Quadrajet issue

[buzzinhalfdozen]

Have a freind with a big block, mildly cammed with a Q-jet that will not idle. Has a rebuilt carb can turn mixture screws in all the way engine still runs, says it's very rich, has completely closed throttle blades then just cracked open, still idles rich. Since the mixture screws seem to have no effect on how it idles can we assume it's bringing in fuel elsewhere? Could the pri. metering be the issue? Been a while since I've even seen a Q-jet, but doesn't it have a piston and hanger that pulls down with vacuum to seat the metering rods? Really can't come up with any other explanation. I've not personally seen the car merely going off what the owner is saying

[gsa612]

If the cam has a lot of duration it might need a lighter piston spring. what you can do is remove the pri. rods and spring and put in 5 steps leaner pri. jets 67's?, then put just the piston back in.See if that don't clean it up. If it does either nip a coil,or get a lighter PP spring. Most S/SS cars run this way,(without rods).I wouldn't drive it on the street with no rods though.You can also check if the bottom well plugs aren't leaking. gsa612

[ron mattson]

Could just need more idle air. There are a few
Different ways to accomplish this.

[buzzinhalfdozen]

Ok, yes he's gave it more idle air, that didn't solve it that merely made it idle faster, still rich. The wells have been epoxied, at idle the power piston should be drawn down correct? Pulling the rods into the jets? Looks like I may inherit this buggy so I'm looking for some things to try. Thanks guys.

[ron mattson]

Take a wooden match or small wood skewer
And stick down air vent and on top of primary
Metering rod hanger and mark height to top
Of vent tube, then fire car up and repeat this
Will tell you if the hanger is functioning while
Running.

[Robert Simpson]

After you do what Ron stated. Disconnect the accel pump, with it running. If it get crisper and idles better, you are rich and vise versa. Dean told me that one, it works. Also you might have to increase the diameter of the passages behind the fuel mixture screws in the baseplate. Example they are .079" open them up to .089". Just a thought.

Robert

[buzzinhalfdozen]

After speaking with the owner of the car today We've decided to ***** can this carb.Going to try and find a source for a street Qjet for this engine, where's the best place? Needs to have eletric choke and pull offs ect. Thanks Joe

[Mark Ugrich]

You could try Sean Murphy. He did the Q jet on my 454 Suburban.It took a couple attempts, but it runs really well.

http://www.smicarburetor.com/

[Jeff Kempton]

Originally Posted by buzzinhalfdozen

After speaking with the owner of the car today We've decided to ***** can this carb.

Joe, if that's the original carb the owner should hang onto it in case he ever decides to restore the car in the future. Just sayin'.....

[Alan Roehrich]

Originally Posted by buzzinhalfdozen

After speaking with the owner of the car today We've decided to ***** can this carb.Going to try and find a source for a street Qjet for this engine, where's the best place? Needs to have eletric choke and pull offs ect. Thanks Joe

Good choice. I have seen the Edelbrock Q-Jets show up on ebay new every so often. I've also seen some NOS Rochester carbs show up.

Look at newagemetal.com, and get a manual, try this page: http://www.carbkitsource.com/manuals...als/CM355.html

Use that to find carburetor numbers, then look for a good unmolested core to either build yourself or have built.