General Category > Quadrajet Carb Talk and Tips

Q-jet with 3 mixture screws? 17085213

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Cliff Ruggles:
.081" jets would be huge in that carb.

The biggest jets I've ran in one to date were .076" on a pretty "hefty" 454 engines and they were plenty.

I like the 61S rods as they are full taper instead of "stepped".

My 50C rods are the same basic design tapering from .050" down to .036" tips.  I use them in all carbs built here that originally used "M"  series primary rods......

Glutenfreecarbs:
Hey Cliff, does anybody else ever struggle with quick transitions to WOT on these units? This carb has always had a lean spot if you randomly stomp on the gas pedal, which I've been unable to correct with any combination of air valve settings and hanger heights.

Maybe this is due to the uniquely small secondary accelerator wells?  I tend to avoid drilling or modifying castings, but should I delete these partitions to get more of a squirt when the air valve begins to open? Note the fuel  trapped in the "void" spaces after draining the float bowl.

Cliff Ruggles:
The choke pull-off is a BIG player there.  Make sure that it is holding the secondaries tightly closed at idle and that it releases smooth and not too quickly. 

I have the OEM style straight inlet pull-offs in stock, the bent tube variety everyone else is selling these days are HORRIBLE and there is no restriction in them........

blazer74:
I have one of these 17085213 carbs in my collection. Good Info.

Cliff Ruggles:
I personally wouldn't use one outside of it's original application.  They were specifically built for big block engines and Heavy Duty trucks, motorhomes and towing applications. 

Much like Marine carburetors they are calibrated to work on engines that see a lot of heavy load.

Kind of a cool story but a good friend of mine converted his late 1980's Chevy crew cab dually from TBI to a late 70's Cadillac Q-jet some years back.  He did an HEI at the same time.  He tuned and tuned on the big Caddy carb but was never overly happy with it.  Even with APT and playing around with jets and tapered metering rods it just never did as well as he thought it should.

I recommended switching to a 17085213 and had one in the shop.  He made the switch and it worked better for everyplace with improved fuel economy empty and towing......FWIW......Cliff

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