Cylinder head porting & info

[generationjdm]

Nice little article I found makes sense, it's like taking a milk shake and trying to suck the fluid through a large tube and getting no where we you can take a smaller tube with more velocity and getting somewhere.. More velocity equals more air which equals essential more power..

Porting- In the porting process the intake and exhaust ports are carefully reshaped (or should be if the porter really know what he/she is doing) by hand. This reshaping consists of enlarging, straightening, and streamlining to get rid of as much pumping-loss inducing restriction, turbulence to increase the flow velocity of the cylinder head as much as possible while make as much HP as possible. Most of the time ports are straightened by a die grinder and a carbide bit to a line of straight configuration. This straightening process gets rid of any bends that may cause turbulence in the head. This doe grinder that they use also is used to get rid of too cutting marks, sand casting pits, and usual bumps and lumps that are made by the mass production of our cylinder heads. Another process to gain more volumetric efficiency out of the head is called, extrude honing. This is where thick putty like goo full of abrasive is pushed through the cylinder head, enlarging the ports, just like the natural flow of your motor would like them to be. There are limits to porting though. You can make ports to big. Symptoms of a head that has been ported to much are a soggy bottom end, not making power. The other is a lumpy idle. The type of porting for your car will depend on the type of set up you want to run. Turbo cars like smaller port, high velocity ports without a lot of overall port volume. Nitrous and supercharged cars like the bigger ports with more overall port volume. The N/A street motors like the smaller, high velocity ports, like the turbo cars. Drag N/A motors will tend to like the bigger ports, this gets rid of the bottom end, but they want top end so it really does not matter.

1. Valve jobs- this is another major factor in getting the most out of your head. Truly, a 50% of head flow gains can be found in the valve job.

Stock valve jobs are usually either one-angle valve job or two-angle valve jobs. One-angle valve jobs, is just done on the seats surface, two-angle valve jobs are a seat cut and a smooth throat cut. The high performance valve jobs have three-angled cuts, one on each side of the valve seat.
1st- there is a throat cut typically around 60-70 degrees. This will help the ease of the air’s transition to the 45-degree valve seat cut.
2nd- there is a 45-degree valve seat cut, which is literally where the valve actually seats.
3rd- this is called the top cut. This cut is immediately after the seat cut and is typically 30-20 degrees. This cut also helps to reduce valve shrouding of the airflow past the valve (or before if we are talking about the exhaust valve) as the valve starts to lift of the seat. There are five-angled valve jobs, but I think for the most part they are not needed, that is why I am not going to get into the five-angle valve job process..

Read this link you will find good info about large port having less velocity verse small port having much more. http://www.patentstorm.us/patents/64...scription.html

[generationjdm]

V8 Engine builders words...
there seems to be a HUGE mis-understanding about port size and how it potentially effects your engines torque range,
port size should be thought of more as a restriction to reaching necessary flow than a benefit to making a significant torque curve PROVIDED your [COLOR="black"]matching the total engine component list to the intended rpm range and expected hp peaks the engine will be expected to produce and run at!
its not port size but the ports cross sectional area and length matched to the other components like the engines displacement,compression, cam timing and bore/stroke ratio PLUS the exhaust systems designed scavage effiecincy range at any give RPM level has a major effect on results, the size of the ports in your cylinder heads are one of the least[/COLOR]> THATS RIGHT I SAID THE LEAST important of the factors that determine where in the rpm range your engine builds its best power, while its true that smaller port cross sectional areas due cause the airflow speeds to increase,its also very true that the runner length and cross sectional area of the intake used, the compression ratio and the cam timing and the design of the header primary tubes are at least two to three times as important simply because they control the airflow thru the cylinder to a much greater extent, and the engines stroke and total displacement are extremely important, changing JUST the displacement and cam timeing has a HUGE EFFECT on WHEN and HOW the airflow in the ports gets its vacuum signal and how the port responds to that change in pressure.

[generationjdm]

REALLY GOOD ARTICLE http://www.importtuner.com/tech/0509...ads/index.html

[NogaroAvant]

nice read, confirms a lot of what i have read in the past and have discussed with machinists on other projects (VR6 head porting). I am going to be keeping my 2.7 heads on my project car. I will be having minimal porting done, but more "bowl" work than anything, as well as rebuilding the valve train to handle ~8k rpm safely... whether it sees it will be determined on supporting hardware and tune. I also plan on designing/making an alternative to the stock manifold, maybe adding some volume to it as seen on other designs, as well as a custom y pipe. One thing at a time...

[generationjdm]

nice read, confirms a lot of what i have read in the past and have discussed with machinists on other projects (VR6 head porting). I am going to be keeping my 2.7 heads on my project car. I will be having minimal porting done, but more "bowl" work than anything, as well as rebuilding the valve train to handle ~8k rpm safely... whether it sees it will be determined on supporting hardware and tune. I also plan on designing/making an alternative to the stock manifold, maybe adding some volume to it as seen on other designs, as well as a custom y pipe. One thing at a time...

