1977 Qjet coughs and sputters

[stushug]

I have a 1977 Grand Prix. I just had the engine rebuilt (stock specs). The carb was leaking from a lot of different places so I had it rebuilt also. Now, if I go past 1/4 of the way with the gas pedal, the engine coughs and sputters, while barely accelerating. I checked ignition, compression, wires and plugs and everything is fine. As long as I don't go past about 1/4 throttle, the car accelerates fine. It also idles perfectly. Looking for some help on this, any suggestions would be greatly appreciated.

[Frank400]

Looks like it's running out of fuel.  I once had the same problem when I forgot to install the spring under the apt screw and the primary rods were going own all the way, almost blocking the jets. 

    What is your carb number and with what kind of parts was it rebuilt ? 

[stushug]

Frank,
Top row of numbers: 17057274  Second row: 1517 ARN. The carb was rebuilt by Dennis Barker, so I assume the quality of parts were good. I'm thinking it may be getting too much fuel, I can always smell it, and the mileage is down to about 6mpg. The car used to get about 10-12 city and about 15-17 highway. I pulled a plug today and it's pretty loaded with carbon. I'm attaching a picture. Thanks for the help!

[Frank400]

    Very good unit, and that is most likely the original from your car, 1517 is the date code, 151st day of 77.  Did you ask Mr. Barker about your issues ?

[stushug]

Yes, I've spoken with him over the phone, but it's very difficult to work that way. He's located in Colorado and I live in Pittsburgh, PA.

[Frank400]

A simple test would be to pull the power piston up (thru the vent) and see if the same thing happens.  I'm pretty sure I read somewhere about how to fabricate such a hook/tool.  Maybe it's in the Doug Roe book or a Delco Rochester service manual.  Not that complicated.

[stushug]

I don't understand how to do that.

[77cruiser]

Piece of wire bend a hook on it & go down through the bowl vent.

[stushug]

I assume I do this while the engine is running and work the throttle after lifting the piston?

[stushug]

Today I went to try what you suggested Frank, and I think I found the problem. When I looked into the vent, I saw that the gasket between the carb body and the top has that hole completely closed off. Just to make sure, you meant the round vent just in front of the primaries that sticks up into the air cleaner, correct. Should that hole be blocked off? Maybe Mr. Barker made a mistake and placed the incorrect gasket?

[Cliff Ruggles]

Unlikely the gasket has anything to do with it.

That is an excellent unit, same exact part number I've been using for decades and it's successfully powered 4 different engines in my Ventura from 300hp to over 550hp.

If it were assembled correctly with good parts it would be flawless.  That carburetor doesn't even need any help anyplace for what you are doing, they are as delivered one of the very best q-jets every made.  Time to look a little deeper, I'm sure it's something very easy to correct.

I would also never "assume" a rebuild has good parts in it.  I have many parts that we use custom made for us because the ones from the suppliers don't make the grade.

This includes the "blue" accl pump seals, they are complete JUNK, and swell up and fail quickly in this new fuel.......Cliff

[stushug]

Before the rebuild, the car ran fine until one day the carb started leaking profusely. There was fuel all over the intake  manifold. I had dropped the car off for a front end alignment and they called to tell me they couldn't get the car started. I had it towed back home and sent the carb for repair. When it came back is when I noticed the acceleration issue.

Cliff, when you say look deeper, what would be the next step? Do you think I need to purchase one of your rebuild kits to make sure I have better parts? I would have no problem there. The car is barely driveable as it is running now.

[Cliff Ruggles]

That would be the first place to start, install good parts and verify correct float height, sealing at the gasket under the fuel inlet seat,  make sure the power piston hanger arms are exactly level and even, pressure test the bottom plugs, check throttle plates for full closing/alignment, and look for obvious mistakes or problems like a leaking accl pump check ball, sticking power piston, not sealing the gasket well between the main body and airhorn (warped) etc, etc......Cliff

[stushug]

Which kit do you recommend? My carb is a 17057274

[Cliff Ruggles]

I would use the SR kit, it has everything to do a complete/correct rebuild on that carburetor and get it up to par for this new fuel......Cliff