quadrajet jet suggestions?

[mobileaudio25]

I have a 355 sbc with dart shp heads, performer rpm manifold and a qjet carb. I recently went to dyno it and at 6000 rpm the car was being starved 24% of the fuel needed for the motor at that rpm :shock: :? 😢 :x :| I did a little tuning, but it was still 15-20% shy. How many jet sizes up do you think that i need to go?

 

[DoubleV]

Just install some richer secondary rods. Are you sure your fuel pump is providing enough fuel for you at that RPM?

 

[pontiacgp]

If your running out of fuel you can change the float for a brass one. It's smaller than the plastic float so the bowl can hold more fuel. You can also use a larger needle and seat to allow more fuel flow into the bowl

 

[mobileaudio25]

I'm pretty sure the fuel pump is able to keep up, I'm running an aftermarket holley fuel pump . I think 110 gph? One thing that I need to do is remove the stock carb filter though, shouldn't that help some? Someone said if I ran 2-3 sizes up on the jets and thinner secondary Rods that I should be in the ballpark ?

 

[Pontiac455]

Just install a holley 750 vac secondary carb. Check yer vac at idle in gear so u will know what pwr valve u need.

 

[mobileaudio25]

I don't want to change carbs because I just had this one rebuilt and I like the sound of them

 

[Pontiac455]

Yer gonna have to do some modifications to the Q-jet to get it set up. Dont get me wrong i love the Quads my self, did alot of modifying to em. Just alot more work than a holley. I would request grabin the book How To rebuild and modify Q jets by cliff ruggels... This will help tremendiousally.

 

[mobileaudio25]

I'm not going to be doing the work, my mechanic is and he is very carb savy. We're going to change a few of the internals and I'm just looking for ways to help and fix my problem

 

[pontiacgp]

if he is carb savy then I'd suggest to leave it with him. I tell my q-jet guru what I have in the engine and what I expect for it and he does his magic.

 

[techg8]

check your jets and rods as they are and calculate the metering area so that when you up the jet size you know what rods to put in with the new jets. This will maintain your lean cruise but richen your power mode.

what number Qjet do you have in there now and do you know if its stock calibrated currently?

See what you have in there now and bump it up a size or two.

Other than that youre be looking at recalibrating the air bleeds to make use of the larger jets without going too rich on the primary side.

I also agree that you can accomplish a lot with just more aggressive secondary jets. If WOT fuel is the only concern, go with richer secondary rods until you have to change the primaries.

my two cents