Q-Jet Question? Needles and Jets.

[veinbar]

I have a '75 and up Q-Jet w/o the computer controls. It has the jets and needles in it for a 307ci, but it's going on a 357ci. I need to change the jets and needles. It has an electric choke, but other than that, no wires. I know that the needle length in Q-Jets changed in '75, so the needles are not interchangable from the earlier style to the later style. Here is my question.

Are the needles and jets interchangable with the computer controlled Q-Jets? I did not find a carb like mine on a 350ci, but i found several later computer controlled models on 350s. They are seemingly identical, and I'm willing to bet that the needles and jets are all interchangable. I'm just not certain.

So... I know the needle lengths in Q-Jets change in '75, so does that make all Q-jets '75 and up interchangable?

[Zoomad75]

Here's the best thing you can do. go to the bookstore and buy the book titled "rochester carburators" It breaks down every thing for the q-jet's rods, jets and hangers and what the compatibility is between models of q-jets. Just so you know the rods can be different lenths, thickness and taper. The rod hangers are different too with holes for the rods in different spots or a different bend. The book tells you what the markings on each mean and gives a good baseline to start with for a particular size engine.

From memory, the computer controled q-jets had a mixture control solonoid that didn't touch the rods/jets or hanger. Those parts will probably be different than earlier (shape/size) but might be able to work. I'm betting they are a tad leaner than you would want to be.

Here's what my Dad and I did to obtain a good variety of rods/jets/hangers. Every time we went to the boneyard and saw a q-jet we pulled the rods/jets/hanger and tagged it for what it came from. We got stuff off of engines as small as 305's to 500 inch caddys and everything in between. The stuff is worth gold when tuning a q-jet. That was 15 years ago and qjets were a little more plentiful to find in the boneyards. Now if you can't find what you need in the boneyard, Edelbrock does sell the tuning parts for q-jets since they sell new ones. Expect to pay $$$ for a small variety. Jet is another company that specializes in q-jets that might sell the tuning parts, but I don't expect them to be cheap either.

[veinbar]

that's a good start. thank you for the tips. I might need to bring my q-jet along with me to the bone yard. We'll see if things cant be matched up there. Thank you.

[Zoomad75]

I wouldn't take your carb into the boneyard. Trust me, I worked at a couple and they might charge you for your own carb when you come back out!

All the jets/rods/hangers are marked. Just take what you can, bring them home and use the book to decipher what they are.

You can get the rods and hanger without removing the top of the carb. One small screw and pull the rods/hanger up and out. To get the jets, you will have to remove the top of the carb (which includes the choke linkage) then you can get to the jets.

[veinbar]

ok, so i found the correct numbers that I am looking for. These are the correct jets and needles for a '76 & up Q-Jets for a 350ci. Here they are...

primary metering rods "needles": 50m
primary jets: 73 thousandths
secondaries: DR (which are apparently are standard in all '76 and up Q-Jets)

So atleast i know what I'm looking for now. The only question is, where do i find them?

[Zoomad75]

Boneyard, Edlebrock or Ebay. GM don't carry those parts anymore.

You know the phsyical dimensions of the rods and jets, but that's not how they are marked on the parts themselves. They should have a two letter mark stamped into them like "AA" or "BC". I'd convert the measurements over but I gave my book to my Dad as he's my resident Carb expert. Unfortunately they are not numbered like a holley jet is where it's easy to tell the size. You got to get the book!! Borders or Barns & Noble should have it. It's published by HP Books.