port and polish

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Neo10's
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port and polish

Postby Neo10's » Tue Jun 25, 2002 1:56 pm

Iv been hearing alot about have a port and polish done to your engine to increase hp. The term isn't new to me since i used to do that on Gran Turismo. But what exactly is done when a port and polish is done to your engine, and how much would one cost?
Mike

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Sound_Miata
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Postby Sound_Miata » Tue Jun 25, 2002 3:34 pm

if you do the labor of removing the head yourself, it can be a bit cheaper. But it involves removing the head of the motor, and taking to a machine shop. The intake side is then enlarged and casting defects removed from the runner surfaces. It can also involve enlarging the valves as well and polishing that area around the valves. This can improve flow into the head allowing more air and fuel to mix evenly creating a better burn and more power.
Here is a good example of before and after
http://www.gvii.net/dlralt/installation_photos/031302_before.jpg
http://www.gvii.net/dlralt/installation_photos/031302_after.jpg

good headwork will run near 500 for a full job, plus labor if you don't pull the head yourself (and if you do, you will need a new haedgasket).

-Greer
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Shaddow75
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Postby Shaddow75 » Tue Jun 25, 2002 9:28 pm

WOW i need one of those :) !
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sirsloop

Postby sirsloop » Tue Jun 25, 2002 9:40 pm

after you get porting and polishing work, go get a 5 angle valve job...
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Neo10's
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Postby Neo10's » Tue Jun 25, 2002 9:49 pm

What is a 5 angle valve job?
Mike



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Alpine CDA-7893 Deck (comming this month)

New amp, undecied yeat (comming this month)

2 10in 400watt Pioneer subs





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Sound_Miata
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Postby Sound_Miata » Tue Jun 25, 2002 10:13 pm

sirsloop....defend your position on 5 angle....with a good 3angle that uses a radius cut you will be better off in the long run. Because the radius cut will blend it all together.

a "3 or 5 angle" valve job involves cutting the front and backsides of the valve so that you not only enlarge the valve area, but better blend the transition from the head to the valves. The two photos I posted are part of a port/polish and valve job on a 4 valve head (a 1.8L miata to be exact) and you can see the area around the valves where they made the cuts.

-Greer
*Winner of the Beastly 1000th AND 2000th Post*

slappin momma llama on the backside-Joshie-Poo :-D



Vendors: We will allow you to break the laws of physics and the second law of thermodynamics so long as you provide us with a working model.
sirsloop

Postby sirsloop » Wed Jun 26, 2002 7:52 am

I always though a 5 angle would be better because there would be a smoother entry into the cylinder

3 angles is not as round as 5 angles...the easier the a/f gets in AND out of the cylinder the more power you make

I think the difference is pretty minor, the main thing with valve jobs is WHO DOES THE WORK! HAHA...you can get a crappy 5 angle job and have it come out worse than stock...

If i was getting my heads ported you bet I would get ATLEAST a 3 angle while they were off...
sirsloop

Postby sirsloop » Wed Jun 26, 2002 7:59 am

also, while you have your head off its an easy time to index your spark plugs. That is aligning the spark plug outer electode (bottom part you gap) away from the valves on the head. Theory is that the incoming A/F will have a clear shot at the spark and ignite better. People says it works, I guess it can be the kicker between 2 identically moded cars...

its just a PITA to bend over for like 2 hours while trying to index your plugs with the engine in the car :D
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Postby Neo10's » Wed Jun 26, 2002 8:10 am

Ok every one who knows me knows two things. For one, People know me as the smart go to guy for everything. Two they know that I am no mechanic at all, but im trying to learn performance. And what I keep reading is that the spark given to the fuel to create the combustion is basicly the whole principal behind engines. Well of course, seeing how its called the combustion engine. So with that in mind its safe to say if you create a bigger spark.....you get a bigger explosion.....and you get more power to the tires. Now you have the intake witch gives the engine air so it doesnt over heat....right? Is this basicly the principal behind the engine?
Mike



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audio system

Alpine CDA-7893 Deck (comming this month)

New amp, undecied yeat (comming this month)

2 10in 400watt Pioneer subs





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Postby davidjs » Wed Jun 26, 2002 8:15 am

Originally posted by Neo10's
Now you have the intake witch gives the engine air so it doesnt over heat....right? Is this basicly the principal behind the engine?


not quite...

The radiator coolant (ethylene glycol+ water) makes it so the engine doesn't overheat...

The air intake is to mix the fuel (gas) with the air (air), to create a more combustible mixture, that will then explode... liquid gas doesn't explode, it burns... gasoline vapors explode... so once you mix the air with the gas (either with a carb or a fuel injector) it can explode once it sparks...

http://www.howstuffworks.com/engine.htm
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