440 carb size?

[Avalanche]

I have a 1978 440 with 906 heads and standard trans. The motor is stock except the heads, which are from a 1969. I am trying to buy a new carb, does anyone know what size carb will run best? I'm looking between edelbrock and holley (spread bore or square bore?).

 

[Chryco Psycho]

The Math formula will tel you 650 cfm so either the math is flawed or carbs do not flow what they are advertized at . The reality is 2x the CI is about right , Eddy doesn't make a carb this big . Having said that the later 440s used the TQ 850 , so did the 360 , keep in mind the 340 used the 6 pack at about 900 CFM
So now that we have things in perspective we need to know what intake you have I assume it is a stock 440 intake but the 440 used both the square bore carbs & the TQ spread bore . The Spread bore is hard to buy new , holley does have some available but 95% of performance carbs are square bore . I would use a TQ for the spread bore but tuning kits can be difficult to find & it is a difficult carb to work with . My first preference would be a 850 Proform Square bore with Mech or vac secondaries .

 

[Avalanche]

The Math formula will tel you 650 cfm so either the math is flawed or carbs do not flow what they are advertized at . The reality is 2x the CI is about right , Eddy doesn't make a carb this big . Having said that the later 440s used the TQ 850 , so did the 360 , keep in mind the 340 used the 6 pack at about 900 CFM
So now that we have things in perspective we need to know what intake you have I assume it is a stock 440 intake but the 440 used both the square bore carbs & the TQ spread bore . The Spread bore is hard to buy new , holley does have some available but 95% of performance carbs are square bore . I would use a TQ for the spread bore but tuning kits can be difficult to find & it is a difficult carb to work with . My first preference would be a 850 Proform Square bore with Mech or vac secondaries .

I have the stock square bore intake.
It seems that 850 would be a bit too big for a stock 440?

 

[Chryco Psycho]

ok but an 850 TQ is OK on a factory 340/360?
& the 950 CFM 6pack is ok on a 340 .
Everyone does this , under carbs the engine , admittedly I had a bigger cam headers 7 port work done to my 440 but I started with an 850 , it ran OK , went to a 950 & it picked up , so I installed a 1050 & the car ran better yet !! running a 650 on a 440 will limit it to around 4200 rpm , a 750 is what is typically used on a 440 but still limits RPm, the factory used the 850 TQ vacuum secondary on a 360 in 74 with reduced compression Etc not an extremely powerful engine !! I had a customer last year with a 440 67 R/T it had the stock AVS carb & could not chirp the tires , I put a 850 Proform on it & it was a whole different engine .
Your call , you asked for advice , this is my bets suggestion what you do with the info is up to you .

 

[burntorange70]

750 square bore holley is what I would run. Sure you can over carb it but you will give up some throttle response down low to get that extra bit up top. Sounds like you got a street motor and will not be reving the motor up to max RPM much so I would stick with a smaller carb.

If you run a spread bore you run some thing like 850 cfm. They are a demand type carb and will be fine for mild street use.


2bbl carbs have a different cfm rating than a 4 bbl so that 950 cfm is less when compared to a 4 bbl.

 

[Chryco Psycho]

Except the the 6 pack is 2 500 cfm outboards & a 350 cfm center carb , 950 is corrected to 4 bbl rating approx
I have used 850s with no issue & still had improved throttle response over the 40 year old AVS

 

[Cranky]

What is your combination and how are you going to use the car? I ran 1500 (two 750's on a tunnel ram) on a 440 but it was a race engine that turned 7300 rpm. A well tuned TQ works good and gives decent mileage too. 6 pack setup also work well and the outboard carbs only come in when you nail it.....

 

[TinCuda]

If you guys are going to start talking about "money is no option" carbs like six packs and dual four barrels, why not throw a supercharger on it and overhaul the engine to 543 stroker!


I once ran a 440 with a 650 cfm carb and it was a screemer. It probably would have been better with a 750 or 850 but at the end of the day with a stock engine, a 750 will be fine.



.,

 

[Avalanche]

I cant find a 850 with vacuum secendaries and Proform only goes ut to 750.
The biggest carb I can find is a 770 from Holley with vac. sec.

