[2manyT/A'S]

Just put a kit into a 71 Pontiac 455 Q-jet......

Worked well previously,but was sitting for a long time.

It seems to be working normally now but there is a hiccup,just off idle.....worse when cold...it will stall it,with no choke..(choke is disarmed)..gets better when warmed up,but acts like its getting too much fuel,too soon....

I'm guessing power piston spring tension is too soft?

Going to try some searches here & will look at Cliffs book,if I can find it here.

Enging has good even compression,21 inches of vacuum,12 degrees initial,30 degrees dwell & new correct plugs,etc.

Thanks in advance for any input...

[poncho in a can]

what kit did you put in it. (hopefully it was one of Cliff's kits). Cliff's accel pump "rubbers" are the only one's to use of course as they are not affected by ethanol. Others will start to come apart in only a couple of days. (Just one thing to think of). I seriously do not think that it is getting too much fuel due to the power piston as the main jets have little effect on the idle or just off idle. Granted they have some effect but not that much. Most likely culprits would be incorrectly set accel pump or pump rubber that is coming apart. Besides if the spring were too soft the problem would be just the opposite, not enough fuel as the rods would have a hard time "lifting" therefore leaving the thicker part of the rod in the hole, thus leaning the fuel curve. But this could actually be a problem also. Another thing to consider would be some "trash" under the idle tube (at the bottom). these passages must be super clean.

[Kenth]

Engine needs more fuel off-idle/main.

You may start with lightly seating the main circuit adjustable air bleed screw under the triangular cover. This will richen the main circuit some.

The cure is usually a couple of thousands larger idle tubes, idle channel restrictions and main jets. Start small and step up if needed.

What carb-#?

[2manyT/A'S]

OK,back at it....

Carb is a 7041262....

The kit I put in came with alcohol resistant needle/seat & blue acc. pump seal which I understand is correct?

Put in a longer power piston spring.....didn't really make any difference...

Did initially have the pump link in outboard hole but now inboard...

When I crack the throttle,we get a backfire after the hiccup...

Could we have a timing/advance issue here?

OR,is it the acc. pump?

[poncho in a can]

Well, I would check the accel pump system again. I know its a pita but you must have a solid stream of fuel as soon as the pedal is pressed. A visual check is possible even with the engine off. If you do not have a solid stream there are several possibilities. One is forgetting to install the check ball in the accel system. Another would be having the height of the plunger too high (above the slot in the well). the later can be adjusted by bending the tip of the pump lever. If you think the ignition system might be the problem, a points type ignition has plenty of things to go wrong. Condensers that go bad, pitted points, loose shafts and springs that loose their tension. I would not even know where to get a quality set of points nowadays.

[Cliff R]

The kit I put in came with alcohol resistant needle/seat & blue acc. pump seal which I understand is correct?

Those "blue" accl pump seals showing up in over the counter kits aren't worth two squirts of duck poop. They are a soft material and fail in this new fuel. Went round and round with the parts suppliers on that deal, and finally ended up getting our own seal that will hold up in this new fuel.

None of those kits have the correct high flow needle/seat assembly in them either. This effects carburetor performance as it effects fuel level at the same float setting and fuel pressure. This alone could be causing your issues, as a lower fuel level leans up the carburetor everywhere.

The power piston spring would have nothing to do with a performance issue for "normal" driving at light throttle pulling away from a stoplight, etc. The vacuum is high in those situations, and the PP stays down unless the throttle is hit quickly and pretty hard. When that happens, the accl pump adds fuel, and PP raises up to add more fuel to the main boosters.

If you are having issues at light part throttle easing into the throttle, it is most like a lean condition as Kenth mentions above. LOTS of reasons this happens after a "rebuild" in addition to what I stated above......Cliff

First pic is the junk-ars pumps/seals showing up in over the counter kits for the early Pontiac carburetors.

Second pic are the pumps we buy getting our seal put on them (lower right). They show up with light blue and sometimes black seals, ALL fail a test soaking in this new fuel, they swell up and get stuck in the pump bore in a few days. Our seal is unaffected, even sitting in E-85 for over a year!

