q jet questions

[68black_betty]

i got a mildly built 454 prolly around 400 hp at the fly, wanting to throw a quadrajet on there, does anyone know which qjet numbers are the best ones to look for, i know they made some 800 cfms would those work better than the 750 or would it make much of a difference

[Lee H]

A 750 Q-Jet will work very up to about 450 HP.
Posted via Mobile Device

[Bus Ted Knuckle]

any q-jet will work, as long as it is set up for its ORIGINAL application. Just stay away from the last ones. You probably want to get a 4MV though.

[oldgold70c10]

As far as ease of set-up, tuning, adjustment, reliability, go with a 76-77 M4MC. The castings are better. The float position is better. The chances of leaking bottom plugs is virtually nil. Less likely to have warped castings. Integral choke easily converts to electric for no-hassle operation. They are all large venturi castings and will flow up to 850cfm. They have an adjustable part throttle feature that can be easily modified so you can adjust with the engine running. I like Buick models because the small air bleeds make tuning easy, most Chevy M4M-series carbs will have large air bleeds which will make using larger jets mandatory,which makes it harder to set-up. I like the 76 and 77 models because they still have the slot head idle mixture screws, the screwy aneroid-adjusted part throttle was a 75 only feature (though not all 75's had it), and you want to stay away from it. Don't take it all from me, find a copy of Cliff Ruggles book, that's how I learned.

[ChevLoRay]

Shoot, why not try for one of the 850CFM Q-Jets from a Pontiac SD?


Seriously, the 750 will be just fine. If you can find an Edelbrock Q-Jet, they're just right.

[GRX]

Originally Posted by oldgold70c10

As far as ease of set-up, tuning, adjustment, reliability, go with a 76-77 M4MC. The castings are better. The float position is better. The chances of leaking bottom plugs is virtually nil. Less likely to have warped castings. Integral choke easily converts to electric for no-hassle operation. They are all large venturi castings and will flow up to 850cfm. They have an adjustable part throttle feature that can be easily modified so you can adjust with the engine running. I like Buick models because the small air bleeds make tuning easy, most Chevy M4M-series carbs will have large air bleeds which will make using larger jets mandatory,which makes it harder to set-up. I like the 76 and 77 models because they still have the slot head idle mixture screws, the screwy aneroid-adjusted part throttle was a 75 only feature (though not all 75's had it), and you want to stay away from it. Don't take it all from me, find a copy of Cliff Ruggles book, that's how I learned.

^^ Great post all around. Q-jets can be made to perform extremely well. But working with them takes a bit of know-how. Cliff Ruggle's book is a must. Upwards of 1,100cfm is possible. A regular on another forum I contribute to just passed 750hp with his Pontiac 428 & Q-jet carb.

[slikside]

Originally Posted by GRX

^^ Great post all around. Q-jets can be made to perform extremely well. But working with them takes a bit of know-how. Cliff Ruggle's book is a must. Upwards of 1,100cfm is possible. A regular on another forum I contribute to just passed 750hp with his Pontiac 428 & Q-jet carb.

X3...I don't have anywhere near that HP (strictly stock) but Cliff is the man when it comes to Q-jets. I used his book, parts, and throttle shaft bushing service. Took my time and it ran like a champ as soon as I bolted it back on.

[ubtripn]

Not to steal the thread I just have a relatd question - can one buy a new Q-Jet? If so, is it any good?

[oldgold70c10]

If you are wanting an older style 4MV carb, look for an Edelbrock 1901 or 1902. M4MV/C is an Edelbrock 1903 or 1904, or 1906. Edelbrock no longer makes these, but if you find one used, or rebuilt it will be much newer than an original one. All Edelbrock Q-jet parts are interchangeable with original Q-jets. Edelbrock models 1903, 1904, & 1906 all use the 1978 and later style base plate that does not have slotted head mixture screws.