What is the best carb for me?

[hewi]

G'day.

I own a 69 charger with a 383 4BBL in her. Not sure on the year of the motor. 727 auto tranny.
Motor looks pretty standard - no mods etc...

Was running with a 600 holley but this stuffed out so am in the market for a new carb.
What would you guys recommend? DP or VS? What size? Brand? No choke, manual or electric?

Is a 600 a little too small? Not too bothered about fuel consumption, more after one that will give the best performance.

Thanks for any help

Bruce (Hewi)

[Plumcrazy]

I'd put an Edelbrock 1806 on it.

[mikepmcs]

it's a 383.  isn't a 650 a little too small???
i thought the formula was CIx2
383 equals about a 750, am i way off on this??  I got a 600 eddy and I know it's too small.  484 MP cam, 383, eddy perf 383 mani, 727, 2500 stall, i'm looking at the 750 mighty demon.  someone set me straight on this please, cause i'm ready to buy a new one.
v/r
Mike

[Ghoste]

I have a similar setup to yours Mike and I run a Holley 750 vacuum secondary.

[mikepmcs]

ok, i could be talked in to a holley 750.  probably cheaper too, but i just heard demon was pretty much plug and play.  will that holley bolt up to my eddy manifold and what kind of extras am i gonna need to make this work.  i think there is another thread that has a shopping list of parts and i'll try to find that in the meantime. 
thanks
v/r
Mike

[Chryco Psycho]

Iwould use a 750 Holley , Demons are Ok too but still prefer the Holley , if you hav no need for the choke the Street Hp 750 is awesome & will gain HP over almost anything else , it is available in both VS & DP , I prefer the DP personally 

[dodge freak]

I love my DP but if that car does not have 3.55 - 4.10 gears or even high yet, the VS might be better for you. You said it was stock so that means no headers or other good stuff to help the motor rev.

I would get a holley hp 750 VS for it, you can live without the choke. If you have the exhaust cross over open in the intake manifold , the motor will idle fine in a few min. even if its cold outside.

[Plumcrazy]

it's a 383.  isn't a 650 a little too small???
i thought the formula was CIx2

Here's a calculator. http://www.csgnetwork.com/cfmcalc.html

[mikepmcs]

hewi,
sorry to keep hijacking.  looks like the answer to your post is right above this one.

I just got off the phone with holley tech support and told him my setup cause I was liking the looks of the Street Avenger 770, and he said that a 750 would be too much.  I have headers and what i wrote above and can't think of any other mods(i didn't build this motor).  I will be putting 3.55 SG in the rear at some point after summer.  

the tech said i should buy an SA 670. His question was what RPM will I be running it to and I told him around six maybe(wasn't thinking that would be different when my 3.55 is in) I'm thinking he based his decision on that.  I just want something that is gonna git when i want it to.  I'm still with you guys on the 750 or now the SA 770 but what kind of problems will i run in to if any.  It seems like you guys like em pretty well so I'm more apt to take ya'lls advice over any one else's.

oh yeah the debate between double pumper and vac sec too.  I have a very low vac motor due to the cam(mopar 284/284, Lift .484/.484), i'm at 11hg steady at idle but jumps to over 20 when i rack it. is that gonna work ok.
and will it be ok on my eddy perf intake or should i get another one of those too.  

I will in the distant future be putting in either the engle k56 or the one firefighter (ron) always suggests.i just can't think of that one right now.

thanks for your patience and putting up with my ignorance.
v/r
Mike

[Ghoste]

There are a couple differences right there then between yours and mine Mike.  I have a Street Dominator intake and 4:10 gears.  Moves my powerband up a little.

[dodge freak]

The DP carb will bog down if you floor it in the wrong gear. EX. you are going 30 mph and its in second gear, you might not want to go to first but in second with a 3.55 it might not need the secondaries till 45 mph or so. With a 4.1 gear even if you are going a bit to slow, the rpms will climb up fast. A VS carb is more flexible if its to big, but a DP at high rpm's will hit harder.

