Is a worked 850 big enough for an 485 cu in big cam Hemi or is a 4500 in the future?

You’ll definitely want the opinions of more experienced guys than me; but I’m gonna say an 850 - 4150 would be an extremely conservative choice for any 482” mill, especially a healthy Hemi. Would it run good? Sure. But I’m thinking there would be quite a bit left on the table as far as drag strip use. I run a 1000cfm 4150 (pretty similar to an 850) on my street/strip 451, and it runs great. 30 more cubes and the flow capabilities of a Hemi-head..... I would think a large 4500 would be in order.

Thanks,

Best out of the box carb we ever used on a Hemi of that size!

Proform 1050 in 4150 trim.....
https://www.jegs.com/i/Proform/778/67209/10002/-1

Vid to go with the one we ran.......

https://www.youtube.com/watch?v=mrm62S2Fmow

850 will work fine on the street. If you are going to race it and want to make max power then you'll need a good intake and a Dominator.

Thanks, I have a rat roaster with the standard two AFB top and a nice machined single four top, weighting my options here

We raced a 400 inch Hemi in A/SM back in the late 70’s with a Rat Roaster single four barrel and 850.

Every time we cracked the throttle the lid would deform from the vacuum.
Eventually cracked the lid.

Makes me think that carb was a little too small for that engine.
Went a 133 mph at 3400 pounds on 10.5” tire but we couldn’t get it to stick - only went 10.30’s.

Well that depends

http://4secondsflat.com/Carb_CFM_Calculator.htm

https://www.inchcalculator.com/carburetor-size-calculator/

Just google Carb CFM requirements

Everyone already knows this

I have bigger carbs on small blocks just sayin............No matter what anyone sez, I've been pitting Dommys on small and big blocks for years w/great results just go to my FB page and see for yourself.....

The lid I have was made from a 1-1/4 thick piece then milled inside to 3/8 thick. Feels very substantial, plus the bottom has 3 bolt bosses in the center that the lid could be attached also. Like I said the bottom was a later setup for the single four with the cast in dams. I have a milled 4150 carb that’s supposed to flow 900 but it wouldn’t work on my 499 Indy head engine, had to use a 4500 (7320)

I've never had a car yet that didn't run a whole lot faster using a carb bigger than the recommended. That's just my experience.

I had a 302 Maverick in high school. It ran best with an 800 Holley. (And you want to put an 850 on a 485 cu in Hemi?) 351 Cleveland Pro Stockers had 2 Dominators. I was at Sonny Leonards shop one day. He was dynoing an engine with EFI. (I know it's not carbs.) It had 7300 CFM throttle bodies on it. I said "Why so big?" He said because every time we put bigger throttle bodys on it we make more horsepower.

Yep, and a bigger carb smooths out the frequencies making the motor much happier and less "peaky".....do it all the time.....

Have a nice day

I've only work on Mopar race cars but all the motors from the early 331 C.I. hemi up to and including SB LA motors and B and RB as well as 426 Hemi motors have all ran faster at the tracks and made more power on a engine and chassis dyno testing with more air and fuel flow
Be careful on the fuel volume, you can run out of enough fuel to feed the bigger carbs making you think it isn't making more power with more air flow
if you can't enrichen the carbs fat enough to slow the car down in the 1/4 mile you don't have enough fuel delivery
Been there, done that way to many times
EDITED: That formula for CFM seems way to small for real world WOT drag racing results for max power

All that yackin, and you didn't answer the OP's question.....lol...Care to add any experience with all the numbers?

A lot of good replies already. My is also that every time I have added CFM to these larger engines, I have seen more HP.

Do you already have the 850? If so, or if you have access to an 850, why not strap it on and see how much vacuum it pulls at WOT? That would seem a good starting place to me.

Lacking any real engine specs or it's intended use, my first reaction is MORE CARB. 4500 all the way. But that's just me.

Thanks for all the reply’s so far, trying to get as much info to go in one direction. Never had a Hemi on the street before and looking for decent drivability with a four speed and 4.10 gears. I do like the looks-appeal of the AFBs. Single four top is for the 4500 so I’d have to use an adapter for the small carb. Has anyone had experience with the rat roaster and stock carbs?

So, you didn't understand what I wrote?

