Carb Bore VS Intake Rotor Timing.

[Joe Warren]

Thing about why this is true. how much more vacuum dose it take to open a reed than a open window?

Don't think a pipe will draw thew a reed.

Don't need to think...............Everything is explained with equations and solutions: Just dont' feel like hurting my brain to do the trig and calculus.

Man told me one time.... The only place a ideal situation exist is.... on Paper........ enhancing what the mfgers have Offered & Working with what you have is the quickest way to go faster....... But you must decide if you want to do it with Piston Speed (RPM) or Torque and a Larger Prop with more Cup. You cannot have both...... I know David thinks BIG BLOCK!!!! and we have found that they work a lot better the hotter they are......

 

[dwilfong]

Thing about why this is true. how much more vacuum dose it take to open a reed than a open window?

Don't think a pipe will draw thew a reed.

Don't need to think...............Everything is explained with equations and solutions: Just dont' feel like hurting my brain to do the trig and calculus.

Man told me one time.... The only place a idea situation exist is on Paper........ enhancing what the mfgers have Offers & Working with what you have is the quickest way to go faster....... But you must decide if you want to do it with Piston Speed (RPM) or Torque and a Larger Prop with more Cup. You cannot have both...... I know David thinks BIG BLOCK!!!! and we have found that they work a lot better the hotter they are......

Yes heat in the right place. The top end. The cooling head I make separates the head temp from the case. Keeps the case cold and the button and top of the sleeve hot.

Now if wee could get the RPM up and a big bore. long stroke will give you more window area in the same bore.

Will see what is what real soon here with the VAC91 and the 1.01 P/L set in the case. the pistons I am having Scott make have extra compression distance in them to make this work. Should be able to make the transfers taller and the bottom of the ex to get more area.

Will start with the VAC carb at .588 the same as the drum intake bore. will enlarge as testing goes. just not sure how thin you can make the drum walls in the VAC induction and still live.

I still think the RS disk is still a better system but can only work with what is already produced and readily available.

Hope the new 27cc will pan out. Now that is a BIG BLOCK!!!!!!!!!!!!

 

[Joe Warren]

David, Do you you alter the rotor timing only on the rotor or do you cut the case? Also CMB`s 91-101 engines have with .015 rotor clearence... If this remains? There is a thing called Rotor dewell. This is the point that the rotor is leaving the face of the case under (vacuum) and is about to get pushed aganst the carb back plate because of Case (pressure) If you run .015 clearence? You lose many crank degrees that Nothing is going on????? you are changing from a negative (vacuum) state to a Pressure state. Decreasing the running clearence helps start the phases or cycles much sooner. point is.. If you are cutting the case to alter rotor timing? You must make sure that the face plate does not cut the fuel off earlier... before the window on the case closes.

 

[dwilfong]

David, Do you you alter the rotor timing only on the rotor or do you cut the case? Also CMB`s 91-101 engines have with .015 rotor clearence... If this remains? There is a thing called Rotor dewell. This is the point that the rotor is leaving the face of the case under (vacuum) and it about to get pushed aganst the carb back plate because of Case (pressure) If you run .015 clearence? You lose many crank degrees that Nothing is going on????? you are changing from a negative (vacuum) state to a Pressure state. Decreasing the running clearence helps start the phases or cycles much sooner. point is.. If you are cutting the case to alter rotor timing? You must make sure that the face plate does not cut the fuel off earlier... before the window on the case closes.

.002-.003 on the clearance. I do not open the window up much just what is needed to get a good line from the carb mounting surface and the transfer passage. I have a 5" long 1/8" ball end mill that I put in my dremmel and do this by hand. this line is as striate as possible. I call it line of sight porting.

This is also the reason for the angle cut on the bottom of the sleeve. keeps every thing in line and enshrouded from the carb to the transfer ports.

Like I said I pretend the piston dose nothing but get in the way.

the carb at .700 wide and .500 tall fill the window perfect no bending the flow in two directions as with a big round bore carb.

No use going any bigger it wont flow thew the window good.

This sound like a large carb but it only addes .100 of area to the carb. that is less area in total than a .550 round boar carb.

