I have twesked my Quadrajet and thought I was going to get all I was going to get out of my basically stock 1974 350 until I installed an Edelbrock 1406.

I am now able to smoke the tire from practically a standstill without having to power brake it. Very cool.

However I do have a problem that is probably easy to correct. At idle and at a standstill I get a terrible dead spot if I quickly push the peddle to the floor and also if I am say cruising at 40 MPH and go WOT I get a hesitation. I have the problem less if I slowly build up RPM’s before going WOT.

I kind of know if is a flooding situation and need help correcting it. I have time according to the stick and have tried my vacuum advance in both the timed and manifold ports.

Any help will be appreciated and thanks in advance for the help.

Bill

 

I had the opposite experience. Bought an Edelbrock for my big block and never could get it to perform up to par with the Quadrajet. God bless, Sensei

 

Get Lars to tune the quad and you wouldn't have any problems.

 

So it is a carb problem and not a timing problem?

 

If you can just bolt on a new carb and see the difference, get the Qjet rebuilt properly and you will still smoke the tires and it will run through the rpm range!!

You need to make sure the timing and advance curve is set up correctly as well. Timing and fuel delivery will give you good performance.

 

Well, I just spent $240 on a new carb that made a tremendous difference all around with the exception of this one issue.

Why are you suggesting to have the old Q-jet rebuilt by what seems to be one person on the planet who knows how to do them and is probably not doing rebuilds anymore ( think I read that in one of his posts). How about just figuring this out?

Bill

Larrs, are you rebuilding q-jets anymore? if so please PM me with address and cost.

 

You could get the q-jet rebuilt as all are saying, and it would probably be great.

I however went the other route and bought a new carb. My engine is no longer stock however.

It sounds as though you have an accelerator pump issue. Almost all carbs off the shelf have an accelerator pump that is to small, I don't understand this. What happens is when you hit the gas quickly, the vaccum under the throttle blades sucks in a bunch of air real quick and the acc. pump squirts in gas to compensate for this.

On the edelbrock, there is a squirter with 2 nozzles coming out of it in the top of the carb just beneath the choke assembly. This is you acc pump. When you look into the carb with the engine off, and slowly pull back on the throttle linkage, you will see gas coming out of here. You can adjust this by moving the linkage that controls the acc. pump plunger (This is explained in the Carb manual). There are 3 or 4 holes that the linkage can be set in. Try this first and see if it helps, it will give you more or less gas sooner depending on which way you move it. You most likely need more, sooner.

If this doesn't work, then you need a bigger squirter. There is a number printed on the squirters and this is how you determine what size you have. Most auto parts stores sell a pack of 3 that should get you where you need to be. Change them out, and then try adjusting the linkage again, and this should do it for you.

Good luck,

Will

 

Thanks Will,

Makes sense, I was thinking the opposite that I was flooding when going hard on the peddle. I did some goggling and read the same thing you just said. I will try it out tomorrow.

Is this Q-jet and any other carb just a Ford/Chevy type of thing?

Thanks for the help.

Bill

 

The Quadrajet is a superior design. You have fiddled with the carburetor but said nothing about the ignition. The problems you have now may be caused by the ignition.

BigBlockk

Later.....

 

this sounds like a classic case of "to small an acel. pump"

 

I believe that carb out of the box is tuned for maximum fuel economy. That may be your problem. It can also be tuned for good street performance which is perhaps where you wish to go. I am not a carb expert but perhaps someone can make suggestions on tweaking.

http://www.edelbrock.com/automotive/carb_square.html

 

As mentioned above, the 1406 is set up for economy. The 1405 is a manual choke carb setup for performance (otherwise it's the same carb.) I put a 1406 on a zz3 and tuned it with the parts indicated for a 1405 and it ran fine. Over time I tuned it further as needed and will check what I changed later today and will post the part numbers for the rods/springs and pump setting. The motor is in my sons Fiero now and it runs like a raped ape.
I also agree that a Q-Jet in good condition is a better carb, tho...

Daffy

 

Daffy,
I would be very interested in that info. The pic shows why.

Hayman,
I'm curious as to how you adapted a square-bore carb to a spread-bore intake.

 

I put it on a Edelbrock 2101 manifold. Where are you attaching you vapor canister? I don't have a port for it.

Bill

 

Sounds like your not getting enough fuel when you go WOT. Since you cannot increase the actual size of the accel pump on an Edelbrock, you can make 2 adjustments though. On the linkage, there are 3 holes for the stroke length of the pump, which effects the amount of fuel that gets delivered. The other adjustment is the nozzle size. Edelbrock sells a kit with 3 sizes I believe. The nozzle size doesn't affect the amount of fuel, but they do affect the rate that the fuel is introduced into the airstream. Working with these two adjustments, you should be able to tune out that bog. Good luck

 

Stock 1406:
Rods.075X.047 -step up springs yellow - Main jet .098, Sec. .095
Stock 1405:
Rods.070X.047 -step up springs orange -Main jet .100, Sec. .095

Both have the pump link in the middle hole

I see by my notes that the only added change I made was to increase the Sec. jet to .098 and never needed to move the pump link. The carb/motor has always been in 4-speed cars with about 3:36 gearing, so if you're auto trans with lower (numerically) gearing you might want to try the top hole for the pump link.

I would suggest the .070X.047 rods, the orange springs, the .100 Main jet and the .098 Sec. jet and if needed, move the link to the top hole (closer to the carb. body) for a bigger shot from the pump. If you look at the troubleshooting chart on page 32 of the owners manual you'll see that they suggest moving the pump link and perhaps changing the squirter size to cure a stumble. I have always run with manifold, not ported vac. on this carb.
I also suggest the you keep track of the changes in the data log on the last page of the Eddy owners manual.
The carb. fits right on the zz3 manifold.
As suggested above, check your ignition for a good curve and proper timing - I think it was Lars who said that 90% of carb. problems are ignition.

Hope this helps,

Daffy

 

Daffy,
Thanks! Yes the car is automatic (Powerglide).

Hayman,
The only emission device in 1967 is a PCV valve in the neck of the oil fill tube. Simpler times back then. The #1406 is for the older cars. If you look at the link above the #1400 would have been a better choice for the C3s (fuel vapour and EGR ports). Sorry to say that....

But there might be some hints here in the 1979 emissions diagram where one of the two canister hoses going to the Q-Jet is "T"ed into the PCV hose. Perhaps others can suggest options for you.