what carburetor will work best for my 383 ?

[Rubberduck]

In my ´68 Charger I have a 383 (335hp) with a 4-speed manual transmission. It´s all stock.
I usually do not rev it more than 5000 rpm.
Right now I have a 750 Edelbrock on it which ist surely too large.
I think a 650 cfm carb would be the right size for my needs.
But I´m not sure what brand to use. Eldelbrock, Holley or a Demon?
What are your suggestions?



Mario

[Ghoste]

The 750 Eddy likely isn't too large but it also isn't likely using it's full potential.  The 650 would probably be better for a general stock driver type of car.  You will find a lot of posts recommending a 750 Holley dp for your car but if it were mine, I'd get the 650 Eddycarter (maybe the AVS version if it were me).  Sized right for a stock 383 and simple to tune and maintain.

[Rubberduck]

The Edelbrock Thunder Series AVS 650 cfm is what I consider too.
I also want to get better fuel economy, since I live in Germany and gas prices are just crazy here.



Mario

[firefighter3931]

The Edelbrock Thunder Series AVS 650 cfm is what I consider too.
I also want to get better fuel economy, since I live in Germany and gas prices are just crazy here.



Mario

The 650 thunder would be a descent choice for a stock 383. 


Ron

[Mike DC]

 
Yeah, 650 sounds good.   


You'd likely get even more crisp driveability by going down to a 600 carb.  But going down that far is enough to really start biting off your power at 4-5K. 

 

[Chryco Psycho]

makes sense , the factory used 800 CFM Thermoquads on 340s so a 750 must be too big on a 383 

[Ghoste]

Even though I completely agree with you CP, in all fairness most of the those TQ 340's would have spent probably 80% of their time running on those tiny front barrels.  I wonder how much they even fully opened the giant throttle plates on the secondary side?

[Brock Samson]

correct me if i'm wrong but I sure thought the thermoquad on my '71 340 was 850 CFM... 


found a link look a few items down... 

http://www.allpar.com/mopar/mopar340.html

[Just 6T9 CHGR]

makes sense , the factory used 800 CFM Thermoquads on 340s so a 750 must be too big on a 383 

Would leaded vs. unleaded fuel make a difference in today's CFM requirements?

[Rubberduck]

Thank you all for your input.
I didn´t know that fact a 340 used 800 CFM Thermoquads.

If I use this cfm-calculator : http://www.4secondsflat.com/Carb_CFM_Calculator.html
even a 650 cfm carb would be too large.
Lets use the 383 motor with 5500 rpm, 100%  Volumetric Efficiency Of Engine.
The result will be  609 cfm.
But usually a stock engine has around 80% Volumetric Efficiency Of Engine with a result of 487 cfm.

So, what sense would it make to use a 800cfm carb on a 340 engine? This 340 would have to run at more than
10,000 rpm for the needs os a 800 cfm carb.



Mario

[Nacho-RT74]

get a 400 manifold, 72 or 73 better and mount either SB or BB TQ. SBV are 800 and BB are 850 cfms.

TQ are available now on summit, rebuilt by Holley.

being manual car, TQ will give you better throttle response and economich ( mileage, ) plus mostly of the time on street the 2 fronts will be working, and secondaries barelly opening.

Somebody told once here one way to know what could you need is double CFMs by Displacement of engine.

Thank you all for your input.
I didn´t know that fact a 340 used 800 CFM Thermoquads.

If I use this cfm-calculator : http://www.4secondsflat.com/Carb_CFM_Calculator.html
even a 650 cfm carb would be too large.
Lets use the 383 motor with 5500 rpm, 100%  Volumetric Efficiency Of Engine.
The result will be  609 cfm.
But usually a stock engine has around 80% Volumetric Efficiency Of Engine with a result of 487 cfm.

So, what sense would it make to use a 800cfm carb on a 340 engine? This 340 would have to run at more than
10,000 rpm for the needs os a 800 cfm carb.



Mario

Then also Six packs setups are too large even for 440s  , end even more, dual 4bbls cabs for Hemis 

The cfm value I think is for max throttling, so if TQs are sequential throttles and not simutaneous, then you won't have that value working full time, just what engine ask for. Even on simultaneous throttling engine just gets what needs.

That's what at least I have known. A carb never gives more than engine needs, but you can get a efficient carb giving the best flow as posible for a while engine needs, and also be "economic".

Is like an Alternator... You can get a 120 amps alt on car, but if Car doesn't use, then will never provide 120 amps, however will be more efficient giving that little bit power that does need, and quicker response

[firefighter3931]

A carb never gives more than engine needs, but you can get a efficient carb giving the best flow as posible for a while engine needs, and also be "economic".

That is not true and largely depends on the style of carb. A double pumper with mechanical secondaries reated at 850 cfm will give you 850 cfm at full throttle.  Vacuum secondary carbs flow based on engine demand as Natcho described above. 

I've seen lots of engine builds and dyno data over the years and you would be surprised at how much air some motors need to make big power. My own 446 that made 560hp on an all out dyno blast used less than 800cfm of air flow. A bigger carb netted no power increase.... and yes we tried it.

On a street motor my preference is for smaller venturies to promote quick & snappy throttle response as long as the carb moves enough air to keep it happy up top.

Over carbing....like over camming are the most common mistakes most guys make when selecting parts for their builds. 


The Thunder 650 carb is plenty for a bone stock 383 and it will be fuel efficient and have excellent throttle response. No question in my mind which carb i would run on that combo. 

....but, opinions are like belly buttons ; everyone has one ! 



Ron

[andy74]

i ran a 650 edelbrock on my 440 for a summer,great throttle response but sure did kill the top end! gas mileage was about the same but i think because i had to put my foot on it more to get the same performance as the 750 i had before-i still have it if you want to trade,just pm me

[Ghoste]

So, what sense would it make to use a 800cfm carb on a 340 engine? This 340 would have to run at more than
10,000 rpm for the needs os a 800 cfm carb.
Mario

The thing to remember with a Thermoquad is that it is a spreadbore carb and a big difference one at that.  The primary throttle plates are very small in the TQ and the secondary side is big.  Also, the secondaries on a TQ are opened based on the amount of air flowing through it so it may be capable of moving 800 or so cfm but on the 340's it likely didn't have to.

[Musicman]

Eddy 650