Carburetors.......

[AntRant]

Heres acouple of questions i got.... I'm going to probly have a 400HP(+-)460BBF. I'm thinking of a Edelbrock Performer, or Steath Intake. I dont plan on anything over 5000rpm. What is a good CFM? 600,650,700,750? I would like the best fuel economy and performance. And what about Secondary's? Mechanical or Vacuum? Why? I under stand how the secondarys work i just want to know why you perfer either.I'm so confused on this issue......Almost forgot, has anybody run one of those PREDATOR Carbs?
[ August 18, 2002, 07:25 PM: Message edited by: AntRant ]

[77charger]

go with the stealth over the performer.As for carbueration a 750 will do the job a mech is better since you can adjust the secondary jetting.the vac secondary you need to get a few parts to make it work(metering block for rear,spring kit).I myself run a vac secondary carb(holley 3310)but have changed out the rear block and did the spring and it is pretty responsive and when wide open is doing the same job as the dp.I am also running a nitrous unit also.

[HammerDown]

Hey Ant, I'm using a 715 Vac Secondary on a 10:1 468 at 53-5400 rpm's....With the Stealth.
Its plenty of carb!
I had to try my nice big 850 DP...it did nothing for the motor! Its sitting on my bench waiting for MUCH more motor, with MANY more rpm's. (I'll sell it to ya)!!!
[ August 18, 2002, 07:27 PM: Message edited by: HammerDown ]

[HOSS]

I would lean towards the stealth also, I run an RPM performer. I would however run an 850 mechanical.

[AntRant]

Now is the Steath any taller than the Torker I? I have limited space on my CVX20.

[AntRant]

On a Edelbrock i have i noticed the vacuum secondary use what looks like a counter wheight for the secondarys. now as you hit a wake or if you trottle from 1500 to WOT is it possable for the butterfly the rock open and close or does the vacuum hold it?

[Hotcrusader76]

AntRant:
On a Edelbrock i have i noticed the vacuum secondary use what looks like a counter wheight for the secondarys. now as you hit a wake or if you trottle from 1500 to WOT is it possable for the butterfly the rock open and close or does the vacuum hold it?Answer to that is no! It will not move on you.
As for CFM requirements for your engines Horsepower? 1.2cfm per Horsepower is all the cfm your motor will use whether it is 1050 Dominator or 650 Double pumper. So 480cfm is the only amount of air your 400HP motor will pull with that at 5500RPM. When you talk about Holley's advertised cfm ratings, 650, 750, 850 etc; these are catorgories for the venturies and the vacuum signal they respond to, people tend to be mislead into their actual meanings.
For your motor:
A 650 is going to be better off the line and stronger within the lower RPM band.
A 750 is a great choice for upper RPM conditions with little of a sacrafice on the lower end, no big deal with your cubic inches.
The 850 would hurt you alot down low but would be great for the 6K band, but your motor starts to drop off on the horsepower at 5000RPM (dependant on cam specs).
See who gives a shit if a carb flows 750 (advertised cfm) and some speciality shop said it flows 20cfm more with some special trick. They are only changing the vacuum signal, which pulls more or less fuel for your fuel requirements at any given RPM. NASCAR uses 390cfm carbs that flow 750cfm at 7000RPM with 500HP...How is that? Because your motor determines the cfm it wants, not you. But the vacuum signal of a 390 carb is so much different, that at 7000RPM it is sucking fuel like you wouldn't know! I mean guzzling! But the body is only 390cfm....So what! The motor is 500HP and its determining the cfm is wants. That's just physics!
Hope I haven't confused anyone.
Stick with the 750...it is a great move if your consider to move into more horsepower and higher RPMs over-time, for Marine use.
Give us a call if your interested in having one custom built by TPC Racing.

[HOSS]

Hammerdowh, how much?

[Hotcrusader76]

HOSS:
Hammerdowh, how much?Cost?
This all depends on what your needs are and what you want? I offer Anodized Billet aluminum baseplates, severe duty parts, Chrome, polished main bodie venturies, Race Banjo style boosters....I need more info than just a horsepower rating and motor size. On my website there is a form that you fill out so I can determine what will work best for you.
Overall 4779 Double pumpers start at $499 Stock Custom assembled and blueprinted w/ free color choices and can climb up to over a thousand trimmed in all Billet aluminum, Chrome bowls, Marine J-tubes, sealed throttle shafts, HP bodies with adjustable air-bleeds....List goes on. The average 750cfm Double pumper can be close to $600.00.
You can also send in your used Holley carburetor to be reconditioned/overhauled to brand new, with the sames options at a smaller price as well.
It's best to give me a call so I can work a price to suit your needs and wants.
-Ty (877) TPC-CARB

[AntRant]

Hotcrusader76, I'm still a little confused about CFM. If Nascar uses the 390cfm how does it flow 750? Wouldnt 390cfm mean 390cfm?I thought that the advertised CFM meant what the carb would flow of air. Or does it represent somthing else? Can you explain "vacuum signal" then maybe ill get it.