Its your call-how you drive and how the roads are. I live right by the 70 mph zone freeways and 3 or 4 lane roads. I have a 318 hp with a 3.91 gear and a trans with 2.74 first gear, so my holley hp 750 DP works good. I have  a bog problem at 30 if I use 2nd and floor it but at 40 mph its great. At 60 in 3rd same thing but 65-70 and higher its great again. Never use a VS carb, but I have disconnected the secondaries and drove it. Its fun to floor it at 25 mph in second gear but at 35 its out of carb. Maybe I get a VS one day, The older I get the slower I drive.

I think with a 3.55 gear in a 3700 lbs Charger you would be happer with a VS carb, if it was a 3000 lbs Duster with a 3.55 I say DP , its hard to say, but the VS will give you more power at low RPM's and you would lose a Little at high RPM'S. If the secondaries are tuned right it won't be much-15 -20 horses I am guessing.

[mikepmcs]

alright, so more than 1 model of 750.  i'm guessing the 4160 is the way to go for my application. take a look.
v/r
Mike

http://store.summitracing.com/partdetail.asp?autofilter=1&part=HLY%2D0%2D80508S&N=400178+4294919007+115&autoview=sku

[dodge freak]

Nah, thats just the most used. I think the Holley hp are much better. Nothing wrong about having a metering block in back, not that hard to tune. It have a different metering idle circuit in the block, gives a better idle for hot motors. That one you are looking at is for smog motors. Those hp are not cheap, but you are getting the best.

I notice on e-bay its hard to find VS holley hp's, a few DP but only those cheap VS they have. If thats all that you want get a used on from e-bay, there is a bunch to pick from. Be careful on e-bay lots say they have a hp but they are not, just has a few parts.

[mikepmcs]

no, i want the right one.  HP... ok i'll go look for that from summit.  Any suggestions on the manifold.  will my eddy perf manifold be ok or do i need a better one to get the most out of this carb?
thanks everyone so far, you guys are awesome.

v/r
Mike

[mikepmcs]

ok one more try on saving a little cash.  what about this carb? SA770 elec choke and vac secondary

http://store.summitracing.com/partdetail.asp?autofilter=1&part=HLY%2D0%2D80770&N=115&autoview=sku


these are the only 2 HP's that are vac sec and they look the same to me.  please say the 500$ one is ok.  but don't forget the 770 above too.

http://store.summitracing.com/partdetail.asp?autofilter=1&part=HLY%2D0%2D82750&N=115&autoview=sku

http://store.summitracing.com/partdetail.asp?autofilter=1&part=HLY%2D0%2D80529%2D1&N=115&autoview=sku

v/r
Mike

[dodge freak]

Yeah the $500 one is fine, wow that is alot. The $379.00 one looks good too, but for $120 more I get the HP.

On your intake, I am not sure. Yes they make better ones, do you need it ? I would just get the carb and the gears, then see how you like it. Heck with that cam your motor will love the HP carb. All you might need is a better spark box, I like MSD 7 al, but Crane and others make digital box's that some claim are great. When I changed to the msd 7al my motor will idle in gear cold even if it was not run for days. It also seems to help when I get on it, before if I punch it too fast  from a dead stop it bog a little now it just goes . I would upgrade your spark and keep the intake for right now.

[mikepmcs]

ok thanks, i'm on it.  MSD7 spark box and the 750, keep the intake.  this is gonna hurt but i'm ordering it tomorrow. 

wait is this the right ignition box
MSD 7 AL 2 Ignition Box $350.00

or the MSD 7 AL 3 Ignition Box $620.00

that might have to wait, that's a ton of money for me right now.
thanks a ton for the help
v/r
Mike

[dodge freak]

