w8less

i was referring to the opinions are like a$$holes everyone has one. you voice yours about having the 65.

w8less

you read the link i sent you?

Mustangkiler

The only fact in all of this, is that the bigger the throttle body the more high end hp and less low end torque, Either way you go samller to 65 or bigger to 90 its not going to hurt the engine either way its just going to change the way it reacts. Just a matter of if you want low end torque or a high revving high hp engine, dependingo n what you want and using the car for effects which you should get, But again thats just my A$$HOLE.

w8less

although it may be.......it is a very good point

5.0stanger

Just my experience, but early this year I was running a 70mm MAF and a 70mm TB and I could never get my car to run just right. I actually ran a 13.7 at the track, which was the same I ran the year before. So later I switch to a 65mm TB and I went down to a 13.5, TB being the only thing I changed. Then later I upped to a 75mm MAF and 24lb injectors and ran a 13.2. I want to get my car dynoed again to see if I have more power after the TB and MAF changes. This being said, a 65mm TB worked better on my car....from experience.

telsonman

here's my take on things. if you plan on upgrading HCI, then why not just spend your money on a 70mm as opposed to a 65mm, its the same price roughly. i had a 70mm tb and 76mm maf on mine before my hci, and it felt like it made a difference. however, from what i've read, throwing a intake on your car without heads will rob power. i'm not sure if anyone here can back that up, but its what i've heard.

Joel5.0

Anytime the "bigger than a 65mm TB will hurt "torque down low" (yeah....double quote) is mentioned, ALL I see are quotes of editor's in chief, simulations, etc.......but no real facts, experience or......as any good scientist would say.... EMPIRICAL DATA.

1. You can't compare a carburetor setup (which is a restriction by default, dependent on Bernoulli) with a system (EFI) that deals with dry air flow....... the TB is a valve... period. Otherwise, how do old diesel systems work....... the accelerator doesn't control a TB blade, it is 100% open, and relies on the diesel injected into the cylinder....... aren't diesel engines 100% dependent on torque production?...... rather than HP?......

2. I've worked setups with a Cobra intake and 75mm TB, Cartech "coffin" intakes (the equivalent to single plane intakes on carbureted setups, or short runners EFI intakes) on N/A setups with 70mm+ TB's.... and they have yielded better results than the long runner EFI intakes/smallish TB setups.....including auto transmission cars.... as the 80mm TB in the '86 AOD Mustang 100% stock example given.

3. Does my results go against an article of an "editor-in-chief" of a magazine?......maybe........ do I, or should I care?....NOPE!..... my customers have the last word, not a magazine........ they are the ones paying for results..........get it?

4. Same goes with carburetors, anything over 650 cfm is too big for a 302........ wonder why the best results in performance and driveability I got from my two 289 setups, were obtained with a 850cfmDP carburetor....... ask a few 396, 350 chevy and 340 mopar owners.........

Here's my take on things........ if your 302/5.0L EFI setup cannot "handle" a 75mm TB....... you have OTHER areas to work on other than the intake, those are the ones costing you performance and driveability..... not the TB ID.

My

Hamutoff

Ive never said 65 or 85 or ?TB has to be used
I have just stated need to match parts for overall system.
When one argues against the general concensus, one should expect to be asked to produce data or new info. An example is that folks, sven engineers thougth that there was no way to pass the speed of sound. It was considered a Barrier that could not be broken. Well obviously someone challenged that, surpassed it,and changed the concensus opinion.



So, Jasperstang308 when a moderator starts taking stabs at a poster about one thread on another thread becasue he or she does not like what the poster's idea or opinion is, where does that poster turn.... Its unreasonable. If you think you can shut me up my using these methods, you are right. As moderator I suppose you can censor me as you wish. Kinda sucks of you though

w8less

i am in no way censoring you. you are the 2nd person who has ever had a problem with me for some reason and i have been on this forum since 04. PM me with the problem and not take away from this guys post.

5spd GT

A larger throttle body will not hurt torque. Matching it to the inlet is not a bad idea, to avoid pressure drops (small to large) and abrupt turbulence (large to small).

However, it will cause a touchier throttle during tip-in.

The proponents of large throttle bodies go for the "max." Think about the couple guys quoted in this forum. They are straight line guys They go WOT and do not worry about the rest.

To them, "more throttle response" is "touchy throttle" to others.

Do not get them confused.

Read this from ACCUFAB's website.