[Hotcrusader76]

AntRant:
Hotcrusader76, I'm still a little confused about CFM. If Nascar uses the 390cfm how does it flow 750? Wouldnt 390cfm mean 390cfm?I thought that the advertised CFM meant what the carb would flow of air. Or does it represent somthing else? Can you explain "vacuum signal" then maybe ill get it.Without getting all scientific about it, the 390cfm carbs are rated that way because of flow yes (advertised flow on a flow bench)! But not the amount your motor can get from the them. The NASCAR motors pull 750cfm from a 390cfm (flow rating on a flow bench to ensure regulations are adhered to) without a hitch at 7000RPM with motors that can produce 500+HP. The small main bores of the 390 with the anullar boosters create different vacuum signals (with help of the motor pulling air) for the air/fuel ratio to mix. Air coming through the carburetor flows over the booster, kind of like a round airplane wing, creating a low pressure signal inside the booster, drawing fuel (mixed fuel and air from the emulsion circuit, higher pressure) out of the fuel bowls. Changing the size of booster can change the rate and time when the low pressure exists at any given RPM...allowing the fuel to flow with control. (Computer chips in Fuel injection computers decide all this shit for you).
The reason the 650 is better for low end torque on the 460 is because the signal allows fuel to flow at for the characteristics of the 460 Ford and similar BBC. Magazines all the time create stroker 450HP small block motors with 750 Holley Carbs or even Demons...then switch to the 625 or 650cfm carbs and get phemoninal results with the change. This is why "Bigger is not always better".
Now a drag motor pulling air at 9000+RPM at 130MPH needs the signal to respond strong at the higher end. So opening the main body venturies up to 1050, with different boosters and all, changes this fuel demand. This is why the Dominators don't respond worth a shit on the street, unless you have a 3500 Stall converter transmission....but for the street? See what I mean.
Now the metering blocks determine the Air/fuel ratio along with the air-bleeds in the main body. The main body venturies and boosters determine signal.
Sure the stock off the shelf Holley is great for the average user, but to nickel and dime a 20% increase more of HP/Torque potential is can always be worth it.

[Hotcrusader76]

AntRant:
Hotcrusader76, I'm still a little confused about CFM. If Nascar uses the 390cfm how does it flow 750? Wouldnt 390cfm mean 390cfm?I thought that the advertised CFM meant what the carb would flow of air. Or does it represent somthing else? Can you explain "vacuum signal" then maybe ill get it.Yes 390 is the cfm rating....on a flow bench. But if your motor pulls X amount of air....390 is only affecting the signal. So yes you could modify a 650 to work just as good as a 850 on the same motor...but why? It would cost to much to work it, when you could start at the same price with a 850.

[Kamakazi Ken]

Hey "HOT" you started off confusing the hell out of me but as I continued to read your posting it made sense. I had a guy tell me "there is no way" I could make more than 400hp. with my 650cfm carb (460 .030 over)
The first thing he asked me was if it was an 850 when I said no he thought I was yanking him...
any ways
Thanks
K.K. eek! eek! eek!

[RH]

Hotcrusader76 ,
My 460 came with a Edelbrock Performer and a #2779 Edelbrock , Engine was rebuilt 200 hrs ago so I know nothing as far as specs on the motor . How are the Edelbrock carbs compaired to everything else on the market . RH

[Hotcrusader76]

RH:
Hotcrusader76 ,
My 460 came with a Edelbrock Performer and a #2779 Edelbrock , Engine was rebuilt 200 hrs ago so I know nothing as far as specs on the motor . How are the Edelbrock carbs compaired to everything else on the market . RHLOL...to each his own!
Edelbrock? Don't know much other than they aren't easy to tailor for your motor, nor are the parts in abundance.

[Hotcrusader76]

Kamakazi Ken:
Hey "HOT" you started off confusing the hell out of me but as I continued to read your posting it made sense. I had a guy tell me "there is no way" I could make more than 400hp. with my 650cfm carb (460 .030 over)
The first thing he asked me was if it was an 850 when I said no he thought I was yanking him...
any ways
Thanks
K.K. eek! eek! eek! Funny I think...Because Car Craft magazine did a 383 build-up and they pulled well over 400HP with a 625cfm Demon. Don't get me wrong....a 750 is alot better for that 383...but when you want the power curve to dip closer to the 2000RPM range, then by all means use the smaller carb. But when your running down the track, and top speed is the goal, go with a little more cfm and different boosters.
If this was all so easy to understand, then there wouldn't be Carburetor speciality shops. If the shop knows what they are doing, then you shouldn't have a problem getting a carb custom built for your motors characteristics. The more info the shop asks for, the better the carburetor can be tailored. Get as much cam info to that shop so they can figure out your exact power curve, and also provide good head info, casting numbers, or flow data.
Engines and cars all work together in tandem. Not one part being labeled as universal has made a difference in power or torque. IE. Carbs, Heads, Pistons, Ignition set-ups, etc.
Air, Fuel, Spark....Oh yeah!

