What is the best 4bbl carb for oddfire 225 V6?

[sweet66monza]

I am getting ready to fire up the fresh motor and have an aluminum 4 barrel intake installed, but no carb yet. What do you guys recommend for a good carb?

 

[Incommando]

390 CFM Vacuum Secondary
Holley Performance Products 390 CFM Four Barrel Street Carburetor 0-8007

or you might try a 470 Truck Avenger
Holley Performance Products 470 CFM Four Barrel Carburetor 0-90470
but that may need some serious tuning to get to work on a 225. They are pretty popular for 360's even...

 

[derf]

For a V6 like that I'd put serious thought into bolting up an adapter and running a 2bbl Motorcraft 2100/2150. Most 4bbl carbs are too big for an engine that size.

 

[jswatson0917]

 

[Old Dog]

I'm with derf also.

 

[tarry99]

390 CFM Vacuum Secondary
Holley Performance Products 390 CFM Four Barrel Street Carburetor*0-8007

or you might try a 470 Truck Avenger
Holley Performance Products 470 CFM Four Barrel Carburetor*0-90470
but that may need some serious tuning to get to work on a 225. They are pretty popular for 360's even...

I've got a Holley 390 CFM 4 barrel on mine with the Offy manifold and it runs perfect. In fact that 390 CFM carb was built for the V-6 engines back in the day..........The Holley is one of the easiest carbs to work on and very easy to Jet..............
Put a good aftermarket aluminum manifold on it........ton's of torque!
Buy it you'll love it..............

 

[Incommando]

IIRC the 2100 is from 300 to 450 CFMs depending on the original app so the 390 is isn't out of the ballpark. But if you are off-roading the 2100 is one of the best ever while Holleys in general have a rep for needing some work to excel off-road.

 

[tarry99]

IIRC the 2100 is from 300 to 450 CFMs depending on the original app so the 390 is isn't out of the ballpark. But if you are off-roading the 2100 is one of the best ever while Holleys in general have a rep for needing some work to excel off-road.

Incom:

No doubt the MC 2100 is a good little 2 barrel Carb. with a good reputation.
On the other hand the little Holly 390 has done me a great job both at sea level & altitude. If there are some mods that your aware of please pass them on I would be interested. Also, If I already had a 4 barrel manifold personally I would probably stay away from the adapter. Just my Opinion.

 

[BajaEdition]

I have never had any luck with a 4 barrel on a 225 built for a jeep
maybe the marine version but the tourque is to low on the Dauntless Buick 225 V6 in the jeep version
put a big 2 barrel on it. the motorcraft one is great

 

[Incommando]

Incom:

No doubt the MC 2100 is a good little 2 barrel Carb. with a good reputation.
On the other hand the little Holly 390 has done me a great job both at sea level & altitude. If there are some mods that your aware of please pass them on I would be interested. Also, If I already had a 4 barrel manifold personally I would probably stay away from the adapter. Just my Opinion.

I wasn't trashing on the Holley just noting that it can be made better, especially for serious off-camber stuff and climbing/descending angles. I swapped an intake and a 390 onto a 231-powered Skyhawk and it really helped. As you know the 231 is the direct descendant of the 225. But that is a completely different app and intended usage.

There are dozens of sites with tips for improving a Holley for off-road. The 390 usually isn't mentioned but the same principles should apply. Just one example:

Offroad tricks for Holley 4 barrel carbs | ClassicBroncos.com Tech Articles

The mod most often mentioned is the vent tube.

My favorite 4-v ever for off-road is a Q-jet. They don't call them hillbilly fuel injection for nothing. The downside is that you would need an adapter for your intake and I doubt there is one small enough for for a 225.

 

[tarry99]

I wasn't trashing on the Holley just noting that it can be made better, especially for serious off-camber stuff and climbing/descending angles. I swapped an intake and a 390 onto a 231-powered Skyhawk and it really helped. As you know the 231 is the direct descendant of the 225. But that is a completely different app and intended usage.

There are dozens of sites with tips for improving a Holley for off-road. The 390 usually isn't mentioned but the same principles should apply. Just one example:

Offroad tricks for Holley 4 barrel carbs | ClassicBroncos.com Tech Articles

The mod most often mentioned is the vent tube.

Incom,

Hey, no problem.....the beauty of these forums is Opinions.

I can only testify to my own experience with the Holley 390 cfm. If it had been or was an issue it would have long ago found its way into the garbage can.

And thanks for the reference material. I did do that crossover vent Mod years back.

Ultimately , use,acceptance & performance of any part usually boils down to simply , just who's turning the wrenches.

 

[Tinman22]

I have used all of the above on different motors of different sizes with good results but mathematically speaking a 225 ci motor at 4500 rpm at 83% volumetric eff. (typical of oem combos) it would require 243 cfm at even 100% it still only requires 292 cfm. If it were cammed to run 7500 you would be at 405 at 83% and 488 at 100% v.e.

 

[tarry99]

I have used all of the above on different motors of different sizes with good results but mathematically speaking a 225 ci motor at 4500 rpm at 83% volumetric eff. (typical of oem combos) it would require 243 cfm at even 100% it still only requires 292 cfm. If it were cammed to run 7500 you would be at 405 at 83% and 488 at 100% v.e.

