True! It is a battle within my self on just how far to take the engine. I want the truck to run 11's in the 1/4. I mainly been trying to decide how far I want to take the engine and then start the n2o. That is why I want to be able to just drive the truck around now. I have been in or around racing all my life. I want a "street" truck. It has to go 11's if not faster. That is the main and only true goal in my project. Like I have said though between now and then I might decide different about the soild cam. I only plan on driving the truck to work on pretty days and maybe take the wife around town on the weekends. Also track time. I just don't know if a hydo cam could give me what I need. I still trying to figure every thing out.

I know it is a pain in the butt to set lash. Kinda fun though! You have to say!

 

Back to the stripped squirter threads... If you plug the hole you will lose off idle drivability. The squirter gets it fuel supply from the accelerator pump which is on the bottom right front corner (looking from the bumper back). You'll see a small arm with a spring tensioned screw coming from it to the throttle linkage Normally this is a 30cc pump, with the option to install a 50cc. It allows the engine rpms to build enough to pull fuel out of the main metering block for part throttle response or when you decide to hammer down on it. As for interchangability, you can get a different main body as long as it is of the same style ie... 4150, 4160, and so on. The proform main body is a good choice if you don't want to have the choke housing which will improve airflow but you will have to hold the gas open until it idles after warming up.

 

I looked at the protoform looks nice. But I think I found a friend with a 750 without the kick down. I think I am going to try and put this on until I can pull the engine.

 

All a helicoil is is basically new threads. You buy the thread inserts, drill bit and screws in a set. Get one just slightly larger than the stripped hole. You then use the bit with a stop on it if necessary, put in coil, then new screw. Should be a simple job. Good Luck.

 

The heli-coil will fix the threads and not screw up anything. As for the tubes, if they come out I just push them back in and stake the suckers in on opposite sides. Never had one come out either and I worked on thousands of carbs having been a marine mechanic. BTW the stock 460 carbs are 600cfm not 750. Also saving money on a carb is stupid, by the best High preformance carb you can find and it ain't no metering rod carb.

 

The holley that came stock on my 83 F250 was 750 and I've had two or three of the bolts break trying to remove the tubes and usually end up breaking one or both of them as well. I just pull it all out and block it off. No more leaks.

 

Ford used a Holly carb made to their own spec's numbered 4180. They were all 600cfm carbs as they were used on a number of different engines. As far as I can remember Ford never used bigger than a 600 on any of the standard engines except a few hi-po engines the CJ's and Boss engines come to mind. A truck engine? never.

 

The question about your 770 being big enough is easly answered using a formula recommended by holly is as follows:

max rpm x total cubic inches devided by 3456
Then you will not get 100% of this, more on the range of 80 to 90% max on a street car.

This is an example:

6500 rpm X 557 ci =3620500 devided by 3456 =1048 (rounded) x 85% = 890cfm

All these numbers are just an example, the formula will work with any cubic inch and rpm.

Hope this helps

 

That formula has been around for better than 50 years and you know what, it works very well. My '69 428CJ had a 735 cfm Holley(a 780 with bell booster venturis to boost air velovity and limit volume in the primaries) from the factory and the stock motor with C-6 shifted at 6000 rpm's. The formula says the motor need right at 735 cfm to turn those revs.

 

Thats right Bear, and your 600 you talked about is all a stock 460 needs because at factory stock it would not pull more than 80% max, and that may be jenerous saying it would pull 80%.

A lot of people buy to much carb.

 

And over carburating causes a loss of low speed performance by causing a stumble that most people using the seat of the pants system of testing sense as harder acceleration. When in reality is is slower against the clock because of the stumble. The stumble is caused by the air flow dropping to or near zero in the venturis when the over sized carb is cracked open. Another reason why a vacuum secondary is better that a double pumper in most cases other than all out race engines, which really suck on the street.

 

I'm sorry, but with all due respect, that is just plain incorrect.

A stumble is just that--a stumble, sometimes called a "hesitation".

This is a situation that occurs when the throttle is mashed, and there is a momentary "hesitation" that occurs before the engine surges forward.

If we're talking about something in the carburetor that is causing a "stumble" or "hesitation" (as opposed to many different other issues, such as improper ignition timing, vaccuum leaks, one or more cylinders with low compression, etc.), this is almost always caused by an improper accelerator pump shot, and has nothing to do whatsoever with the size or CFM rating of a carburetor. It could even occur if the carburetor was rated at 200CFM!

