Rochester Quadrajet Carburetor Air Bleed Comparison and Testing

In the name of continued attempts to iron out the ideal fuel curve calibration on my non OEM Low Compression 1969 400 Buick Big Block in my parts chasing 1985 Suburban C20, I refine the Jet and Metering rod combination as well as I play with a larger Air Bleed from a different carburetor to see if it works better in this application. Eureka, It's a Home Run!

[@tombrown879]

Dallas. I remember drilling out and tapping the bleed holes on my carb in high school. then i could use holley style jets to screw in there. worked great. but i cannot remember the thread size to save my life. Also when i was a kid. i remember my uncle. that had a machine shop off of the Enis TX dragstrip had what looked like a small protractor and needle, that would measure the blade angle. then he would recreate that blade angle on the bench, to see how high out of the bore the needles were. then sometimes he would cut the fat part of the needle down more tward the narrow part of the needle, to tune in the part throttle mix. I have never seen one since. Great little tutorial. Thanks.

[@jodycalhoun6319]

Great vid. I like 400's of all makes and models.

[@tcapo514]

my 87 El Camino runs so good it doesn't need a engine check light I took the ball I took the light bulb out. NO PROBLEMS

[@raylaux8295]

Back in the 80's I rejetted in less than 30 min. Made my 800 cfm Q-jet externally adjustable.

[@pacman3908]

They were awesome carbs in there day but very quirky .known to wear out throtle shaft bushings. But wen they are tuned good will give a holley carbed car close race. Good video thanks

[@ruggyshorey60]

I just rebuilt my first quadrajet carb for replacing efi on my 89 dodge pickup I got the top all back on looked over on the bench to see that plastic piece that goes by the float 😆 but I got it after a wile. your videos were helpful thanks!

[@mr.roddersneighborhood2740]

Nice work! Glad I could help and hope you enjoyed the videos.

[@stevesadusky8634]

Thanks for the video Dallas! Brings back memories in my younger years rebuilding the quadrajet carburetors. Question; can you still get the rebuild kits at the auto parts store?

[@mr.roddersneighborhood2740]

Yes you can

[@PCMenten]

If you removed the EGR, you need to recurve the distributor. The distributor for EGR has much more part-throttle spark advance.

[@mr.roddersneighborhood2740]

Done long ago…

[@72chevelle156]

for WOT why didn't you change the secondary rods? you didn't even need to open the quad for that...

[@mr.roddersneighborhood2740]

Problem was driveability and over rich condition at part throttle. I leaned it out quite a bit and wanted to make sure there was not a lean condition apart knock.

[@72chevelle156]

@@mr.roddersneighborhood2740 My mistake . thanks for keeping the qjet alive...

[@Driven_Dragon]

What kind of trans and torque converter do you have? Thx

[@mr.roddersneighborhood2740]

Switch Pitch Turbo 400 with a dual stall converter.

[@richardmoerke9329]

Never ending. I didn’t see the part about the Circuit. ???

[@mr.roddersneighborhood2740]

The air bleed circuit? I’ll go watch it again?

[@joe-hp4nk]

Trying to improve a quadrajet is putting lipstick on a pig. You can't improve a fundamentally bad carburetor.

[@mr.roddersneighborhood2740]

Bad in whos book? They ended up on every single American manufacturers vehicles.

[@joe-hp4nk]

@@mr.roddersneighborhood2740 Because they were cheap.

[@moritzbramreiter7104]

@@joe-hp4nk yeah right, a really internally complex, highly adjustable and adaptive carburetor is cheap. Yeah those GM engineers, really threw it together cheap back in the spring of '64. It's short production run is also notable running from 64 to 90 only, feeding engines from 130 HP to 420+ HP. Total failure.

[@joe-hp4nk]

@@moritzbramreiter7104 Exactly, goes to show how cheap they were. Car manufactures use the cheapest parts they can, hence the aftermarket.

[@terrygonyon4490]

@@moritzbramreiter7104 They also came on Ford Mustangs with a 429.

[@racer44x]

You just made that carb even leaner especially because of the main air bleed being .030 bigger more air the leaner it will be plus the smaller jet and fatter metering rod

[@mr.roddersneighborhood2740]

It was rich at idle and part throttle, that is exactly what I was trying to correct and it worked great.