The 7 al 2 is fine , the 7 al 3 is for drag racing, you don't need it. I have hear people have problems with it anyways. Now msd has the 7al+plus box for $570 or so, its too much, why they messed around I don't know, they had the 8 and 7 al 3. Anyways, when I called Summitt last year the sales guy was like no-no it burn up on the street, I  called msd they said with the right coil 7251 or 7261 it run all day just fine, its the 7 digital boxes you can't run on the street. Called Summitt again, was told no-no again, I told him what msd tech said, he put me on hold for 5 min. and said well they said it be ok, but I think you should get the 6 al. Thats what I had for 8 years, I wanted a new box and something better. Well I am very happy I got it, seems like my motor runs great everyday, not some days are better than others. Some guy on e-bay has some new 7al box's that have Mopar on it, hes got them at $249 + $15 to ship. I HAVE NO IDEA how they are, It sounds to good to be true, but his feedback is good. I buy my stuff from Summitt, only a manifold or hard to get part I get on e-bay, but just though I say something.

You can't have too much spark, with more and more gas having ethanol in it you need a strong spark, otherwise you just think its something else.

[mikepmcs]

thank you

i'll buy new from summit.

v/r
Mike

[dodge freak]

You are right its a ton of money, I was so worry I was throwing my money away, everybody kept saying the 6 al is all you need. Maybe, but like I said now it idle cold in gear, rough but does not stall. So I am happy, I paid more than $350-it was $375 I think, and I got the 7251 coil this spring, you need good wires too. Its a pain, and with gas $3 and going higher yet it makes me so happy I have what I do. Not sure if I do it all over again, but its a blast to drive.

They way I see it, if you are going to spend $379 for a carb or $250 for a spark box, you should just pay a liitle more and get the better stuff. Did not always think that way, but I leaned the hard way.

[Mike DC]

 
With new carbs & ignition parts, the weaker stuff ususally costs 2/3 as much as the good stuff.  Might as well get the good stuff. 

Besides, do you wanna spend $1000 on some high-end coated headers or aluminum cylinder heads or something, and then piss away the extra 40 hp on a bad carb setup? 

 

[mikepmcs]

Well, I did it.
Just got back from the emergency room.
Here's the summit slip.  I just hope I notice a difference from what I have on there now.
I'm pretty sure i got all the right stuff. Let me know if I left something out.  My wires are brand new accel but i need to make sure they aren't sold core.

Part #  Item  Box  Status  Price  Qty  Price
 
HLY-0-82750  CARBURETOR    Ready to Ship on 07/06/06  $499.95  1  $499.95
 
HLY-20-36  THROTTLE/CRUISE STUD GM    Ready to Ship on 07/06/06  $17.39  1  $17.39
 
HLY-20-7  LEVER EXT    Ready to Ship on 07/06/06  $6.88  1  $6.88

  MSD-7220  IGN SYSTEM 7AL-2 RACE V8 ONLY    Ready to Ship on 07/06/06  $380.88  1  $380.88
 
MSD-8251  COIL HVC PRO POWER    Ready to Ship on 07/06/06  $118.88  1  $118.88
 
SUM-800115  GAUGE FUEL PRES LIQUID FILL 15    Ready to Ship on 07/06/06  $16.95  1  $16.95
 
SUM-G1710  PRESSURE FITTING    Ready to Ship on 07/06/06  $5.88  1  $5.88
 
SUM-G3100  9-1/4" CHROME FUEL LINE    Ready to Ship on 07/06/06  $15.95  1  $15.95

Thanks for the help so far fellas. 
v/r
Mike

[dodge freak]

If you don't notice a difference with all that, you need to see a doctor. On your spark plugs MSD saids to gap them .050-.060. Thats too much , Smokey Yunick in his book Power Secrets claims motors make no more power after .040 and all a bigger gap than that just increases resistance and encourage misfire and crossfire. So I run .038 , I am not going to be changing plugs every month. You Might Have Wanted a New Coil Wire, thats all I can think of, the msd wire fits the coil better and it carrys all that power, Change it every year or 6 months if you drive it year round. And rev Chips, they give you 7000, 8000 rpms , they used to give a 6000, but no more so you might want that its nice to have, Auto Zone might sell them I think.

