Carburetor running rich after rebuild

[gthumb]

I recently managed to screw up changing the power valves on a Holley using AED PVs. They come with soft rubber gaskets instead of the firm, composite gaskets Holley provides. I wasn’t cautious enough about ensuring the gasket stayed in the machined recess of the PV and it seemed to tighten up OK. But it got trapped/pinched on the shoulder of the PV gasket recess causing a fuel leak. Actually it was a major fuel leak - the engine wouldn’t even fire So probably not your problem but I’ll throw it out as one remote possibility. I learned to hold the metering block horizontal and screw the PV into it from the underside so that gravity helps keep the gasket in place.

Thank you for revealing this possibility. I will check that. I used a Holley kit.

 

[gthumb]

Idle feed restrictors are small jets in your metering blocks. There will be 2 in each block.

Yes, the two round flat head jets are in (one on each side of power valve). I didn't replace them, used the same ones that were in the carb prior to the rebuild.
Would changing the dual feed fuel line have any effect on the volume of fuel getting into the engine? I imagine the carburetor is a metering device regardless of how much fuel is being provided to it. The new fuel line has a 3/8" diameter compared to a 5/16" diameter, and the connection at the fuel bowls had to be changed to bigger nuts to accommodate the larger connections on the new fuel line(see picture)

 

[gthumb]

Thank you for revealing this possibility. I will check that. I used a Holley kit.

To AR67GTX, here is the Holley kit I used. 37-754

 

[WileE]

Blue exhaust indicates its burning oil. Black exhaust indicates too-rich mixture. You have two problems here.

 

[gthumb]

Blue exhaust indicates its burning oil. Black exhaust indicates too-rich mixture. You have two problems here.

Thank you for your input. Hopefully by resolving the fuel issue, which I am attributing to being the cause of fouled plugs and blue smelly gas-like exhaust, I will be able to assess the possibility of burning oil. At one point, I was no longer able to start the car because the plugs were so fouled(despite being new). I cleaned them, put them back in, and it fired right up. But they are getting fouled again (I took the #1 plug out to check after running the engine for a while)

 

[Dave6T4]

If your engine backfired a couple of times, your power valve is likely toast.

 

[gthumb]

If your engine backfired a couple of times, your power valve is likely toast.

With the power valve being damaged, does that mean that more fuel is being allowed through the carb?
I guess I will replace it and see how the change affects the running condition. Thank you.

 

[RussT Plymouths]

What was the number on the power valve you took out, and what is the number on the one you installed?

 

[RussT Plymouths]

Summit lists 4 pages of different valves, many with different engine vacuum settings and flow rates.

I copied this from one of the listings:

Holley Replacement Power Valves

Holley replacement power valves are an important component in the power enrichment circuit of Holley's performance carburetors. They operate by using engine vacuum to control their opening and closing rate. When they open, additional fuel is supplied to the main system during heavy load or under full power situations to eliminate hesitation and bogging--ensuring the smooth delivery of power without any drivability concerns. They're available in many different vacuum ranges to time the system's operation to your specific requirements, and they come in your choice of single-stage, two-stage, and high-flow designs. A gasket is included.

 

[gthumb]

Summit lists 4 pages of different valves, many with different engine vacuum settings and flow rates.

I copied this from one of the listings:

Holley Replacement Power Valves

Holley replacement power valves are an important component in the power enrichment circuit of Holley's performance carburetors. They operate by using engine vacuum to control their opening and closing rate. When they open, additional fuel is supplied to the main system during heavy load or under full power situations to eliminate hesitation and bogging--ensuring the smooth delivery of power without any drivability concerns. They're available in many different vacuum ranges to time the system's operation to your specific requirements, and they come in your choice of single-stage, two-stage, and high-flow designs. A gasket is included.

Thank you RussT for the information. I am up in Canada, but I'll use your forwarded info to aid in choosing the correct one. I believe I currently have a 6.5

 

[gthumb]

What was the number on the power valve you took out, and what is the number on the one you installed?

