Editing Porting cylinder heads

==Preamble==
The purpose of this article is to acquaint engine builders on the tangible benefits of cylinder head porting and making more power through the porting process. Cylinder head porting or 'porting' as it is known in the hot rod circles, is classed by some as '''black magic''' in the engine building process. Proper porting procedures will result in getting the largest volume of air/fuel mix to the combustion chamber in the shortest amount of time. Porting works hand in hand with valve grinding and seat cutting.

==Areas to look for==
During the manufacturing and machining processes of a cylinder head, there are areas that are left unfinished. This is due to cost/time restraints imposed on the manufacturers, especially OEMs.

When a port is machined for a seat, often a lip is left below the seat. This lip is sometimes semi-removed using a type of tapered reamer that helps smooth the transition from the seat into the pocket portion of the port. But because this is done quickly and by machine and not carefully and by hand, there is still almost always places where improvements can be made.

[[File:EXH PORT.jpg|thumb|400px|left| Arrows indicate lip left after the machining process. This needs to me carefully removed so the transition from the seat to the pocket is smooth.]] <br style="clear:both"/>


Another example of areas that need attention. This is a BBC head that has had some work done to it already:

[[File:049 bowls.jpg]] <br style="clear:both"/>


== Porting tools and materials ==

===Die Grinders===

===Grinding wheels and abrasive cartridges===

===Polishing wheels===

===Layout dyes===
[[File:DYKUM BLUE TUBE 001.jpg|thumb|100px|Dykum blue layout dye]]
One common type of metal dye is machinist lay out paste, dykum blue, prussian blue, etc. Comes in a tube, is thick enough to be spread out with a piece of paper towel, etc. After it sets up for a few minutes, the scribing can be done.

Another type comes as a liquid in an alchol base that can be sprayed or wiped on. When the alcohol evaporates, the dye is left behind for scribing.

==Porting methods==

===CNC machining===

===Pressurized abrasive honing===

===Hand porting and polishing===

==Step by step porting methods==
Before you go out and grab your tools and start grinding on those $1000 Edelbrock heads you just bought, STOP. Porting requires practice, so do exactly that, practice on a set of old nondescript heads that you picked up at the local auto recycler. Try out your tools and see what they do. Remember to use the correct tool for cast and aluminum heads so you do not ruin the tool and hurt yourself. After you feel confident with working with your tools, we will go on to explaining what we want to accomplish in each segment.

===Gasket matching===
This is a simple process whereby we will match thermostat housing to an intake manifold for better flow of coolant from the engine to the radiator. Begin by cleaning off the surface of both housing and intake mating surfaces. Remove all gasket material and glue with acetone and a gasket scraper. True the surface of slight imperfections by using a mill/bastard file place flat on the gasket surface  working the file back and forth. The shiny sports are the highs and the dull ones are the lows, true these surfaces. When a flat surface is obtained,paint the surface with Dykem dye, lay a new gasket on the surface and insert the bolts in the holes of the intake to center the gasket over the openings. With a scribe, scratch along the gasket edge around the opening. When complete, remove bolts and gasket. This will reveal a scribed line in the purple dye that you will be enlarging up the opening to. 

*If this is an aluminum intake, chuck up a open cut burr that is used for aluminum, and spray it with WD40 or similar lubricant. This will make cleaning the tool easier, reduce friction and heat. 
*Put your safety glasses and respirator on and start up your die grinder. Note which way the grinder turns, clockwise. 
*Gently ease the burr against the upper portion and draw it along the intake opening working in a clockwise motion towards the bottom. Just lightly feather the burr and adjust pressure against the surface as you grow more accustom to the process. Trim more and more, as you come closer to the scribed line, stopping when you are one line's width away from it. 
*Blow away any of the metal splinters that were made by the burr. Keep your work area clean. 
*Begin removing material again from a different area until the entire open area is within a line's width of your scribed line. 
*Remove your burr, and chuck up a sandpaper roll of 80 grit. 
*Gently move it around the perimeter of the opening once or twice. Check the surface for texture and note how close you are to your scribed line. 
*Chuck up a 180 grit roll and move around the perimeter again one more time. 
*Finish off by tilting the roll 30 - 45 degrees of angle and go around the outer edge and remove the sharpness off that edge. 
*Blow off the sanding dust and clean the gasket surface. 
*Place the gasket on, insert your bolts and check to see how the gasket fits the opening now. 
*Match the housing to the gasket to the surface the same way as you did the intake and you should have a perfect match. 
*Apply this process to the other gaskets on your heads for optimum flow.

==Other related areas==
===Installing screw in rocker arm studs===
[[File:POW351300.jpg|thumb|400px|left|Stud puller/tap guide for SBC]] <br style="clear:both"/>

==Photos==
{|
|[[File:Comb_chambers.jpg|border|thumb|left|400px]]
|[[File:Short_side.jpg|thumb|left|400px]]
|}
{|
|[[File:Exh_2.jpg|border|thumb|left|400px]]
|[[File:Exhaust.jpg|border|thumb|left|400px]]
|}

{|
|[[File:Intake.jpg|border|thumb|left|400px]]
|[[File:Intake_Edelbrock.jpg|thumb|left|400px]]
|}

==Milling the deck==
When the decks of the block or heads are milled to raise compression, or to true the surfaces, or to correct the [http://www.crankshaftcoalition.com/wiki/Quench '''quench measurement'''], often the ends of the intake and/or the intake flanges need to be milled to correct the port and bolt hole misalignment this can cause. Whether this is necessary depends on the amount of material removed and the angles involved. In the case of the Chrysler B/RB and Pontiac engines, nothing needs to be removed from the ends. 

It should be taken into consideration that when the heads are milled, the geometry changes and piston to valve clearances will be closer.  

See '''[[Milling cylinder heads]]''' for more info.

==References==
*If you like the hands-on video approach, this is it: [http://www.youtube.com/watch?v=35O7mkLncHU CYLINDER HEAD REBUILD - VALVE JOB AND PORT & POLISH ON DVD]

===Compression calculators===
*[http://www.wheelspin.net/calc/calc2.html Static compression ratio]
*[http://www.empirenet.com/pkelley2/DynamicCR.html Dynamic compression calculator] by Kelly
*[http://www.kb-silvolite.com/calc.php?action=comp2 Dynamic compression calculator] by KB

==Related links==
*Check out the videos of CNC porting here: [http://www.centroidcnc.com/cnc_porting_machine.html CNC Cylinder Head Porting and Engine Block Machines]
*Looking for tools and abrasives, try here: [http://www.ruffstuff.com/ Cylinder Head Abrasives]
*A more technical approach: [http://hubpages.com/hub/Cylinder-Head-Porting-101 Cylinder Head Porting 101]
*A great article on valve shrouding: [http://www.diyporting.com/Shrouding.html Valve Shrouding] from diyPorting.com	

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[[Category:Engine]]
[[Category:Cylinder head]]
[[Category:Undeveloped articles]]
[[Category:Undeveloped Engine articles]]
[[Category:Undeveloped Cylinder head articles]]