Porting & Polish Manifolds.
07-18-2012, 01:11 AM
#1
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Porting & Polish Manifolds.
Anyone ever do a port & polish on an intake/exhaust manifold? Does this actually work in increasing power/performance? Or are the gains not worth the time/labor?
07-18-2012, 01:25 AM
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Originally Posted by KJamesJR
Anyone ever do a port & polish on an intake/exhaust manifold? Does this actually work in increasing power/performance? Or are the gains not worth the time/labor?
07-18-2012, 01:46 AM
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I hear Showroom Stock racers port and polish just about everything just to squeeze every last bit of performance out of their cars.
While I have my new manifold sitting out. I thought of perhaps doing a "mini" port & polish job on it with my Dremel. It doesn't look too difficult. Just line the tubes up with the gasket so you don't over grind. Open it up a tad with a grinding stone, sand with 120 grit, then buff. Really you're looking for smoothness over size.
While I have my new manifold sitting out. I thought of perhaps doing a "mini" port & polish job on it with my Dremel. It doesn't look too difficult. Just line the tubes up with the gasket so you don't over grind. Open it up a tad with a grinding stone, sand with 120 grit, then buff. Really you're looking for smoothness over size.
07-18-2012, 02:44 AM
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This is a good idea. I've been wanting to do this myself.
Just be sure to gasket match the head too. The only problem i see is...Will the stock cpu beable to make air fuel adjustments for the p&p. esp on 97-01 models. but with full exhaust,cold air int. and better injectors... i say go for it and report back.
Just be sure to gasket match the head too. The only problem i see is...Will the stock cpu beable to make air fuel adjustments for the p&p. esp on 97-01 models. but with full exhaust,cold air int. and better injectors... i say go for it and report back.
07-18-2012, 02:47 AM
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Originally Posted by KJamesJR
I hear Showroom Stock racers port and polish just about everything just to squeeze every last bit of performance out of their cars.
While I have my new manifold sitting out. I thought of perhaps doing a "mini" port & polish job on it with my Dremel. It doesn't look too difficult. Just line the tubes up with the gasket so you don't over grind. Open it up a tad with a grinding stone, sand with 120 grit, then buff. Really you're looking for smoothness over size.
While I have my new manifold sitting out. I thought of perhaps doing a "mini" port & polish job on it with my Dremel. It doesn't look too difficult. Just line the tubes up with the gasket so you don't over grind. Open it up a tad with a grinding stone, sand with 120 grit, then buff. Really you're looking for smoothness over size.
07-18-2012, 10:02 AM
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You have to be careful, the casting is pretty thin on some places of the intake. I cleaned up the ports and made all six match each other as close as I could on my 99+ manifold.
07-19-2012, 08:32 PM
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Originally Posted by Bustedback
You have to be careful, the casting is pretty thin on some places of the intake. I cleaned up the ports and made all six match each other as close as I could on my 99+ manifold.
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07-19-2012, 09:18 PM
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A more responsive engine and a nice smooth powerband. I may have lost some low end power, but there was a gain in top end grunt.
07-20-2012, 11:12 AM
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This is something I know a little bit about. I worked my way through school rebuilding Harley motors, including porting and "polishing" intake and exhaust tracks in the heads.
The goal of porting is to improve the quality and quantity of the air flowing through the system. Pumping loss is one of the larger power losses in an engine. It's the difference between drinking a milkshake through a coffee stirrer vs through a garden hose. Much less effort required to get your milkshake through the garden hose.
Typically, before modification is done, you want to use a flow bench to get baseline readings on your part. I know that the everyday home wrencher won't have one sitting in the corner, so we'll deal with generalities in improvements rather than fine tuning each aspect of the intake/exhaust track.
The area where you'll see the biggest gain (in the head) is the area just upstream from the intake valve (also known as the pocket - the area after the bend, between the valve guide and the valve seat).
When modifying the track, your goal is to get even flow velocity throughout the cross section of the track.
Larger is not always better. When building a highly modified motor, you need those larger ports because the motor operates at such a high speed that the actual size of the port becomes a restriction. These motors are designed to develop their power at very specific points in their RPM range. Generally, larger ports flow more fuel/air at higher RPM's but sacrifice torque at lower RPM's due to lower fuel/air velocity (as was seen by Bustedback in his post above this one).
