What carb to use

[cudablue]

Hey gang,
I'm a newbie.
I just had my 340 rebuilt. It will be about 375 HP. It has an Edelbrock perfomer intake. 4 Speed tranny.
I'm thinking 650 Holley, doublepump, mechanical secondaries, electric choke.
I'd like some recommendations.

Thanks!

 

[ramenth]

What's the usage for the car? Street? Strip? A combo of both?

 

[cudablue]

Hi Robert
Oh, I guess that would help.. DOH!
I will not be on the strip. This is a street machine only.
The rear end is a posi 3.2? gear.
Though it is damn near a nut and bolt restoration, I will be driving it. No trailer queen here.
thanks!
Rick

 

[Rob C]

Well, if the OE T-Q is out, then a 650 carb will do. Not more than 750 for this build.

If I knew what the cam and ascco. parts were, It would be easier.

 

[burdar]

If its a near nut and bolt job I'd use the Thermoquad. Now if the engine doesn't look anything near stock...you could use an Edelbrock. I here they are good all around carbs.

 

[ramenth]

Well, if the OE T-Q is out, then a 650 carb will do. Not more than 750 for this build.

If I knew what the cam and ascco. parts were, It would be easier.

Kind of fond of the T-Q for the build myself, but if the manifold is already square bore...

rumble's got it right, got any more info for us? Cam specs and heads would be nice to know, too. If you're flowing a lot then a smaller carb won't do much for you, not enough and a big carb will go the other way. But that's for CFM selection.

Personally, I like the Holley Street Avengers.

 

[nqkjw]

Well,since you're chasing ideas I'll throw in my 2c.
375 is a nice turn of hp for a driver.
I like Holleys and would go 650 or 700dp if you want go or a 750vac if economy is important.
I've recently come to grips with tuning edelbrock carbs and I'll have to admit they tune better for the street but I went quicker with holleys but using more fuel.
I'm not good enough to recommend the correct Edelbrock size but if you do go this way then spend a little extra to get a Thunder series rather than a Performer.The ability to adjust the secondary opening is well worth it IMO.
Or to look at it inversely...the inability to adjust the secondary opening on a Performer can be a real pain.

 

[ramenth]

Well,since you're chasing ideas I'll throw in my 2c.
375 is a nice turn of hp for a driver.
I like Holleys and would go 650 or 700dp if you want go or a 750vac if economy is important.
I've recently come to grips with tuning edelbrock carbs and I'll have to admit they tune better for the street but I went quicker with holleys but using more fuel.
I'm not good enough to recommend the correct Edelbrock size but if you do go this way then spend a little extra to get a Thunder series rather than a Performer.The ability to adjust the secondary opening is well worth it IMO.
Or to look at it inversely...the inability to adjust the secondary opening on a Performer can be a real pain.

That's because the Thunder series is modeled after the old AVS. I swear the AVS was such a great streetable carb you could poor sand into the filter and the carb would still do it's job. It was just a reliable and easy tuning carb. Remember, too, it was some comparably low CFM AVS's which set on top of our engines before the TQ came along. 650 CFM was seen as a good choice to sit on a 383 with this carb.

One of the nice things about the TQ is that the spread bore, the secondary air door, along with the secondary circuit allowed for some relatively massive CFMs to sit on comparably small CIDs (800 CFM on a 318?) without choking the living s*** out of the engine.

 

[nqkjw]

That's right.
Basically a Performer is an AFB and a thunder is an AVS

 

[ramenth]

If the Thunder series is as reliable as the AVS, then it's a good carb.

 

[cudablue]

Hey gang,
I'm back. I'll try to get the specs tomorrow.

Here is what I'm looking at right now.
http://www.summitracing.com/parts/HLY-0-76650BL/

I appreciate the input.
rick

 

[Rob C]

nice lookin carb. do they come in a 700 cfm size?

 

[ramenth]

nice lookin carb. do they come in a 700 cfm size?

X2. Do they come in 700?

 

[Oldschool]

I have always used the oldschool way of figuring out carb size. It works really well, at least it does for me. This little rule of thumb is for stock or mild builds. Radical builds will easily handle more.

Take the cubic inches of the engine and double it. In your case, it is 340.

340 X 2 = 680 cfm

Example, I am running 528 CI in a medium build Hemi. I run two HP Holley 750's on a crossram. 727, 3800 converter, 410 rear, 31" tall tires, 3500 lbs and it handles it just fine. It actually lays down a better 1/4 mile number with 2- 1050 dominators, but I never run them on the street.

Keep in mind this for stock to mild. If you are pushing 375 hp then a 700 or 750 will work great. I am a fan of the Holley HP series. If you don't need a choke very often where you live, they are the ticket. Just my old 0.02

 

[ramenth]

Well, Oldschool, that's definately and old school formula and one which works. I agree with you, though, that 700 would probably fit the bill for this, but having the cam and head specs would be nice, too.

I will kind of disagree with you on the choke. If you live in very warm climes where a pat of the throttle will introduce enough fuel to fire, then yeah, but a properly set choke will also help cut down on cylinder wash.

 

[cudablue]

Hey gang,
I decided on the Holley Model 4150 Ultra Carburetor. I'll keep you posted once it is fired up. Hopefully in the next few weeks. On the testing unit anyway. IT will be a while before it goes in the car.
Thanks for the advice!!
rick