[AntRant]

Hotcrusader76, Thanks for break'n it down!!!Finally some one who explained it in terms i understand. :D :D :D

[HOSS]

hAMMERDOWN, WHAT DO YOU WANT FOR IT?

[HammerDown]

Sorry about that Hoss...I may have a local who's intrested in it.(for his car). I rebulit it about 6 months ago...stock jets and pwr valve. When I took it off the boat, I again tore it down, sprayed wd-40 on all the parts and bagged it up.
If he backs out, I'll e-mail ya.
PS. it comes with a braided fuel line and VDO guage.

[Unchained]

HotCrusader76, Thanks for your carb engineering input, For my application, Blown 540, I just bought off the shelf 850 Holleys and bolted them on and have run for three seasons. They have run pretty well right from the start. Close to stock jetting also and the plugs read OK. What mods does it entail when companys sell special blower carbs? Am I missing something? I know I don't need boost referencing. I would send them in for mods if I thought I would get more performance.
Mark

[Hotcrusader76]

Unchained:
HotCrusader76, Thanks for your carb engineering input, For my application, Blown 540, I just bought off the shelf 850 Holleys and bolted them on and have run for three seasons. They have run pretty well right from the start. Close to stock jetting also and the plugs read OK. What mods does it entail when companys sell special blower carbs? Am I missing something? I know I don't need boost referencing. I would send them in for mods if I thought I would get more performance.
MarkFor a dual set-up, having both carburetors identical is very crucial. Making sure the fuel is being drawn out, when air is being pulled through a set of forced induction carbs @7-8psi is difficult, unless you have the correct signal at the boosters. Running 8psi or so requires annular boosters for optimum performance in a dual set-up. Making sure the floats all weigh within grams of each other is important for air/fuel ratios, in respect to fuel float levels. Ensuring that the transition slots are identically positioned on "both" baseplates is another great asset to have on acceleration...
Basically alot of blueprinting!
Interpreted as: measureing and correcting for flaws or tolerances out of "specs" within the cut metal. Yeah you can just bolt two carbs on and go, but there is so much more potential with delicately massaged carburetors. They are the Air/fuel ratio for heavens sake....Two of the three variable in the whole equation "air, fuel, spark". So why isn't more attention paid to this system? Got me...
Boost referencing is something I would recommend for a street driven blown car, or even a mild track driven blown car. Boats though? Block those puppies off and run her hard! Being that most boats of this nature are at 5-6K all the time, the powervalve is only used about 10% or less, of the time.
If you ran the carburetor with a 10hg pwr valve (dependant on your motors vacuum), at 2000RPM or so, your motor might be at 15hg+ or so at that RPM, meaning the valve is going to shut around 12hg (with a 10.5hg rated pwr valve). So if you cruise at 3000RPM, at the least, then your engine vacuum on acceleration, might never dip below 13hg or so, meaning the pwr valve was never able to even open to assist on the acceleration. Why? Because your motor is pulling enough fuel at that point from the boosters via the main well jets, and the carburetor continues to perform as it should. Power valves? Alot of controversie on the issue...
Note- 660 center squirters are the best dual carbs for a "street driven" motor....Proven over many years to be that, also.....They don't have power valves...and come from Holley that way! Hmmm ..Nuff said! http://www.plauder-smilies.com/thinkerg.gif
Motors with more radical cams,when less vacuum is produced....nearly always require to block these pwr valves off.....or if there is so much cam they probably don't even run carburetors, but maybe Hilborn injection systems or something. When vacuum is too low...they just don't make pwr valves with low enough hg.ratings.
Ok...no more confusion at this point. http://www.plauder-smilies.com/eek2.gif
-Ty

[S/C Rebel]

AntRant:
Now is the Steath any taller than the Torker I? I have limited space on my CVX20.Yes, it is. I don't have any figures (holley.com will have height values for the Weiand). but I have the Stealth and a friend runs the (original) Torker, both on 460's. I have read the Stealth is better (broader), but for the RPM range jets operate in I hardly think it matters (the Torker makes good power above 2500). Your money is better spent elseware (like the carb) IMO. As for carbs, I've been happy with my 800 dp Holley and my friends boat works very well with a 750 vac sec Holley. If your concearned with economy go with a vac sec carb.
[ August 22, 2002, 06:04 PM: Message edited by: S/C Rebel ]