Car runs extremely rich

[ID89GT]

Okay well I got this new car that I have been messing around with. I finally got my valve adjust figured out, now I am trying to figure out my rich running condition..

The car has a fresh rebuilt 351w bored 30 over. Had an edelbrock torker 2 intake, and a Holley 600 DP carb. The plugs are extremely black from fouling and I have a smoke coming out the passenger side tail pipe only. I checked compression and it is great all around, so I know the smoke isn't from a head gasket or anything.

First problem is I know nothing about carbs at all I was taught EFI not carbs. I have done some research and found out how to do the mixture screw adjustment with the metering block using a vacuum gauge. Well the problem I have run into that is that the car only has about 5 inches of vacuum at idle since it has a larger cam in it. Is there a different way to go about doing this or does that sound right? No matter what I turned the screw to it stayed at about 5 inches..

Also another problem I have run into is the base timing. It has the mechanical vacuum advance which im not entirely sure on how it works, but when I disconnect the vacuum line and have the timing light on it reads at like 30 degrees. When I bring it down to like 15 degrees the car barely runs, is it really suppose to be that high? Or is something wrong here?

Any help or tips would be great, im new to the whole carb thing so bear with me here haha. Im not sure what you need for info but let me know and I can get whatever you want.

 

[BlackGT89]

Several things can make a carb run rich:

-Jets that are too large (sometimes come rich right out of the box, try jetting down a size or two, read the plugs to keep up with fuel mixture)
-Back barrels sticking partially open
-Power valve that has been damaged (especially if you have had a backfire)
-Internal leaks
-Floats that are sticking (they can be sticking because of physical contact or because they have developed a leak and are taking on fuel causing them to get heavy and weigh themselves down)
-Float is just set incorrectly
-Choke is hanging
-Fuel pressure regulator set too high
-Air bleed ports on top of carb are blocked

Just a few thoughts, hope this helps.

 

[ID89GT]

So more than likely I will have to take it off and practically do a rebuild then i'm guessing. Hmm, how hard is to rebuild lol

 

[HISSIN50]

Why do you only have 5" of vac?

 

[BlackGT89]

Yes the vacuum is way too low. Look for any vacuum leaks, spray carb cleaner around your intake and see if the engine speeds up (preferrably on an engine that's not too hot). Are you sure you adjusted the valves properly ? That could cause a low vacuum reading as well. Don't pull the carb off just yet.

 

[ID89GT]

I am pretty sure I did the valve adjust right. Put the cylinder at TDC so both valves are closed, put the right feeler gauge in there and adjust, then tighten the lock nut. It had a bad tapping before but after I did the valve adjust it is a lot better.


Could it be vacuum leaks causing my low vacuum? I just figured it was from the larger cam because in the Holley carb videos on youtube it said a larger cam will cause low vacuum. When I rev it up the vacuum shoots up on decel like a normal engine up to like 18 but at idle is sits right around 5 or 6.

 

[BlackGT89]

Humm, hard to tell what is happening. Yes a vacuum leak could give low vacuum readings, but then you should be getting a lean mixture and possibly a fast idle. So the two seem to conflict each other since you are running rich.

Is it possible you could have an exhaust restriction, are you still running exhaust with catalitic converters by any chance ? I know you are carbed, but just asking. If the cats get clogged the back pressure could cause a low vacuum reading. Just a shot in the dark there. If the vacuum gauge oscillates quite a bit that could indicate valves that aren't sealing properly for some reason. You mentioned a ticking noise, has the engine been over reved, like a missed shift or an agressive down shift ? If so the pushrods could be bent. But hopefully you have a simpler problem.

 

[ID89GT]

It had a horrible tap due to excessive valve lash in the valvetrain. It has mechanical lifters in it so it will have some noise, but when I got it it was pretty excessive. Since doing the valve adjust the tapping is gone, and now am trying to fix my rich mixture. I have done compression tests on it and got 150 all around.

As for the exhaust, there is no cats or anything. It is a off road h pipe with the side pipes that can be used for electric cutouts. Then it just goes to flowmasters and tailpipes just before the bumper. The engine is practically all new.