Useing what I know these typical carbs will flow and figureing your 226 engine running at 2000 RPM and doing it's hard work at a lower speed than that will not need any more carb than something from a WD45, D-17 or Gleaner E. 

 

I have some nice take off cores, some bead blasted and rebuilt ones and some real grungy take off's if you would like one.

The ramblings of an idiot continue....

 And BTW read about stock tractors in my earlier topic carefully..... It is NOT necessary to build an engine to win at local, for fun pulls. Simply buy or inherit a decent running  tractor and tune it.. reseach the local rules ..make it your own. .    It isn't brain surgery...... or we would have found a cure for you....

You are either

A. Jerking chains

B. A whole lot less knowledgeable than I ever gave you credit for previously,,,,and that wasn't much,,,, believe me.

 

Because I don't have countless hours to alienate you this week.....we know you're an idiot and we don't need to prove the same thing every 2 weeks.

 

But I do think with those timeing issues you think you have, you need to find someone to index crankshafts properly when grinding. 

Here's a pic that fits are town clown pretty good. Too much inbreedin going on.

 

 

 

Now, when the magic carb BSers want to fool idiots  into thinking they own some magic wand for carbs they simply flow them at a higher vacuum such as the 3" vacuum that is standard for flowing 2 barrel carbs or pic whatever reading you want, the higher you run the vacuum the more CFMs yo can crow about.  Then add some polish, put it in a bright colored box with Hi-flow written on it and idiots like you line up to buy them.

Just when we think you can't get any dumber... The ramblings of an idiot continue. 

 

 

 

 

 

 

Anyway I said when I have time I'd give a little explanation of the carb sizeing.

 

1st rule to understand is that air is not drawn into the engine by the cylinder.  No matter what you may think or believe it simply isn't true.  Air is pushed in by atmospheric pressure, not drawn in.  An engine makes more power at sea level than at 10,000 feet right.  The oxygen content is abut the same at both, but the air is much denser at sea level, it's got more "push" to get it into the cylinder. 

 

Still don't believe it, why does a turbocharged engine make more power?  the air is forced into the cylinder, for every atmosphere of pressure, the engine thinks it's double in size.  Our naturally aspirated 301 for example makes 80 HP, give it 15 psi of boost and it's got more power, 30 PSI and power has doubled.  At least in theory, there's a loss from thermal inefficeincy.

 

It takes a certain amount of "depression" or lack of pressure for a carb to work properly.  That is the difference in pressure from atmospheric to the manifold, intake port.  Cylinder pressure may be less, the valve restricts flow, the manifold, the intake port is not a verry efficeint place to transfer air. 

 

The standard testing pressure or "dperession" is 1.5"hg or 1.5" of mercury for a 4 barrel carb.  2 barrels are rated at 3"hg.  1.5" hg is about 20.4" H2O and 3"hg is about 40.8" H2O.  So if I'm compareing some flow numbers I'm going to test and rate all these single barrel updraft tractor carbs at 40.8" H2O when I pull a test on them on the flow bench.  It takes more depression or a greater pressure differential for them to work over a 4 barrel downdraft carb.

 

It also takes a lot more air speed through these single barrel carbs to vaporize the fuel.  They just are not as good at drawing fuel out of that large straw and out of the sump than a nice Holley is with booster venturi's.  We need to keep more pressure differential in the single barrel updraft in order for it to work properly.  Or in simple terms, the air speed needs to be higher to vaporize the fuel.

 

So why will an engine make more power with a 4 barrel downdraft on it than a single barrel updraft?  It gets more air through the downdraft.  Atmospheric pressure is able to fill the cylinder better, there's less pressure difference, meaning that the air is free to fill the cylinder more so than through the updraft.  Well sort of anyway...... we'll cover more on that later.

 

So now we understand that it takes more air speed through that single barrel updraft to make it function.  What happens when it's to big?  The air speed is to slow and it does a poor job of picking up the fuel it needs to carry.  The signal from the cylinder is transfered to the venturi through the valve opening, the intake port and the manifold.  This signal is what the carb needs in order to pick up and carry the fuel.  A poor flowing head, poor valve angles, poor flowing manifold will not transfer the signal as well as one with improvements.

 

Now we see the importance of head, cam, manifold work.  The engine is the same size, but it's much easier for that atmpshpere to find it's way into the cylinder, which brings us to rule # 2, which is air does not like to turn corners.

 

It's got to snake it's way into the carb, bend, go up through the venturi, around the throttle plate, in a manifold and around a bunch of bends and corners before stumbling on a valve and into it's usefull place in the engine.  With the downdraft, we eliminate some of these corners. 

 

So the original poster wants a carb to feed his 226 engine at 2000 RPM.  The standard formula is Displacement X RPM divided by 3456 = Carb CFM rateing.  So 2000X226 / 3456 is 130 CFM. 

 

But we don't want 130 CFM, our engine is not efficient use, and 2000 RPM is to high, in the 2000 RPM rateing, we probably want peak torque to be at 1600, meaning that it'll be fine at 2000 or at 1200.  Then take some for the ineffiiciency of the engine and we want closer to 100 CFM for it, a little more is great.  