Was thinking about that VS carb, you know IF you ever want to change it to a DP all you would need is a different base plate and main body and a rear fuel bowl ,Holley sells all brand new. Yeah it be like $300 but you might find all or most on e-bay. Thats a great carb you have and even before you change to 3.55 it work great. after you put in 3.55 you might want to change the spring to a lighter one. You want the lightest spring with no bog.

When I hook my MSD box I had the pick up coil wires out of the dist. backwards, it idle ok but had no power, felt like I was towing a boat. I switch them and its been  great ever since. MSD tech guys are ok, they try to sell you stuff but then they do get it right. I had a hot missfire a month ago, MSD was not much help, I change the pick up coil, the  other coil, cap , rotor--It was a spark plug wire, mine were 6 months old but a boot touch the header and spilt. The MSd 7 was so strong it missed fire when hot but my old 6 unit did not. MSD thought my 7 box went out, but no I found the bad wire after I got my box back. MSD did send me 2 brand new wires for free, I ask for 1 so that was nice. I hope everything goes smooth for you, if not we be here, and so will Holley and MSD tech.  Those rubber mounts for the coil and box are a pain, I took a block of wood and some rubber washers for the box and coil to sit on, the box I have in front where the vapor can went, and the coil up by the dist. Home depot has all that, its up to you, maybe you can get those mounts to work, they think you are going to pull you whole car apart, no thank you.

I hope you love your new stuff as much as I love mine--heck I have been busy and did not drive my car for a week, it started up fine and ran great again. Did see a little blue smoke when it first fire, but MSD unit took care of that, no stalling or misses. Those 4 corner idle screws take time to set, but you get it right.  OH I just look , carb has 2 idle screws yeah you got a perfect street carb.Good Luck and have fun now.

PS I am a OZZY freak as well as a Dodge, other bands are good but Ozzy always has and always will be the "best". I have a kick butt stereo in my car and Live at Budokan is my favor's cd on the road.

[mikepmcs]

makes sense then, i'm an OZZY freak too!
thanks, i'll keep this post handy to read again when I get the stuff probably monday.
thanks again
v/r
Mike

[dodge freak]

Summit is great, log on to their web site and have your id # or order # and phone # it tell you who is shipping it and then you can go there and see what day you get it. They might send it fed. and you get it Sat.

[mikepmcs]

one box came with the msd today, so i'm just drinkin beer and mocking it up.  you said you ran your box by the can? are you talking right next to the battery then on the core support.
ordered the comp wires yesterday as well cause i just noticed my brand new accel's have little razor blade cuts all over them,     can't even imagined how that happened, they are brand new for pete's sake.  i did have my hood open all day at the last car show but i can't think anyone would do that here in maine.
oh well, now i got the right stuff and am ready to wqire it up.  i have no points so i'm guessing i will be running the purple and green wire setup.
now i just need to figure out what to disconnect??? The red wire on the new msd box if i read the instructions right, says i can use the existing + side wire on the old coil to tap that power, is that right??
ok well here's some pics of my setup  in the house and i'm gonna try and take pics as i go.  before and after stuff so in the future we can reference that and if i have any lessons learned sort of thing.

[dodge freak]

First I have Mut of a Mopar, its in really nice shape but its a St Regis-you might have seen them on the A-Team taxi cab wars or T J Hooker anyways I ripped everything out, lean burn, vapor canister, etc. That does take some room, I put my where the vapor can was, it was right where the battery is but the other side, it can go even in the trunk but its more work. MSD saids to wire the heavy positive and negative Right to the battery. Thats what I did, use 12 gauge wire or 10 if its a long ways. Fine a 12 volt lead that is 12 volts only when the key is on the run postion that goes to ING. The coil leads go to the top 2 C+ and C- with the red positive lead going to C+ and the black negative lead going to C- . The pick up wires from the dist go to M+ and M- what I did was to take a old pick up coil and snip the lead off 5 " from the plug it go either way on to the dist, this way you don't have to cut yours and its nice if you need to pull the dist. there is a male and a female post on that rubber boot I call the post thats bare metal male and the one in the boot thats in the rubber female . Hope you follow me-I am using 2 boots 1 coming out of the dist and the 2nd is the one I snip off my old pick up coil . The male post coming out of the dist is + and goes to M+ the female post thats in the rubber part of the boot goes to M- . This is the only "hard" part, like I said I messed up the first time and had them backwards so if they are not right the motor will run poor and just switch them- no harm- but I just look at mine and thats how it is. Thats is it, to mount it I got a 15" by 3/4" board of wood and screw the wood down with long sheet metal screws, I then screw the box to the wood with wood screw and used rubber washers under the box-no mounts too hard to use but it looks like you have a nice area to work so its up to you, I drive hard and its been fine that way. ON the coil I used 2 small prices of wood like 1" by 5" and screw it to the sheet metal by the dist, I then used wood screws again and screw the coil to the wood.

