Quadrajet Problem Solving > Dialing in your rebuilt Quadrajet carburetor

What rods/jets needed to dial this in?

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Cliff Ruggles:
I will say that I've ran my 17057274 on 5 different engines now and haven't touched the jetting. 

I did have to step up the idle system once when I installed my first 455 engine with a pretty "hefty" cam in it.  I've used the APT system to fine tune part throttle A/F for each engine, but the main jets, primary and secondary metering rods are still the same and have been for all 5 engines........Cliff

EspriTA350:

--- Quote from: Cliff Ruggles on April 16, 2020, 03:24:13 AM ---I will say that I've ran my 17057274 on 5 different engines now and haven't touched the jetting. 

I did have to step up the idle system once when I installed my first 455 engine with a pretty "hefty" cam in it.  I've used the APT system to fine tune part throttle A/F for each engine, but the main jets, primary and secondary metering rods are still the same and have been for all 5 engines........Cliff

--- End quote ---
Only idle circuit and APT adjustments for a 455 with a cam huh... that's great!!

Edit: missed the part where you said all jets and rods were the same for 5 different engines.. wow! Guess there's one less thing I have to worry about.

Cliff Ruggles:
Keep in mind that I don't have to re-jet or add fuel because all of my engines are high compression, tight quench, and very well chosen camshafts.  They also have excellent flowing heads on them. 

This actually improves VE and BSFC so there isn't any need to throw more fuel at them even though each one I've done has more power than the one before it.

Also consider that all N/A engines operate in similar parameters as far as A/F ratio requirements are concerned.

Of course IF you lower compression and start throwing in camshafts with really tight LSA you will need a LOT more fuel at idle, off idle and lower RPM's to make them happy.  It's been that way for the near 50 years I've been in this hobby and unlikely to change anytime soon.......Cliff

EspriTA350:

--- Quote from: Cliff Ruggles on April 20, 2020, 06:46:21 AM ---Keep in mind that I don't have to re-jet or add fuel because all of my engines are high compression, tight quench, and very well chosen camshafts.  They also have excellent flowing heads on them. 

This actually improves VE and BSFC so there isn't any need to throw more fuel at them even though each one I've done has more power than the one before it.

Also consider that all N/A engines operate in similar parameters as far as A/F ratio requirements are concerned.

Of course IF you lower compression and start throwing in camshafts with really tight LSA you will need a LOT more fuel at idle, off idle and lower RPM's to make them happy.  It's been that way for the near 50 years I've been in this hobby and unlikely to change anytime soon.......Cliff

--- End quote ---

Interesting. Well since I will be increasing compression a decent bit to 9:1 (stock is supposed to be just a lil below 8:1. Yow.) and the cam + heads were matched to each other for an all-round improvement everywhere, from what you say I expect it won't need much more fuel at all. I have not dialed in the quench though.

Cliff Ruggles:
Quench needs to be tight, especially in a Pontiac build with iron heads.  I would NOT build one with more than .040" quench distance for any reason........FWIW....

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