General Category > Quadrajet Carb Talk and Tips
blow through quadrajet in a box questions....
A.G.V.chevyfreak:
Can also be that primary needles isn't lifting enough (or on the lean side for the boosted setup) It has pressure from both sides of the piston. And the pressure in the box is a tad more than in the manifold.
You can check what gm did on the Pontiac ta 301 turbo motors. The piston is boost referenced. With the later style jet it is easy to reroute a external passage and blocking the manifold side port,Will see if i have any pics of what was done) and with no spring the apt stops it from going fully down if adjusted so not running too lean at cruising.
I did the same thing to use a jet on 4-71 blower setup that i want to fit on a 250 inline six. Still something i want to build. ( its a case of too many ideas and not enough cars. )
Cliff Ruggles:
The power piston requires external boost reference with a check valve from the intake side (manifold vacuum) so it doesn't pressurize under boost.
I much prefer to set them up to run straight off the jets and not use a power piston or primary metering rods for blow-thru applications.
You will need several items to keep things happy with that much power potential. I high flow N/S assembly, correct jets, MAB's and small tipped secondary metering rods......Cliff
A.G.V.chevyfreak:
Found them. The port in first pic is normally down into manifold for vacuum, on this carb its external reference.
Frank400:
looks like a nice set-up. Any pics with the carb all boxed up ?
shnitzel:
Thank you very much fro all of your knowledge and advice! i thought forums were dead, not around here there not!
those pictures are excellent. and just to clarify, i plug the hole in the bottom of the carb, and i route the vacuum line out of the box and to manifold vacuum. right?
if im correct with this thinking, ill try that tomorrow night when we work on the car. and after i will get real carb #'s for you.
after we get it close, im sure well be ordering some parts from you cliff ;)
when we get it out and running decent ill try to get some pics for you. i dont use phones, or cameras... so i have to try a little harder than most ;)
shnitzel
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