Went back and looked to see if I missed what you said.
Something about having a nice day???
If you have something to say that’s constructive I’m all ears, I’ll listen

I did, and its a great baseline, cubes X rpm = yada.........but a Hemi is a bit different in its air and fuel needs. I have run as big as an 1150 dominator on a 431 cube hemi on the street, and it was actually a decent carb over a bunch of others I tried. On that 431 hemi, the best setup I ever ran was a set of dual 750 eddy carbs with all the choke stuff removed on a rat roaster with a 1" lid spacer, and 1" carb spacers and all the internals modified. That was the only setup that beat the old school dommy.

An 850 on a Hemi is pretty restrictive and will actually run out of breath at 5k on a 484 Hemi. On a 440 mild stroker, an 850-950 is about perfect, but on a Hemi with heads flow typically +380cfm out of the box, its a big restrictor. even with a mild cam. Think about it, they put dual 600's on a stock stroke 426 hemi......Now a days we are putting dual 800's on the 540 and bigger hemis....They like big carbs, they like fuel, and they like air.....More than the formula accounts for.

I love tinkering with carbs on engines. I can typically find the best jetting and timing with most combo's....But for the 484 Hemi, I gave you the best results we have found with more than 20 years of messing with them. The 1050 Proform 4150 is a beast and one of my favorite out of the box carbs. We have tried a lot of carbs over the years. The only one I would like to try again somtime is an SV1.....The one I had, I did not spend enough time on it before I sold it, but I think I could have eventually got that to work really well. It showed some nice promise, especially in the idle circuit.

On anything not out of the box, I call Dominic at Thumper carbs and we discuss it. Even on my little 512 400 stroker, I think the 1050 custom Thumper dommy might be restricting us a little. Wish I had more money, cause I would have a shelf full of carbs.

We put Hemi's in everything.....Guess who gets to tune most of them....

Just a few I have had the pleasure to tune and work on...

Thank you I’ve seen the light.!

Yes, the Hemi has different demands and an 850 would be a truck carb for hauling logs and trash hell, I'm going to an 1150 which flows 1250 on my baby 470 and the last one I tested was a beast.......all this formula nonsense doesn't apply as much today imo and several who have tried my Dommy's all agree. Less is NOT more or better.....

I keep reading how certain engines need more air, etc.

The carburetor only knows vacuum. What the chamber and valve gear look like has nothing to do with it.

So here is a fact, and this happened at the drags back in 1984. A guy running a MK1 Ford cortina stick car with a Rover 3500cc V8 motor (215ci Buick), had hdrs et. etc. and a 600 Holley. I lent/persuaded him to try my modded 850DP which prob flowed near 900cfm on his car after much pi$$ taking by him that my carb was too big for my 340. And yes you guessed right, he went 2/10ths quicker, throttle response wasn't so good of course but. Why did he go faster if big carbs don't work?...............faster run was made within 1 hour of previous same conditions.

I've seen both the Buick and Oldsmobile 215 C.I.heads, neither one had decent intake ports or camshafts
My point is even a small C.I. economy deigned motor like those like more air and fuel flow for better performance at the drags

Vacuum is one part of the equation but comp, manifold, rpm's cubic inches, single or dual ALL have an effect on the needs and every time I go bigger on certain motors they pick up and some a BUNCH......

Its something to really try to understand why you get this effect. My 340 also went almost 2/10ths faster with that 850DP rather than the 750DP it came with yet I was only using around 6100rpm tops@the traps at the time on stock unported 2.02 heads and only 10:1CR, headers and a strip Dominator with 2" spacer so a nothing special motor.

An engine will only pull the air it needs with a certain head design/bore/stroke/rpm etc. yet a bigger carb always seems to work at the strip defying any method you care to use to calculate its needs. But its not always the case on a dyno, We ran a 950HP holley on a 589ci street wedge motor, only 10:1, had race heads that probably flowed in the 340cfm range@ the solid roller cams max lift of .625", and a 440-2 intake, it pulled 1.9hg vac@wot at 5800rpm and went to 2.0@6000 suggesting the carb was too small, yet when a 1050 Dominator was tried with an adapter it only made 3hp more, that could've been because it wasn't dialled in or the adapter?. but I have read a few times that on similar big ci motors of that size a Dom only made a max of around 10>15hp more if that than say a big 4150, its all combo related I guess but there is no real reason why 1 carb of only 100cfm more can make a 2/10ths difference on a smaller motor and on a large motor that actually needs at least 1050cfm+ of air according to calcs and a dyno it doesn't quite work that way, perhaps at the track it would be a different story and the better way of trying things out. Maybe things need stepping up to 2 x carbs for real gains on big ci motors with enough valve lift of course and rpm. Or perhaps my thinking is somewhat off?

sorry for slight hijack

I ran a 1050 Dom on a little 405ci small block and was gonna change to a 1150 but I sold the engine

I think it is the A/F density charge in the cylinder. Bigger carb, less restriction and pressure drop.