THE AIR PUMP UNDER YOUR HOOD
By George Klass
What size throttle body or carburetor do I need?
Good question but the real question should be “how many cubic feet per minute (CFM) of air will my engine require?”
An engine is an air pump. Based on the size of the engine (displacement) and how fast it will be spinning (RPM), it will pump out a certain amount of air. Works just like an air compressor. Of course, there are many variables to CFM requirements, such as cylinder head flow capabilities, intake and exhaust manifold flow capabilities, etc., but the basic engine block will pump a certain amount of air over a specified period of time, measured in cubic feet of air per minute.
If the engine is to be carbureted, it should be a relatively easy decision to pick out the correct sized carburetor. Carburetors are defined by CFM. If your engine calls for (or pumps out) about 664 CFM, the correct choice is probably a 650 CFM carburetor. Unfortunately, throttle bodies are rarely defined by CFM ratings. Instead, most throttle body manufacturers define their throttle bodies by the inside diameter of the unit, measured at or around the throttle blade, and usually in Millimeters (MM). Unless you have a direct correlation between the measurement in MM and the related CFM of that particular unit, the selection is going to be based on “best guess”.
And to further complicate the “guessing” process, all throttle bodies of the same dimension, do not have the same CFM rating. You might think that Brand A’s 75 MM throttle body would flow the same as Brand B’s 75 MM throttle body. Such is not the case, because all throttle bodies have a “major obstruction” in the middle of the air path, namely a throttle blade and shaft. How well the air flows over and under this obstruction will define the CFM a specific throttle body will flow. A big fat shaft with the attachment screws for the blade sticking up into the air stream will impact the CFM of that throttle body.
While most enthusiasts with EFI engines continue to purchase throttle bodies based on Millimeter size, caring little about the actual CFM ratings, the carb guys purchase carburetors based on CFM ratings, caring little about the size of the throttle plates. Score one for the carb guys.
But, back to the original question, “how much CFM do I need”?
Below is a chart with the CFM requirements, based on displacement (in cubic inches) and RPM. This chart will work for any piston engine with any number of cylinders. After you have determined the CFM for your specific engine combination, you can then choose the corresponding throttle body or carburetor size to best fit that combination.
DISPLACEMENT………….6000 RPM……….6500 RPM……….7000 RPM
280………..…………………486………… ……..527………………..567
290……..……………………503………… ……..545………………..587
300………..…………………521………… ……..564………………..608
310……..……………………538………… ……..583………………..628
320……..……………………556………… ……..602………………..648
330………..…………………573………… ……..621………………..668
340……………..……………590………… ……..639………………..689
350……..……………………608………… .…….658………………..709
360………………..…………625………… ……..677………………..729
370………………..…………642………… ……..696………………..749
380………………..…………660………… ……..715………………..770
390………………..…………677………… ……..734………………..790
400………………..…………694………… ……..752………………..810
410………………..…………712………… ……..771………………..830
420………………..…………729………… ……..771………………..830
430………………..…………747………… ……..809………………..871
This chart should give you a general idea of the amount of air your combination will pump. Engines will pump less air because of the restrictions in the cylinder head or intake manifold design or valve lift, or all three. But, the chart still gives you a ball park starting point.
One other thing to know. A carburetor requires air speeding over the venturi to draw the gasoline into the mixture. Using too large a carburetor (high CFM rating) will usually cause derogatory performance in the lower or midrange. This is because the lower air velocity is inefficient in mixing the gasoline with the air. In general, and particularly for street use, a slightly smaller carb (less CFM) will give better overall performance.
With an EFI system, this is usually not a problem. The throttle body only controls air flow. A computer monitors the gasoline supply and the mixing of gasoline and air takes place inside the intake port, and not inside the carburetor. Using an oversize throttle body is not nearly as detrimental to low and midrange performance as is using an oversize carburetor.
So, to find the CFM ratings of a carburetor, all you need to do is to look in any catalog from Holley, Edelbrock, Barry Grant, etc. That’s how the carburetors are listed. To find the CFM ratings for a throttle body is going to be more difficult, unless you happen to choose an Accufab throttle body.
Below are the various throttle body sizes and corresponding CFM ratings for the Accufab throttle bodies. Because the Accufab throttle bodies are designed to “race engine specs”, the flow ratings are going to be greater than most of the other aftermarket throttle body designs, so don’t automatically expect a “75 MM Brand B” throttle body to flow as much as an Accufab 75 MM unit.
65 MM - 664 CFM
70 MM - 787 CFM
70 MM - 896 CFM (Race version)
75 MM - 924 CFM
75 MM - 1045 CFM (Race version)
80 MM - 1142 CFM
85 MM - 1322 CFM
90 MM - 1369 CFM
105 MM - 1550 CFM
Cobra (’96-’98) - 1284 CFM
Cobra (’03-’04) - 1696 CFM
Lightning Pick-up (’99-’04) - 1696 CFM
So, there you have it.