There appears to be a misconception here--first off, if an engine experiences a "stumble" or "hesitation", it won't "feel" faster. It will feel *slower* as a result of the stumble.

Secondly, if the vehicle feels like it's "bogging" (a completely different phenomenon), then that should be a clue to anyone driving the vehicle that there is something wrong.

"Bogging" occurs when you floor the throttle and the engine is SLOW to accelerate, such as if the ignition timing has been instantly retarded.

If a car is "bogging", again, it won't "feel" faster--it will feel just like I described--like the ignition timing has been retarded.

Do you see the difference between a "stumble" or "hesitation" and "bogging"?

This is true as a general rule for the street, but if someone set their car up with the right components, it might be faster than a vaccuum-secondary carburetor.

They would need to be VERY good about tuning it, and they would have to select their parts exactly right to make this work, but there are people out there who can and have done this very thing.

This is not exactly true, as I'll explain below:

There have been some discussions in this and other threads regarding whether a 750CFM carburetor is "too big" for a 460; this should put that question or issue to rest, once and for all.

The Motorcraft Model 4300-D/4350 series carburetor was standard equipment on ALL 460's, both passenger car AND trucks from 1973 through 1978, and it was rated at 750CFM.

These were STANDARD and STOCK 460 engines, and during that timespan, they were low compression, low performance smog engines.

In 1979, perhaps in a dual effort to eliminate the carburetor division (they probably realized at that point that the future for them was fuel injection, and would be implementing EFI on *all* their vehicles within less than 10 years, which would mean they would have no use for a carburetor division to supply carburetors for their engines any longer) and most likely to improve fuel economy, Ford purchased and then started installing Holley 4180-series carburetors on these engines; these particular carburetors were rated at 600CFM.

For proof of these applications, here is a listing of rebuilt carburetors and their applications, straight from the Holley site (though this particular list is only for trucks, they were also used on all the passenger car 460's):

http://www.holley.com/Reman/DomCarb/FordTrk.html

Ford ALSO used this Motorcraft series on the 351 C.J and H.O. engines until they quit building Clevelands after 1974.

Furthermore, as to issue of whether or not a 750CFM carburetor is too large for a 460 or not, just think about this for a minute:

Ford has hundreds (if not thousands) of extremely well educated engineers, with degrees upon degrees, who spend literally tens (maybe even hundreds) of millions of dollars performing test upon test to determine the best combination on an engine to offer to the public, and then uses the 750CFM 4300-D/4350 series carburetors on the engines mentioned.

Based on that fact, I can say with all certainty (as I have said in other posts regarding this subject) that a 750CFM carburetor is not too large for a 460, or the factory would have never used them on their STOCK, low-compression SMOG engines.

 

How in the h*ll can you claim that a "hesitation" is when the "engine surges forward"? Either you are unaware of the definition of "hesitation" or don't care. The hesitation is caused by the air velocity dropping to low to suck enough fuel to make the engine rev up. I agree you can cover up a hesitation with a big accel pump shot, however the 30cc pump ain't always big enough with large cid engines or big cams, hence the 50cc pump on race carbs.

The reason the hesitation feels faster is because of the longer pause before the go happens. The mind plays many tricks on us and this is one of them.

A vacuum secondary or air valve carburator will only feed an engine as much air as it can handle. Otherwise not open all the way if the engine doesn't need it. That's how the 4300 series carbs get away with the larger capacity, cause engine doesn't use it. Ford used 780 carbs on hi-po engines never street truck engines. Also truck and car engines are not identical. Truck engines are torque beasts and need even less carb than a car engine due to the lessor cams run in truck engines.

I used to work in the Beechcraft airplane factory in the experimential dept. I can't tell you how many times engineers knew lots of theory and nothing about what does and doesn't work in the real world. Besides if factory engineers are so smart why is it there is an after market Hi-po business? I'll tell you why because the factory never engineers for anything for other than cost effectiveness in building.

