We found that you need to flow an engine complete, head bolted on the block with the manifold carburettor, and air cleaner. Of course we flow em first separately. We let air into the air cleaner and pulled air out from the bottom of the oil pan. We also tried drilling the piston full of holes and monitoring the whole works. That didn't seem to teach us anything useful, but as we added components to the induction system, airflow slowly dropped - except when we pulled it through the exhaust pipes and measured what went into exhaust port with a good set of headers for that application, then airflow always rose! When you work out valve size differential in a cylinder head, the best always had bigger intakes than exhaust, and the intake port always flowed more air than the exhaust port. It's possible to have too much exhaust port and valve size and hurt an engine's performance. We sized the head and added all the components for the total induction system, and then did the same with exhaust side. Well, guess what? Airflow out of both sides got damn near even. Another point to consider in working out engine components: There is a big difference in acceleration characteristics of a carburetted engine vs. an injector pressurized fuel-delivery system. The carburetted engine is very sensitive to pressure changes in the main fuel-delivery area, and injected engines are much more forgiving. The injector gets fuel delivered by manufactured pressure. The carburetted one depends on the airflow and pressure of the differential at the carburett
PORT GRINDING TIPS
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In porting stock parts you gain very easily, but with many man-hours. As a rule, you will need a large collection of cutters for grinding cast iron. Buy at least carbide grade, the cheap cutters ain't worth a damn even when they're new; they don't cut and they're dull in nothing flat.
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In porting stock parts you have to remove a lot of material and most times you have to add filler to bring up the lows. That only works on the intake; the exhaust side is too hot and won't stay. Watch your step going through to the water jacket. You can tell when you are getting in trouble by the sound of the cutter. The best method is to get a sample cylinder head and a sample intake manifold. Take them to a good "Do-All" saw and slice 'em up 'bout every inch and look them over before you take off with the wild-assed grinder in hand.
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Before you fire up the grinder, be damn sure you've got very good eye protection, and a smart move would be to wear a good respirator and take the time to light the work area well, don't be stupid like I was. I supported an optician and eyeglass maker for 30 years. I'm lucky I ain't blind. Plus, it hurts like hell till they dig the metal or rock out of your eye.
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Don't try to weld cast iron, ain't over 20 guys in the United States that know how. Aluminum is easy to weld but that takes a lot of know-how, and after you weld, you must reheat-treat a cylinder head. A welded head or manifold, iron or aluminum, jumps all over hell and has to be re-machined, and as a rule they shrink, and ports and bolt holes need work to realign. If rules permit, you can rework an iron manifold intake, iron exhaust headers, and iron cylinder heads, and easily pickup 100 horsepower on a 350-cubic-inch engine. As a matter of fact, in the last 30 years, a Chevy or Ford 350-cubic-inch engine got 300 of the 700 horsepower from cylinder heads, manifolds, combustion chamber shape, piston design, and with less camshaft. In a very stock class with iron heads, there is 'bout 30 to 40 horsepower to be had with the best valve and valve seat preparation. In this case, you deal with the seat area below differently than you do with a premium cylinder head.
Top
PORT POINTS
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Let's get on with what we are trying to find out. How do we change it, and most Important, what is good? Let's consider a port that's cast in the cylinder head. Wait a minute. I need to back up. In the beginning I said we were gonna consider gasoline as the only fuel. Now I need to add that we are also only going to talk: pushrods, four-cycles, and V8s. There's not that much of a difference in other engines, but we can't get down to the nitty gritty with every type of engine, only those racers who already know the art would be able to follow it - and they ain't gonna read this anyhow. The intake and exhaust entrances and exits are called ports. The intake manifold is called the conduit runner.
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The engine sees the intake manifold from the air cleaner to the combustion side of the intake valve. The exhaust circuit is from the combustion-chamber side of the valves to the end of exhaust system. So each is one long shape, as the engine feeds and exhausts, and each cylinder has a specific size. Let's say 45 cubic inches. Every revolution you are gonna fire four-cylinders. Every 90 degrees another four cylinder needs filling. So you can figure out how big a port or conduit has to be mathematically as long as you know what the ambient pressure is at the beginning of the system and what pressure drop there is across the cylinder. You know it as vacuum. Because that varies, you have to use straight math and check how many times you have to fill the cylinder a minute. Then figure out the size the runner has to be, to fill it 100%.
