[importsmasher]

I am trying to get my Quadrajet dialed in, and I would like some guidance. I got a kit from Cliff, and rebuilt the carb myself. This is on a 74 GTO, with a 455 (6x8 heads, comp cams 280 cam, RA manifolds), 4-speed and a 3.42 12-bolt. The car runs good, but when you hit the gas, it doesn't bog, but it doesn't accelerate like it used to, and you can feel the power increase around 3,000 rpm. I had a Holley on this engine (on the same stock intake with an adapter), and when I hit the gas, it would immediately blow the tires away. It doesn't do that now. I switched to the Quadrajet when I put the drivetrain into my 74 GTO (I had it in a 73 Ventura previously), so I could keep the shaker scoop. I did an initial adjustment of the secondary air valve spring per Cliff's book, and it is still doing the same thing. I have read Cliff's book a couple of times, but I haven't found anything else (maybe I should read it again....). Should I tighten the spring, or loosen it, or should I be looking at something else? Is this just trial and error, or is there a methodology to figure this out? The carburetor is the only thing that has changed on this engine. I am contemplating re-installing the Holley and making my own base for the shaker, or bolting the scoop to the hood....

Carburetor tuning is probably my weakest area of expertise (which is why I ran a Holley in the first place....less complicated), but I like the concept of running a Qjet. Any suggestions are appreciated.

Thanks,
Importsmasher

[gtofreek]

The only two things I can suggest is loosening the tension on the air valve until it just has light pressure snapping it shut when you tap it with your finger. If it bogs, tighten it slightly. Doesn't take much of a turn to adjust. Just a little at a time until it doesn't bog.

If you get it as loose as you can, but it still doesn't respond, then you may look at the vacuum canister that holds the air valve shut until you loose vacuum. I have heard of people drilling a small hole in the vacuum can to let it release sooner. Also, the secondary metering rods play a big part it it's responsiveness. If you have the big, fat tipped rods, it won't respond good.

Maybe Cliff will chime in. He's MUCH better at tuning q-jets than me.

[importsmasher]

Thanks, GTOfreek. I am operating on the assumption that the metering rods, jets, and the vacuum canister are all correct, as I got them all from Cliff after I gave him my engine specs and carb number. I will play with the air valve spring and see what happens.

Thanks, Importsmasher

[Cliff R]

What is the carburetor number?....Cliff

[importsmasher]

Cliff, it's 17057258. I bought a complete kit from you about 4 years ago, and it took me a while to get it rebuilt and up and running.

Also, while you're here, I have tried several times to register on your forum, but I never get the confirmation email, so I can't finish the registration process. Can you help with that?

Thanks,
Importsmasher

[GOAT WHORE]

Originally Posted by gtofreek

If you get it as loose as you can, but it still doesn't respond, then you may look at the vacuum canister that holds the air valve shut until you loose vacuum. I have heard of people drilling a small hole in the vacuum can to let it release sooner.

This is my guess and its covered in Cliffs book.

[Cliff R]

Those are nice units. Check the unloading rate of the pull-off, it should open quickly, in less than 2 seconds. Set the secondary spring about 1/2 turn after it contacts the pin.

Send an email about not being able to register here:

cliffshp@embarqmail.com

I'll fwd it to our website provider....Cliff

[importsmasher]

Thanks Cliff! I will check the pull off rate and adjust the spring.

Also, I sent you an email regarding your forum.

Thanks again!

Importsmasher

[bluesmobile]

If you have full movement of the throttle under the hood (check with a helper in the car pushing down the accelerator pedal), then another thing to check which has bitten me on 2 different Quadrajets:

The secondary lockout stayed engaged when it should have released. The secondary lockout is covered in Cliff's book and his good advice is to disable it. It is supposed to be disengaged when the choke comes off, but many times it is not disengaged and only the small primaries are opening with full throttle...major disappointment in the power department!

Jeremy

[geeteeohguy]

I have run into exactly what bluesmobile stated with the cold lock out lever. If out of adjustment or hanging up, you will not get any secondaries at all.

[importsmasher]

Thanks, guys. I have run into the secondary lockout issue before. In 1998, when I first built this engine and had it in my Ventura, I took it to the track and it only ran 14.2. I was getting ready to replace the carburetor (not the same Qjet I have now) when I discovered the stupid little lockout...ripped that off and the car immediately ran 13.3.....That is the first thing I disable on a Qjet now. I have also verified that I am getting full throttle (double checked that again today).

I played with the air valve adjustment today, and verified that the pull-off releases in less than 2 seconds, but I haven't driven the car with these changes yet....

Thanks,
Importsmasher