You need to sit down with a calculator and use the afore mentioned formula. It not only works but will demonstrate why most hot rodder over carburate and if they use vacuum secondary carbs they get away with it because the carb covers their error by not opening fully. Back in the 70's I worked in a dyno shop. The boss was a champion drag racer in 3 different classes in super stock. Many a time we dyno tuned a guys car and we would see the the secondaries didn't open all the way. This is known by mechanics as to big a carb. Also the formula is printed in the Ford Muscle Parts books. Gee, maybe you assume to much to be a certainty.

I have been hot rodding engines for better than 40 years now and worked as a professional mechanic for 25 years. Plus I raced cars and boats and even won a National Championship or two being my own mechanic. But if you insist on knowing more than me then I guess my signature must be wrong, NOT!

Bear 45/70
Old age and treachery will out do youth and enthusiasm everytime

 

Let's get the definitions of the words used straight here:

1.) Hesitation or Stumble--a condition where, when the throttle is opened, the engine coughs, misfires, "stumbles" or nearly dies (and sometimes does).

2.) Bog--a condition where, when the throttle is opened, the engine accelerates at a greatly reduced rate, until such a point where the engine is operating within the RPM range at which it makes sufficient torque to accerlate the vehicle in question. Perhaps a better way to describe this condition is a "lack of response" when the throttle is opened.

Therefore, if a car has a "hesitation" or "stumble", and if we are talking about a symptom of a carburetor, as I stated in my previous post, that means that it is an accelerator pump issue, not an issue of a carburetor being "too big".

To further illustrate the differences and why it's important to distinguish between them, let's talk about some physics for a minute and discuss what makes a carburetor work and why. You may or may not know all this, and if you DO, it's for the benefit of those who DON'T:

Physics Facts:

Nature abhors a vaccuum; it tries to equalize any "pressure differential" that occurs. That means that if there is a lower pressure in one area and a higher pressure in another, when a means of connecting those two different pressures occcurs, higher pressure "rushes in" to try to equalize that "pressure differential".

Air is not "sucked into" an engine, rather it is pushed into the engine due to a pressure differential between the low pressure created by the downward stroke of the engine, and the higher atmospheric pressure pushing it into the cylinder in order to "equalize" that differential.

The "Venturi Effect" is a phenomenon where, if a stream of air or fluid runs through a restriction, it's velocity increases (this is oversimplified, but it will do for the purpose it's intended here).

When air or a fluid flows through a venturi, it creates a "low pressure" area.

All fuels require a certain amount of air (oxygen) in order to burn, and this amount is known as it's "air-fo-fuel ratio". The supposed "perfect" mixture of air and fuel is known as the "Stoichiometric" ratio.

Carburetor Facts:

A carburetor uses the low pressure created within a venturi to cause atmospheric pressure to "push" fuel into the stream of air, where it is mixed with the air and atomized.

When you open the throttle blades of a carburetor, the sudden rush of air into the engine causes an extremely "lean" condition, and in most cases will cause an engine to "stumble", hesitate", or in some cases, even die.

To overcome that issue, engineers created the "accelerator pump" decades ago, which enriches the airflow enough that the engine can "catch up" with the increased airflow and allow the carburetor to add the correct amount of fuel for the amount of air going through the venturis.

How a BOG occurs

We already discussed the reason for an accelerator pump--it is to eliminate the instantaneous lean condition caused by the sudden opening of the throttle plates (which subsequently causes the "hesitation" or "stumble").

A bog occurs, however, if the accelerator pump is already shooting the correct amount of gas into the carburetor, and the air/fuel mixture is correct, but, the engine has reduced "response".

As it relates to a carburetor, if you have too large a carburetor, or a too rich condition, this will cause a lack of throttle response.

Due to the "Venturi Effect" described above, it is a fact that air flow will have a higher velocity flowing through a smaller opening, and that's the case with throttle plates, too.

Therefore, a carburetor that has larger throttle plates will cause a reduced velocity, which will in turn reduce the amount of air flowing into the engine when the throttles are opened fully at LOW SPEEDS than the smaller throttle plates.

HOWEVER--it is important to note that these conditions are NOT a "stumble" or "hesitation" condition--they are a lack or reduced amount of throttle response, also known as a "bog". The car WILL accelerate (or continue to accelerate), it's just at a reduced rate.

That, my friend, is known as a "bog", as I've illustrated above

True, but if the engine needs it, it will feed it. That's why putting a larger carburetor on an engine almost always increases the power it makes (to a point), as long as the carburetor is set up right.

