I finally got the car running again. For those that don't remember I added aluminum Pro Lightning 200cc 64cc heads, 650 Holley DP, Crane aluminum 1.6 roller rockers, hedman long tubes. All on a GM Goodwrench 350 and a Comp 268xe cam, hydraulic. New plugs and wires. And F-Bird88 if you read this, the plugs you recommended I had them cross referenced to AC Delcos instead of Champion.

The car idles very rough and I have to keep my foot on the gas a little to keep it running. Also, when the idle goes down a bit to near cutting off or even at 600 or so with foot on the gas, I hardly have any brakes. I assume lack of vacuum with the brake booster. Now, if so is this due to the low idle, or more because of the addition of higher ratio rockers increasing the lift of my cam to 509/512?

While accelerating the car if given too much gas wants to backfire thru the intake/carb a little. The choke isn't an issue, and the timing is fine. I drove the car 10 miles home and there was shaking/vibrating throughout the car. When I got home the was some black/carbon buildup on the inside of the carb.

Here's what I'm wondering.

1. The gas is the same since October and I estimate 1 gallon at most left in the tank.

2. The carb is straight out the box, with no jetting done to it.

3. The distributor has a stock coil. Will I need a higher output coil to burn all the fuel properly.

Do any or all of the above seem like possible culprits for the rough running?
I won't be able to work on it for another week, so I figured I'd ask and get your input.

Thanks.

 

I had a problem with my Edelbrock 1406 doing the backfire thing through the carb under load. A/F ratio was off on my carb.

 

It's rather rare to be able to take a carb out of a box, bolt it on, and have it already optimized to the setup.

Your low vacuum may be dropping the power valve and making your mixture excessively rich. I wouldn't sweat the ignition until the carb is adjusted.

 

I figured about the carb, but didn't think it would make it run that bad. It even says in the directions it's made to be put on out the box for performance eventhough some tuning is needed. I didn't think it could be that bad. Guess that will have to be looked into.

What's the first tuning route with the carb I should take?

 

Oh, I forgot to mention there was some oil spray on the valve covers after the drive home. Looks like some of the intake bolts may have came a little loose.
This would create vacuum leaks correct?

 

Could be the valves are not adjusted right.
The carb should run fine out of the box with just a float
level adjustmant and setting the idle fuel mixture.
Pull all the plugs and do a compression test.
Is the carb flooding?

 

The valves are adjusted correctly.
May sound dumb, but how do I adjust the float? And the idle fuel mixture?

As far as flooding, the car starts up fine.

 

Remove the blowl site plugs one at a time. Have the car running
on level ground. The fuel should be right at the site plug hole.
Adjust the level by loosening the float screw and turning the float nut to set the fuel/ float level.
Adjust the idle mixture screws for best vacuum at idle.

IF the power valve has a lower rated vacuum value than the motor produces at idle (in gear) it will have to be changed.

Look down the carb to see if fuel is dribbling out the booster venturis at idle. The needle and seat may have dirt stuck in it.

 

Looks like it may be a leaky intake gasket. There is some black marks where the intake meets the heads near the valve covers. Indicating a leak at the exhaust.

I'm hoping that's it. I'll take the intake back off on SAt.