It's one of those things you can theorize and calculate all you want to, but real world results can and will vary.
An 850 is too small for the hemi in question here.

There is only ONE force at work in the intake system: pressure differential. Flow of any substance (solid, liquid, gas, plasma) goes from high pressure to low pressure without exception.
How it gets there varies quite a bit, but that's all there is. All of those rotating and reciprocating bits do is connect and/or regulate 2 volumes with different pressures.

There's also what I call "Frequency smoothing" meaning on most hot motors a smaller carb will be snappier and produce more vacuum across the board and unfortunately at max rpm's. By going to a bigger carb we smooth out the frequency's and like duration, it moves the power-band up accordingly and makes em easier to drive especially on the street and in a traction limited deal it helps a bunch cos I've been doing it w/great feedback from customers and my Dart loves the bigger carbs up to a point then the signal to the boosters is not happy therefore it draws more air than fuel and goes lean where a smaller carb can go rich up top because of the vacuum draw being greater(restriction).......

I thought that's what progressive secondaries were supposed to help with?

Doesn't matter if the carbs too small and my 9-second 470 HATES 4150's even 1100+ cfm as it makes it too peaky down low and will not support up top.........

....the way forward is clear for us.

Actually I meant, if the carb is too big, don't progressive secondaries help smooth out the response?
Also thinking of something like a TQ with small primaries for good throttle response, but huge secondaries for wide-open.

If it's too big then it draws less fuel through the boosters making it leaner so that MAY help but I'm not sure on that w/out trying it and seeing for yourself. Smaller less powerful motors are usually easier to tune but many factors come into play like, weight, vert, gears, altitude fuel etc......

Actually I meant, if the carb is too big, don't progressive secondaries help smooth out the response?
Also thinking of something like a TQ with small primaries for good throttle response, but huge secondaries for wide-open. [/quote]
My dealings with carbs, both multiples and singles with progressive linkage is the right foot determine how smooth the car responds to the throttle peddle
Many carbs will bog or backfire if opened to quickly when not tuned properly, multiple carbs included.
As far as tiny primary carbs with great big secondary carbs like the Quadrajet and Thermoquad carbs can be made to run well, the fuel distribution at WOT to each cylinder is another tuning issue to deal with though also
As far as smooth operating, being a drag racer I like no bogs or back fires
Tune it until you love it

In addition to the velocity-operated (AVS, Q-J, TQ) and counter-weighted (AFB) secondary air doors, some also have a dash-pot (vacuum diaphragm with a bleed hole) which slows the linkage activation as an additional tweak against bogging. These can easily be added to existing linkage and made adjustable by using a jet as the air bleed regulator. It can be open to the air (not filtered) and easily accessible because the air doesn't enter the intake tract.
IMHO some manifolds for staggered bore carburetors (Holley 4011, QJ, TQ) were simply made by altering the flange footprint and bolt pattern of an existing square bore manifold - but no thought as to moving the carburetor forward to improve the inherent front-to-rear bias. Has anyone seen attempts to re-locate with dyno or track results? This may even be legal (or at least nearly invisible)!

Driveability is very subjective. Driveability on the street with a four speed transmission can be super touchy. I'd start with the dual AFB setup since those carbs have nice idle circuits and driveability is usually pretty nice. I've seen people asking crazy money for those rat roaster intakes so another option is to sell that stuff for a pile of cash and then go buy something that will work really well on the street. I can't tell from your questions if you are more into driveability or looks. If you just want something to look great and you don't really care how it drives then the rat roaster is a good choice. If you want to be able to drive the car smoothly at slow speeds down residential streets then you should probably pull the trigger on a different intake.

I’ll define drivability for me, no bogging, no idling at 1500 rpm, no having to keep patting the gas to keep running. I want the hammering hard hitting rapid sound FOR ABOUT TWO-THREE hours, then I’ll drive the SRT auto Challenger. LOL

If it was my car I'd probably keep the rat roaster intake and put a dual Sniper setup on there with a Hyperspark distributor. A dual throttle body EFI setup would have a fighting chance of working on that intake. I'm not going to guarantee that it will be super driveable, but it would be easy to tune.

Does sound attractive