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 FAQ: Headwork 
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Post FAQ: Headwork
Tuan is an engine builder who posts on <A HREF="http://www.hondavision.com" TARGET=_blank>www.hondavision.com</A> <BR> <BLOCKQUOTE><font size="1" face="Verdana, Arial">quote:</font><HR><I>Originally posted by Tuan </I><BR><B> Image <P>Now that I have your attention gentlemen:<P>Cylinder head porting - Is it a black art or is there some science applied?<P>Well, not being a headporter myself, I wanted to learn some info that the consumer should receive so that he/she can make informed choices from the many available head porters, either locally or the big names out there. I'm going to give it a shot.<P>1. Basic Headporting Terms </B><P>If you are unfamiliar with terms used in head porting and want pics and definitions for basics, please check out this site first. I found it helpful even though it relates to domestics:<P> <A HREF="http://www.sa-motorsports.com/diyport.htm" TARGET=_blank>http://www.sa-motorsports.com/diyport.htm</A> <P><B>2. What discussions should you have with your porter before he starts work?</B> <P>I think you may want to mention to the porter your displacement, redline, cam spec profile, type of intake manifold (plenum and runner size), TB size, rod ratio, compression ratio, header layout and primaries diameter/length, whether you are going all motor/forced induction, daily driver vs trailer queen, octane, where you expect the power gain to be and how wide....did I miss anything? Ask him which one of these are key to determining his porting method. If he does not answer you in a way you can understand, suspect that your headporting may not be as custom fit as they make things out to be and that the headporting may be a cookie cutter assembly line process. These high volume, one size fits all porting shops are the ones you want to say adios to and stay away from.<P><BR>Sizing the port volume and shaping the ports to your needs can only be based on this info.<P>You may also want to discuss whether you want a 3 angle or 5 angle valve job (cost difference vs gain in power) and other upgrades: springs (what will be your ultimate cam and redline you want to use), retainers (do you need ti retainers, really? or can you get more value spending in other places?), valve guides (cooler silicon-bronze valveguides needed or not?), and valves (stainless for high heat forced induction applications) .<P>With respect to oversized valves and stainless steel valves: are they worth the extra cash? Oversized valves are a trickle down from domestics and tends to make the engine peakier with a narrower powerband in all motor engines. They are beneficial in high compression, high heat N/A applications and in forced induction. Stainless does not afford a noticeable gain in hp for the cost in terms of the valvetrain weight savings. The weight saving sales pitch is more hype (Titanium is another story but is not durable for the street). Again IMHO, only in high heat applications stainless steel valves may be justified.<P>A 3 angle valve job may be all you need for the application you want. Don't get pulled into having to get a 5 angle job if the headporter cannot justify the added cost in terms of expected gains. Is it worth having more time on the Serdi machine to get 2 extra concentric angles cut on the head valve seat? The valve seat IS a major area along with quench area where big gains in flow quantity and flow quality are made.<P>Even if you do not get silicon-bronze valve guides, have them inspect the valve guides after porting around that area and replace any damaged or worn ones.<P>Some shops offer you the option of portmatching everything from the TB to the intake manifold to the intake port. Some also portmatch the header to the exhaust ports. Some people advise against portmatching and suggest you place a step slight increase in diameter as you move further downstream of the flow direction, in order to create an anti-reversion effect at each junction. I personally prefer the stepped approach over the portmatch approach.<P>You may want to mill your head to get more compression ratio but I advise against this, since you lose piston to valve clearance permanently. This prevents using higher lift cams in the future unless you use a thicker head gasket which decreases quench area (increasing the risk of detonation). Milling may weaken the structural strength of the head. On a Bseries, for every 7 thousandths milled off you gain about 0.3:1 CR. You also retard your cam timing since the distance from the cam lobe center to the crankshaft centerline is reduced. Removal of every 12 thousandths of an inch off the head deck equates to 1 degree of cam retard on a B series engine. You must advance the adjustable cam gears to get back to true zero cam timing after milling.