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Documented Build... L67



Not against you Matt, just curious. I have heard this multiple times but WHY is the D shape so needed?

Logically you would think matching the gasket would be the best because it would allow for the exhaust to flow out as efficiently as it could... but Logic doesn't always apply to automobiles.
 


It's a reversion dam.

Prevents the air from traveling back into the cylinder.

Exhaust/inlet flow aren't steady. They cycle. Makes things more complicated.
 
dont they call that savaging? as each cylinder fires, the other one that just fired is pulling gasses back, fighting the other cylinder from letting the fired exhaust out? in the manifolds that is.
 
Scavenging is drawing the exhaust away from the cylinder head.

You can optimize the timing by optimizing the lengths and where they reach.
 
matt5112 said:
Yup, they are ruined.

Need the D shape.
Click to expand...

This is getting aggravating, the "experts" at my local machine shop are the ones who scribed the cylinder heads and told me to start porting. They have cost me a ton of money already :mad:




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Love how you drilled the whole lol. So what I'm getting at is for the intake side it's good to gasket match it for the port. But for the exhaust side you want to port it more toward a D shape? Any pics just for reference?
 


You aren't the first to make that mistake, so don't feel bad.

Lots of people have run heads with gasket-matched exhaust ports without issue....they might not be as quick as they should be, but no reliability problems.
 
Here is a set I did a month ago. Pic's aren't the best because I took them with my phone.

2012-10-09_22-19-05_818.jpg


2012-10-18_00-38-16_717.jpg



Ported on the Right, stock on the left.

2012-10-10_22-52-48_927.jpg



The floor is only smoothed out and polished. Not much air flows down there, and you'll lose velocity from removing material there.
 
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Not all that much you can do on the intake side....gasket matching isn't necessary since the cross section of the LIM runner is smaller than the stock head intake port.
 
Damn bro, you got a mirror finish on those exhaust runners, nicely done. So far bad advice and poor decisions have cost me over 2500 dollars, no better way to learn in my book.

Sent from my Galaxy Nexus using Tapatalk 2
 


I always figured linking good material is just helping people and that's why we are here, to help people.

And to make Bio's life hell.

But otherwise, to help people.
 
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