"Polishing" as a method of increasing power is also a myth (on the intake side). Intake ports are left intentionally "rough" as it encourages liquid fuel that lands on it (though the injection process) to vaporize more quickly. A mirror finish inhibits that, and you end up with liquid fuel running down the wall of the intake track into the combustion chamber...not very efficient. (If you flow both the polished and "rough" tracks on a bench, usually the difference is under 2%-your fuel vaporization is more important that those 2%). Exhaust track, on the other hand, since it is dry, can be polished to increase laminar flow and get those gases out.
As far as lining up the gasket and starting to cut, I'll let someone smarter than me address that:
GASKET MATCHING VS PORT MATCHING
This is a commonly misunderstood subject. Many people think and believe the proper method of port work is to use whatever gasket comes in the box as a template to determine what size the ports or runners should be. It's not that easy or simple. I have seen many sets of heads destroyed by using this method. They look impressive to the untrained eye. You might even show some improved performance over stock, but overall you've created some airflow issues that can't be fixed. To assume that the gasket is an intelligent being would also be to assume that the gasket maker knows what size your ports should be. That is to assume also that the gasket maker knows your cubic inches, cam size, carb cfm., gear ratio, valve size, and RPM operating range, and more. Here's the story on gaskets. If gaskets protrude into the runner then shave or cut the excess off so that it doesn't obstruct air flow. That's it! Don't use gaskets as templates.
PORT MATCHING aka DO NO HARM
Now that we have that gasket matching issue out of the way let's finish the rest of it. It would be real nice if ports and their manifolds that pair up to them were the same size and shape, but that doesn't happen often enough. So we need to deal with what we have. Let's say the exhaust manifold has a smaller opening than the exit out of the head. In that case we need to open the manifold to match the head. But what if the manifold opening is larger, then what? Do we open the head up to match the exhaust manifold? No. If you do open the head to match you will create a "slow" spot in the air flow. Terrible! If the air flows through the runner and hits a wall, such as a protruding gasket or a manifold the air "trips" and "stumbles" causing turbulence, and impedes air travel. But if the flowing air falls over the edge and into the manifold there's little harm done. The point here is the "Doctors Oath" of "do no harm". It's not an ideal situation but it is better to leave it alone that to make things worse. The same logic applies to the intake airflow, it can fall into the intake runner of the head from the intake manifold, but you don't want it to stumble into the gasket or the lip of the intake runner. The idea here is to minimize the bad, maximize the good, and "Do no harm". So bigger is not always better. Grinding away where ever you get the notion can cause the air flow to slow and thus losing the pulsing, charging, ram air effect, and extraction benefits we need. Port matching is done after the head is ported.
My thought is that if you are just going to do some touch-up work, I'd use the dremel to remove casting marks, protrusions, etc. in the intake/exhaust manifolds while you have them off. Just smooth things up and see what difference is made.
If you don't want to touch the head, I understand - it's a big project to do that.
Take some pictures and let us know your results!
The goal of porting is to improve the quality and quantity of the air flowing through the system. Pumping loss is one of the larger power losses in an engine. It's the difference between drinking a milkshake through a coffee stirrer vs through a garden hose. Much less effort required to get your milkshake through the garden hose.
Typically, before modification is done, you want to use a flow bench to get baseline readings on your part. I know that the everyday home wrencher won't have one sitting in the corner, so we'll deal with generalities in improvements rather than fine tuning each aspect of the intake/exhaust track.
The area where you'll see the biggest gain (in the head) is the area just upstream from the intake valve (also known as the pocket - the area after the bend, between the valve guide and the valve seat).
When modifying the track, your goal is to get even flow velocity throughout the cross section of the track.
Larger is not always better. When building a highly modified motor, you need those larger ports because the motor operates at such a high speed that the actual size of the port becomes a restriction. These motors are designed to develop their power at very specific points in their RPM range. Generally, larger ports flow more fuel/air at higher RPM's but sacrifice torque at lower RPM's due to lower fuel/air velocity (as was seen by Bustedback in his post above this one).
