I have a 71 460 with Dove-c heads little bit of porting done. No major modifications. Edelbrock intake, hooker super comp headers, mild cam. It is going into a 81 F-150 converted to staright axle dana 60 HD front and Dana 80 rear with 4.10's with 38 inch swampers. I am using a NP 435 tranny. I use the truck alot off road but also drive it almost on a daily bases. I was wondering which carb I should use or at least what size carb any help would be appreciated. I would really like my truck to be extremely reliable and start all the time and if not to much to ask I would like it to idle.

 

my 780cfm vacuum secondary holley turned my stock 460 into a tire burner, i set the floats, put the mixture screws 1 1/2 turns out, put the timing at 14*BTDC and havent touched it in 3 years (except for the timing).....when its not 20 degrees outside it purrs like a big cat at 650 rpms all day long..........a 750 would probably do you just fine, if it doesnt seem like enough carb when you put it on there its real easy to put bigger jets in it and get it closer to 850cfm, but i believe 750 will be ideal for your truck....

 

Thanks for answering it seems very hard to get people to respond to carb questions. I will probably go with a 750 or somewhere right around there I will probably stick with holley don't really like edelbrock. Possibly a truck avenger

 

What is the max rpm you plan on turning with the engine and where does your cam make horsepower. These questions need to be answered before an intelligent carb choice can be made. Just because something worked for Johnny doesn't mean crap with your motor. There is a formula for carb size for an engine, however you need to know max rpm to make it work.

(RPM times CID) Divided by 3456 = CFM

That's max RPMs
CID in inches

Example 4500 X 460 = 2070000 divided by 3456 = 598.9583 CFM

Which is why stock 460's have a 600 CFM carb with vacuum secondaries.

For a street engine it is always better to be conservetive with CFM and always have vacuum secondaries.

 

i tried that formula and it said i needed a 599 cfm carb, well, i had a 650 on my stock 460 and it had less guts than a 6 banger and got about 6mpg, with it timed right and a good tune up i couldnt even come close to breakin the tires loose, let alone pull a heavy trailor. since i put the 780 vacuum secondary holley on it i cant keep the tires from spinning, plus i can almost pull the trailor i hauled at work right out from under the ditch witch that was on it, not to mention i now get 12-14 mpg if i keep my foot out of it. that formula, IMHO, is good for finding the CFM rating for a 6 cylinder, i know about all the arguements that support it so dont get all mad because im stating my opinion about it, i just know what works on the various 460's ive worked on in past years,not just my own.... another example, my friend bought a 79 F-250 SC with a stock 460, it had a 650 holley and no guts at all, he found a 750 double pumper at work that was run on a circle track car, we kitted it and put it on the 460, BAM!!! another tire shredder that will pull your house down the street, and niether of these engines bog out or fall on their face like people say they will with a 750 on 'em....if you dont believe me, look me up if your ever in oklahoma city and my friend or myself either one will make a believer out of you like we have all the others..........i have a question for ya, if a stock small block chevy 350 calls for a 650 cfm carb how in the world would that same carb hold up to a big block Ford 460?? i use that comparison because i put a 650 holley on a camaro for a guy, and it seemed like the engine was still starving for gas, but a 650 is what every parts store told me was the application for that motor........i dont see how a small block 350 could need a bigger carb than a big block 460, just dont sound right.......

 

First off the stock carbs on the 460's were all 600 CFM, however the 4180 carb is an emissions carb and without work gets poor performance and mileage. The 780 is to big and the only reason it works better is that it is a preformance carb and calibrated as such. It's cheaper and not hard to mod the stock carb. The reason the extra CFM isn't hurting is because the secondaries are not opening all the was. The vacuum controller only feeds the engine what it can use. The small block chevy is over carburated and gets away with it by reving quickly, very light car and better gearing. But make no mistake, it is overcarburated. My 428 CobraJet came with a 735CFM carb and that more made 425HP at 6000 rpm. Do the math it works. By the way a double pumper on the street is crap, they will bog badly and you will never know it unless you have a drag strip to see the 60 and 120 foot times. They belong on race engines only. It's same deal as running a tunnel ram on the street, looks cool but it won't preform for crap.
The reason the parts store guys tell you to run a 650 is because the majority of them only now what they are told to sell. They be parts boys and not racers. Besides a 650 cost more than a 600 and they make more money. If you are believing parts counter boys then I have some water front property for sale. Oh yeah, back in my youth I loved being sent to Kansas, Oklahoma, Texas and anywhere in the southeast, the street racers were all ***** and show. But I went home with their money everytime and usually won at the track too. I have got the trophies to prove it too. Their money I spent on extras.

 

never said i believe them, i do believe the reference books they all have though, and thats what i found the numbers from. most parts stores i go to i have to draw them a map to get the right part so i know what your saying about the employees. like i said, im not trying to diss the formula, im going on what ive done and have seen done with my own eyes because they are about the only thing i trust. as far as the double pumper im with you, they dont belong on the street, but the truck i spoke of runs like a scalded dog and he doesnt mind only getting 5mpg.

