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hey just got a WB tonner and it has a 253 with a vacume secondry carb on it ...... i think it is standard ..... anyways the secondry's dont work i have had the filter cover of and tried to see what i could see but all i could see confused me ........
there is vacume to the push me pull me pot thingamy :D
i think the quadrant may be in thi wrond position
my last few cars have either been 80's bimmers or 60's & 70's mini's b4 that i had a torrie with a standard 186 in it so i got no idea about this s*** ..... can help ya with su problems :D bastard things they are ........
anyways thanks for ya help
MJ
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It should be the standard Rochester quadrajet M4MC.
I think it is working but if you are looking down the carb and pull the throttle wide open the top plate over the secondaries will not open. and if the motor is running and you open the throttle wide open the flap will only partly open then close, but when driving on the road she will open, she is all about vacuum you know.
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move the secondarys by hand to make sure they are not mechanically challenged,free them up with WD40 or CRC
AND see if they work then..ps 4 barrel on a 253?hope its a small one.alot of fuel for a small V8(450 CFM IS GOOD)any bigger it would wanna have some work on the engine to use the fuel.just my opinion others may have differing ideas,i've just found alot of these engines are overfueled all the time.
Jim in Adelaide...DONT LISTEN TO BULLS@#T LONGER THAN YOU HAVE TOO! |
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Didn't the Blue 253 use the Q-jet? Have vague memory of one............
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quote:
Originally posted by Premier 350
Didn't the Blue 253 use the Q-jet? Have vague memory of one............
Yes, that's right, the blue 253 in WB, VC & VH came standard with the 4 barrel quaddy, and HEI too. Cheers, Mick _______________________________________________________________ Judge a successful man not on how he treats his peers, but on how he treats those less fortunate. |
Cheers,
Mick
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Judge a successful man not on how he treats his peers, but on how he treats those less fortunate. |
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Hi All,arent they a smaller one thou,or the same as a 308 roch.?My brother had a holley on his 253,a 750cfm torana hatchback and all you could smell was fuel,fuel,fuel.I told him to go to a rochester but he just sold the car complaining about MPG.
SHOULD A KEPT IT.
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Strictly speaking, a Rochester Q-Jet is not a vacuum secondary type carburettor, but it is similar. The secondary flap is referred to as an 'air valve'.
The beauty of this type of 4-barrel is that the carby is never 'too big'. The engine only get as much air as it can 'suck' in. So putting a 'huge' Q-Jet on a 'little' 253 V8 will still work well. They are the best carby for a street driven V8, much more reliable & drivable than a traditional vac secondary or a double pumper style carby.
There are 2 separate secondary butterflies in a Q-Jet. There are the 2 flaps that you can see on the top rear of the carby & there are 2 more below them in the throttle body itself. The 2 in the throttle body will open as you press the accelerator pedal, but no secondary air enters the manifold until the upper air flaps open. These are 'sucked' open against preset spring pressure & the force of a vacuum diaphragm. The rate that the vacuum diaphragm relaxes & the tension of the spring (which is adjustable) governs the opening rate of the secondaries.
If the spring is set too stiff, the car will lack top end power because the secondaries aren't opening as required. If the spring is set too soft, the air flaps will open too quickly & the car will bog down (huge flat spot). If the vacuum diaphragm is not working (or missing !!) the same will happen, the flaps open too quickly & the car will bog down.
It's best to think of a carby as a controller of the air/fuel mixture not just that it can 'over fuel' an engine.
Any experienced carby guy worth his money can tune these with their eyes closed.
Dr Terry
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I think he's talking about a holley.
Jim in Adelaide...DONT LISTEN TO BULLS@#T LONGER THAN YOU HAVE TOO! |
Jim in Adelaide.. |
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