Quadrajet Help was (Quadrajet Id)

[thumper61]

I just bought a 87 Monte Carlo with a swapped in center bolt valve cover small block and it is converted to an older Quadrajet.
I am trying to Id the carb, its number is 17057530 and looks like it is off a 77 Caddy. Is this a 800 cfm carb. The car runs and dies I am thinking it is floating out due to the gas smell. I am looking to rebuild this carb but is this too much carb for a stock 350 (what I was told it is) I plan on swapping out cam, headers and intake but I want to get it running right first.

 

[DRIVEN]

Re: Quadrajet ID

I run that same carb on a 400 in my El Camino. It's tuned pretty rich for my engine. I would guess it's really rich on a 350. I'd look for another carb to start with. Something closer to 600-650 (Holley or Edelbrock) range if your engine is pretty mild. Maybe a mid-70s Qjet from a 350.

 

[dogsht]

Re: Quadrajet ID

A q-jet by tripple venturi design is never to big. Ie it can be very responsive even at part throtle changes even on small displacement engines as it always has good vacuum & air speed.. If its set up for a 77 caddy 425 it may need pimary jet changes or even hanger change. Find a qjet guru. If its from a 77 caddy that is an ideal hi performance street car carb.

 

[pontiacgp]

Re: Quadrajet ID

A q-jet by tripple venturi design is never to big. Ie it can be very responsive even at part throtle changes even on small displacement engines as it always has good vacuum & air speed.. If its set up for a 77 caddy 425 it may need pimary jet changes or even hanger change. Find a qjet guru. If its from a 77 caddy that is an ideal hi performance street car carb.

x2

 

[billyjack]

Re: Quadrajet ID

I'm not familiar with that exact carb number, but I've adapted other big-block carbs to work just fine on smaller displacement engines. My experience has been that the big-block carbs are often set up with large primary jets as insurance against leaning out under extended full-throttle operation. Pull the air horn and see what jets and rods you have. Something around a 70 jet and 42 rod should be just fine for your application. Primary jet size does affect idle quality, but not enough to cause flooding. I'd look at the float and float settings first.

Bill

 

[techg8]

Re: Quadrajet ID

yes that is an 800cfm Quadrajet for bigblock Caddy.

It will need to be recalibrated for use on a stock 350. rods and jets to lean it out would help, but dialing the air bleeds and channel restrictions - looking at the entire calibration - is the way to get the most out of your setup

keep in mind that often the bigblock Qjets had big Idle air bypass passages which are just plain no good on a smallblock.

 

[thumper61]

In the picture I see a passage is just to the outside and below each primary. Is this a idle bypass passage? There is some metal debris or something plugging this up, so I reopen it or what?

Also the main jets are 66 and I bought some 71's today, the metering rods are 39's and non apt, should I pick up some apt 41's or so?

I was looking at different carbs last night and it looks like quadrajets go for a little now so I would not mind getting this one to work.

BTW thanks for all the earlier help.

 

[techg8]

yes those are the idle air bypass holes in the main casting. There is a corresponding passage in the air horn above the venturis and holes in the baseplate that allow a certain amount of air to get into the engine without passing the venturi. Big blocks usually need this to keep throttle angle low at idle to avoid Quadrajet nozzle drip.

On a small block, those passages should be plugged. They must have been plugged on the last rebuild.

a .030 spread in rod-jet size is a good start point. you can tune the APT lean cruise once youre driving. do yourself a favor and tap the air horn and put a pipe plug where the aluminum plug was above the APT screw. This will provide easy access to the screw for tuning on the fly. Unless you have the tool for adjusting the APT screw, you can slot the top of it so it can be adjusted with a small screwdriver.