 

[ALLAN YUEN]

h34r: What about brass button ? No any word ? :huh: better than alumium button? and will eat on top piston?

 

[tnrcboatracer]

Harry Byrne developed the 'MAXimizer' sliding pipe coupler. It would typically slide the pipe through a mixer setup on the rudder.

 

[Charles Perdue]

David, Do you you alter the rotor timing only on the rotor or do you cut the case? Also CMB`s 91-101 engines have with .015 rotor clearence... If this remains? There is a thing called Rotor dewell. This is the point that the rotor is leaving the face of the case under (vacuum) and it about to get pushed aganst the carb back plate because of Case (pressure) If you run .015 clearence? You lose many crank degrees that Nothing is going on????? you are changing from a negative (vacuum) state to a Pressure state. Decreasing the running clearence helps start the phases or cycles much sooner. point is.. If you are cutting the case to alter rotor timing? You must make sure that the face plate does not cut the fuel off earlier... before the window on the case closes.

.002-.003 on the clearance. I do not open the window up much just what is needed to get a good line from the carb mounting surface and the transfer passage. I have a 5" long 1/8" ball end mill that I put in my dremmel and do this by hand. this line is as striate as possible. I call it line of sight porting.

This is also the reason for the angle cut on the bottom of the sleeve. keeps every thing in line and enshrouded from the carb to the transfer ports.

Like I said I pretend the piston dose nothing but get in the way.

the carb at .700 wide and .500 tall fill the window perfect no bending the flow in two directions as with a big round bore carb.

No use going any bigger it wont flow thew the window good.

This sound like a large carb but it only addes .100 of area to the carb. that is less area in total than a .550 round boar carb.

David, is this the carb that you posted a pic of recently with the 5 holes in the spray bar?

Charles

 

[dwilfong]

David, Do you you alter the rotor timing only on the rotor or do you cut the case? Also CMB`s 91-101 engines have with .015 rotor clearence... If this remains? There is a thing called Rotor dewell. This is the point that the rotor is leaving the face of the case under (vacuum) and it about to get pushed aganst the carb back plate because of Case (pressure) If you run .015 clearence? You lose many crank degrees that Nothing is going on????? you are changing from a negative (vacuum) state to a Pressure state. Decreasing the running clearence helps start the phases or cycles much sooner. point is.. If you are cutting the case to alter rotor timing? You must make sure that the face plate does not cut the fuel off earlier... before the window on the case closes.

.002-.003 on the clearance. I do not open the window up much just what is needed to get a good line from the carb mounting surface and the transfer passage. I have a 5" long 1/8" ball end mill that I put in my dremmel and do this by hand. this line is as striate as possible. I call it line of sight porting.

This is also the reason for the angle cut on the bottom of the sleeve. keeps every thing in line and enshrouded from the carb to the transfer ports.

Like I said I pretend the piston dose nothing but get in the way.

the carb at .700 wide and .500 tall fill the window perfect no bending the flow in two directions as with a big round bore carb.

No use going any bigger it wont flow thew the window good.

This sound like a large carb but it only addes .100 of area to the carb. that is less area in total than a .550 round boar carb.

David, is this the carb that you posted a pic of recently with the 5 holes in the spray bar?

Charles

Yes it is. but I removed the spray bar in the pick. It was real small with that bar. also you can't tune the eng by ear with that bar as you know.

The numbers I don't think where right. don't have the time to test it to get it right.

This is your baby anyway. when you going to have some for the 1.01?

David

 

[Charles Perdue]

This is not a Zoom Carb or a good copy. This is a lot of your problems in burning pistons. IT WILL NOT WORK. This design will not accurately meter the fuel/air mixture. This is part of your problem in burning pistons. It is difficult to burn a piston with the right fuel/air mixture.

Charles

 

[Charles Perdue]

Many records have been set with motors that have the intake rotor timing number optimized and a barley larger that stk carb. I`am just saying that a BIG BORE carb is not always the answer to going faster. There is a lot to be gained in getting the intake rotor timings correct. So the engine can make good vacuum. Todays race engine we let the prop be the governor of the engines abilty to turn high RPM. I know if my engine is whaing Rpm before it comes off the corner iam going to add more cup...... And yes charles thinking of the center openings in the spary bar comes from his older days of building automotive carbs.... Thermoquad carbs ran these same degsined carb spray bars??