I hope this helps- you spent good money so I don't mind helping you. This is good-get that box running and then put the carb on. This way if someting is wrong you know its the box and not the carb.

[mikepmcs]

Hey, i started another thread called msd install.
http://www.dodgecharger.com/forum/index.php/topic,15845.msg176982.html#msg176982

i'm posting up pics.  I really appreciate your help so far, please stay in on the other thread cause i will probably need any tips i can get
i got you on this one.  c+/- you are talking coil and m+/- you are talking magnetic pickup, right?

ok my batt is on the drivers side and i'm gonna have to install on the pass side, just no room on a 69 and plenty of room on the pass side.  i'll put it around where the orange box is and the coil near by.  i'm gonna half to get some 10awg cause i'll be running wires straight to the battery  + and -.  the red wire is the only one right now that i can see i'm gonna have a little trouble finding the right ignition on power feed to. ok i'm just lazy but i was thinking the existing setup might have that already done for me.  i'll be mounting with the mounts provided but i do like your wood idea. i have a lot of room on that side to mess around(yeah i don't like drilling in to the inner fender but hey, it's all about performance right.

ok enough for now, i need a beer.
thanks so much for your instruction so far, it's PRICELESS!!!

v/r
Mike

[hewi]

G'day.

My DC is running a pretty standard 383 Big Block.

Is this carb too big?

http://www.trademe.co.nz/Browse/Listing.aspx?id=63531613

Also, is a year a bit long just to be sitting?

Cheers,
Hewi

Ps. Price is in NZ dollars

[mikepmcs]

Hewi
I'm gonna say yes to the 1150 holley, too much for a stock motor, but people much smarter than me will chime in.
i'm running a holley 750 hp right out of the box and it does fine, i have a moderate cam(mp 484), msd 7al ignition, 8251 coil and msd super comp 8.5's just like was suggested in this thread.  it runs like a champ.  no stumble but a little rich(my eyes are burning right now).  now i just need to learn how to tune it.
I hope i don't blow my motor.  i just dialed in the timing again at about 37* at 2800 rpm.  no vac advance hooked up to the dist.  took it down the road and it seemed to do ok.  i have 2.7's in the rear so no holeshots but it didn't stumble when i romped on it.  my only concern is that it stays revved up now when i let off the gas at idle, still haven't figured that one out yet, maybe i need a stronger return spring but i thought mine was plenty strong.  it seems like it's sticking or something. who knows??
anyways to answer your question, i think that would be good on a race application with a built motor.
v/r
Mike

[dodge freak]

I use two springs on mine-one from the throttle bracket on the bottom and the other in front from the throttle level to a post on the intake. Its hard to get the right springs some are strong enough but you can't open the throttle all the way. Bet you don't even know what jets are in it, maybe 73 or 72 -what ever they are go down in the front side 1-2 sizes. Holley says always move 2 jet sizes at a time but I can feel one size. You won't hurt anything by it a Little to rich-too lean yes, thats why I go just a little smaller on the jet. NO rods like the eddy carbs-yea - the power valve opening you can change but its most likely at 6.5" which is fine. I doubt if its opening, some people run a 5" or even 4 or 3" but thats for very hot cams. When the vacuum goes under the power valve rating-like 6.5" thats when it opens. They go as high as 10.5, 8.5 is good for stock motors but all holleys come with 6.5" .Have you try the idle screws, thats all it might be, it should be jetted very close to what you need. The float level too matters ,take the little screw off the side of the bowl and see if the fuel comes out, it really should not motor freshly turn off until you push on the fender to rock the car. You need to get a Holley repair and tune book. Too much to cover but its easy. I use those gloves the dentist uses, gas stinks.

