Porting heads - Intake airflow ??? w/ pics
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Porting heads - Intake airflow ??? w/ pics I'm doing mild port / polish on a set of heads. I bought a used set and took some pictures before I began. On the intake side, I noticed some discoloration in some areas, I assume due to EGR passing. This kinda gives me a window into how the air flows through the port.
BLUE ARROWS: There is a visible discoloration where air flows from the top of the intake down into the chamber.
GREEN ARROWS: Clean looking areas. No visible discoloration.
YELLOW AREAS: More discoloration, shows heavier buildup on the floor.
RED ARROWS: A visible buildup on the outer portion around the orifice to the gasket edge.
<img src="http://www.z71.net/intake1.jpg" alt=" - " />
90% of porting posts talk about keeping up airflow speed and not removing too much material. It looks like the RED arrows show a visible bottleneck that would hinder airflow. I didn't want to remove enough material to gasket match the ports. But should I round over the edges or flare them out a bit just to decrease the resistance entering the head? I am being cautious with this project and want it done correctly, but do want them to be worth my effort.
Any opinions?
* One other side note - The EGR discoloration isn't evenly spread across all ports in the head. Possible proof that since EGR doesn't get evenly distributed by the intake manifold, than neither would nitrous.
<small>[ October 22, 2002, 09:35 PM: Message edited by: BigTex ]</small>
BLUE ARROWS: There is a visible discoloration where air flows from the top of the intake down into the chamber.
GREEN ARROWS: Clean looking areas. No visible discoloration.
YELLOW AREAS: More discoloration, shows heavier buildup on the floor.
RED ARROWS: A visible buildup on the outer portion around the orifice to the gasket edge.
<img src="http://www.z71.net/intake1.jpg" alt=" - " />
90% of porting posts talk about keeping up airflow speed and not removing too much material. It looks like the RED arrows show a visible bottleneck that would hinder airflow. I didn't want to remove enough material to gasket match the ports. But should I round over the edges or flare them out a bit just to decrease the resistance entering the head? I am being cautious with this project and want it done correctly, but do want them to be worth my effort.
Any opinions?
* One other side note - The EGR discoloration isn't evenly spread across all ports in the head. Possible proof that since EGR doesn't get evenly distributed by the intake manifold, than neither would nitrous.
<small>[ October 22, 2002, 09:35 PM: Message edited by: BigTex ]</small>
Staging Lane
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From: Houston
Re: Porting heads - Intake airflow ??? w/ pics What you are seeing is the injector spray pattern washing deposits off the port wall. Airflow is not always what it seems, I have learned that through flowbench testing. Be careful, enlarging the port entry without modifying the bowl and short side radius areas will not improve flow. Removing material without access to a flowbench is a shot in the dark. Taking material from the wrong area can actually reduce flow! Good luck,
Paul j.
Paul j.
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Re: Porting heads - Intake airflow ??? w/ pics Thanks Paul. You mean all the dark buildup on the outside of the port is from injector spray? It is thick like the buildup on the exhaust side, so I thought it had to be EGR. Either way, would taking the angled edge off opening be any benefit? With build up on it, it looks like a restriction.
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Re: Porting heads - Intake airflow ??? w/ pics Just my opinion...Of all the things I pride myself of being able to do, head porting is the one thing I leave to the experts, since it is scientific and one of the most important in the combination as a whole...my personal preferance being Brian Tooley at TEA. props!!
Re: Porting heads - Intake airflow ??? w/ pics </font><blockquote><font size="1" face="Verdana, Helvetica, sans-serif">quote:</font><hr /><font size="2" face="Verdana, Helvetica, sans-serif"> Either way, would taking the angled edge off opening be any benefit? With build up on it, it looks like a restriction. </font><hr /></blockquote><font size="2" face="Verdana, Helvetica, sans-serif">If I understand you correcty, you want to reduce or eliminate the sharp edge at the intake flange because of the dark stain on the face of the flange. A large percentage of the stain is from the intake charge seeping between the manifold and head. It stops at the "O" ring seal which means the actual port opening is a bit smaller than the stain represents.
IMO concentrate your porting efforts in the valve bowl and short turn radius. Minor mis matches at the manifold/head entrance don't mean as much to a street/strip engine as a high rpm race engine. Have a reputable machine shop do the valve job and let 'er rip!
Good luck,
Richard <img border="0" title="" alt="[Smile]" src="gr_stretch.gif" />
IMO concentrate your porting efforts in the valve bowl and short turn radius. Minor mis matches at the manifold/head entrance don't mean as much to a street/strip engine as a high rpm race engine. Have a reputable machine shop do the valve job and let 'er rip!
Good luck,
Richard <img border="0" title="" alt="[Smile]" src="gr_stretch.gif" />
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Re: Porting heads - Intake airflow ??? w/ pics Thanks for the input. I have removed all casting material, but have been very conservative otherwise. My main goal to begin with was to polish everything and get them milled. I have tried not to change the shape or contours of the air paths. That said, there is still about a 7mm corner around the intake port opening to the edge of the intake gasket. That is why I asked the question. It looks like it would impede air entering the runner. I'll post some in progress pics later today.
Richard
Richard
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Re: Porting heads - Intake airflow ??? w/ pics Richard your concern is valid, but intake manifold opening is smaller than opening in head. so mismatch is in proper direction. Any change in dimensions can change air speed and cause turbulence. What i am saying is, head opening is large enough not to be a restriction but port matching intake can and may help relieve turbulence which will help airflow, not because of bigger dimensions, just because of cleaner transition from intake to head.I have port matched my ls6 intake to my 5.7 heads dimensions but i still need to test for gains. These heads are complex compared to old school motors so you should get some coaching to port them effectively.
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