Mr. Joe, I must be getting senile in my old age, because for the life of me, I cannot remember any such spraybars in the quadrajet carbs.

I agree with you completely with not oversizing carbs.

Charles

 

[John Beardslee]

Many records have been set with motors that have the intake rotor timing number optimized and a barley larger that stk carb. I`am just saying that a BIG BORE carb is not always the answer to going faster. There is a lot to be gained in getting the intake rotor timings correct. So the engine can make good vacuum. Todays race engine we let the prop be the governor of the engines abilty to turn high RPM. I know if my engine is whaing Rpm before it comes off the corner iam going to add more cup...... And yes charles thinking of the center openings in the spary bar comes from his older days of building automotive carbs.... Thermoquad carbs ran these same degsined carb spray bars??

Mr. Joe, I must be getting senile in my old age, because for the life of me, I cannot remember any such spraybars in the quadrajet carbs.

Charles

Didn't they have metering rods that were full of holes or maybe it was the Carter AFB's - I forgot all about those once I started working with the Holleys.

Thanks, John

 

[Mark Bullard]

Many records have been set with motors that have the intake rotor timing number optimized and a barley larger that stk carb. I`am just saying that a BIG BORE carb is not always the answer to going faster. There is a lot to be gained in getting the intake rotor timings correct. So the engine can make good vacuum. Todays race engine we let the prop be the governor of the engines abilty to turn high RPM. I know if my engine is whaing Rpm before it comes off the corner iam going to add more cup...... And yes charles thinking of the center openings in the spary bar comes from his older days of building automotive carbs.... Thermoquad carbs ran these same degsined carb spray bars??

Mr. Joe, I must be getting senile in my old age, because for the life of me, I cannot remember any such spraybars in the quadrajet carbs.

Charles

Didn't they have metering rods that were full of holes or maybe it was the Carter AFB's - I forgot all about those once I started working with the Holleys.

Thanks, John

One of them did. And I was like Joe that it was the Rochester but it may have been the Carter's.

But I don't think the holes do any good on our motors. The real trick is to get the end of the spraybar in the right place of the bore. Plus I don't think that the fuel stays in vapor or atomizion when it gets into the bottom of the crankcase. But when the mixture is put under crankcase pressure this is when the mixture is atomized.

So this goes back to the thought of rotor and port timing of what is to much or what can we get away with.

 

[Greg Hahn]

I have bin messing with the pipe Scott made for me and it will suck the guts out of the case. the needle is over two turns out from where it was with the MACS pipe.

The only problem is it is hard to tune. the volume is large with this pipe and it stows a large mixture load in the pipe then the sharp rear angle slams it all back in.It hits like a sledge hammer. I call it the piston breaker. but it drops off bad after you hit the RPM tune of the pipe.

Some more changes should make it gentle. But it did show me how the right front half will draw all the way to the carb.

Can you telescope the pipe and have a servo shorten it on demand? Always thought that would be trick.

jeff,

to answer your question on the slipper pipe, yes being able to adjust the pipe length would do much the same as changin the intake it all works together. Problem is the gain is small with a slippy unless you're dealin with track length issues. We use slippy pipes in kart racing where gearing is fixed and can't be changed to accomidate the length of the straight away. With boats if we had to negotiate 500 or 1000 foot straightaways then a slippy would be the trick since we could never put enough prop on to properly use the straight length and still come off the corner and then launching becomes another issue.

see you Saturday

gh

 

[Charles Perdue]

Many records have been set with motors that have the intake rotor timing number optimized and a barley larger that stk carb. I`am just saying that a BIG BORE carb is not always the answer to going faster. There is a lot to be gained in getting the intake rotor timings correct. So the engine can make good vacuum. Todays race engine we let the prop be the governor of the engines abilty to turn high RPM. I know if my engine is whaing Rpm before it comes off the corner iam going to add more cup...... And yes charles thinking of the center openings in the spary bar comes from his older days of building automotive carbs.... Thermoquad carbs ran these same degsined carb spray bars??