<P>Lastly, but most importantly, if you are running all motor, you should discuss where along the rpm range you expect to have the biggest gains. Expected powerband location and width can help the porter zero in on what areas of the head he needs to reshape or open up to get you those targets.<P>If you're on a budget, you want to get things that will improve longevity and make big differences in performance. Try not to get coerced into adding things on in a nickle and dime way which look pretty and do very little in terms of actually gaining hp. <P><BR><B>3. Quoted Flowbench Numbers</B><P>Please take some time to read this very insightful article by a Pro Stock Drag Racer. Yes, I know he drives a honking blown V8 but the concepts do apply even to hot rod Hondas. As the man says, a big old sewer pipe flows excellently on a flowbench but when you attach it to a pumping engine and then add fuel, the engine performance and acceleration ability sucks.<P> <A HREF="http://www.rehermorrison.com/techTalk/16.htm" TARGET=_blank>http://www.rehermorrison.com/techTalk/16.htm</A> <P>The take home message here is don't rely soley on flowbench numbers. They only reflect flow quantity or how much volume the head can move at a certain rate. It measures flow capacity. The units are cubic ft per minute (cfm). It does NOT measure the speed at which that air is travelling (ft per second) and it does not tell you whether it can keep the fuel in the form of of a mist or atomized (mixture quality). Air-fuel mixture quality during cylinder filling, valve timing, and header length/layout will affect whether the flow bench numbers mean anything in reality. The target exhaust flow to intake flow ratio quoted by most people, for normally aspirated engines, is exhaust cfm should be around 65-80% of inlet cfm but no one rule is true for all circumstances, at all vacuum pressures, at all rpms (midrange rpm vs peak rpm). For forced induction and nitrous, the exhaust to intake flow ratio is usually 110% or more.<P>Some N/A people use the formula relating hp to target flowbench flow in cfm:<P><B>Potential hp = [0.43 x cfm @ 10 in. water] x no. of cylinders</B> <P>or<P><B>Potential hp = [0.256 x cfm @ 28 in. water] x no. of cylinders</B><P> <A HREF="http://www.racetech.com.au/custom.htm" TARGET=_blank>http://www.racetech.com.au/custom.htm</A> <P>Some people look at the redline to calculate how much ballpark flow is needed for 100% volumetric efficiency if the displacement is known:<P><BR>Again one formula at a fixed vacuum does not describe the complexity of achieving both flow capacity and flow quality. Here's why:<P> Image <P>This is a pic by Jim McFarland comparing the volumetric efficiency vs rpm curve (red) to the torque vs rpm curve (black). Notice that they are almost identical. In the areas where they do <B>not</B> line up, increasing air flow does not play an important factor in making more power. Other factors do. At rpms <B>below</B> peak torque, air-fuel <B>mixture quality</B> or <B>flow quality</B> ( and not flow capacity) determines whether you gain optimal torque . At rpms above peak torque, the ability to remove burnt exhaust gases out of the cylinder determines torque output. So "mixture quality" is huge for acceleration and performance. It's not just about flowbench numbers and how much you can stuff into the cylinder.<P><B>4. Comparing Methods of Approach to Headporting</B><P>Okay so I have some time on my hands and thought we could look at some comparative porting by 2 very well known big name headporters and invite members comments and experiences: DPR and Endyn headwork. <P>Why these 2? They have very different porting philosophies and approaches.<P>DPR is where Gary Kubo (or Lisa Kubo's husband ..I'm sure he doesn't mind being called that) , Tom Fujita at Portflow, and Joe Alaniz of Alaniz Technologies and Erick's Racing all got <I>some</I> of their experience and so their work are a derivative of the DPR approach. <P>Endyn is well known, if not controversial, to the import scene. You either like the advanced high tech approach to what they do or you hate them for their darker "cloak and dagger" reputation. There's no middle ground: You either like Endyn or hate them. Nevertheless, they bring to the table some pretty advanced techniques that no-one else uses that work.<P>cont'd -> <HR></BLOCKQUOTE>

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David Coleman
I used to know alot about MX-3's, but not so much anymore. Oh well.