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We know all kinds of things cause drag-pressure, differential changes in route that vary from cylinder to cylinder and that varies with throttle angle, RPM, torque, engine temperature, and local ambient air changes. This is way over the average cat's head. So we are reduced to sticking with a rough size, making it bigger or making it smaller in some cases by welding or using epoxies or resins. But epoxies and resins won't work with heat, at least I've never found any that can take exhaust temperature for 15 minutes. But, here's what we can do. let's talk intake conduit.
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Bolt the manifold to the cylinder head, get some quick-setting rubber (head porting experts can tell you where to get it and it's not real expensive), take a port, say number one, tape the intake mouth of it closed (good high-speed safety tape will do), lube the inside of the conduit from one end to the other so when the quick-setting rubber sets (if mixed right, it is two or three part chemistry) the lube works as a release agent so the cold-set rubber can be pushed out yep, you might have to push like hell, but it will come out. Wipe the grease off, and then sit there and admire your invention. As a rule, they are l4 to 18 inches of the damnedest mess of size and shape changes you ever saw of anything.
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Pure-bred overhead cam engines look like what you would expect, but these are the compromises you have to make to the cooling, location of head bolts, and pushrods. Also, to use a common intake manifold to eight cylinders, how do you keep all the runners the same considering where the valve bore centers are compared to where the bore centers of the multi-bore carburetor are? Now you have an idea of why it took 48 years of changes to make better heads, manifolds, and exhaust systems for the Ford and Chevy pushrod engines and why you can expect them to continue to get better the longer they play with them. You are like a juggler trying to control 24 balls at once.
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Let's go back to our weird looking head manifold conduit sample. You'd like to have a shape that could flow the required working fluid to 100% and fill the cylinder every time from idle to 9000 RPM. Can't be done. At best, you could do good for a range of 1500 RPM, for real good only 500 RPM, but to be perfect, a range of 5 RPM is it. You are always either too big or too small except for that lousy 5 RPM, so you have to compromise.
bullet
On a short track, shoot for torque off the corner; on a long track where RPM hardly varies, go for horsepower. Everybody who runs from second on back is short of horsepower, right. Now, the above is in reference to acceleration. As you look at that rubber imprint, mark it off every 1 inch of it's length, as accurately as you can. Then measure the size of that 1 inch, and figure its area. If you can't measure it because of its complex shape, take a hot wire or rubber knife and cut the whole damn thing into 1 inch sections, marking them 1 through whatever. Put them individually in a calibrated glass of water to see how much they displace and record the measurement.
bullet
Now I've got to review the Bernoulli effect. Every change in shape or size will affect the velocity of the working fluid through that specific area. You say, I already knew that. But as you increase velocity, you have to pay for that energy some place. Every time you reduce the velocity, you waste some energy that you've already paid for. And here's how you pay for it: It takes 'bout 240 horse-power to turn a Winston Cup motor 8400 RPM. That's damn near all valve spring, compression, and expansion of the working fluid. Rings and bearings are only a small fraction of the friction. In a four-cycle race engine, the entrance and exit of a conduit is critical for maximizing flow. The space between is only one given size. For example, does a plumber use tapered or multi-size tubing to go from point A to point B? Nope. Now you can change shape and size of a given conduit and maintain a given size, but the mass flow will drop because of the energy wasted in varying the velocity.
Top
CNC HEADS
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Well, the changing world is giving us a lot of help. There are now cylinder heads and intake manifold designers who can put all of this in their computers and come up with a new port, - so far these aren't worth a damn either. But there are port designers, sharp independent porters like Mike Chapman of Salt Lake City, Robert Yates and his crew in Winston Cup, and four or five others who can get manifold and ports about right. A genius named Kenny Weld from Kansas City has designed programs and machinery that can machine ports so that they're all exactly alike. They're ready to run with no handwork except for the valve seat, and at same time, he'll machine all the combustion chambers within 0.0002 or 0.0003 cc of each other. Robert Yates and Ernie Elliott have machines that do almost all of it and do it well, but Kenny Weld was the cat who solved the one time impossible task.
bullet
Why mention it? Well, with this equipment and knowledge, the cost is gonna drop like a rock so more of you can afford it. Let's go back to our rubber part again, it's now in a bunch of pieces. Can we reduce any of the bends? Can we change the size in various places to reduce the number of velocity changes in its passage? Dealing with stock parts, as manufactured, there is untold room for improvement, but with high-buck after market parts, it don't come easy anymore.
bullet
Working with a flowbench is a cut and try deal. Half of the improvements were accidents. It's not possible to see with the naked eye dimensional changes and estimate angles, so you have to make a set of patterns for every inch and blend it in inch by inch. A good check for size is to cc the ports.
bullet
It's also important to consider that just having a cylinder head near perfect don't mean anything unless the intake manifold is matched to each port and the total flow of all eight Systems is equal. What I'm getting at is that it's like making eight exhaust pipes the exact same length, but some will have more and meaner bends. To have even length is great, but even flow is the real answer. Same with intake and exhaust flow.