[hemigeno]

I know a lot of guys swear by the C.I. x 2 = CFM for carburetor sizing, but I disagree with that calculation.  Hewi, the Holley tech you were talking to earlier was giving you the same advice I would give you if I were calculating the optimal CFM for your engine.  Here is the formula that an OLD-time carburetor guy gave me, and it's been backed up by a couple of engine gurus that I deal with every now and then:


       [Engine CID]  x   [Expected RPM Maximum]
---------------------------------------------------------------      =    Optimal Carburetor CFM
                               3456


So, for your 383 engine, with maximum 6,000 RPM, the calculation goes like this:

         383  x  6,000                    2,298,000
-----------------------------   =    ---------------    =   664.93  CFM optimal
              3456                             3456

Based on that formula, anything larger than the 670 carb that the Tech recommended is wasted potential CFM.  Your engine is only going to pull so much air through the venturi, and putting a larger carburetor on only slows down the air going through it.  When that happens, your carb is harder to tune, more prone to bogging down, etc.

I'm nowhere near the engine expert that Chryco, Ron and some of you other guys are, and I'll leave the Vacuum vs. mechanical secondaries debate for others.  However... I have heard over and over from some very savvy engine and carburetor guys that the biggest mistake most people make when working on their engine (especially street engines) is oversizing the carburetor.

Do what you want to, but I agree with the 670 cfm recommendation you were given.



Geno

[Ghoste]

There is a factor for volumetric efficiency but that depends on cam, heads, exhaust and so forth.

[hemigeno]

There is a factor for volumetric efficiency but that depends on cam, heads, exhaust and so forth.

I agree, but I was told that the same formula I posted would handle most of the cam/head/manifold combinations seen on anything but a race motor.

[dodge freak]

On a vacuum secondary carb it only runs on the primary until the engine needs more. On a 750 carb thats only a 500 until the secondaries open. Thats why the factory went with those, Chevy had them on the 327 motors and 302.

[firefighter3931]

I know a lot of guys swear by the C.I. x 2 = CFM for carburetor sizing, but I disagree with that calculation.  Hewi, the Holley tech you were talking to earlier was giving you the same advice I would give you if I were calculating the optimal CFM for your engine.  Here is the formula that an OLD-time carburetor guy gave me, and it's been backed up by a couple of engine gurus that I deal with every now and then:


       [Engine CID]  x   [Expected RPM Maximum]
---------------------------------------------------------------      =    Optimal Carburetor CFM
                               3456


So, for your 383 engine, with maximum 6,000 RPM, the calculation goes like this:

         383  x  6,000                    2,298,000
-----------------------------   =    ---------------    =   664.93  CFM optimal
              3456                             3456

Based on that formula, anything larger than the 670 carb that the Tech recommended is wasted potential CFM.  Your engine is only going to pull so much air through the venturi, and putting a larger carburetor on only slows down the air going through it.  When that happens, your carb is harder to tune, more prone to bogging down, etc.

I'm nowhere near the engine expert that Chryco, Ron and some of you other guys are, and I'll leave the Vacuum vs. mechanical secondaries debate for others.  However... I have heard over and over from some very savvy engine and carburetor guys that the biggest mistake most people make when working on their engine (especially street engines) is oversizing the carburetor.

Do what you want to, but I agree with the 670 cfm recommendation you were given.



Geno

Geno is bang on the money here.  The 2 x cid works well for a race type build that spends most of it's time at high engine speeds and low speed operation isn't a consideration. Too big of a carb is difficult to tune and often results in poor throttle response/bogging etc.... on the street.

Fwiw, if you want to use VE (volumetric efficiency) in your calculations the correct factor is .80 unless the heads are heavily ported.


