Will this work for me?

[krue]

Friend of mine gave me an Edelbrock 1407 carb he had on a shelf. Shows to be a 750 cfm carb? Will that be ok on my stock 350? How hard is it to rebuild and tune an Edelbrock?

[jsbgump]

It will most likely be too much carb. The 600 works great on a stock sbc

[Southedisto]

I think its too much also.

[Longhorn Man]

What's the Quadra jet rated at.... 850?

[krue]

Originally Posted by Longhorn Man

What's the Quadra jet rated at.... 850?

That's what I was thinking.

[Longhorn Man]

The AFB carb, while not as complicated as the Quadrajet, has real small primarys,a nd big secondaries... so normal cruising is on a small set of breathers, then when you open it up, it has huge lungs.
Will it be too big?
Maybe.
Will you know it from the drivers seat?
Probably not.

[krue]

It's worth rebuilding, especially for what it cost me. If nothing else I'll be motivated to build a motor to match it.

[clay68c10]

I have the 1411 and it is easy to recalibrate. I've had holleys before and the edelbrock is way easier to tune. As far as the size, I'm with longhorn man... 750 cfm at wide open may be too much, but it's free.

[John Fabris]

I am under the impression that an engine will only take in as much air as it is build for, so an engine build for a 600cfm, will only use that much and if you run a 750cfm carb, that carb is able to provide up to 750cfm, but the engine will only use 600.

[Joeys Toy]

Old mechanic once told me that it is better to over carberate than to starve the engine. Had a 780 spread bore double pumper on a stock 350. His advice was to put smaller jets in the primary and enjoy the secondary. Loved that car till I totaled it. Much younger and dumber then!!!

[MDC]

Seems like what John and Joey are saying sounds familiar, but it's been a long time since I've messed with carbs. I have one I need to build and swap too.

[bskylerj]

Although it is better to have more fuel than not enough the 750 is to big in it's stock form These are easy carbs to rebuild but you should take the jets down a few, both the primary and secondary ones. You should also adjust the clip[ on the needle to help not dumo as much fuel. You do not want to dump to much fuel in and have it wash out your cylinders. Just my 2 cents.

[davidh]

Originally Posted by bskylerj

Although it is better to have more fuel than not enough the 750 is to big in it's stock form These are easy carbs to rebuild but you should take the jets down a few, both the primary and secondary ones. You should also adjust the clip[ on the needle to help not dumo as much fuel. You do not want to dump to much fuel in and have it wash out your cylinders. Just my 2 cents.

I agree.I would have this carb jetted down. I had a truck I took in trade a few months back. It had the big eddy 750 on it and was almost new. When driving it from a stop light there was some major hesitation from being too much carb for stock 350 via performer intake. A buddy some years back had his oversized holley rejetted and it ran much better. Just need to find someone who knows what they are doing.

[krue]

Thanks guys.

[68Stepbed]

Speaking from experience, the best carbs on a stock 350: 500 edelbrock or 500 2bbl Holley. Unless your turning 8K, a 750 is useless on a 350. Don't mean to burst any bubbles, but that is from my experience.

[krue]

Originally Posted by 68Stepbed

Speaking from experience, the best carbs on a stock 350: 500 edelbrock or 500 2bbl Holley. Unless your turning 8K, a 750 is useless on a 350. Don't mean to burst any bubbles, but that is from my experience.

I'm curious why so small? The quadrajet I'm currently running is at least a 750 and the only reason I'm looking at the edelbrock is it was free and it's WAY easier to tune.

[68Stepbed]

Originally Posted by krue

I'm curious why so small? The quadrajet I'm currently running is at least a 750 and the only reason I'm looking at the edelbrock is it was free and it's WAY easier to tune.

The cfm rating on a carb is how much air it can flow at max. velocity. In other words, if you use this equation: cid x max rpm / 3456 = cfm, that is all the air the engine can pull at WOT at full rpm. In a case of a stock 350, that equation looks like this: 350 X 5000 / 3456 = 506.3657. The amount of air pulled into the engine also has to match the amount of fuel to atomize together properly. Aftermarket carbs are simple air/fuel mixers. They have a determined air flow rating(cfm) and calibrated approx. to the amount of fuel needed for that cfm. You cannot change the airflow rating on aftermaket carbs, only the amount of fuel. I don't know much about q-jets, but I know they have some kind of air(cfm) adjustability. Q-jets are very complicated carbs. That's why they work so well when calibrated right and run so bad when wrong.

It also depends on usage of the vehicle. A street vehicle needs to hold steady rpm's for extended periods as well as have good throttle response for stop and go situations. The smaller carb has better fuel atomization because there is less fuel an air to mix. The bigger carb sends so much more air and fuel that it has a harder time to mix before reaching the combustion chamber.