Top
PORT GRINDING TIPS
bullet
In porting stock parts you gain very easily, but with many man-hours. As a rule, you will need a large collection of cutters for grinding cast iron. Buy at least carbide grade, the cheap cutters ain't worth a damn even when they're new; they don't cut and they're dull in nothing flat.
bullet
In porting stock parts you have to remove a lot of material and most times you have to add filler to bring up the lows. That only works on the intake; the exhaust side is too hot and won't stay. Watch your step going through to the water jacket. You can tell when you are getting in trouble by the sound of the cutter. The best method is to get a sample cylinder head and a sample intake manifold. Take them to a good "Do-All" saw and slice 'em up 'bout every inch and look them over before you take off with the wild-assed grinder in hand.
bullet
Before you fire up the grinder, be damn sure you've got very good eye protection, and a smart move would be to wear a good respirator and take the time to light the work area well, don't be stupid like I was. I supported an optician and eyeglass maker for 30 years. I'm lucky I ain't blind. Plus, it hurts like hell till they dig the metal or rock out of your eye.
bullet
Don't try to weld cast iron, ain't over 20 guys in the United States that know how. Aluminum is easy to weld but that takes a lot of know-how, and after you weld, you must reheat-treat a cylinder head. A welded head or manifold, iron or aluminum, jumps all over hell and has to be re-machined, and as a rule they shrink, and ports and bolt holes need work to realign. If rules permit, you can rework an iron manifold intake, iron exhaust headers, and iron cylinder heads, and easily pickup 100 horsepower on a 350-cubic-inch engine. As a matter of fact, in the last 30 years, a Chevy or Ford 350-cubic-inch engine got 300 of the 700 horsepower from cylinder heads, manifolds, combustion chamber shape, piston design, and with less camshaft. In a very stock class with iron heads, there is 'bout 30 to 40 horsepower to be had with the best valve and valve seat preparation. In this case, you deal with the seat area below differently than you do with a premium cylinder head.
Top
PORT POINTS
bullet
Let's get on with what we are trying to find out. How do we change it, and most Important, what is good? Let's consider a port that's cast in the cylinder head. Wait a minute. I need to back up. In the beginning I said we were gonna consider gasoline as the only fuel. Now I need to add that we are also only going to talk: pushrods, four-cycles, and V8s. There's not that much of a difference in other engines, but we can't get down to the nitty gritty with every type of engine, only those racers who already know the art would be able to follow it - and they ain't gonna read this anyhow. The intake and exhaust entrances and exits are called ports. The intake manifold is called the conduit runner.
bullet
The engine sees the intake manifold from the air cleaner to the combustion side of the intake valve. The exhaust circuit is from the combustion-chamber side of the valves to the end of exhaust system. So each is one long shape, as the engine feeds and exhausts, and each cylinder has a specific size. Let's say 45 cubic inches. Every revolution you are gonna fire four-cylinders. Every 90 degrees another four cylinder needs filling. So you can figure out how big a port or conduit has to be mathematically as long as you know what the ambient pressure is at the beginning of the system and what pressure drop there is across the cylinder. You know it as vacuum. Because that varies, you have to use straight math and check how many times you have to fill the cylinder a minute. Then figure out the size the runner has to be, to fill it 100%.
bullet
We know all kinds of things cause drag-pressure, differential changes in route that vary from cylinder to cylinder and that varies with throttle angle, RPM, torque, engine temperature, and local ambient air changes. This is way over the average cat's head. So we are reduced to sticking with a rough size, making it bigger or making it smaller in some cases by welding or using epoxies or resins. But epoxies and resins won't work with heat, at least I've never found any that can take exhaust temperature for 15 minutes. But, here's what we can do. let's talk intake conduit.
