Carb selection in-put

[CUSTOM/10]

I'm looking for in-put on carb selection for my build. Here's what I have:

Vortec 383 full roller motor
906 heads 3 angle valve job
Com Cam XR264HR
Dual plane air gap intake
700R4 trany
3.73 gears
about 9-1 compression
33" tires

This is going in a 4x4 that will see 99% of it's time on the road. No real 4 wheeling, more of a street machine.

Thanks !!!
Gary

I'm currenlty leaning towards an Edelbrock Thunder Series 650 vac. 2nds
AVS # 1826.

[Greasey Harley]

Edelbrock carburetors leave a lot to be desired (IMO). They don't tune well, they don't make good power and they don't get good fuel economy.
They look shine though, that's about it.
I would opt for a good Holley or a QudraJet.

[Fldawg]

I went thru 3 carbs before finally picking one, i'm not a fan of the edelbrock either, if your not worried about mileage go with a holley 650 or750 double pumper.but if you can find a good quadrajet i'd get that. there's always the holley 600 vac.sec. hope this has helped

[CUSTOM/10]

I have a 750 Demon on the shelf, but not sure if it would be a good choice for my application. I was thinking it would hurt my low end performance.
I want to have good off the line response & decent mileage, sacrificing top end a bit wouldn't be a big concern.

Holley is the only carb I've had, so I don't have any other experience to compare it to.

[jrdv]

I went with a Fast EFI on my last 383. It is so nice to hit the starter on a cold morning and it fires right up.

I live at about 6500 feet and regularly drive down to about 3000 feet and up to 9000 feet. It never runs rich or lean.

I spent years messing with carbs. Some good, some bad, didn't matter the brand. I'm going to start replacing them with EFI when I can.

It took about 10 hours to put on.....

I have the same setup as you except for the 700r4.

[CUSTOM/10]

I agree that EFI would be the best way to go, and I was thinking of going carb now to get it going, then possibly go FI later.

How much $$$ am I looking at to do FI ?

[68C15]

Originally Posted by CUSTOM/10

I have a 750 Demon on the shelf, but not sure if it would be a good choice for my application. I was thinking it would hurt my low end performance.
I want to have good off the line response & decent mileage, sacrificing top end a bit wouldn't be a big concern.

Holley is the only carb I've had, so I don't have any other experience to compare it to.

750 is too big until you get to about 3500 rpm. I'd go with either a 600 or 650. But with your stated wants, a 600 is right in the game. In a perfect world with gobs of money and carb bulding/tuning experience a modified 500 would be nice for your truck. Or take a 600 and swap the front boosters to stepped annular. You'd loose CFM but pick up unbeleivable throttle response and MPG

[mcm1209]

Holley or Holley style carbs. Don't like Edlebrock carbs.
They just don't tune well In my opinion.
I ran a 406 SBC with 2.02 valves, Lunati .525 lift cam and a victor jr intake. Had a Holley 650 DP running 13:50 at the track, in a 1990 SCSB. Had a 750 on there before but it was just too big.

[jrdv]

Originally Posted by CUSTOM/10

I agree that EFI would be the best way to go, and I was thinking of going carb now to get it going, then possibly go FI later.

How much $$$ am I looking at to do FI ?

I got the master kit off ebay ( Camaroguy was the seller?) for $1800 shipped. I spent another $400 on extra fuel line and a MSD digital ignition ( bought a set from Summit which includes distributor and ignition box).

I already had HEI, but I read that HEI doesn't give a clean rpm signal. I just decided to do it right and upgrade to the MSD.

You will love it if you decide to go this way.

John

[CUSTOM/10]

I do have a Holley 600 I could take from my old truck, but it would need a complete rebuild. It's been sitting for a while. Is 600 cfm good for a 383 with how I plan to use it ?

[mcm1209]

For what it costs to rebuilt the carb i would give it a try. See if one of your buddies has a 650 and compare how they both act on the engine.

[CUSTOM/10]

I may have to rename the project to "Money Pit" "LOL"

Going the FI route I'd also have to change my fuel delivery system, it's currently a mech fuel pump.

So I think for now I'll stay with a carb for time / cost / and simplicity reasons. Then look at FI down the road.

[jrdv]

Originally Posted by CUSTOM/10

I may have to rename the project to "Money Pit" "LOL"

That sums up building one of these old trucks. You will put way more money into them than you will ever get out of selling it.

Accept this and you will be happy!

[CUSTOM/10]

Oh I was well aware of that before I even started.... "LOL" I have no plans to sell it until I can no-longer enjoy it !

Originally Posted by jrdv

That sums up building one of these old trucks. You will put way more money into them than you will ever get out of selling it.

Accept this and you will be happy!