 

A venturi is an orfice.  Every orfice has a coefficient of flow.  Good, bad or otherwise.  A venturi has a pretty good flow coefficient.  Meaning that a venturi can flow more air per square inch of area than a straight pipe can.  Take that straight pipe and put a radius around the end, it'll flow more air, radius the inlet and the outlet and it'll flow even more.  GIve it a better radius, like the end of a tuba or a velocity stack and it'll flow even more for a given size and test pressure, or lack of pressure (deprression)

 

Our "orfice" or venturi can flow about 180 CFM per square inch of area when tested in the updraft carb.  So a carb with a 1.12" diameter venturi can flow about 180 CFM of air. 

 

So if I take a carb with a 1.12" venturi and flow test it, why does it only flow 130 CFM?  The math says it should flow 180 CFM but it doesn't.  If I take and increase the inlet and discharge coefficient of flow, it will flow more air.  When I get it perfect it'll flow the 180 cfm but it's a long road to get it perfect.  It needs help to get the air lined up with the venturi, it needs lots of bowl modifications.  These single barrel updraft carbs have verry little short side radius for the air to bend around and line up with the venturi.  They have a thick throttle shaft and throttle plate for the air to have to go around once it exits the venturi.

 

So do some bowl modifications, trick the air into going around a longer radius to line up with the venturi, thin the throttle shaft, but shape it like an airplane wing, leading edge on front and a short radius on the back side.

 

The choke shaft and choke blade are another source of loss.  I've seen a lot of them removed because people think it helps to take them out.  It doesn't.  Typically a carb flows less air with the choke removed than with it in.  Take and rotate the choke blade a few degrees to offer a little "lift" to the incomeing air charge and direct it into the venturi better, the carb flows more air with it lifting the air than with it laying flat.

 

We wanted a carb for a 226 CID at 2000 RPM.  Can anyone tell me how large the venturi is in a TSX 464?  It's about .940" in diameter.  In stock form that carb has a hard time to break 100 CFM mark on the flow bench.  Lets take the .940" venturi and figure out what it could flow in theory.  In a perfect world up to about 130 CFM.  THough currently without any carb enhancements it's closer to 100 CFM.  Rember what we wanted for a 2000 RPM engine in the first place?....... right in that area.

 

Also rember we need a lot of air speed for this single barrel updraft carb to work.  More air speed is better, provideing our "resistance" to atmospheric pressure isn't to great to harm performance.  Excessive depression is robbing power.  We need enough to make things work, but to much means things are to restrictive.  Rember the turbocharged example, boost is positive pressure.  The more pressure, the bigger the breath of air.  An engine running at 25"hg depression makes verry little power, in fact it's enough to idle. The same engine at 7"hg depression is makeing some power. 

 

We don't need a bigger venturi, the carb is sized pretty good for it's application.  The carb is even better with a little help in terms of bowl mods, throttle shaft mods, throttle plate, etc.

 

Maybe I want to feed a 380 CID Allis at 2064 RPM, lets say that the cam is ground, nice head and manifold work, etc. I did everything I could to maximize the flow coefficient of the orfice leading from Mother Nature into the engines cylinder.  The rules say I can peak out at 2064 RPM, so I may figure I want peak torque at say 1700 for an engine package that will perform well all the way through it's expected operating range...... I want to put about 180 CFM rateing on that engine, or a carb with a 1.2" venturi, and everything optimized in the carb.  I want to work dang hard perfecting the airflow pattern through the carb...... I could put a carb on with a 1.9" venturi, but the engine is going to run and when the load hits, it's going to fall on it's face. 

 

This 380 CID operating at that speed can use a TSX 66, 67 or like carb.  Minne Moline used them.  A bone stock one cleaned up flows roughly 130 CFM.  With a custom venturi made to blend into the bowl, some throttle shaft work, and lots of scientific bowl work that carb can be made to flow in excess of 180 CFM.  Guess what's a great match for these engines.

 

A larger venturi can be made to work well with less signal.  The use of a small venturi inside a large venturi or the use of a "booster" venturi is helpfull getting a stronger signal at the fuel nozzle.  I can now run a venturi that is a little to large and help the low speed performance through the booster.

 

Some of you used this carb from "dumb luck" some from others reccomondation, or others tried a few things and found it to be a good match......well guess what?  you're right.  A Holley 1150 Dominator is a poor choice for this application.  The engine is to small and moveing to slow, the manifold and the ports to restrictive for our atmpshpere to push it's way into the engine with enough speed to carry any fuel in form to make any power.

 

 

 

 

 

mlpankey wrote: Put to small a venturi on it and you will choke it even more if yor air speed hits the magic number. Simple sentence but a true one.

Duuurrrrr!! Way to go caption obvious!  You really are bright, maybe you're finally learning something! 

Have you ever met Marty, or been in his shop? You really do talk like a man with a paper a$$ you spineless prick. You have nothing to show besides the fact that you are a retard with a keyboard.

Spunky, your old man must have jerked off on a flower pot, you really are a blooming idiot. Go away troll.

 

Key word being "reputable" Pank is a legend in his own mind only. One engine pieced together in the bathroom of a buddy's shop and it went KABOOM!    after 5 runs and lots of time searching the internet and playing with online calculators.  Hooks, wins and intelligent posts talk but BS walks and Pank has worn out a lot of shoes.

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