): 268/276
Duration @ .050 (Int/Exh): 227/233
Gross Valve Lift (Int/Exh): .489/.504
LSA/ICL: 110/106)
eddy performer rpm heads 64cc 180 runners
new 1 wire alt wired to + on starter
AC delco HEI
20* initial timing

vids;
chevelle idle - YouTube

chevelle idle1 - YouTube


any advice would be appreciated, thanks!

sqzbox 08-17-2012 06:24 AM

Sounds like a vacuum leak or blown power valve.

oldbogie 08-17-2012 11:39 AM

Quote:

Originally Posted by SJSS (Post 1583565)
First off, thanks to all that helped me with the WOT bog issue shes cured of that issue, now on to the next one :smash:

After curing the bog issue she ran out of gas, I fueled up her up with 93 and she'd start, but not idle where I had her previously set (750-8) if I didnt keep the rpms up it would die. When I set the idle to around 1000-1100 it would run on its own, but do this annoying wandering idle... it would go from 1100 down to 600ish and bounce around then eventually die.

When it was running I was getting about 6-7psi for fuel, I charged the battery with my truck just in case and changed the fuel filter (smaller inlet so fuel dropped to about 5psi with new filter) and it didn't change anything.

here are the specs and some vid's I dont know where else to turn (everything is new or rebuilt)

350 4 bolt main
4 relief flat tops
eddy air gap
holley 750 vac sec
lunati 60103 (Advertised Duration (Int/Exh): 268/276
Duration @ .050 (Int/Exh): 227/233
Gross Valve Lift (Int/Exh): .489/.504
LSA/ICL: 110/106)
eddy performer rpm heads 64cc 180 runners
new 1 wire alt wired to + on starter
AC delco HEI
20* initial timing

vids;
chevelle idle - YouTube

chevelle idle1 - YouTube


any advice would be appreciated, thanks!

The down side of running out of gas is that all the crud in the tank is now at the mouth of the pick up tube in the tank. The chances of some of this stuff getting past the filters is high simply because there is so much of it and the forces pulling and pushing through the system are high. It's probable that something has ended up in the carb's idle curcuit.

Bogie

SJSS 08-18-2012 04:57 PM

So after letting it run at a high idle for a while I checked for vac leaks and came up empty handed, as a last ditch effort I messed around with the idle screws checked timing and all connections then tried to bring the idle down and voila! It was happy chugging along at 750ish rpm... Could idle mixture cause an erratic idle? If my battery was close to dead and the alternator wast charging it could that cause an erratic idle?

spikebot 81 08-19-2012 07:51 AM

SJSS, I was fighting a odd idle condition also and here is what I found.

I have a very similar engine combo
60103 luanti cam
rhs heads 180cc runners 64 cc chambers
600cfm edle carb
9.48 to 1 compression
mallory hei distr.

With the engine idling at 1000rpm vacuum is 14" at the intake manifold. If I lower the idle speed the vac drops. At 750rpm the vac is aprox 12". The vac canister starts to hunt at this level, meaning it does not have enough vacuum to keep the canister fully engaged. I can feel the vac can pulsing at lower rpms which is directly connected to the distributor advance plate, therefore causeing the timing to advance and retard very fast. Not good. I can live with with a idle speed of 1000rpm but with a auto trans that puts the idle at 750rpm while in gear which is right where the vac can starts to drop out. I beleive crane makes a adjustable vac can that will operate at lower vacuum but havent looked into that area yet.

Currently this engine is set at 24deg initall, 12 deg mechanical advance and 12 deg advance on the adjustable vac can (which is stock from Mallory). I was running the vac advance on full manifold vacuum port. Yesterday I hooked the vac hose to the ported vac connector on the edle carb and now the idle is solid and steady. More testing is on line for today but honestly I have been fighting this odd idle problem since the new engine was installed in march of this year. All this time I've been searching for a electrical problem causing the miss at idle but I'm very confident it is the vac advance system causing the trouble. Hope this helps.


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