Qjet jetting recomendation needed

[77crewcab]

I am rebuilding a carb for my truck and need some help deciding what jets and rods to run. I currently have 32B/DH with 70 jets. I plan on keeping the DH and go with a G hanger. I also have some 73 and 77 jets and some 51B rods. What combo would you suggest? This is for a crewcab dd with some towing and stock 454. I understand the rod/jets should be about 30-33 sizes difference just wondering where to start. The rebuilds from summit, edelbrock etc run 36B/69 just wondering it if should buy those sizes or just make sure the difference hits 30-33.

 

[rhuarc31]

Well, arent' you opening a can of worms. The first thing to remember is that the 30-33 separation can be a good guideline, BUT ONLY AT IDLE AND PART THROTTLE. You see with only 2 exceptions all Qjet primary metering rods are the same diameter at the tip, so at full throttle the jet size is what controls how much fuel (and of course the secondary rods). So for a carb that's dialed in across the board you really need to jet for full throttle then pick a metering rod to match. As for a jet recommendation, I'd keep what you've got if you're 454 is stock, it should be pretty close. If you're going with headers and a free flowing exhaust you might step up to your 73's. There's a pretty good article on qjet tuning here http://www.florida4x4.com/tech/quadrajet/qtune.pdf
it also has some listing of what came stock in different motors that may help you find a starting point.

 

[77crewcab]

Thanks thats a great article that really explains a lot. But it didn't have the factory set up for a 77 454 truck. Any body know what that would be? The article is based on starting from stock specs for adjustment so I need to try and find the stock setting.

 

[77crewcab]

ttt

 

[Bad Karma]

I have a '77 C-15 Suburban, 454 with an Edelbrock 1902 Quadrajet on it. I use the Sub to tow my rockcrawler on an 18' trailer. The carb was set up perfectly for me right out of the box. 36B primary rods, 69 main jets, DR secondary rods, runs great! Been running this carb for almost 5 years now.

 

[77crewcab]

Thanks for the reply. I have already decided to try that setup and ordered the 36B and a jet kit from 65-72. My DH rods are actually a little richer than the DR so should be good there.

 

[Bad Karma]

Where did you order your rods and jet kit from? I noticed some wear on my primary rods during my last rebuild and want to replace them and the main jets next time.

 

[77crewcab]

http://www.carburetion.com/quadrajet.asp Now that I think about it I actually got the 37B rods cause they didn't have any 36Bs but plan to just start with 37B/70 just bumping it up one notch. The jets I ordered in a wide range to help with tuning but also cause my dad needed some for a carb he is working on so we split the cost on the jets. Summit also has the rods under edelbrock parts and they are about $3 cheaper but I don't think they have the 36B either.