Running Rich

[RZ_70coupe 11]

I'm out of options. A least my brain is empty.

 

69 with 302 2v. Has been smoking for a little while now with bad fuel milage. Pulled the plugs and they were black.

 

I rebuilt carb, replaced plugs, wires, cap, rotor (Pertronix electronix are ok), coil and checked timming. Still smoking and fouls plugs if too much around town driving (1 day). There is a fuel smell in the smoke indicating rich. Another forum asked carb jet size, they are 050 (stock I believe). I verified the float was set right to eliminate overflow.

 

HELP :surrender:

[RZ_70coupe 11]

I'm out of options. A least my brain is empty.

 

69 with 302 2v. Has been smoking for a little while now with bad fuel milage. Pulled the plugs and they were black.

 

I rebuilt carb, replaced plugs, wires, cap, rotor (Pertronix electronix are ok), coil and checked timming. Still smoking and fouls plugs if too much around town driving (1 day). There is a fuel smell in the smoke indicating rich. Another forum asked carb jet size, they are 050 (stock I believe). I verified the float was set right to eliminate overflow.

 

HELP :surrender:

[jmlay 80]

If you provide the carb information this might help. Have you checked choke settings? Checked power valve?

[jmlay 80]

If you provide the carb information this might help. Have you checked choke settings? Checked power valve?

[RZ_70coupe 11]

It is the original 2brl Holley. The choke has been checked, then disabled and re-checked. The Power Valve was replaced during rebuild.

 

Now my understanding of PV is remove old, replace gaskets, install new. There are no additional adjustments. Correct?

 

In the rebuild directions it is called the Economizer Valve and screws into the bottom of the bowl. Correct??

[RZ_70coupe 11]

It is the original 2brl Holley. The choke has been checked, then disabled and re-checked. The Power Valve was replaced during rebuild.

 

Now my understanding of PV is remove old, replace gaskets, install new. There are no additional adjustments. Correct?

 

In the rebuild directions it is called the Economizer Valve and screws into the bottom of the bowl. Correct??

[rangerdoc 22]

How are you metering screws set? Try turning them in all the way (not tight though) and then back them off 1 1/2 turns. Then run the car for a bit and check your float level again.

[rangerdoc 22]

How are you metering screws set? Try turning them in all the way (not tight though) and then back them off 1 1/2 turns. Then run the car for a bit and check your float level again.

[LoneWolf2U 136]

It is the original 2brl Holley. The choke has been checked, then disabled and re-checked. The Power Valve was replaced during rebuild.

 

Now my understanding of PV is remove old, replace gaskets, install new. There are no additional adjustments. Correct?

 

In the rebuild directions it is called the Economizer Valve and screws into the bottom of the bowl. Correct??

 

Yes but it is possable that the wrong gasket was used.

From your discription you have a internal fuel leak.

Easiest way to check is bring eng up to operating temp and remove air cleaner.

Shut down eng and watch the top opening of the carbs air horn for vapors or fumes rising from it.

That ia a tell tale sign that its leaking down into the intake and is the cause of your rich condition.

[LoneWolf2U 136]

It is the original 2brl Holley. The choke has been checked, then disabled and re-checked. The Power Valve was replaced during rebuild.

 

Now my understanding of PV is remove old, replace gaskets, install new. There are no additional adjustments. Correct?

 

In the rebuild directions it is called the Economizer Valve and screws into the bottom of the bowl. Correct??

 

Yes but it is possable that the wrong gasket was used.

From your discription you have a internal fuel leak.

Easiest way to check is bring eng up to operating temp and remove air cleaner.

Shut down eng and watch the top opening of the carbs air horn for vapors or fumes rising from it.

That ia a tell tale sign that its leaking down into the intake and is the cause of your rich condition.

[foothilltom 33]

I find it helpful to review the various "circuits" in a typical carb to better diagnose stuff like this.

 

Your "idle circuit" is adjusted as rangerdoc suggested. I'd be surprised if a rich idle circuit is to blame given how little fuel is actually involved here, but it's possible. You also said that the rich behavior occurs with "around town" driving, which would tend to steer me away from the idle circuit.

 

As a test, you could clean up your plugs, re-install, and let the motor run at idle only for a few minutes. Stand behind the car and see if you can detect a rich smell from the exhaust. Pull a plug and check for the tell-tale rich signs. If so, lean out the idle-mixture screws as Ranger suggested.

 

The fuel level in your bowl dramatically impacts the hydrostatic pressure that feeds the jets. If the fuel level is too high, ouila, rich. With the engine running at idle, check the sight screw and make sure fuel is just barely reaching the bottom of the hole. Fuel should just trickle out if at all. If you get more of a stream of fuel, adjust your float/needle.