Mr. Joe, I must be getting senile in my old age, because for the life of me, I cannot remember any such spraybars in the quadrajet carbs.

Charles

Didn't they have metering rods that were full of holes or maybe it was the Carter AFB's - I forgot all about those once I started working with the Holleys.

Thanks, John

One of them did. And I was like Joe that it was the Rochester but it may have been the Carter's.

But I don't think the holes do any good on our motors. The real trick is to get the end of the spraybar in the right place of the bore. Plus I don't think that the fuel stays in vapor or atomizion when it gets into the bottom of the crankcase. But when the mixture is put under crankcase pressure this is when the mixture is atomized.

So this goes back to the thought of rotor and port timing of what is to much or what can we get away with.

Mark, differences of opinion is why we have races.

Charles

 

[Joe Warren]

Many records have been set with motors that have the intake rotor timing number optimized and a barley larger that stk carb. I`am just saying that a BIG BORE carb is not always the answer to going faster. There is a lot to be gained in getting the intake rotor timings correct. So the engine can make good vacuum. Todays race engine we let the prop be the governor of the engines abilty to turn high RPM. I know if my engine is whaing Rpm before it comes off the corner iam going to add more cup...... And yes charles thinking of the center openings in the spary bar comes from his older days of building automotive carbs.... Thermoquad carbs ran these same degsined carb spray bars??

Mr. Joe, I must be getting senile in my old age, because for the life of me, I cannot remember any such spraybars in the quadrajet carbs.

Charles

Well back up another 20 years and think of the Thermoquads quadrajet was too modern??

 

[Charles Perdue]

Joe, the minute us elders leave the room and you are without our guidance, you kids start running wild with your misbehaving and speculations.

Charles

 

[Joe Warren]

Joe, the minute us elders leave the room and you are without our without guidance, you kids start running wild with your misbehaving and speculations.

Charles

Yes Sir.......True.... Whats your point? wait till we start talking about a new hydro with rear boom tubes????? :wacko: :blink: :huh: when are you exting the room again??

 

[John Beardslee]

Hey Joe,

Or anyone else, will the eagle tree equip measure negative numbers? I used to use a water monometer to set up the weber carbs on racecars and the 3cylinder Triumps (cycles). I set up a stack in front of each carb and it would pull water from baby food gars up a clear vinyl lines over a scale to measure flow. If the eagle tree stuff will measure neg numbers then it might be possible to set up a simular test on a twin. Note: the two engines in a twin do not live in the same life, ie: as you stated in a turn the load is different, your plug readings are about the only indicator you have as to what is going on in the chamber, short of holing a piston - did that more times that anyone knows.

Thanks, John

 

[Charles Perdue]

Joe, the minute us elders leave the room and you are without our without guidance, you kids start running wild with your misbehaving and speculations.

Charles

Yes Sir.......True.... Whats your point? wait till we start talking about a new hydro with rear boom tubes????? :wacko: :blink: :huh: when are you exting the room again??

Rear boom tubes, now you have gone and told everyone.

 

[dwilfong]

View attachment 36577

This is not a Zoom Carb or a good copy. This is a lot of your problems in burning pistons. IT WILL NOT WORK. This design will not accurately meter the fuel/air mixture. This is part of your problem in burning pistons. It is difficult to burn a piston with the right fuel/air mixture.

Charles

Charles I have not burned a hole in a piston in a long time and never in my 1.01's.

Now I have snatched a few off the rod in the last two test.

All carbs have a emulsification tube on them. thats the reason a holly will acted funny if it sits to long with out fuel. the holes get corrosion on them and mess the mixture up. then you need to buy a new metering block to fix it.

Heck your lawn mower eng has it on it.

One cycle carbs it called the needle jet.

This system is as old as the eng it's self. I would like to see any carb with the exception of our little carb that don't have one.

Now gettting every thing right. That is a whole diffrent story best left to the pros.

David