Quadrajet 4MV too small?

[C20-67_N_MO]

I have this 7029202 DH 1350
which I searched for and came up with this carb was used on a 350/255 & 350/300hp 1968-1969 or 1970 engines. The 1350 would be 135 days into what I am guessing is 1970 which is odd considering what the other specs are showing for this carburator.

Given that my Suburban has an Olds 455ci engine would you not think this would be a bit small and choke the CFM rating down on this big air pump?

[Willys47]

I would look at the jetting for it and make sure the secondarys will open fully.I think most qj are about 750 cfm.

[Lee H]

This carb is from a 69 vette 350 CI 300 HP with automatic. This carb came with rather small jets from the factory, 67 main jets and 42 rods. Most Hipo combos used low 70s jets. A quick search of my records indicate the 455s use 71/72 jets with 43/45 rods. A properly set up Q-Jet will fed that beast of yours with no problems at all. Just make sure you get an accelerator pump that is ethanol safe or you'll get that dreaded of idle stumble after just a few miles.

[C20-67_N_MO]

Thanks for your input guys.

I need to get a choke setup on this carb.

It's rather difficult to start w/o it.

Has an Edelbrock Torker II intake, and a blocked off EGR valve plate. Can I somehow find an exhaust coil choke that will work on this carb or should I be looking at my local salvage yards?

[Lee H]

If you can not find the old parts you could go electric. Edelbrock part number 1932 is a good choice.

[capev86]

a 350cid will not use more than 600cfm without forced induction, so a 750 q-jet should be fine for that 455. there was an 800cfm q-jet available in the early days that found its way onto the muscle cars. you could always have your carb bored out if you have a super high output engine and spend a lot of time at max rpm.

i ditched the original 2bbl on the 307 in my 72 burb c20 in favor of an edelbrock performer intake (idle-5500rpm) topped with an 80's q-jet. turns out i picked up one with a temp controlled accelerator pump. the temp fix was to turn it back so it runs right when fully warmed up. between that and no choke t-stat hooked up it takes a bit to get it started but it is not my daily driver and i will have the correct type of carb on there eventually.

the carb had been rebuilt recently and was on a 305 so i figured the jets were about the right size for that 307. i covered the whole setup with a dual snorkel air cleaner base from an early 70's chevy car with the big top of my dad's old 84 burb c10 350/700r with the towing package. it takes a big 14x5in air filter and will look awesome once i get it painted up in gm black. i like when i can use factory parts to hop-up a vehicle and get a custom combination that is completely bolt in and looks like it came that way.

[IMG][/IMG]

[C20-67_N_MO]

Originally Posted by Lee H

If you can not find the old parts you could go electric. Edelbrock part number 1932 is a good choice.

Yeah I would rather keep it simple and go this route; as I was hoping there was one that fit for this old dog. Thanks appreciate the assistance, but this kit is for the converstion from hot air to electric. Guess I will need to do some more googling.

[quote=capev86;4358136]a 350cid will not use more than 600cfm without forced induction, so a 750 q-jet should be fine for that 455. there was an 800cfm q-jet available in the early days that found its way onto the muscle cars. you could always have your carb bored out if you have a super high output engine and spend a lot of time at max rpm.

i ditched the original 2bbl on the 307 in my 72 burb c20 in favor of an edelbrock performer intake (idle-5500rpm) topped with an 80's q-jet. turns out i picked up one with a temp controlled accelerator pump. the temp fix was to turn it back so it runs right when fully warmed up. between that and no choke t-stat hooked up it takes a bit to get it started but it is not my daily driver and i will have the correct type of carb on there eventually.

the carb had been rebuilt recently and was on a 305 so i figured the jets were about the right size for that 307. i covered the whole setup with a dual snorkel air cleaner base from an early 70's chevy car with the big top of my dad's old 84 burb c10 350/700r with the towing package. it takes a big 14x5in air filter and will look awesome once i get it painted up in gm black. i like when i can use factory parts to hop-up a vehicle and get a custom combination that is completely bolt in and looks like it came that way.


How do I know for sure my Quadrajet is at least a 750cfm carburator?

Does the model number confirm that fact? As I could not find a reference to it at all; only the application it was on as stated by Lee H and my own research.

[capev86]

all factory GM Rochester Quadra-Jets were 750cfm except for the few 800's the built in the early days for some of the muscle cars.

[C20-67_N_MO]

Okay thank you.

Don't know much about these carbs.