 

Your jets control the amount of fuel in your primary circuit. It's possible somebody reamed out those 50's over the years. Jets are super-cheap so I might suggest (assuming the above is all good) you buy 48's (don't step down more than 2) and install them. Your primary circuit is my #1 suspect given your description.

 

The Power Valve can be troublesome. It is rated to open at a certain level of vacuum to provide additional fuel during acceleration (when vacuum drops). The rebuild kits don't often tell you what type of PV they come with and you can easily wind up installing one that opens too soon (rich) or too late (lean). In your case, you could even consider installing a plug instead of a PV and see if this helps your rich behavior.

 

The Accel pump is among the suspects, but I'm thinking to a much lesser degree.

 

Let us know how you do! Good luck.

 

Tom

[foothilltom 33]

I find it helpful to review the various "circuits" in a typical carb to better diagnose stuff like this.

 

Your "idle circuit" is adjusted as rangerdoc suggested. I'd be surprised if a rich idle circuit is to blame given how little fuel is actually involved here, but it's possible. You also said that the rich behavior occurs with "around town" driving, which would tend to steer me away from the idle circuit.

 

As a test, you could clean up your plugs, re-install, and let the motor run at idle only for a few minutes. Stand behind the car and see if you can detect a rich smell from the exhaust. Pull a plug and check for the tell-tale rich signs. If so, lean out the idle-mixture screws as Ranger suggested.

 

The fuel level in your bowl dramatically impacts the hydrostatic pressure that feeds the jets. If the fuel level is too high, ouila, rich. With the engine running at idle, check the sight screw and make sure fuel is just barely reaching the bottom of the hole. Fuel should just trickle out if at all. If you get more of a stream of fuel, adjust your float/needle.

 

Your jets control the amount of fuel in your primary circuit. It's possible somebody reamed out those 50's over the years. Jets are super-cheap so I might suggest (assuming the above is all good) you buy 48's (don't step down more than 2) and install them. Your primary circuit is my #1 suspect given your description.

 

The Power Valve can be troublesome. It is rated to open at a certain level of vacuum to provide additional fuel during acceleration (when vacuum drops). The rebuild kits don't often tell you what type of PV they come with and you can easily wind up installing one that opens too soon (rich) or too late (lean). In your case, you could even consider installing a plug instead of a PV and see if this helps your rich behavior.

 

The Accel pump is among the suspects, but I'm thinking to a much lesser degree.

 

Let us know how you do! Good luck.

 

Tom

[RZ_70coupe 11]

OK, I gave up :surrender:

 

I pulled the carb and manifold off the 69 and replaced it with the Holley 4brl and Sumitt manifold I had on my 70.

 

It purrs like a little kitten. No smoke or gas smell in the exhaust. Drove it to work today and it was like a new engine. The car was getting 10-11mpg. Today it got 19.7mpg at 75mph.

 

So there is still a problem with the 2brl but I think I'll leave the 4brl where it is and just buy a replacement for my 70.

 

I want to thank everyone for there help. :clap::thumbup1:

[RZ_70coupe 11]

OK, I gave up :surrender:

 

I pulled the carb and manifold off the 69 and replaced it with the Holley 4brl and Sumitt manifold I had on my 70.

 

It purrs like a little kitten. No smoke or gas smell in the exhaust. Drove it to work today and it was like a new engine. The car was getting 10-11mpg. Today it got 19.7mpg at 75mph.

 

So there is still a problem with the 2brl but I think I'll leave the 4brl where it is and just buy a replacement for my 70.

 

I want to thank everyone for there help. :clap::thumbup1:

[rangerdoc 22]

LOL! I guess that'll do it. Man...I can't wait to get rid of my 2bbl.

[rangerdoc 22]

LOL! I guess that'll do it. Man...I can't wait to get rid of my 2bbl.

[danno 128]

This was interesting and I was hoping for an answer for the 2bbl problem. My milage is equally as bad, but the answer should be to fix my carb rather than a larger solution. I will check my main jets and PV. Carbs are so simple, it almost cannot be anything else.

[RZ_70coupe 11]

One thing I remembered about a week after rebuilding the 2brl. On first crank the car burped through the carb. I did not think a lot about it at the time and it left my memory banks. But having 20/20 hindsight is one of my many talents. This could very easily have damaged the new PV and caused the continued problem. With $$ tight I am planning on installing the 2brl assembly to replace the removed 4brl on my 70. I purchased a new PV for the install. It will be another couple of weeks befor the actual start-up and longer befor it gets on the road. I'll post any udates as I find them.

 

Thanks All