[David Brown]

X2 on what Cliff said. Years ago, I used to buy kits from NAPA. When they started adding crap to the gas (before ethanol), I used to also buy a separate accelerator pump from NAPA that was said to be impervious to the various additives. For the most part, they worked pretty well. But when 5% ethanol was added, they too failed. Now it is up to 10% and it is much worse. Over the counter kits might work for a short time and may not completely fail for a while. But when they start to fail, many people just complain that quadrajets don't work. A kit from Cliff has never failed me and any carb I build works flawlessly. Replace the kit!

[Blued and Painted]

Back fire through the carb is lean mixture and/or late timing. Double check Ig timing first. Then check and repair pump circuit. Float level could be the problem. I like taking the top off on the car, shortly after running to see how much gas is actualy in the bowl. It should be at least 3/4 full with float still installed.

[2manyT/A'S]

Originally Posted by Cliff R

The kit I put in came with alcohol resistant needle/seat & blue acc. pump seal which I understand is correct?

Those "blue" accl pump seals showing up in over the counter kits aren't worth two squirts of duck poop. They are a soft material and fail in this new fuel. Went round and round with the parts suppliers on that deal, and finally ended up getting our own seal that will hold up in this new fuel.

None of those kits have the correct high flow needle/seat assembly in them either. This effects carburetor performance as it effects fuel level at the same float setting and fuel pressure. This alone could be causing your issues, as a lower fuel level leans up the carburetor everywhere.

The power piston spring would have nothing to do with a performance issue for "normal" driving at light throttle pulling away from a stoplight, etc. The vacuum is high in those situations, and the PP stays down unless the throttle is hit quickly and pretty hard. When that happens, the accl pump adds fuel, and PP raises up to add more fuel to the main boosters.

If you are having issues at light part throttle easing into the throttle, it is most like a lean condition as Kenth mentions above. LOTS of reasons this happens after a "rebuild" in addition to what I stated above......Cliff

First pic is the junk-ars pumps/seals showing up in over the counter kits for the early Pontiac carburetors.

Second pic are the pumps we buy getting our seal put on them (lower right). They show up with light blue and sometimes black seals, ALL fail a test soaking in this new fuel, they swell up and get stuck in the pump bore in a few days. Our seal is unaffected, even sitting in E-85 for over a year!

Thanks everybody for your input.......I DID put the check ball in.... and once you get past that initial "hiccup"....it seems to rev out fine......SO...I just ordered a couple of your acc. pumps (on site) and will advise on progress....Hopefully it's THAT simple...

Just curious....do all the Pontiac Q-jets of that era 68-74 use the same pump?

[Cliff R]

The Ram Air carburetors used a pump that is cut for a rubber boot.

We do not use the early style pumps, we will send the later style with a crimped on retainer to keep the body from pulling off the shaft, and later style seal with garter spring to keep it in contact with the pump bore. Our pumps also include custom wound springs and a new retainer. Do NOT mix any of the parts (not sure why folks do this, but we see it done frequently), toss out the old springs, pump, etc and use the new parts as a unit......thanks for the order.....Cliff

[2manyT/A'S]

Ok,great....I'll get a couple cut for the boot next order.......Have 78 & 80 q-jets ..will your pumps fit these also?

[Half-Inch Stud]

Sounds like a Cap-Rotor phasing check needs to be done. Or the Dizzy is off a tooth.

[2manyT/A'S]

Originally Posted by Half-Inch Stud

Sounds like a Cap-Rotor phasing check needs to be done. Or the Dizzy is off a tooth.

That thought had crossed my mind.....BUT....would it run that GOOD if we were off a tooth?

The 21 inches of vacuum is ROCK solid........almost too good to be true.

Perhaps we are advanced one tooth?

I've owned this car for along time,but never really worked on it or driven it....OR attempted to tune it....until recently...

[2manyT/A'S]

OK,NOT a timing issue......swapped carbs today from a good running 70 400 onto the 71 & no hiccup anymore.....put the rebuilt 71 carb on the 70 & now it hiccups/backfires.....

Compared the pumpshot/squirt & the 70 carb appears to be WAY healthier than the 71....so hopefully Cliffs new acc. pump will cure the issue...

[2manyT/A'S]

Got the new pumps from Cliff on Friday..........installed one in the "patient" and it's CURED!

Thanks to everybody for their info & thanks to Cliff having the RIGHT parts to keep our Pontiacs running RIGHT....