Ron

[dodge freak]

Well I think the factory's knew what they were doing when they had a 273 dodge motor with 2 - 500 cfm 4 bbl carbs as a high performance option. Or all the GM motors that had a 750 Q-jet on them-the Q-jet went on everything from the small 305 motors up to the 454 motors. It was able to do that cause the primary's were so small that even a low power 305 motor would run ok cause the secondaries would not open up much if at all. The 454 motors ran ok too because the secondaries would kick in fast cause the primary's were too small for it.

Maybe it is better to have to small of a carb compare to having too big of a one , but if you use that chart a 500 cid motor that spins to 5000 rpms would need only 723cfm carb. So a 750 would be too big for it. No way! Thats why they make vacuum secondaries carbs. The primary's stay close until the motor needs more air. Just cause it says 750 does not mean it flows 750 all the time. A 750 flows no more than 500 on just the primary's and thats without a choke, a 750 Q-jet flows about 250-300 on just the primary's.

There is good reasons racing motors have 1100-1200 cfm carbs and they only rev to 7500 or so . I am not saying any street motor should run those carbs, but a 750 vacuum secondary carb can work well on most motors if it has the right spring in the secondaries, might not give the best gas milage and be harder to tune than a 600 but it would not be crazy to run a 750 instead.

[hewi]

Hey guys (and girls  )

What do you think of this carb for a 383 BB?

http://www.trademe.co.nz/Browse/Listing.aspx?id=63116836

Would this be a good carb for me?

Cheers
Hewi

[dodge freak]

Thats one of those "phony" hp carbs. Well if he got the right metering blocks for it and base plate , yeah it be ok, but I bet he didn't , just the blocks is all you need. I would also stay with a vacuum secondary one. DP are for 4.1 gear cars and still they needed headers and a hotter than stock cam, the vacuum carbs are a better choice unless you know what you are doing and have the right set up for them.

[mikepmcs]

Hewi
what's the price on that carb, it wouldn't show it when i pulled up the ad.
v/r
Mike

[Rubberduck]

here´s a calculator for the  cfm:

http://www.4secondsflat.com/Carb_CFM_Calculator.html

I think 600cfm or 650cfm would be fine.
A bigger carb just needs mor gas.

Mario

[Beer]

I was shocked with my Stroker Smallblock when I saw the dyno and what the airflow used was on the 402.
I put had an edelbrock 800 on it, and it dyno'ed at 414 HP on 580 CFM IIRC. I will double check those figures when I am home, but I was expecting it to be high 600 to low 700's in the CFM. I may swap the carb out to a smaller one when it gets into the car.

[hemigeno]

here´s a calculator for the  cfm:

http://www.4secondsflat.com/Carb_CFM_Calculator.html

I think 600cfm or 650cfm would be fine.
A bigger carb just needs mor gas.

Mario

Thanks for that link, Mario...  already added it to the Favorites

Incidentally, I ran the same engine parameters that Hewi is using (383, 6,000rpm), and it kicked out the exact same 664.93 CFM figure.  More importantly, that number was listed as the 100% Volumetric Efficiency value, and if Ron/firefighter's 0.80 VE figure is used, the carb sizing is knocked down to 532 CFM.

I also don't take the factory's installation of a particluar size of carburetor as a cancellation of Bournelli's Principle.  Tom Hoover will quickly tell anyone who will listen that the Hemi would have performed better with a single 4bbl, but the public's perception of the motor would have suffered.  You can get OK performance from multi- and large-carb setups, mostly by utilizing progressive or stepped linkages, or finding some other way to limit how the throttle plates open up.

The use of vacuum secondaries does help, but the very fact that airflow through the carburetor is dictated by the engine's demand means that you are not utilizing the carb's full potential.  This can be proven mathematically.  If that's the case, why put it on there if it's not going to be used?  All it does is make the engine harder to tune.  It won't kill a car's performance to slightly oversized its carb, but it does not help it at all to put a huge one on there.  The POTENTIAL airflow is there, but IMHO the downsides far outweigh the bragging rights (and that's all the positives you get) from having a really large carb on your engine.