Thanks for everyones advice.

 

[Chryco Psycho]

Thermo quad is available in 850 & 1000 cfm vacuum secondary

 

[jvcuda]

Avalanche,Go with a Holley 750DP. I have that carb on my '73 CUDA,440 w/346 heads,3400 stall convertor,3.91 gears,295/55 MT ET street radial. Drives great on the street,and goes high 11's at the track. John p.s. no bs here's a time slip:

 

[Avalanche]

Avalanche,Go with a Holley 750DP. I have that carb on my '73 CUDA,440 w/346 heads,3400 stall convertor,3.91 gears,295/55 MT ET street radial. Drives great on the street,and goes high 11's at the track. John p.s. no bs here's a time slip:

Is that on a stock motor or has it been modified?

 

[jvcuda]

'72 block was decked .012,mopar .484 cam,hydraulic flat lifters,isky adjustable rockers,Ly rods, trw pistons.Cast iron 346 heads with a mild port polish. Eddy Torker intake,heddman hedders,2 1/2" exhaust. Cuda has power steering,brakes.Runs on 93 pump gas with a little vp110 added at the track. So,I would say slightly modified.
john

 

[mopartim]

If mpg is a consideration, go with the thermoquad, because of those small primaries your car will get much better mileage . And yet they have the rather large secondaries for great WOT. Go to the summit web site and type in thermoquad. They have quit a few, maybe one for your year, and you don't have to scour the swap meets hoping to find a good one. I just took a nice 750 holley off my Challenger that worked just fine except for the mileage, and put the stock carb back on and love it.

 

[TinCuda]

Just FYI, The rule of thumb equation for how big your carb should be is:

Carb CFM = cubic inch displacement X engine max RPM / 3456

or

440 X 6000 / 3456 = 764 CFM



.,

 

[Juan Veldez]

Always remember , too little of a carb is better than too much carb! It's all about efficiently burning the fuel/air mixture. So, if your on the fence, go a less in the cfm's.

 

[Juan Veldez]

Oh, and nice reaction time on the above time slip!

 

[jvcuda]

Oh, and nice reaction time on the above time slip!

Thanks Juan, Yes I think you are better off with a smaller carb on the street,better response. My car with a 950 on it, is faster at the track by over a tenth.

John

 

[Chryco Psycho]

Just FYI, The rule of thumb equation for how big your carb should be is:

Carb CFM = cubic inch displacement X engine max RPM / 3456

or

440 X 6000 / 3456 = 764 CFM



.,

Yeah & if you believe that I have some swamp / ummm nice real estate for you !!!
My 440 ran far better with a 1050 dominator over an 850 DP & try to explain the approx 950 cfm 6 pack on a 340

 

[moparleo]

Just remember what an engine really is. An air pump. You can only put in as much air as you can get out. Regardless of the cfm rating of the carb. Rating does no mean actual flowing that much unless you are driving at max RPM, high lift, long duration cam, head work etc...Thats why the cylinder head is the biggest restriction to air flow.. When you put headers on the engine if it is tuned correctly, it tends to run a little lean. That is why you usually get an increase in mpg. the next step is to play with jetting to get the correct a/f mixture again. Put a larger carb on and now the camshaft / and cylinder head is the restriction. Just think of a funnel. No matter how large the opening is you can only flow what small end allows out. For normal, legal speed driving you will be running mainly about 2-3,000 rpm. You don't need a very large carb to be efficient in that rpm range. So the question is, economical turn key ,no fuss reliability or the constant fiddling and tweeking required with a high RPM driving style. Real race cars are for the strip and street cars are for the street . Thats why we have toys. To play with when we want to, not when we have to, to provide daily trans port for work, family, etc...The smaller the carb, the less money you have to spend to make it efficient.
Personal preference is the Edelbrock Thunder series AVS " adjustable air valve " 750cfm #1806. No below thw foat fuel leaks like the Holleys , easy to adjust secondary air valve. Factory adjustment and jetting will be very close to ideal. Turn the key and drive....