AN EXAMPLE--back in 1981, I had a '67 Nova Super Sport that had a (presumably) stock 307 in it (someone had taken out the original 327 and put this one in it). The engine had a set of headers, and a Carter 9000 Competition Series 750CFM carburetor on it, and it had phenominal throttle response under light to moderate throttle, and decent response under full throttle. I was puzzled about that, so I asked my boss at the shop I worked at, and he told me it was because the throttle blades are larger, and takes less opening than a smaller throttle blade to equal the flow through those front venturis.

That car also had a Muncie M-20 (wide-ratio) 4-speed and a 3.08:1 "open" differential, and with that combination pulled down an honest 22MPG on the highway--I measured it several times to make sure. Not too bad for a carburetor that was "too big".

There is no dispute that the carburetor on that engine was far too big for the displacement and the RPM level I was shifting at (according to the formula AND common sense), but the combination worked fine, due to the fact that it was a vaccuum-secondary carburetor with an "air door" similar to the Quadrajets from GM and the 4300-series from Ford.

Maybe so, but let's talk about FACTORY carburetion for a minute:

* Chevy had DUAL 4-V 283's back in the '50's, and the CFM rating for those engines was probably AT LEAST 750-800CFM
* Chevy had a 780 Holley on it's famous Z-28 engines (both the 302 and the LT-1 350), as well as many of the higher-performance Corvette smallblocks
* GM put 750CFM-830CFM carburetors on engines from 327c.i. all the way to the 500c.i. Cadillac engines for DECADES, and never had a problem with overcarburetion.
* Chrysler put DUAL Carter AFB's on some of their 426-wedge, Hemi and 440-Wedge engines.
* FORD put DUAL HOLLEY carburetors on some of their High Performance engines, including the infamous 427 High Riser
* FORD put the 4300-D/4350-series carburetors on ALL 460's from AT LEAST 1973 through 1978, INCLUDING the Trucks during those years
* FORD even put that 4300-D/4350-series carburetor on the 351C H.O and C.J engines, as I pointed out previously--which, by the way, were the ONLY 4-V engines available from 1972 through 1974.
* FORD put HOLLEY 735CFM carburetors on the 428CJ
* FORD put HOLLEY 780CFM carburetors on the Boss 302, Boss 351 and Boss 429 engines
* FORD put HOLLEY 780CFM carburetors on the 429CJ engines
* FORD put GM QUADRAJET carburetors on the 429SCJ engines
Not a SINGLE ONE of those engines mentioned would have the capability of using ALL of the CFM those carburetors provided, according to the forumla. HOWEVER--every single one of them performed beautifully.

That is innaccurate, and I have supplied the proof of that with that link I provided in my last post, showing that the 4350-series was the ONLY carburetor used on ALL 460's from 1973 through 1978, and the 4300-D/4350-series Motorcraft is a 750CFM carburetor.

Also not true. Having worked at a division of GM for 8 years, I can tell you that the BIGGEST part of what they try to do when they design has to do with trying to provide a balance between reliability and profitability.

That means that the engineers will make a change on a part that will save a MIL (that's one thousandth of a penny) UNLESS that change also means that reliability will be reduced and cause increased WARRANY costs.

THEREFORE--they design an engine that is "reasonably" powerful, but they don't "tune" it to the ragged edge because that would affect not only drivability but reliability. Those are two VERY IMPORTANT FACTORS that engineers at auto manufacturers deal with every day.

Well, my friend--I have been working on cars for nearly 30 years; I worked professionally as a mechanic for 10 years before I went to work at GM, and my last job in the industry was as a shop foreman at a local Ford dealership.

MOST of my work has been dedicated to high performance engines and Hot Rods over the years, so I know a thing or two about performance myself. I even had the priviledge of working with the Late Great Smokey Yunick on a project once back in the late '70's.

I would add more, but I've reached the "character limit" for the post

 

Hesitation is in the dictionary, look it up. Don't be making up your on defintions for words that have been around long before I was born. I was understanding physics almost half a century ago. You don't get a vacuum if the pressures are the same on both sides of the carb(too big a carB will do that to you) and all the accel. pump in the world won't help if there is no air flow or not enough to move the fuel no matter how delivered.