bullet
Bolt the manifold to the cylinder head, get some quick-setting rubber (head porting experts can tell you where to get it and it's not real expensive), take a port, say number one, tape the intake mouth of it closed (good high-speed safety tape will do), lube the inside of the conduit from one end to the other so when the quick-setting rubber sets (if mixed right, it is two or three part chemistry) the lube works as a release agent so the cold-set rubber can be pushed out yep, you might have to push like hell, but it will come out. Wipe the grease off, and then sit there and admire your invention. As a rule, they are l4 to 18 inches of the damnedest mess of size and shape changes you ever saw of anything.
bullet
Pure-bred overhead cam engines look like what you would expect, but these are the compromises you have to make to the cooling, location of head bolts, and pushrods. Also, to use a common intake manifold to eight cylinders, how do you keep all the runners the same considering where the valve bore centers are compared to where the bore centers of the multi-bore carburetor are? Now you have an idea of why it took 48 years of changes to make better heads, manifolds, and exhaust systems for the Ford and Chevy pushrod engines and why you can expect them to continue to get better the longer they play with them. You are like a juggler trying to control 24 balls at once.
bullet
Let's go back to our weird looking head manifold conduit sample. You'd like to have a shape that could flow the required working fluid to 100% and fill the cylinder every time from idle to 9000 RPM. Can't be done. At best, you could do good for a range of 1500 RPM, for real good only 500 RPM, but to be perfect, a range of 5 RPM is it. You are always either too big or too small except for that lousy 5 RPM, so you have to compromise.
bullet
On a short track, shoot for torque off the corner; on a long track where RPM hardly varies, go for horsepower. Everybody who runs from second on back is short of horsepower, right. Now, the above is in reference to acceleration. As you look at that rubber imprint, mark it off every 1 inch of it's length, as accurately as you can. Then measure the size of that 1 inch, and figure its area. If you can't measure it because of its complex shape, take a hot wire or rubber knife and cut the whole damn thing into 1 inch sections, marking them 1 through whatever. Put them individually in a calibrated glass of water to see how much they displace and record the measurement.
bullet
Now I've got to review the Bernoulli effect. Every change in shape or size will affect the velocity of the working fluid through that specific area. You say, I already knew that. But as you increase velocity, you have to pay for that energy some place. Every time you reduce the velocity, you waste some energy that you've already paid for. And here's how you pay for it: It takes 'bout 240 horse-power to turn a Winston Cup motor 8400 RPM. That's damn near all valve spring, compression, and expansion of the working fluid. Rings and bearings are only a small fraction of the friction. In a four-cycle race engine, the entrance and exit of a conduit is critical for maximizing flow. The space between is only one given size. For example, does a plumber use tapered or multi-size tubing to go from point A to point B? Nope. Now you can change shape and size of a given conduit and maintain a given size, but the mass flow will drop because of the energy wasted in varying the velocity.
Top
CNC HEADS
bullet
Well, the changing world is giving us a lot of help. There are now cylinder heads and intake manifold designers who can put all of this in their computers and come up with a new port, - so far these aren't worth a damn either. But there are port designers, sharp independent porters like Mike Chapman of Salt Lake City, Robert Yates and his crew in Winston Cup, and four or five others who can get manifold and ports about right. A genius named Kenny Weld from Kansas City has designed programs and machinery that can machine ports so that they're all exactly alike. They're ready to run with no handwork except for the valve seat, and at same time, he'll machine all the combustion chambers within 0.0002 or 0.0003 cc of each other. Robert Yates and Ernie Elliott have machines that do almost all of it and do it well, but Kenny Weld was the cat who solved the one time impossible task.
bullet
Why mention it? Well, with this equipment and knowledge, the cost is gonna drop like a rock so more of you can afford it. Let's go back to our rubber part again, it's now in a bunch of pieces. Can we reduce any of the bends? Can we change the size in various places to reduce the number of velocity changes in its passage? Dealing with stock parts, as manufactured, there is untold room for improvement, but with high-buck after market parts, it don't come easy anymore.
bullet
Working with a flowbench is a cut and try deal. Half of the improvements were accidents. It's not possible to see with the naked eye dimensional changes and estimate angles, so you have to make a set of patterns for every inch and blend it in inch by inch. A good check for size is to cc the ports.
bullet
It's also important to consider that just having a cylinder head near perfect don't mean anything unless the intake manifold is matched to each port and the total flow of all eight Systems is equal. What I'm getting at is that it's like making eight exhaust pipes the exact same length, but some will have more and meaner bends. To have even length is great, but even flow is the real answer. Same with intake and exhaust flow.
Top