Tinman good points,

We know that in order to calculate true Volumetric Efficiency which is the actual amount of air the engine ingests compared to the theoretical maximum trapped per cycle one must first know what the Mass air flow volume is for any given cylinder.

Knowing at a minimum the swept volume , flow numbers on the cylinder heads, manifold,carburetor,exhaust system and air density would also be needed to even closely make a theoretical calculation at Wide open throttle.

In regards to the carburetors mentioned above the only known is the published Flow numbers of each carburetor at "Wide open throttle" and since none of these would normally see "WOT" for any length of time the comparisons given may be of no consequence.

 

[mtnwhlr]

Tinman22 and tarry99 you two blow me away with your knowledge

 

[sweet66monza]

Lots of great info here!

Honestly im not a big fan of holleys, never been able to get em to work for me and dont like the design. Dad wants me to go with a spreadbore 500-650 cfm edelbrock, but from all your info that sounds like way too big

 

[tarry99]

Lots of great info here!

Honestly im not a big fan of holleys, never been able to get em to work for me and dont like the design. Dad wants me to go with a spreadbore 500-650 cfm edelbrock, but from all your info that sounds like way too big

Monza,

Nothing truly is going to be perfect,and we all know there are plenty of choices out there. That 500-650 CFM is probably a larger than needed carb for that old 225 Odd-Fire in it's stock form.
But having said that your going to have to work on something to get it to your own personal liking so pick something you like and go to work.

 

[Incommando]

The dirty little secret of a vacuum secondary carb is that it is rated by maximum air flow at WOT. However, the engine will only draw the CFM that it needs when opening the secondaries. The problem is that on most of these carbs the stock settings for the jetting/needles/whatever allows a higher fuel flow in the larger CFM carbs than a small engine can handle and they generally have a more aggressive tune via accelerator cam profiles and springs to allow the secondaries to open sooner and to squirt more fuel as well as flow more air. On a highly tunable carb like a Holley you can usually customize the carb to meet your engines fuel flow needs. Ever notice that GM used a 750 CFM Q-jet on basically every application? 307? 750 cfm. 403? 750 CFM. 455? 750 CFM. Some apps had an 800 CFM rating but for the most part most everything that had a 4v q-jet carb used a 750 CFM version for a couple of decades. Although a Q-jet has mechanical secondaries they are technically controlled via air flow, not throttle postion, and act like vacuum secondaries. They "custom tailor" themselves to the air flow needs of the engine in the same manner as the other vacuum secondaries.

By starting with a smaller max air flow CFM rated carb you are probably getting closer to the right "out of the box tune" for a smaller engine. But the main point is that as long as you can restrict fuel flow on both the primary circuit and the secondaries to a usable amount the max air flow CFM rating really is not very important on a tunable vacuum secondary carb. As the 390 has been used on tons of V6's succesfully it would seem that the stock tune of the primary jets is close to on the money for that app and that even if your engine will not draw 390 CFM at WOT it is not an issue as 390 CFM is not being forced into the cylinder, only the required CFM is being drawn in.

 

[tarry99]

The dirty little secret of a vacuum secondary carb is that it is rated by maximum air flow at WOT. However, the engine will only draw the CFM that it needs when opening the secondaries. The problem is that on most of these carbs the stock settings for the jetting/needles/whatever allows a higher fuel flow in the larger CFM carbs than a small engine can handle and they generally have a more aggressive tune via accelerator cam profiles and springs to allow the secondaries to open sooner and to squirt more fuel as well as flow more air. On a highly tunable carb like a Holley you can usually customize the carb to meet your engines fuel flow needs. Ever notice that GM used a 750 CFM Q-jet on basically every application? 307? 750 cfm. 403? 750 CFM. 455? 750 CFM. Some apps had an 800 CFM rating but for the most part most everything that had a 4v q-jet carb used a 750 CFM version for a couple of decades. Although a Q-jet has mechanical secondaries they are technically controlled via air flow, not throttle postion, and act like vacuum secondaries. They "custom tailor" themselves to the air flow needs of the engine in the same manner as the other vacuum secondaries.

By starting with a smaller max air flow CFM rated carb you are probably getting closer to the right "out of the box tune" for a smaller engine. But the main point is that as long as you can restrict fuel flow on both the primary circuit and the secondaries to a usable amount the max air flow CFM rating really is not very important on a tunable vacuum secondary carb. As the 390 has been used on tons of V6's succesfully it would seem that the stock tune of the primary jets is close to on the money for that app and that even if your engine will not draw 390 CFM at WOT it is not an issue as 390 CFM is not being forced into the cylinder, only the required CFM is being drawn in.

Incom: Right, Right, & Right ....all Good points and precisely the point I was making earlier regarding WOT...
First off both the 2 barrel 2100 & the 4 barrel 4160 have primaries that are if not the same sized are very close to each other at I believe 1.562" each?
So no matter how you get there 2 barrel versus 4 your only getting what the engine requires via the CFM ingested air flow. DONE!
And If you don't mind playing with the Carb I still like the ability to custom tune the 4160 with all the aftermarket tuning parts available from Holley Performance. Just my Opinion!