Rochester quadrajet

[LoneHawk]

Hi all. My quadrajet is set up in a way that the secondaries don't open until im way beyond full throttle. This just doesn't seem right. Can I get some feedback on this topic please?

 

[Hole Denn]

check your vac

 

[crew chief]

You can adjust the spring tension on the secondaries. This should be done in very small increments as it will bog down if it is softened too much. 1/8 of a turn at a time.
Do this by backing of the locking allen bolt while holding the screw, then loosen the screw for earlier or tighten for later actuation.

 

[Smitty]

You can adjust the spring tension on the secondaries. This should be done in very small increments as it will bog down if it is softened too much. 1/8 of a turn at a time.
Do this by backing of the locking allen bolt while holding the screw, then loosen the screw for earlier or tighten for later actuation.View attachment 247998View attachment 247997

yes.. that is a possible but it is at the END of a long list of things to try
don't do this first up, you have to check/fix the basics

first thing.. do your secondary throttle valves actually open? have seen carbs that they never open on and you will never got the air valves to work if they dont

then is the secondary airvalve shaft seized? does it allow free movement by the air valves? Distort the top cover by overtightening and hey... secondary air valves will not open
and
related.. do you have a working secondary air valve cam? the cam in the middle? is it jammed? they do ...

do you have a secondary pulloff that works as it should? if not, mostly likely jammed and the air valve will never open
does this have the correct vac signal so it allows the secondary air valves to open when they should

is either vac break (front or rear) holding the choke in the wrong place?

is the float height correct?
is the fuel pump up to supplying the carb? (test it.. no lower than 4psi please)
is the fuel inlet filter blocked? starving the carb

is the power piston stuck or jammed?
and is the APT adjustment correct for that carb?
are the primary needles straight and seated correctly ?

is there dirt/crud in the bottom of the fuel bowl?

is the check ball worn? (there is only ONE on a Quaddie)

also other simple stuff, is the cable actually opening all the bits it needs to? (don't larf, an incorrectly set cable may only give 70% performance)
no air leaks.. in the bottom throttle body gasket?
no air leaks in the throttle bottom cross shaft? (just rebuilt 2 Quaddies that had this problem, they were worn so rebushed the shaft)

is the secondary lockout adjustment correct?
is the secondary OPENING adjustment correct?
is the secondary CLOSING adjustment set correctly?

and NOW...we do the air valve spring adjustment outlined above


that help???



ps... in the middle of rebuilding 3 Quaddies and they are the tests I check/perform on all rebuilds

 

[LoneHawk]

You can adjust the spring tension on the secondaries. This should be done in very small increments as it will bog down if it is softened too much. 1/8 of a turn at a time.
Do this by backing of the locking allen bolt while holding the screw, then loosen the screw for earlier or tighten for later actuation.View attachment 247998View attachment 247997

Oh good I think that will sought out the hesitation thank you

 

[LoneHawk]

yes.. that is a possible but it is at the END of a long list of things to try
don't do this first up, you have to check/fix the basics

first thing.. do your secondary throttle valves actually open? have seen carbs that they never open on and you will never got the air valves to work if they dont

then is the secondary airvalve shaft seized? does it allow free movement by the air valves? Distort the top cover by overtightening and hey... secondary air valves will not open
and
related.. do you have a working secondary air valve cam? the cam in the middle? is it jammed? they do ...

do you have a secondary pulloff that works as it should? if not, mostly likely jammed and the air valve will never open
does this have the correct vac signal so it allows the secondary air valves to open when they should

is either vac break (front or rear) holding the choke in the wrong place?

is the float height correct?
is the fuel pump up to supplying the carb? (test it.. no lower than 4psi please)
is the fuel inlet filter blocked? starving the carb

is the power piston stuck or jammed?
and is the APT adjustment correct for that carb?
are the primary needles straight and seated correctly ?

is there dirt/crud in the bottom of the fuel bowl?

is the check ball worn? (there is only ONE on a Quaddie)

also other simple stuff, is the cable actually opening all the bits it needs to? (don't larf, an incorrectly set cable may only give 70% performance)
no air leaks.. in the bottom throttle body gasket?
no air leaks in the throttle bottle cross shaft? (just rebuilt 2 Quaddies that had this problem, rebushed the shaft)

is the secondary lockout adjustment correct?
is the secondary OPENING adjustment correct?
is the secondary CLOSING adjustment set correctly?

and NOW...we do the air valve spring adjustment outlined above


that help???



ps... in the middle of rebuilding 3 Quaddies and they are the tests I check/perform on all rebuilds

So they are not opening unless I engage the secondaries manually. All the functions seem to be functioning except the secondaries. The choke and lockout all good 4 example. This is a rebuilt carby

 

[crew chief]

The air valves at the top of the secondary ports will not move when actuating the accelerator by hand, only the secondary throttle blades will move. The secondary blades that will move are the ones pointed out in the pic, (the shiny ones) the ones i am manually opening are vacuum operated, this is what makes the quaddy a good choice in that it is kind of variable in size. Hope I have understood what you were asking, Smitty has given you a good list of things that really need to be sorted first though.

 

[LoneHawk]

Very helpful thank you