 

Why can't we all just get along? Run whatever carb you want on it, it's your choice. Just because someone says it's wrong, doesn't mean it is. That formula works great for very, very mild street engines and tow vehicles, producing awesome low end power and torque. If you modify a number of things, not just one or two, a larger carb will work better. If that formula was the "Be all, end all" then NHRA and IHRA Pro Stock racers would be running way less than the 2400+ CFM that they do. Go with what works. If I had the cash, I'd put a 750 or larger double pumper on mine, but, for reliability sake, and the fact that I have a VERY heavy right foot, I'm going to rebuild and tune my stock carb, which, FYI, is 580 CFM, not a 600.

 

See there you go talking about what you don't know. In a race, not street race, but prue race engine you go 20 to 30 percent oversize because that engine will never need to make power down low, where down low is where a street engine lives. I wasn't aware that a Factory Ford 428 CobraJet was a
"very, very mild street engines and tow vehicles, producing awesome low end power". Pure stock in a 3800lbs car with a 200 lbs driver it ran in the 13's with street tires. I built one for a pure race car and that one was 3400lbs and went 12.90 the first time out. Ran 12.20's at over 120 mph in the end. Oh yeah, I towed with the stock one. So I know, from expereince what I'm talking about. BTW I also set 3 world records and won 2 National Championships while racing boats, doing all my own engine work and set up and driving. What are your qualifications to talk about setting up carbs on engines?

 

I used to race the heck out of my old Schwinn Stingray and I built that sucker for ball bustin landings after rocketing 6+ feet horizontally from a jump. I don't know jack about performance carburators except how to follow instructions on rebuilding and rough setting the screws. I am in the market for a good carb for my freshly rebuilt 1968 460 in my 74 F250 4x4. I need information and would appreciate you guys holding on to your testoserone for a few to just get out some good info. Differing opinions are fine and we will sort through the plethera of info to come to our decision. It's just hard to read when people are mean to each other. That is not what this site is all about. You're all great and have so much to offer the other members. Lets be nice okay?
Thanks in advance, Tim

 

maybe he missed that part.....im not on here to prove i know more than everybody, id be a fool if i thought i did....

 

Sorry about my sarcasm. It slipped. I hope I didn't offend anyone....

 

Congratulations on your achievements, I have great respect for what you have presented to us. I mean that sincerely. But you asked my qualifications to be setting up carburetors on vehicles, so, let's see if you can understand this. I am not a crew chief on anything but my brother and I's race truck, which I also share the driving duty's. By the age of 10, I knew more about Holley carbs than some of the guy's we raced with, and by 11, I was setting up Holley 2 and 4 BBL's to run on the street. By 12, I was rebuilding Motorcraft 2 barrels, which run perfectly to this day. I am not an award winning crew chief or driver, but I have enough common sense to set up a carburetor for the respective vehicle and characteristics it will be used for.
A 428 Cobra Jet was a hell of an engine, but you must consider that technically, the carburetor was still oversized. The proper way to use the formula is ( (MAX RPM x Engine CID)/ 3456 ) x Volumetric Effeciency

Using your 428 x 6000 RPM ceiling= 2,568,000 / 3456= approx. 735 x .9( a very generous 90% Volumetric effeciency) we arrive at 661.5 CFM required. Care to dispute Holley's own math?

 

First off a Holley field rep laid this formula on me while I had a part time job while stationed at McConnel AFB in 1970. I was working at a dyno show and the ower held records in 3 Super Stock classes at the same time. I listened , learned and try to pass on to others what works in the real world. I watch way to many guys find out what Grumpy Jenkins had on his race engine and then find they had nothin' but a street slug that looked pretty. BTW the vacuum secondaries will cover up the 10 to 20 percent oversize as the won't open all the way. Oh yeah, the factory numberwas 6000 rpm on the CJ, but it saw 6500 often during races. If you run the numbers for a 460 at 4500rpm you get 598 and the formula works at that number as long as you don't go with a duble pumper, which is a street no-no. Had along weekend and was a little tired the last couple of nights. How about I apologize for get snotty and let it go at that? That because my youngest is older than you are. Oh yeah, my favorite race set up was a tri-power off a 406 on the 428CJ. A lot of little holes are better than a couple of big ones, this is why the 960cfm triple Holleys worked. The 428CJ was closer to a real race motor than a street engine and thats why a large carb was necessary. One last note, my favorite saying is as follows and is true;

Old age and treachery will out do youth and enthusiasm everytime!

 

I dont want to start any fueds but obviously you guys know a hell of a lot more about carbs than I do. I've got a 68 429 with DOVE heads and Edelbrock Performer RPM intake, comp cam 226/234, hooker super comp headers. 11 to 1 compression. I did the Holley math thing and got 730. My cam is made for 1500-5800RPM. If I get a 750 will it be too much? If I get a 650 will it be too little. My uncle suggested I go with the 650. Hes built a lot of motors but not a lot of performance stuff. I am hoping for the best possible performance on a budget so any suggestions?