Rode in the passenger seat for the first time today

[Jim Stoltz]

The new carb on my Allegro is driving me insane. I get that tuning a Quadrajet is a bit of an art, but it's been giving me fits. When I get the choke to work properly, it locks the 4 barrels out. When I get the 4 barrels to work, the high speed idle won't set. I've been going in circles.

Anyhow, I wanted to demonstrate the issue to my brother. He wanted to drive. I obliged. I've never ridden in the thing as a passenger. My brother did really well driving it. He's a locomotive engineer and said it felt like driving a train on the street. 4BBL worked, choke not so much. That fine line.

It was really cool sitting in the passenger seat. I need to teach my GF how to drive it. She'll never do it, but I can dream can't I? Same with my limo. I've only ridden in the back once when my brother drove it. But my passengers have fun....

[Russell E Johnson]

I hope someone here can give you an idea about the choke and 4 bbl problem, I am having the same problem with the Quadrajet on my mh.  I am about to give up and put on a 650 Edelbrock.

[Jim Stoltz]

It's been 25 years since I had to mess around with a Quadrajet. Back in the day, I replaced every one I had with a Holley with a manual choke :) But on this motorhome I was determined to make the stock carb work. It's running really rich and won't pass an idle tailpipe inspection (NJ). High speed idle doesn't kick up on a cold start, so it barely runs until it warms up. I can live with that, but would rather it functioned properly. I have some more reading to do I guess.

[Russell E Johnson]

Fortunately our 87 Southwind is old enough that I do not have to get it smog tested here in Arkansas.  Even after I had the carb completely rebuilt and adjusted by a mechanic mine also barely runs with no high idle when cold and will only run after it is warmed up.  Maybe it is the nature of the beasts? :)

[Russell E Johnson]

OK, but as Jim said cannot get both the 4 bbls to kick in and have the choke working properly.  How do they interact so we get one or the other but not both?  I am confused by quadrajets to begin with so I do not understand how the 4 bbls are effected by the choke working or not working.

[Russell E Johnson]

Thanks Jack, I will check on this next week, right now we are in the middle of moving and the big day is this Saturday.  Thank you for explaining how the secondaries and the choke interact, I was afraid that I was going to have to disassemble the carb.

[Jim Stoltz]

Thanks Jack.

Mine won't go through emissions so I was going to try a "lean drop" tune (it's just an idle sniff test). It sounds like what you described above. What about the left screw? Mine's a double-D type screw and I have the tool for it.

[Jim Stoltz]

Thanks! They do fall out sometimes ;). I need to change the oil anyway. It's the fresh oil that I put in it when I fired it up for the first time after a 7-year nap. It looks good, smells a bit fuel-ish. It has about 700 miles on it now.

I did a compression check because I'm getting what seems to be a lot of crankcase pressure. Compression is 150 PSI across the board, but in the process I found that all the plugs are black with carbon. Not fouled, but they don't look great. It's still running rich I guess.

[Jim Stoltz]

So following your advice, I was able to get the choke to close all the way. I adjusted the pull-off so it opens about 3/8" and cranked up the idle speed. It turns out this stuff isn't set by the rebuilder "out of the box". The pull-off was the whole way out which pulled the choke open right away. Tightening that adjustment closed it to the 3/8" when started. I was afraid to make big changes to that fast idle screw, but sure enough after about 3 full turns the idle came up to around 1500 RPM. I have not verfied, yet, that the 4BBL lockout cam is releasing. I'll take a look at that later.

My issue now is that something is binding with the high speed idle cam and mechanism on the side. I let it cool off and opened the throttle all the way. The choke snapped shut, but not all the way. If I manually open the throttle and tap the high speed idle cam, it will fall down into position and the choke will close the rest of the way. Ditto when it warms up - the high speed idle cam isn't releasing unless I tap on it. I'll have to take a closer look at it, but I'm starting to understand how it's all related now!

[Jim Stoltz]

The choke releases like it should, but the fast idle cam is still binding. It doesn't always set itself when it's cold. Worse, while driving the fast idle cam will kick up and it will stick at the high RPM. If I goose the throttle it will sometimes drop back down, but not every time. Something is keeping the choke from opening all the way. I'll have to mess with that cam to free it up (it's not the adjustment on the thermostat housing). It feels like hard interference rather than something that needs lubed.

[Jim Stoltz]

It's actually not working both ways. Tried a cold start and the choke is closing but not completely, and not enough to kick up the fast idle. It's that mechanism binding. I'll have to goof around with it some more over the weekend. I have a new set of header gaskets to install so I'll be tinkering anyway.

[Jim Stoltz]

So the binding was between the high-speed idle lever and the secondary lock-out cam. I have no idea why they were interfering with each other. I was able to get it to work as it should, but there's no reason it can't go back to binding up again. There seems to be a fair amount of travel for that lock-out cam on the stud. It can position itself where it works fine, or slide closer to the carb body and cause some binding. I'm thinking maybe a washer or spacer of some kind behind it might work. But I don't want to interfere with it's operation either. 

[Jim Stoltz]

Woo hoo! It's functioning like it should now. Thanks Jack!

It jumps to 2500 RPM on a cold start so I backed it off a bit, but it slowly got down to the warm idle of 700 RPM (where I set it). Once it's cold again I'll see what RPM it starts at.

It had a lean stumble coming off of idle so I turned both idle mixture screws out 3 turns. It seems much happier now, but I'm not sure what the sniffer will say. I'll try a lean drop tune before I run it through. I'm just happy to have the choke working. It's getting cold here at night and it would not run without a lot of gas-pedal work.