Sorry, did not see this message. I took out a 6.5 and the same went in.
It is my understanding that you can check the status of the power valve by turning the idle mixture screws all the way in while the engine is running. If it stalls, the power valve is good. I did this, and the engine would stall. This makes me believe the power valve is good.

 

[WileE]

Who did the rebuild ? Were the same (configuration ) gaskets used ? Why are you running mechanicals ?

 

[Geoff 2]

A leaking PV has no effect on idle. The idle screw test in post #31 does not prove anything related to the PV.

The PV is part of the main cct. Enough air speed [ increase in engine rpm ] has to pass through the throttle bores to activate the main system [ main jets ]. If the PV was blown, then the carb would be very rich at this higher rpm, but not at idle.

 

[gthumb]

Who did the rebuild ? Were the same (configuration ) gaskets used ? Why are you running mechanicals ?

I did the rebuild. I compared the gaskets received in the Holley rebuild kit to the gaskets removed, and they were the same. This carburetor has been in my vehicle for more than 25-30 years, and it ran just fine. What would you recommend? I am thinking of purchasing a new one if I cannot get this one straightened out. I don't use the choke, I keep it open all the time. Are you recommending one with an electric choke?

 

[gthumb]

A leaking PV has no effect on idle. The idle screw test in post #31 does not prove anything related to the PV.

The PV is part of the main cct. Enough air speed [ increase in engine rpm ] has to pass through the throttle bores to activate the main system [ main jets ]. If the PV was blown, then the carb would be very rich at this higher rpm, but not at idle.

Would you then be recommending replacing the PV as Dave6T4 suggests is necessary

 

[AR67GTX]

If you have a hand vacuum gun you can test the power valve. Or you could use a manifold vacuum hose on an idling car. Put some hose pieces together to step up to a diameter larger than the orfice, put a little silicon or chassis grease on the end of the hose to seal good, hold it against the PV and pump it a couple of times and see it retracts the valve. If so it’s working. That and the correct style gasket are the 2 major things that can go wrong with them other than selecting the wrong size.

 

[gthumb]

If you have a hand vacuum gun you can test the power valve. Or you could use a manifold vacuum hose on an idling car. Put some hose pieces together to step up to a diameter larger than the orfice, put a little silicon or chassis grease on the end of the hose to seal good, hold it against the PV and pump it a couple of times and see it retracts the valve. If so it’s working. That and the correct style gasket are the 2 major things that can go wrong with them other than selecting the wrong size.

Thank you for this information. I greatly appreciate your help and your technical tip.

 

[WileE]

I did the rebuild. I compared the gaskets received in the Holley rebuild kit to the gaskets removed, and they were the same. This carburetor has been in my vehicle for more than 25-30 years, and it ran just fine. What would you recommend? I am thinking of purchasing a new one if I cannot get this one straightened out. I don't use the choke, I keep it open all the time. Are you recommending one with an electric choke?

Well, you had a good running carb before, no reason why it still shouldn't be. It appears something went awry by your rebuild. Some good comments here, I'll add that the idle air bleed holes may be clogged, try cleaning those with gumout.

 

[gthumb]

Well, you had a good running carb before, no reason why it still shouldn't be. It appears something went awry by your rebuild. Some good comments here, I'll add that the idle air bleed holes may be clogged, try cleaning those with gumout.

Logically, I believe you are correct. Just gotta figure out where I went wrong. I know my initial setup after the rebuild was incorrect with respect to fuel bowl levels and idle screw position, and my plugs got really fouled, experienced backfires, rough idle and it got to the point where the car wouldn't start. Removed and cleaned plugs, confirmed idle screw position by checking the size of the idle circuit slot in the carb, fuel bowl levels confirmed, idle mixture screws turned out 1 - 1 1/2 turns out. Car started right up, but exhaust is slightly blue, and plugs getting carbon buildup. It's possible the new power valve has been damaged, or my rebuild was not good.
What part of the rebuild could cause this type of condition?

 

[hunt2elk]

Like stated previously, the power valve has absolutely nothing to do with the idle circuit, unless it is blown out. And that seems to be where the problem is, correct?