Buick qjet

[mcx]

hello...new member as of today!...picked up a clean qjet and need some help from the regulars....carb# 7043240 LA 3562    primary jet 73    primary rod 37    secondary rod CT
secondary hanger L......any Info as to what it's from and if it has the correct jet/rod parts would be appreciated....I believe it's a 800cfm version from the pix in Doug Roes old book(it came with the carb) LOL....thanks. Mike

[carmantx]

1973 Buick 455. It is 800 cfm.
Original with 73 jets, 44B primary rods and CT secondary rods.

[mcx]

Thanks for verifying...44b?..I guess someone was modifying in its past life LOL....do the codes tell what model of Buick or it's just for any 455 engine?? how about manual vs auto trans?  Thanks, Mike

[Cliff Ruggles]

The 1971-74 Buick 455 carbs typically act a little lean on the primary side so it's not uncommon to find either larger jets, smaller metering rods or combination of both in them.

Far easier to free up the APT system and install one of our external APT screws and stick close to the stock jet/metering rod set-up for most applications.

The 7041540, 7041240, 2240, 3240 and 4240's are all auto transmission carburetors....Cliff

[mcx]

The installed 37 primary rod was missing a "b" stamp? This means it had the later incorrect style?  would that cause running issues?  Thanks,Mike

[Cliff Ruggles]

They made "37" rods that were not "B" suffix.  The "B" series tapers slightly on the upper section then again more quickly down to the .026" tips.  I use and prefer them in the early APT models.

Later rods would be stamped 37 with a J, or K after the number (they may have made others) and they are shorter than the early style.......Cliff

[mcx]

Cliff...thanks for the info, I really like this site..I ordered your book today from Amazon, it's a used version which is perfect for this qjet!...i have been cleaning it up and trying to follow the paths within to understand it better....I figured out the idle air bypass from base plate to airhorn, it was a little confusing till I finally noticed those notched out sections in the primary air horn bores(pretty cool to see how the air gets around the closed throttle plate)....I also tried pulling out a idle tube, not pretty ,but at least I know what size it's tip is down there, .032. to .033ish to purchase.....I checked out the APT in the base plate, it's capped off still..is that APT set screw the same size as a mixture screw?.  Thanks, Mike

[Cliff Ruggles]

We make and sell an external APT screw with a spring on it to hold it's adjustment.  We also have everything you would need to set up that carb exactly for any particular application, have done thousands of the Buick units over the years and know exactly what they need to be up to par for any set-up......Cliff

[mcx]

I had much better luck removing the second idle tube, it came out so nice it could probably be reused LOL....I made a effort to remove the base plate APT..drilled the apt cover and it came off easy...apt was soaking for a day and used map gas to heat it up....that screw is  fused permanent..screw head ended striping..than tried drilling out the whole screw...no luck , than moved on to the Dremel cutting disk to slice a channel....its a cluster fcuk!!..i quit!!!   I ended up using JB Weld Marine putty and sealed the damage up..frustrating..but at least its back to where it was originally.

[Cliff Ruggles]

Those screws are often case hardened.  They can be difficult to drill out and easy to break the "ears" off as well.

I'm close to 100 percent successful at removing them, but I get more practice than most!

To drill them out you have to "pierce" them with a really sharp/hard punch.  The insides of the screw are relatively soft and once the drill bit gets a good start they drill out pretty easily......Cliff

[mcx]

I finally got your book in the mail today and its excellent...and it actually has a pix of the same  QJET I'm overhauling(rated second desirable) LOL...i keep rereading the section on air  bleeds (top/bottom,airhorn) and look at pixs to see which is what is on mine....it's actually unfortunate the book came today, yesterday I pulled the secondary well tubes and modified as shown in the Doug Roe book drilling those multiple tiny holes, as used on the Ford Cobrajets!!!  I read in your book DO  NOT DRILL THOSE HOLES,...at least they can be pulled out easy and replaced....it's a shame, they looked like the real ones.

[Cliff Ruggles]

The Ford CJ units were the only factory Q-jets to use that modification.

If you are using secondary POE (all models didn't use it) adding holes to the tubes will have them start sucking air instead of fuel pretty quickly unless you have some HUGE holes leading to the wells to the fuel level high enough.

We have Q-jets on foot braked applications well into the 9's over 135MPH and do NOT use drilled tubes in them, and have never observed any improvement from doing it.

For the big Buick Q-jets do NOT modify any of the airbleeds, idle or main, they don't need it. 

They will need idle tube, DCR's, and bypass air modifications based on the application, and different jets/metering rods.  We can help out with that even without the working APT, and supply the correct high performance parts to rebuild it as well.......Cliff

[mcx]

Cliff...thanks for sharing about not touching idle/main bleeds....I also drill  opened up the secondary air bleed tube restriction, that is shown in the Roe book...it's where you drill out the large secondary plugs and open up that channel and than flip the main body and open up the connecting channel,it's a restrictive dog leg bend...was this worth doing in your opinion?
...your book was spot on with the lower gasket locating bumps cracking off easily with my cave man disassembly....i had to mix some epoxy and use the gasket as a temporary mold to reform the two bumps, it worked decent with some file work...almost looks stock LOL

[Cliff Ruggles]

Unless the plugs are leaking leave them alone.  Nothing waiting for you opening the passages under them.....Cliff