Picking a carb for my 393.

[GSP393]

I'm trying to decide on a carb for my 393. The Holley website says 800-850 cfm, I'm leaning towards the 850. I've thought about an 830, but I want to run a choke and the Holley doesn't have one.
I've got a stroked 351w, forged flattops, Weiand Stealth intake, 210cc/58cc
2.055/1.60 Canfield heads, 600+ lift cam with a 5 speed.
Carb guys please chime in.

Thanks, George

 

[89-347-LX]

i recomend calling up pro system carburaters and see what they have to say
on of the best whens it comes to carbs

 

[85_SS_302_Coupe]

I second the call a pro idea. You can probably get away with either one but they'll tell you exactly what'll be best for squeezing every last hp out of your combo. The badder the engine the more important sizing is.

Also is there a reason you wanna run a choke? I don't run one on my 650 and it fires right up even in freezing temps.

 

[GSP393]

I wanna run a choke so there won't be any question about starting. I'll plan to give them a call and see what they say. I did a few of the formulas and they both came out close to 850 cfm.

 

[Fast63]

I would run an 850 for sure. 830 = probably the same, so get it if you want the choke. If you are looking at an all out drag car, 950.

 

[Wallzy]

What is the max RPM are you planning on turning with your motor, this and the engine size are the biggest factors.

 

[GSP393]

6,500

 

[GSP393]

I've looked at Quickfuel and Holley 850's. It'l most likely be one of them, I just want something out I can run of the box if possible so I won't have to do much tuning.

 

[85_SS_302_Coupe]

Just be weary of the huge carb recommendations....not pointing anyone out in here but it's the hugest myth since police cars being high performance. Too much carb is WORSE than not enough carb.

The comment about RPM is a good point, because if your carb is huge/too big, it's not even gonna start breathing until the higher RPMs and if you're shifting at 6k then your carb is barely awake by the time you shift and you lose performance. You don't want "extra carb" you want "just enough" carb. Also remember that running a little lean actually makes more hp than running super rich so jetting the hell out of it isn't going to make power either.


As for tuning, if you get a Holley or a Holley based tuner carb, this is your Bible:
http://www.holley.com/Store/product.asp?ID=36-378

That'll be the best $20 you ever spent if you deal with a Holley carb.

 

[GSP393]

Thanks for the advice, I emailed Summit tech. I'll see what they have to say. I still have a while to research it before I need to buy one. At $400-$500+ a pop, I want to do it right the first time.

 

[85_SS_302_Coupe]

If i were building a 393, this would most likely be the carb that i would buy. I don't race for a living so i don't personally have a need for a custom built carb, although they would probably still be worth a tenth or two in the quarter. This beauty here is one BAMF carb

http://store.summitracing.com/partd...306299+1051506944+4294900251+115&autoview=sku

 

[GSP393]

The only 830 I've found with a choke is the QuickFuel. I know a choke probably isn't something that I absolutely need, but if I ever had to drive the car on a cold day, I don't want any hassles.

 

[85_SS_302_Coupe]

I thought the same way but i've had mine without a choke for almost 3 years and it only needs a little pumping before you turn the key and it fires right up. Granted, it won't just sit and idle right off the bat, you've gotta give it some gas and crack it open a few times for 30 seconds or so but after a couple minutes it's ready to go.

 

[GSP393]

I'm in Canada right now where it's about 15 degrees Fahrenheit. My Mustang's in Texas, but it's been here before and I had it Michigan when I worked there a few years ago during the winter months. I don't plan to bring it back up here, but if I ever do, I don't want to have to buy another carb. It's probably a non issue, but I can get a Holley 800 or an 850 both with a choke for under $469.

 

[86bluecobra]

6,500

I doubt you will need a 850 or a 830 if all you plan on running the engine to is 6500rpm. The reason for going to a larger cfm carb is because you need all that air. You need all that air when you start running the engine well above 6500rpm. I really think you will be over carbing the engine if all you are going to do is run it to 6500rpm. My 750 is over carbed for my 351w. I run a 10 to 1 afr. Not by choice but just because I have not got around to jetting it. It doesn't really hurt performance any to over carb unless you are running way to rich like me. It is a good Idea to talk to an expert but I highly doubt you will need that much carb for 6500rpm.

 

[86bluecobra]

Just noticed you are running a wiend stealth aswell. A dual plane like that IMO will hold your combo back. It really needs a vic jr. On the other hand you are only planning 6500rpm. But i still believe a vic jr will make more hp and torque with your 393.

 

[Fast63]

well, he has big heads and a big cam. He will be moving a lot of air. I don't think 6500 is classified as "only" 6500 for a 393 either. That's like spinning a 302 8000+rpm when you calculate piston speed.

 

[GSP393]

My uncle has a Cobra kit car with a stroked Windsor and a 750cfm. He says it's too small of a carb and I'm running a bigger cam.

 

[85_SS_302_Coupe]

He would make a little more peak hp with a Vic Jr but i dunno about torque. My buddy has one on his 500hp 393 and it's crazy. You can mat the gas in 4th and blow the tires apart. He said redline was around 6800RPM so he might even pick up some peak hp around redline but you can't beat the Stealth for a street intake. Even with the extra cubes you'll give up a little bottom end on the street, and then if you're running a huge cam you're already losing bottom end.

 

[GSP393]

I'm for sure going with an 800 or an 850. For what it's worth, here are my cam specs.

hyd. roller.
dur @ 050
in 248
ex 253
lift
in 585 ex 612
112 lobe sep.