Quadrajet for 253

[ari666]

Is that suppose to be funny?

why would it be? primary and secondary metering are completely seperate from each other. locking that flap means the secondary rods dont lift, thus no extra fuel, no extra air. youre basically running a 230CFM twin barrel.

granted, its not gonna deliver extreme power, but if over carburation becomes a problem, its the easiest fix.

 

[Smitty]

Yes, it is vacuum operated, but the spring applies pressure to the secondary air flap (not the secondary throttle plate) and allows you to tune out the dreaded "bog" common to 253s running any carb rated too large for them. The secondary throttle plate will still open when called upon, but the amount of air available to it will be restricted....not starved as such.

part correct..
the spring setting on the secondary air valve flap on a Quaddie dictates at what point the air valve starts to open
and if set correctly, will deliver the amount of air (mixed with fuel as the secondary needles rise in line with the air valve)
so the engine gets exactly the right air/fuel mixture it needs

the Quaddie is not called ' a vac on demand' carb for nothing

 

[magnetvh]

Is there a visual difference with a 253 and a 308 quaddy. I have 2 in my shed and dont know if they are from a red or blue 253/308 or the year they were made.

 

[Aussie V8]

Is there a visual difference with a 253 and a 308 quaddy. I have 2 in my shed and dont know if they are from a red or blue 253/308 or the year they were made.

Only the part numbers. I don't think they indicate whether it's a 253 or a 308 carb though only the qjet model (170), the year made, emissions, the GM division (8 for Holden), and then manual or auto. There will be another number under that and that may be the 253 vs 308 id but I don't know, it looks like Smitty is up on all of this though.

 

[ari666]

there are about 10 billion different bodies. different chokes, different primary pumps, different vac ports.


and i have NFI which one is which

 

[vkberlina]

Lol another reason why injection is the way to go

Sorry but I couldnt help myself

 

[Smitty]

there are about 10 billion different bodies. different chokes, different primary pumps, different vac ports.


and i have NFI which one is which

its actually not that bad...

leaving aside the very early ones used here (which really were Chev ones)
all Quaddies from about 77 on (eg LX Torana HZ and VB on) really all used the
later 'high cfm' body (look for the lump down the venturi) and then ...
apart from some different vac connections in the throttle body, some different jets/needles
and that really it was only TWO lots - for 253 and 308 engines, they are all the same
(...EX FACTORY!)

its only when you start playing...coz you stuck a lumpy cam in with no vac or a shitty idle
that the amount of variations needed become large . But if you understand the 4 systems
used in a Quaddie, doing adjustments is a piece of cake !

mind you, it also helps that I have been playing with/fixing/modifying/repairing them for 35 years... lol

 

[Smitty]

Lol another reason why injection is the way to go

Sorry but I couldnt help myself

I like to fix and tune my engine's induction with a screwdriver...
sorry but I couldn't help myself

 

[vkberlina]

I like to fix and tune my engine's induction with a screwdriver...
sorry but I couldn't help myself

I like to hop in and turn the key and drive the thing

 

[Smitty]

I like to hop in and turn the key and drive the thing

I get in the race car...

turn on the power arm the battery
turn on both the fuel pumps
turn on the fan switches
turn on the ignition
power up the instruments (by turning the key a tad)
set power to the starter motor via a big red missile switch


and push the button