[67 cst swb]

My opinion...
The old school "chart" says you would need a 715cfm carb, which they don't make. So your looking at a 700cfm. You said you wanted good low end power, so a slightly smaller carb won't hurt. I think the Edelbrock Thunder Series 650 vac. sec. AVS # 1826 is a good choice. BUT... be sure to read the tuning guide that comes in the box... If you don't follow their tuning guide... you will think that carb is junk. It will take you some time/days to get it tuned properly. But once you get the tune solid, you will not have much for issues. Most people don't have the patience for Edelbrock Carbs, but they are not rocket science... Read the guide book!!!
A Holley style carb is ok choice also. But I would stay with a Vac. Sec. carb... Not that a Dbl Pumper would not work... but, they are intended for wide open throttle usage.
The only draw back to a Holley style carb is they are so prone to contaminants clogging the needle & seat... usually when you least want it to happen. You should always run a quality fuel filter between the fuel pump and the carb, but Edelbrocks carbs are more forgiving of crap in the fuel.

Remember... Opinions are just like carburetors... there are millions out them out there...

[Elefuntman]

Personally I think the Edelbrock is a much better choice than the Holley for your application. In my experience Holleys need constant attention. The Edelbrock is very tunable with the ability to change jets and metering rods as well as when the secondaries come into play, the rear air valve can be played with. As for CFM I would go big, I don't know what CFM they are available in. On an old car I used to race I used an 850 Thermoquad, now that is what I would really use on it if it were mine, cheap to pick up at a car swap meet, very easy to find rebuild kits and very tunable, but that's just me.

[CUSTOM/10]

Yes I'm getting a lot of opinions, But that's what I asked for. Everyone has given input and it will all be taken into consideration in my decision. Even the carb calculators don't agree with each other. They left me with anything from 518 to 770 cfm.

Currently I'm thinking 650 - 700 cfm, vac 2nd, What mfg ??? Don't know !

I don't want to go big because I'll loose my low end and street drivability. I also don't want mech 2nd.

So everyones in-put has gotten me closer to a decision.

Thanks so far !!!! Keep it coming !

Does anyone know of a really good carb sizing calculator, one that take in all the variables in making the choice ?

[67 cst swb]

Originally Posted by CUSTOM/10

Currently I'm thinking 650 - 700 cfm, vac 2nd, What mfg ??? Don't know !

I don't want to go big because I'll loose my low end and street drivability. I also don't want mech 2nd.

I think your right on the money in your thinking...

[67 cst swb]

Originally Posted by CUSTOM/10

Does anyone know of a really good carb sizing calculator, one that take in all the variables in making the choice ?

What I have used for years...
So I guess you would say my "personal calculator" is:

engine cid + engine cid - 50 cfm = carb cfm
now...
if you want low end? you would round that cfm number down to closest cfm available...
if you want top end power? you round up to closest cfm available

If your mostly stop and go partial throttle usage? Vacuum Secondaries
If your mostly wide open throttle? Double Pumper

If you street driven auto transmission? Vacuum Secondaries
If you have Manual Transmission? Double pumper, but drive it like you stole it

If you like messing with your carb occasionally or more? Holley or Holley-like
If you don't mind some initial tuning then wanna leave it alone? Edelbrock

If you wanna buy a new carb, pull it out of the box, put it on and do not want to have to tune it one bit? Good Luck! for every one person that got away with this, there 5,000 people that dream of being that 1 person.

Obviously there are huge exceptions to this rule of thumb. But for 90% of the vehicles needing a new carb... this has worked me well for almost 30 years of selling carbs and/or being in the car/truck life.

Also... If you have a Holley carburetor and in your tuning you are now 10 jet sizes larger or smaller than the factory installed jet size (see Holley catalog) your carb is either too large or too small.
If your 10+ jet sizes smaller than stock, your carb is too large
If your 10+ jet sizes larger than stock, your carb is too small

[truckster]

You're just not going to be able to beat a well-built Quadrajet. It's got good mileage with conservative driving, and flat-out performance when you decide to get on it.

Plus it's a decent off-road carb, if you decide you want to play in the great outdoors.

[CUSTOM/10]

Thanks 67, you've helped considerably !

[CUSTOM/10]

Any thoughts or expirience with Quickfuel carbs ?

I was thinking 680 cfm VS ?

[68C15]

67, your recommendations are spot on for a car being driven hard and raced. Mine are based on street/highway performance.

A Demon with removable air bleeds is good or you could have your Holley machined for them. Either way, this is one very important tuning method. But keep in mind, carb selection and tuning is but one part of a whole package. If you make changes, do them one at a time

[Mike C]

Call Holley. They are happy to help with choosing a carb.

You can't pick a carb based on your "general usage" IMO. You need to pick the right carb for your combination. You've spent good money on an stroker engine and a roller camshaft. Now you want to "economize" it with a too small carb?

The first thing I would do is run the Demon 750 because it's paid for. If you want to buy a new one, my recommendation would be a 750 HP for the kind of motor you built. No choke, 4 corner idle, screw in air bleeds. And as a close second, a 4779-3 double pumper which would have a choke.

Your combo should be in the 400 hp range I would think, and with that in mind, it needs a 400 hp carb. My 355 with just a little more cam than yours has a Barry Grant 750 that's ported, polished, and profiled to flow 1040 cfm and it starts, idles, and runs better than the 700 double pumper it replaced.

[CUSTOM/10]

This is what Quickfuel is recommending: http://www.quickfueltechnology.com/c...arburetor.html

I'm waiting to hear back from Holley !