Edelbrock 600 cfm or 650 cfm

[HyeBronco]

Hi everyone, Quick question I have a 68 Bronco with a Ford crate 302 motor that is running an Edelbrock 600 cfm carb. I just got a call from the tuning shop and they have told me the carb has been running lean and something on it is broken so I need to replace it. I am not a very mechanically inclined person so I was wondering if I should replace it with the 650 cfm Edelbrock instead of the 600 thats on there now. Thanks in advance for any of the upside and downside with switching.

 

[bronconut73]

600 is fine.
What is broken?
All the little pieces are available if you google around a bit.

 

[blubuckaroo]

If you're determined to replace it, get the correct size. A 500 CFM (1403) would be a better fit.

 

[DirtDonk]

Agreed. But what crate engine are you running? One of the more powerful ones? If so, maybe a larger carb is called for.
And it's not size alone that creates a lean condition. You can easily re-jet any of the carbs for a richer mixture to compensate.

Even if they're not the best off-road carbs for most, they're one of the most easily tuned and tweaked of all carbs. Jet and needle and spring changes can be done in literally seconds.
Of course, for real twiddling around with the mixture, one of their Track Packs (if they still call them that?) can get VERY EXPENSIVE very quickly. Better to have an idea of where you need to go first. Or sell off the remaining stuff to recoup your expenses.

We should probably have a "Community Track-Pack" around here for Classic members to fiddle with anyway. A few bucks each and one kit could handle a lot of carbs probably.

Good luck either way. I ran the 500 and the 625 (Carter rating before Edelbrock) and they both ran well. The 500 was better, but the larger one worked perfectly fine.

Paul

 

[ugly74]

What on it is broken? Call me a cynic, but im wondering if the mechanic needs a new carb, so talked you into buying a new one, so that he can have yours (and it needs a $10 part or something).

 

[HyeBronco]

600 is fine.
What is broken?
All the little pieces are available if you google around a bit.

Hi not sure whats broken, something on it isn't closing all the way. Thanks for your help.

 

[broncnaz]

Most likely you dont need a new carb. If something is not closing correctly on a edelbrock then its probably just a linkage adjustment that is needed. You just bend the linkage until whatever is open is closed. If its lean for other reasons then it may just need to be rejetted. Or theres a vacuum leak and thats why its running lean. Most 600 cfm carbs are setup to run on a 350 ci engine even then they tend to be a little rich so it shouldnt just be lean on a 302.
If you do get a new carb I would also say a 500 cfm would be better than either the 600 or 650.
In the end while you may not be mechanically inclined it kinda sounds like your tuner is not to mechanically inclined as well. I would take some time to learn about your carb they are not that hard to figure out and there are plenty of people on this site that can help you figure it all out.

 

[BRONCROB]

What he said^^^^^^^

 

[HyeBronco]

Thanks everyone for your comments. Greatly appreciate it!!

 

[jckkys]

The Edelbrock 650cfm is an AVS carb. They have slightly larger secondary venturi and throttle bore dimensions. Since a 302 is unlikely to use all the secondaries of either carb you would see no difference. The 500cfm primary boosters could make your carb a 500cfm and actually improve things.

 

[TwoDalesDad]

A 450. Would be more than enough for a302. If you are running a lean condition ,before you do damage to your crate motor take a plug reading to determine just how lean you are. At around 2000-2300 RPM kill your engine...well turn it off...pull your plugs....with a magnifiying glass....get a great look at all four corners at least.....milk chocolate is the shade you want.....WHITE WILL BE EXPENSIVE.....BLACK WILL BE POOR MPG....CHOCOLATE....LITE BROWN...IS WHERE YOUR ENGINE EILL BE HAPPY. YOU MAY ALSO NEED TO CHANGE YOUR HEAT -RANGE..OF YOUR SPARK PLUGS......PAY ATTENTION AS MISTAKES ARE COSTLY...

 

[broncodriver99]

I really doubt the carb needs replaced. Pretty much the only time you replace a carb is if the throttle shafts are worn out or you want something different.

 

[nathan.hall1]

I run a 500 on my 351 and it runs great plenty of power that little sucker is a4x4 hotrod

 

[joshnjulie1]

I have the 1406.
Anyone have a 500cfm laying around in great shape they are not using. I cannto solve my carb problem and would like to bury this 1406 in the ground and give it a proper burial.

I will trade it outright.

 

[blubuckaroo]

I've always felt safer running a bit rich. I guess that's why I always smell like exhaust. %)

 

[jckkys]

As I pointed out the primary booster venturis are the difference between a 600 and 500cfm AFB-Performer. There is a 500cfm AFB on Ebay now for $20 that could be a source for these parts. There is also a vender-manufacturer selling AFB 600 to 500 restrictors, also on Ebay. He's asking $65 for 4 of them. I don't know why 4, since each AFB only has 2 primary venturis, but they are machined from aluminum and look to be of good quality. The primary metering jet and rod would also need to be swapped for those used on the 1403-1404 models.

 

[broncnaz]

As I pointed out the primary booster venturis are the difference between a 600 and 500cfm AFB-Performer. There is a 500cfm AFB on Ebay now for $20 that could be a source for these parts. There is also a vender-manufacturer selling AFB 600 to 500 restrictors, also on Ebay. He's asking $65 for 4 of them. I don't know why 4, since each AFB only has 2 primary venturis, but they are machined from aluminum and look to be of good quality. The primary metering jet and rod would also need to be swapped for those used on the 1403-1404 models.

Dude take into account the OP's experiance with carbs you cant just say buy this and swap this on and it will work when the OP has little knowledge of what your talking about. Let him get what he has working first then he can worry about other mods.
While you and I can play with this stuff with little issue not everyone is at that level. Keep the suggestions simple for those that are not in the know. Its good info but really doesnt help the OP get his bronco running correctly. Not trying to demean you or the OP but you have to consider the facts in the post.

 

[jckkys]

In my opinion the "tuning shop" is taking advantage of the OP. My post provides info he can use to keep himself from being ripped off. A new Performer is $320 minimum, and we can all agree he doesn't need one. The "tuning shop" will want a lot more, plus labor. The info I shared could allow him impress these guys that he's not an easy mark. The info also helps those reading this thread who can do the work themselves. Carburetor knowledge is being lost, as we loose the generation who possessed it. Surprisingly few gear heads these days know that the only difference between a 500cfm and 600cfm AFB is the primary booster venturi. As a high school kid 16 yrs. old, I rebuilt my first Holley 4bbl. I made a few mistakes, but you have to start somewhere. Any business that calls itself a "tuning shop" can repair a new carb, unless they dropped it on the floor and broke an ear off.

 

[broncnaz]

The point is his tuning shop doesnt seem to be able to do much except tell him to buy a new carb. The PO himself said hes not well versed in this area. Not saying your info is bad just think its would be better to get him running correct first before doing mods that dont fix his main issue.