Dont foget the full valve job haha

[AK1RA07]

Thats all nice and well in theory, but the question remains is a 2.8 head too large for an upgraded turbo application.. Sure, turbo cars in theory like smaller ports for higher velocity, but just as a port can be too large for an appication, a port could be too small for a turbo appication pushing more air than the stock head was designed for, correct?

[generationjdm]

Thats all nice and well in theory, but the question remains is a 2.8 head too large for an upgraded turbo application.. Sure, turbo cars in theory like smaller ports for higher velocity, but just as a port can be too large for an appication, a port could be too small for a turbo appication pushing more air than the stock head was designed for, correct?

These are facts, saying the larger 2.8 is better because of the larger ports is a theory

[generationjdm]

I have a great comparison coming to all, my car is a gt2560 car with all the 2.7 parts but for the cams there 2.8, which i wish i left then stock.. Knightriders car is a gt2560 same kit as mine and has all the 2.8 stuff with rs4 components on it. he should make more top end then me but i think i will make more low to mid then him and spool faster for sure

[AK1RA07]

These are facts, saying the larger 2.8 is better because of the larger ports is a theory

My statement is a fact though, isnt it?. To use your milkshake analogy.. if you're drinking your milkshake but the waiter is sitting at the table with you filling your cup faster than you can drink it, you get a brain freeze and the table cloth gets all sticky, no? I agree, I have no hard evidence that a 2.8 head is too large/small/just right for Goldielock's turbo S4..

I have a great comparison coming to all, my car is a gt2560 car with all the 2.7 parts but for the cams there 2.8, which i wish i left then stock.. Knightriders car is a gt2560 same kit as mine and has all the 2.8 stuff with rs4 components on it. he should make more top end then me but i think i will make more low to mid then him and spool faster for sure

One car is not necessarily worse than the other though I guess we all just need to know which one is right for our own application. I can't wait till your cars are up and running.

[generationjdm]

I have all winter and haven't touched the car since it turned key 3 months ago if that tells u and others how much i really care about the car anymore haha

[generationjdm]

taking apart the heads and cleaning them, Valve Job, bowl work, reassembled heads to seals. $400-500.00 which will yield roughly up to 75% of the gains you will get. Full port job and those things mentioned starts at 1500.00+ and may yield 25% of the total gain. So lets say the heads picked up 40whp which is a lot, is an attentional 10hp worth the 1k extra to get the works?

[sCeRaXn]

Thats all nice and well in theory, but the question remains is a 2.8 head too large for an upgraded turbo application.. Sure, turbo cars in theory like smaller ports for higher velocity, but just as a port can be too large for an appication, a port could be too small for a turbo appication pushing more air than the stock head was designed for, correct?

It wont be too big, but it might not be the most suitable for your application. While were on the subject, lets talk about the benefits of porting. Alot of people think about porting only when it comes to making big power. This is a shame because porting can be very benefecial in almost any setup...even if youre only looking to max the performance of k03's. Like ive said many times before...bowl work, valves, and a good vj will help increase both volume and velocity throughout the full range of lift. This will increase throttle response and power throughout the rev range all while keeping the same spool time as you had before(could decrease it with the right parts combo). This goes for k03's, k04, rs6's, tials, Gt's or any other turbo setup you want to put on it.

Now lets talk about valves and valve jobs. Let me start by saying that theres no such thing as a high flow or high performance 3 angle valve job. I see this quite often when reading ads for head porting. You can change the top and bottom angles all you want, but youre still limited by the sealing angle...which is 45deg on basically every head thats been made since the 50's. Some valves will require a different angle depending on the size of the valve and valve seat, but its not very common for it to differ from 45deg. 5 angle vj's can help flow a little bit, but youre usually forced to sacrafice the amount of surface area available for the valve to seal against the seat. The smaller surface area has also been known to cause ridges on the back of the valve(hat)...which kills airflow around the valve and gives a nice spot for carbon build-up. So with the 5 angle vj you gain some airflow, but you have to sacrafice some reliability.

A raduis vj is by far the best option. With a radius vj you still have the 45deg sealing area, but you can keep it the same size as the stock 3 angle sealing area. You can do this because the radiused area before and after the sealing angle cause the air to skip over it. So not only do you gain a large amount of airflow(more than porting in some cases), but you also mantain stock reliability. Alot of people shy away from radiused valve jobs because they can get pretty expensive. However, these people dont know the real advantages of it. Most of them dont take the fact that a radius vj also involves bowl work into consideration either. This is a must because the bottom radius starts in the bowl, before you even get to the valve seat.