L82sharkvette

Hey forum,

My L-82 is stock internally except for a higher performance cam. I'm running a Holley 600 vacuum secondary, and i recently bought a vacuum gauge to tune my air-fuel mix, it reads at about 12 degrees manifold vacuum, my main concern is i didn't see any difference when i would turn the screws in or out. Since i couldn't see any change i just positioned the screws 1-1/2 turns out counter clockwise. As i saw a video saying that is a good starting point for adjustment in a 350. What do y'all recommend i do?

I'm by no means an experienced mechanic, so forgive me for my ignorance on certain things.

Thanks, Gary

corvetero

That's sorta low. It's the read steady? You may have a leak somewhere in the system.

cagotzmann

When I had my L48 Stock in my 78. I would get 17+

What cam do you have that only gives you 12 ?

L82sharkvette

The prior owner had it installed when the engine was rebuilt.

The reading bounces a good bit.
I'm going to check it again tomorrow morning, I'll get back to yall.

Thanks, Gary

MelWff

if you turn the mixture screws all the way in the idle should drop and possibly even stall, if not you have a problem, vacuum leak or power valve or both.

Jebbysan

If it is bouncing...you have a potential leak at the intake manifold......
Take an unlit propane torch and "sniff" it around the tops of the runners.....if the idle changes.....you have a leak sir.
This explains why the idle screws do nothing as well........

Good luck,
Jebby

MotorHead

I would put an 18 thou piece of wire in each Idle Fuel Restrictors located in the main metering block to get back some adjust-ability with your mixture screws.

SH-60B

Is it a normal idle RPM, around 650 RPM? If its high, like 850 or more, the primaries might be strating to open, and those screws will have less effect on idle.

caryb78

How does the car run? Power brakes work?

Reaper19

Have you checked your timing? Try adjusting the timing up or down and adjusting the carb mixture screws as suggested with each change. As others mentioned, bring your idle down to 650 or less, but it sounds like you might have a more aggressive cam that will not let you idle that low. Or there is a vacuum leak. Plug up all the inlets on the carburetor temporarily and then one by one start plugging in all the vacuum lines again, you may find the culprit that is leaking. It took me a while but after rebuilding my engine and carb I went through the exact same scenario and found it was a combination of leaky vacuum lines, leaky vacuum valves, evap canister and carb tuning.

Good Luck