Carb gurus, can you please help?

[shane96ranger]

I'm looking for a carb for a friend for a GM Vortec 4.3 V6. The motor wasn't originally carb'd, but I got found a place that has carb'd intakes for them. Anyway, it has a Holley on it now that's a POS (see pic). We want to buy a brand new carb for it, but I am having difficulty finding what we need. The base holes are 3 3/4" X 2" from center to center. We need a 275-300 cfm according to an online calculator. Any advice on what I could use here?

I don't know squat about carbs, in fact I hate them. But fuel injection was going to be too difficult for this use. The motor is on a transmission dyno and having all of the sensors and such was going to be a big PITA.

Any help would rock!

 

[gwaii]

you sure that's a holley?

from the little bit i can see it almost looks more like a rochester.i'm assuming it's 2bbl.

 

[martin]

A carb from a jeep 4.2 would probably be close but I have no idea of the bolt pattern. You could always make an adapter if necessary.

 

[shane96ranger]

you sure that's a holley?

from the little bit i can see it almost looks more like a rochester.i'm assuming it's 2bbl.

It is a Holley. It's cast into the top of it. But it is supposedly a Rochester base, I think it's called a small base IIRC. And yes, it is a 2bbl.

 

[gwaii]

It is a Holley. It's cast into the top of it. But it is supposedly a Rochester base, I think it's called a small base IIRC. And yes, it is a 2bbl.

ok,i know the one.

there's better holleys out there,you get the one with the float bowl that bolts on like the 4bbls-basically they are just half a 4bbl and much more tuneable.i think i would be leaning toward one of those if i were shopping for a 2bbl,i don't remember the designation on them,though.

 

[ForOffRoadDriving]

i tried to dig up some info on the carb you have pictured, just to get an idea of what CFM it is, but all i was able to come up with was a carburetor repair kit (gaskets and stuff). i believe the model gwaii was thinking of is the 2300, its a 2bbl 350cfm

 

[gwaii]

i tried to dig up some info on the carb you have pictured, just to get an idea of what CFM it is, but all i was able to come up with was a carburetor repair kit (gaskets and stuff). i believe the model gwaii was thinking of is the 2300, its a 2bbl 350cfm

yup,that's the one.

if you've got to use a two barrel,that's the one i'd go with.

 

[shane96ranger]

i tried to dig up some info on the carb you have pictured, just to get an idea of what CFM it is, but all i was able to come up with was a carburetor repair kit (gaskets and stuff). i believe the model gwaii was thinking of is the 2300, its a 2bbl 350cfm

I was only able to turn up repair kits as well, which is why I asked here. I don't understand Holley's numbering system. It seems like they all have two different part numbers and some people use one number and some people use the other one. That looks like what i need though! Thank you so much. Is an extra 50cfm going to be too much carb for it?

 

[chvlfrk]

Imo>>

Put a Holley 600cfm vacuum secondaries carb on it, it will be fine. I've seen the same carbs on 4 & 6 bangers, just a good overall carb.

If you was closer, I'd loan ya one to see how he liked it............I've got 2 ofem in the garage.

 

[RatDog8o8]

I'd rather rebuild either a Holley or a Motorcraft carb any day, than to mess with a Rochester. Less parts, better tune-ability.

An 1850/4160 4V Holley is what I ran on my F-150 (400m) & my Bronco (302), and also on the '74 Datsun I used to have with the 302.

Might be a bit much for the Vortec.....I'd stick with the 2V 2300.

 

[ForOffRoadDriving]

I was only able to turn up repair kits as well, which is why I asked here. I don't understand Holley's numbering system. It seems like they all have two different part numbers and some people use one number and some people use the other one. That looks like what i need though! Thank you so much. Is an extra 50cfm going to be too much carb for it?

I believe the reason that we keep finding only carb kits and no info on the carb is because it was an original equipment carb on some, car somewhere, some time. holley's paper back books only cover their performance or aftermarket carbs, so i wasnt able to find the exact "R" number listed in their book, only numbers that were close to it but they were 650 and 750cfm. its a bummer because that will tell you the cfm, what the standard jet sizes and settings are, and so on.

 

[gwaii]

I believe the reason that we keep finding only carb kits and no info on the carb is because it was an original equipment carb on some, car somewhere, some time. holley's paper back books only cover their performance or aftermarket carbs, so i wasnt able to find the exact "R" number listed in their book, only numbers that were close to it but they were 650 and 750cfm. its a bummer because that will tell you the cfm, what the standard jet sizes and settings are, and so on.

this is exactly the case.the carb in the first post is an original-equipment unit,set up for a particular application.this is why i figured the 2300 would be a better choice-it's an aftermarket carb that can be tuned to your application.and,as ist's based on the most popular 4bbl ever made,parts and information are easy to come by.

 

[shane96ranger]

I believe the reason that we keep finding only carb kits and no info on the carb is because it was an original equipment carb on some, car somewhere, some time. holley's paper back books only cover their performance or aftermarket carbs, so i wasnt able to find the exact "R" number listed in their book, only numbers that were close to it but they were 650 and 750cfm. its a bummer because that will tell you the cfm, what the standard jet sizes and settings are, and so on.

this is exactly the case.the carb in the first post is an original-equipment unit,set up for a particular application.this is why i figured the 2300 would be a better choice-it's an aftermarket carb that can be tuned to your application.and,as ist's based on the most popular 4bbl ever made,parts and information are easy to come by.

This makes sense. My friend told me it was given to him by a guy he built a TH350 for as part of payment. It only starts if you dump gas in it, and then it runs like crap. I think maybe the accelerator pump is shot. Either way, he's put thousands into the rest of the engine dyno.....so I asked him why the hell are we messing with a cheap junkyard carb. So he said "yeah, I see what you mean.....let's get a brand new one".

He is in North Carolina for the next few days, so I'll get his credit card and order the 2300 next week. Thank you guys for your help. Finding the intake and a dizzy was easy......I don't know jack about carbs and what fits what!

 

[gwaii]

This makes sense. My friend told me it was given to him by a guy he built a TH350 for as part of payment. It only starts if you dump gas in it, and then it runs like crap. I think maybe the accelerator pump is shot. Either way, he's put thousands into the rest of the engine dyno.....so I asked him why the hell are we messing with a cheap junkyard carb. So he said "yeah, I see what you mean.....let's get a brand new one".

He is in North Carolina for the next few days, so I'll get his credit card and order the 2300 next week. Thank you guys for your help. Finding the intake and a dizzy was easy......I don't know jack about carbs and what fits what!

good plan....but keep in mind that out of the box the new carb will be tuned for an 'average' type of setting.as there is no way for holley to know what application it's going on some tuning is expected.you may get lucky,but you may also get more of an education on carbs than you'd figured on.

 

[RatDog8o8]

good plan....but keep in mind that out of the box the new carb will be tuned for an 'average' type of setting.as there is no way for holley to know what application it's going on some tuning is expected.you may get lucky,but you may also get more of an education on carbs than you'd figured on.

That's the good thing about Holley (and FoMoCo/Motorcraft) carbs. Very few parts when rebuilding, and great tune-ability. I think there's what....22-24 pieces total on a Motorcraft 4v? Not too many more on a Holley 1850/4160.

So, IMO, the carb-ucation that may arise will at least from a good "teacher"!