"Polishing" as a method of increasing power is also a myth (on the intake side). Intake ports are left intentionally "rough" as it encourages liquid fuel that lands on it (though the injection process) to vaporize more quickly. A mirror finish inhibits that, and you end up with liquid fuel running down the wall of the intake track into the combustion chamber...not very efficient. (If you flow both the polished and "rough" tracks on a bench, usually the difference is under 2%-your fuel vaporization is more important that those 2%). Exhaust track, on the other hand, since it is dry, can be polished to increase laminar flow and get those gases out.
As far as lining up the gasket and starting to cut, I'll let someone smarter than me address that:
GASKET MATCHING VS PORT MATCHING
This is a commonly misunderstood subject. Many people think and believe the proper method of port work is to use whatever gasket comes in the box as a template to determine what size the ports or runners should be. It's not that easy or simple. I have seen many sets of heads destroyed by using this method. They look impressive to the untrained eye. You might even show some improved performance over stock, but overall you've created some airflow issues that can't be fixed. To assume that the gasket is an intelligent being would also be to assume that the gasket maker knows what size your ports should be. That is to assume also that the gasket maker knows your cubic inches, cam size, carb cfm., gear ratio, valve size, and RPM operating range, and more. Here's the story on gaskets. If gaskets protrude into the runner then shave or cut the excess off so that it doesn't obstruct air flow. That's it! Don't use gaskets as templates.
PORT MATCHING aka DO NO HARM
Now that we have that gasket matching issue out of the way let's finish the rest of it. It would be real nice if ports and their manifolds that pair up to them were the same size and shape, but that doesn't happen often enough. So we need to deal with what we have. Let's say the exhaust manifold has a smaller opening than the exit out of the head. In that case we need to open the manifold to match the head. But what if the manifold opening is larger, then what? Do we open the head up to match the exhaust manifold? No. If you do open the head to match you will create a "slow" spot in the air flow. Terrible! If the air flows through the runner and hits a wall, such as a protruding gasket or a manifold the air "trips" and "stumbles" causing turbulence, and impedes air travel. But if the flowing air falls over the edge and into the manifold there's little harm done. The point here is the "Doctors Oath" of "do no harm". It's not an ideal situation but it is better to leave it alone that to make things worse. The same logic applies to the intake airflow, it can fall into the intake runner of the head from the intake manifold, but you don't want it to stumble into the gasket or the lip of the intake runner. The idea here is to minimize the bad, maximize the good, and "Do no harm". So bigger is not always better. Grinding away where ever you get the notion can cause the air flow to slow and thus losing the pulsing, charging, ram air effect, and extraction benefits we need. Port matching is done after the head is ported.
If you don't want to touch the head, I understand - it's a big project to do that.
Take some pictures and let us know your results!
07-20-2012, 06:53 PM
#10
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Sorry for the wait. Been doing this project on and off now, taking pictures as I go. I'm not opening the ports up. rather taking the high spots down, and smoothing everything out. My camera is not so good (phone). I do have a high def camera floating around, but I can't find it.
Basically, I'm using a Dremel. With a carbide bit, taking down the bulk and "roughing" it out, much like painting. Then I've moved to a grinding stone, this is for flushing out the roughing process. Creating actual shape. Then a carbon steel wire wheel, followed by 120 grit paper wheel, taking this about 2" in. I've only done two ports thus far. Taking my time making sure I get it right.
Basically, I'm using a Dremel. With a carbide bit, taking down the bulk and "roughing" it out, much like painting. Then I've moved to a grinding stone, this is for flushing out the roughing process. Creating actual shape. Then a carbon steel wire wheel, followed by 120 grit paper wheel, taking this about 2" in. I've only done two ports thus far. Taking my time making sure I get it right.
07-21-2012, 08:30 AM
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"Polishing" as a method of increasing power is also a myth (on the intake side). Intake ports are left intentionally "rough" as it encourages liquid fuel that lands on it (though the injection process) to vaporize more quickly. A mirror finish inhibits that, and you end up with liquid fuel running down the wall of the intake track into the combustion chamber...not very efficient. (If you flow both the polished and "rough" tracks on a bench, usually the difference is under 2%-your fuel vaporization is more important that those 2%).
07-21-2012, 06:24 PM
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