[dodge freak]

Well all I can say is that I went from a 650 DP carb which I got cause I did not want to over carb then after using it for 5 years put the profrom main body on when they first cam out it noticed a nice improvement. The engine is a 318 bore .030 with headers and 3.91 gears with a 2.74 first gear. Why it ran better if it needs only 450 cfm I have no idea, just sometimes real world works better than mathematically.

Its your money, go do what I did-buy a 650 carb then later on upgraded it to a 750. You may be surprise. I do have a MSD 7 al box and I know if I had the Mopar chrome box it would bog a little, it helps burn the fuel. Even over the 6 box I seen a improvement. I used to have to slowly -like a full second- floor it from a stop , now I can just punch it and it sounds nice and crisp. The closer your motors like stock the smaller the carb should be. With the 750 you have room to grow, if thats what you want.

[firefighter3931]

One other thing to consider is that the factory allways used a dual plane intake manifold. The divided plenum basicly has one side of the carb running 4 cylinders and the other side of the carb running the opposite bank....there is no left to right (venturi) sharing. When using a dual plane manifold the carburator requirement is higher so that's why the factory was often a little on the generous side.....think of it as a pair of 2bbl carbs running a pair of 4cylinder engines. Also with the carbs being vacuum....it was an "on demand" useage as opposed to a mechanical secondary which forces the air/fuel down the engine's throat. Just because a vacuum secondary carb is rated at 850 cfm doesn't mean the engine is using all of it.

Fwiw, mine was dynoed with several different carb and intake manifold combinations. The biggest carb didn't actually make the most power....surprising huh ?  The motor made as much as 560hp in one configuration and was pulling just over 800 cfm at 6500 with a VE reading of 110%....this is a pretty efficient motor that would be hard to duplicate with a factory head, dual plane manifold and running on pump gas.

Some things to think about next time you're considering a carb swap....


Ron

[Ghoste]

And with a single plane...?

[firefighter3931]

And with a single plane...?

Actually three....Victor, TM7 and the Street Dominator which is the one i settled on for a couple of reasons. I will say that this motor did not like the Performer Rpm dual plane....choked the engine off at 6000.

Ron

[Plumcrazy]

here´s a calculator for the  cfm:

http://www.4secondsflat.com/Carb_CFM_Calculator.html

I think 600cfm or 650cfm would be fine.
A bigger carb just needs mor gas.

Mario

Thanks for that link, Mario...  already added it to the Favorites

Incidentally, I ran the same engine parameters that Hewi is using (383, 6,000rpm), and it kicked out the exact same 664.93 CFM figure.  More importantly, that number was listed as the 100% Volumetric Efficiency value, and if Ron/firefighter's 0.80 VE figure is used, the carb sizing is knocked down to 532 CFM.

I also don't take the factory's installation of a particluar size of carburetor as a cancellation of Bournelli's Principle.  Tom Hoover will quickly tell anyone who will listen that the Hemi would have performed better with a single 4bbl, but the public's perception of the motor would have suffered.  You can get OK performance from multi- and large-carb setups, mostly by utilizing progressive or stepped linkages, or finding some other way to limit how the throttle plates open up.

The use of vacuum secondaries does help, but the very fact that airflow through the carburetor is dictated by the engine's demand means that you are not utilizing the carb's full potential.  This can be proven mathematically.  If that's the case, why put it on there if it's not going to be used?  All it does is make the engine harder to tune.  It won't kill a car's performance to slightly oversized its carb, but it does not help it at all to put a huge one on there.  The POTENTIAL airflow is there, but IMHO the downsides far outweigh the bragging rights (and that's all the positives you get) from having a really large carb on your engine.

Edelbrock 1806
Holley Street Avenger 670

[Chryco Psycho]

I don`t use the formula , I have installed 1050 dominators on 3 440s witha minimum gain of 40 hp & as much as 70 over an 850 , + the 6 pack is over 900 CFM rated as a 4 bbl , & it works fine