Let's hear it for the Quadrajet!

[squirrel]

CDMBill generously sent me his old Innovate LM-1 wideband oxygen monitor. I installed it in my 57 Chevy one ton truck, which I recently swapped a 454 into. The engine is mild, has an RV type cam and oval port heads, and an early iron intake with a Qjet. The carb came off a 77 half ton suburban with a 350 that I parted out years ago. I put a new float and carb kit in it before installing it on this truck. It's been running fine, and I calculated the mileage over the last two tanks (over 500 miles) at just over 11 mpg. I live out of town a ways, so most of my driving is what I call "rural", not heavy city traffic, not on the highway either.

Anyways....watching the AFR was interesting. When it was cold and the choke was on, it was usually around 13 or so at idle, and it would go up to 15 or so when I opened the throttle, and drop to around 14 when cruising stead When I got on the road, it was bouncing around 14-15. I got out on the highway, set the cruise to 65, and it settled in at 14.7. When I put the pedal down, it dropped to high 12s.

I'm guessing I don't really have much reason to change the truck over to EFI....

now, on to the 55!

[SpiderGearsMan]

snicker snicker 4M4 q jet with the emissions settings

[ls7gto]

I think I need to play with a LM-1 or Lm-2. Damn you Jim!

[squirrel]

Or an LC-1 and a laptop.

[TheSilverBuick]

That's awesome, cheers to the Q-jet!

[dieselgeek]

Can't argue with a carb that runs an engine that way, it almost sounds like the thing is following a program...

Meanwhile, the kudos probably belong to the modern affordable wideband oxygen sensor!

[squirrel]

The O2 sensor let's us see how well the primitive stuff designed decades before really works.

[dieselgeek]

The O2 sensor let's us see how well the primitive stuff designed decades before really works.

How many carbs have you put an O2 sensor on? I've done maybe 15 and the vast majority of them are running in the 10s at a warm idle. Yours probably runs leaner because the passages are half gummed shut.

[mike343sharpstick]

I think I need to play with a LM-1 or Lm-2. Damn you Jim!

Yes, Damn you Jim!

[squirrel]

How many carbs have you put an O2 sensor on? I've done maybe 15 and the vast majority of them are running in the 10s at a warm idle. Yours probably runs leaner because the passages are half gummed shut.

uh...yeah...

Or it runs leaner because it's an emissions carb, as Jim mentioned.

Aftermarket performance carbs can get away with running richer, so they do. It keeps down the "bog" and "surge" complaints, I imagine.

[Thumpin455]

A good running Qjet will run just like that, they are quite a bit more complex than a Holley, and far more precise than an AFB/Edelbrock carb. The APT carbs will do a great job keeping the right amount of fuel going to it, all you need to do is know how they work then make sure everything is clean and not leaking. The jet passage plugs can leak causing a rich condition, and a telltale sign of that is needing to crank it forever and a day after it sits for a couple hours. If the downtubes are clogged it will run rich and burn your eyes, so apparently the biggest problem with them isnt an issue with that one.

I love my Qjets, if you want to throw them away, just send them to me. I will pay the postage.

[squirrel]

I have about a dozen laying around...I'm hanging on to them.

[milner351]

Nice work indeed Jim.

I have to wonder if a Qjet originally designed / calibrated for a 454 would run as close to Stoich as this one which you pulled off a 350?

Did you change any of the calibration or just clean it and put in new gaskets?

They did run well for many years on many different cars - they do deserve more respect then they get.

I'll never forget one bitterly cold morning in Kalamazoo when most of the cars in the parking lot wouldn't start - the olds 88 with the 307 and the Qjet I'd rebuilt a few years earlier started just like it did when it was warmer, set the choke and crank it up. I must have jumped started a dozen cars that morning. Everyone was trying to get home for the Holidays.

[BigBlockMopar]

Thermoquads.

[Barry Donovan]

I like the qjet. small barrells in primary.

dropping to twelves is quite a squirt..you could get accelerator pump or whatever gets to a be a power valve in tighter.

my own hit the twenties mpg. So beyond lies I could get a sick stomach at what really works.

on a similar subject (working a carb to phenomenal)

I just took this route yesterday with a hitcahi carbed subaru boxer. 1987 never rebuilt, 135k miles. it is not like the others anymore,need to pay attention to fuel.

mileage is in high 30s over more tough going than flat.(less than 3 gallons, heading into hills in the clouds)

I am with you about changing mind about some setups. I look forward to getting a rochestor 2gc dialed into 1781cc..so far it seems a weight in grams on the power valve is the extent of it. I may be more clever than that..that is just first thoughts.