There are two factors that determine how the fuel atomizes: time and space(or area). Time being the length of the stroke. The area being the size of the bore. The two factors that determine cid. A longer stroke allows more time and a larger bore allows more area

The amount of time and area is also a factor in the intake manifold itself. Aftermarket intakes have longer(time) and larger(area) runners. That why carb spacers help. They give the fuel more time and area to atomize.

The camshaft and heads also play a roles in this but I won't get into that now. I hope this didn't confuse you more than help. I've learned that bigger isn't always better and I try to help people with what I've learned.

And sorry for the long post.

[rkarr]

Originally Posted by 68Stepbed

The cfm rating on a carb is how much air it can flow at max. velocity. In other words, if you use this equation: cid x max rpm / 3456 = cfm, that is all the air the engine can pull at WOT at full rpm. In a case of a stock 350, that equation looks like this: 350 X 5000 / 3456 = 506.3657. The amount of air pulled into the engine also has to match the amount of fuel to atomize together properly. Aftermarket carbs are simple air/fuel mixers. They have a determined air flow rating(cfm) and calibrated approx. to the amount of fuel needed for that cfm. You cannot change the airflow rating on aftermaket carbs, only the amount of fuel. I don't know much about q-jets, but I know they have some kind of air(cfm) adjustability. Q-jets are very complicated carbs. That's why they work so well when calibrated right and run so bad when wrong.

It also depends on usage of the vehicle. A street vehicle needs to hold steady rpm's for extended periods as well as have good throttle response for stop and go situations. The smaller carb has better fuel atomization because there is less fuel an air to mix. The bigger carb sends so much more air and fuel that it has a harder time to mix before reaching the combustion chamber.

There are two factors that determine how the fuel atomizes: time and space(or area). Time being the length of the stroke. The area being the size of the bore. The two factors that determine cid. A longer stroke allows more time and a larger bore allows more area

The amount of time and area is also a factor in the intake manifold itself. Aftermarket intakes have longer(time) and larger(area) runners. That why carb spacers help. They give the fuel more time and area to atomize.

The camshaft and heads also play a roles in this but I won't get into that now. I hope this didn't confuse you more than help. I've learned that bigger isn't always better and I try to help people with what I've learned.

And sorry for the long post.

I have to agree... With a bunch of the posts... Technically, 68Stepbed is correct.. however, if you are strictly streeting this thing, I'd have to say that the free carb is too big... The fuel will not properly atomize without proper velocity.. Your mileage will suffer, Your throttle response will suffer..
Just my .02
Hope it helps.

[Longhorn Man]

While formulas will always point to a 500 or so CFM carb, I have yet to see a dyno session where a 350 didn't respond better with a 750 holley, edelbrock, or what ever kind of carb you wanna talk about.
Throttle responce may suffer
MPG may suffer.

[68Stepbed]

Originally Posted by Longhorn Man

While formulas will always point to a 500 or so CFM carb, I have yet to see a dyno session where a 350 didn't respond better with a 750 holley, edelbrock, or what ever kind of carb you wanna talk about.
Throttle responce may suffer
MPG may suffer.

Dyno sessions always work well with bigger carbs because there is no load. when you put that combo in the vehicle with a load, everything changes. The engine all of a sudden can't handle the extra air/fuel.

If anyone doesn't believe me about the 500 Holley 2-bbl, go to a short oval track and see what the superstock late model winners are running. There were a couple of teams here running 600 DP's. They couldn't get good hole-shots out of the turns. They started using the 500's. Now they're in the top three every race.

[72MARIO]

[QUOTE]Speaking from experience, the best carbs on a stock 350: 500 edelbrock or 500 2bbl Holley[QUOTE]

I will also agree with you a 600 is plenty for a motor that does not see past 6000 RPM.

I got a 650 so when the stroker gets built I dont have to spend another $575 +tax on a new carb. Smaller jets and away I went.

The 750 will be plenty you will need to jet it down depending on your cam/motor combo.

[72MARIO]

While formulas will always point to a 500 or so CFM carb, I have yet to see a dyno session where a 350 didn't respond better with a 750 holley,

What RPM range did they actully see a improvement using a bigger carb ?

[thejoker]

Great info 68stepbed. Thanks!


JKR

[crazy longhorn]

The carb can be made to work, but I have to agree with the rest of the crowd......milage will suffer, as well as throttle response. Dont forget to add an insulator gasket, or better yet a 4 hole PLASTIC , or wood insulator. The edelbrock carbs dont run right without the insulator......also , no more than about 5 1/2 psi on the fuel pressure. best of luck...... L

[krue]

Thanks for the input, I'll just hang on to it until I find a motor for it.