Question about Porting
 

Hi all. I was looking at a webpage of a local performance shop and they mentioned they had specials on Porting.

"Port & Polish Machine Work
We have an experienced technician who preforms all port & polish work
Stage I Porting: Intake and exhaust bowl matching & blending
Stage II Porting: Stage I Porting plus intake gasket, matching and full exhaust runner clean-up
Stage III Porting: Stage I & II Porting plus extensive reshaping of intake and exhaust runners"

http://www.performanceexperts.ca/services2.htm

Can someone explain to me what Porting is and what exactly what benefit I would get from doing it to my car? I know that in Grand Turismo 3 I get some nice horse power gains from similiar modifications:p

Any technical would be sincerely appreciated!

all I know is that you can do it yourself instead of paying that much......., but then again you'll take the risk of f#cking something up.........................

well it won't be that bad cause it's in CDN dollars. So no description of what it is? :(

Ummm does anyone know if horespower gains result?

Okay here goes.

Stage I porting: The 'bowl' area is the area directly below the valve in the head. Usually bowl work involves opening up the throat area under the valve, blending the valve guide area into the port (instead of the squared off edges around the guide they are stock), smoothing out the 'short side' radius (also called the port floor) and generally making everything smooth directly under the valve

Stage II porting: smoothing out the exhaust runner (no casting lines or sharp edges) plus gasket matching the intake. Gasket matching means they take the actual dimension of the opening in the intake gasket and enlarge the port to the same size. Then they blend the enlarged area into the port runner which enlarges the runner usually.

Stage III porting: More of the same, but they enlarge the runners to even larger cross sectional areas for more maximum flow.


Now, for what it all means. Not all places use the same criteria for port 'stages'. Bowl work is what most people will recommend as a minimum if you want performance. It's the least expensive, and has a LARGE effect on flow. Making the runners bigger will increase the maximum flow, but at a sacrifice of velocity. Good port velocity will make low end, low velocity will kill it. Cleaning up the runners (smoothing everything) as well as gasket matching are usually the next step and will give good results also since the ports are not usually hugely enlarged, but are larger and smoother so air doesn't get turbulent and cause a flow restriction. This works well with bigger cams and good flowing exhaust and intake. No point in doing this if you are going to use stock cams. The bowl work will work fine with that and still offer decent gains.

Full porting is best if you are using bigger cams, some kind of improved engine management to take advantage of it, or if you are using forced induction. Superchargers don't care about port velocity since the intake is under pressure. All they want to see is no or very little restriction. It's not uncommon for a supercharger app. to lose pressure with a better flowing head and gain a lot of power. The key here is how much air you can move not how much pressure you can create. You want more volume moved.

I'm thinking about getting (or doing) bowl work on my cylinder head. Keep in mind that if you don't know what you are doing you can make a real mess out of a head. It's not a beginner's job for sure. If you take too much off in the wrong place you can end up going into the water jacket or killing flow. One of the big things you want to do is keep flow fairly consistent from port to port. You want the same dimensions on each one as well as the flow to closely match. Otherwise you get an engine that isn't very smooth. Honestly, if you are really thinking about porting you should let someone that knows what they are doing do it. There are a lot of other mods I'd do first before working on the head.

Excellent information. Thanks for the lesson. I think I only followed about half of it because my knowledge of internal engine parts is not the best. However it just went up by about 200% :D

From your description I agree that it's probably something left unitl I've exhausted the rest of the easy power modifications. THe main reason I was looking at it was due to the fact that for the price it actually looked pretty cheap. And any time I can get something in Canada as opposed to the US it saves me mucho dineros :)

Thanks again Traveler you've been a great help and an excellent educator :P

This is in Nova Scotia?? Wow, that's better then what we've got in BC hehe

Good Stuff Traveler.....and very accurate....

the last statement about flow...its REALLY important that all the cylinders match so very closely....or like he mentioned your engine will actually be unballanced.....one cylinder actually making more power than another...ANYWAY.....if you find someone that REALLY knows that they are doing...and does much of this type of work, they will actually have a "flow bench" which is a machine that they will mount the head on and MEASURE the flow through each and every runner to ensure that they match....and make adjustments accordingly. Its as much an art as it is a scinece. And believe me....if you found someone that does this work CHEAP....you can bet it won't be the best job out there....that is for sure.

for a comparison.....I also build high performance air cooled VW motors...have for many years......on the average you can buy a STOCK VW aircooled cylinder head for about $75. so $150 for the pair.....the last motor I built I had a fair amount of head work performed....and by one of the best and most recognized shops in the US.....I had a complete Port and Polish job done (as descriped as Stage 3 above) even had the short intake manifolds ported and polished...and match ported to the heads.....the price.... $850 bones. but then again....when I was done with the engine it made a little over TWICE the HP of the stock motor, it ran on regular pump gas, the car still got 25 MPG.....and would out run Z-28s and Mustang GT's in the 1/4 all day long.....

there is sooooooooo much truth in " you get what you pay for" when it comes to true performance modifications to an engine.

I agree head work is not just a matter of grinding and posihing. The idea is to increase runner velocity, and thus volumetric efficeintcy. While at the same time keeping everything perfectly matched and ballanced. The job of matching each chamber's volume can be very time consumming, yet absolutely necessary. Just setting up a flow bench for a new head can take 1/2 a day, but a hack job only takes a few hours.

When taking to a builder check on multi angle valve seats, an extrude hone job, or how close he says he can match port velocity and test it. Intellegent discussion on these topics is a good sign he has experience. Then consider how long a pro would spend working on a head he's never seen before. It ain't cheap.