July 24 2002, 1:05 AM
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Post Re: FAQ: Headwork
<BLOCKQUOTE><font size="1" face="Verdana, Arial">quote:</font><HR><I>Originally posted by Tuan </I><BR><B>4a) What Are the Differences?</B><P><B>Intake Partial Valve Lift Flow @ Low Lift Angles</B> <P>Some people believe that Honda stock heads flow about as well as they can at wide open throttle and 100% valve lift coming straight from the factory including the Si and GSR (but especially the Accord, Civic, Integra, and Prelude Type R's). The target area for head flow improvement, in a high performance street hot rod/weekend racer, is at low to mid partial valve lift.<P>DPR believes in optimising low partial intake valve lift (< 33% lift) flow.DPR back cut my intake valves in an effort to gain some low lift flow. They believe that at maximum lift, no one can improve on the factory's work and the head flows really well there. So the gain in inlet flow is targeted to the low lift areas. If you have Joe Pettitt's Volume 1 High Performance Honda Builder's Handbook, the chapter on cylinder heads goes into this in more detail. Whether Portflow and Joe Alaniz also believes in improving low lift flow with their seat angles, I don't know.<BR> <P>Endyn does not optimize low intake flow. In fact, Endyn wants no forward <B>or backward</B> flow at all during low partial valve lift. Endyn believes the majority of reversion (or backward flow) occurs at low intake valve lift . Therefore, their valve angles (particularly the last 2 concentric angles) negate any cylinder filling at that time but also negates any reversion which can contaminate the incoming fresh air-fuel. <P>Here is some of their rationale:<P>This diagram shows what happens in terms of pressure inside the intake port, combustion chamber, and header before, during, and after cam overlap.<P> Image <P>Clearly, at the start of cam overlap, the combustion chamber pressure (P3) is greater than the intake port pressure (P1). The header pressure (P2) is less than combustion chamber pressure and so the exhaust gases do escape out the exhaust valves. However, for a brief moment at low lift, the intake pressures (P1) are the smallest and MAY run the risk of having burnt exhaust gases also escape backwards up the intake valve. This dilutes down your fresh air and fuel and reduces power for the next compression and power strokes. Then as the intake valve begins to open further and the exhaust valve begins to close shut, intake pressure is greatest and flow moves forward to fill the cylinder (P1 > P3).<P><BR>So, the 3-5 angle valve jobs are very different in approach between these 2 headporters.<P>I guess you either believe in reversion happening at the intake valve during low partial lift or you don't.<P>We have to stop using the term port & polish. We don't want the polish part. I've already reviewed the idea that having a mirror polished surface on the intake port walls creates more turbulence and therefore, decreases flow quality. See my article on flow quality in this thread:<P> <A HREF="http://www.team-integra.net/sections/articles/showArticle.asp?ArticleID=4" TARGET=_blank>http://www.team-integra.net/sections/articles/showArticle.asp?ArticleID=4</A> <BR> <BR><B> Intake Port Size and Shape</B> <P>What about the intake ports themselves? <P>DPR uses the <B>classic</B> porting approach focusing on taking material off the short turn radius and roof area near the valve guides, without taking off what they consider to be too much material. How much is too much (i.e. hogging out the ports) ? That's proprietary, so please don't ask me for dimensions. I would not know. They say it's by trial and error, and doing tons of heads. This is where the black art part comes in. DPR has interpolated, by experience, how much material to take off and had determined where & when they had hogged out way too much from past mistakes in the early 90's. DPR takes a lot of material around the valve guides off and fills in the are around the valve guides with epoxy.<P>Endyn focuses mostly on the floor to shape their ports into a <B>D-shape</B> (with the flat part of the D being the port floor) and uses what they call <B>"turbulators"</B> or dimples to atomise the fuel as it leaves the injector nozzle. They fill in the injector slot , adding material onto the injector boss itself. The roof area around the valve guide is not removed as much as DPR's.<P>I guess you either believe in tumble fill like DPR or you believe in swirl fill like Endyn. If you think flow quality is worth considering, then you would subscribe to not having as much roof and valve guide area removed and widening the floor at near the short turn radius. <P><BR><B> Combustion Chamber</B><P>At the combustion chamber, DPR uses the classic cloverleaf chamber shape to get more quench area. In their Stage VI heads, they weld on aluminum to the head to achieve extra quench area (also called mechanical octane boost) and achieve a steeper angle from the outer edge of the bowl (or bore) towards the central spark plug location. <P>Endyn spot faces and optimises quench area without using welded on material to get a cloverleaf. Endyn states that if the process of welding on aluminum to the head to get a cloverleaf shape is not done correctly the head is structurally weakened and the valve seats can "walk" or shift during the life of the head.<P><BR>cont'd-> <HR></BLOCKQUOTE>

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David Coleman
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July 24 2002, 1:06 AM
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Post Re: FAQ: Headwork
<BLOCKQUOTE><font size="1" face="Verdana, Arial">quote:</font><HR><I>Originally posted by Tuan </I><BR><B>5. Now On To The Comparison!</B><P>I've collected some pics on the net comparing DPR vs Endyn head porting on a B18C. These are not my photos and so I had no control over the angle of the photo or magnification. Thanks to Tbone for sharing his DPR head pics. The Endyn pics are from their website.<P>The convention here will be that DPR will be shown first then Endyn (alphabetical order...no bias)<P><B> A. DECKS</B><P>DPR Stage V GSR head deck without valves installed yet<BR> Image <P>DPR Stage V GSR head deck with DPR stainless steel valves installed<BR> Image <P>Cloverleaf Combustion Chamber Shape on Jeff Taylor's GSR : Notice the increased quench area from the added welded on aluminum<BR> Image <P>DPR Stage VI Cloverleaf Combustion Chamber: More quench area is your friend against detonation. <P> Image <P>Realtime Racing Type R Head Deck : hmmm<BR> Image <P> Image <P><BR>Endyn Racing B18C5 Deck: note that the quench area is also increased but not as visually stunning as a cloverleaf...but it does the same job effectively. We'll look closer at the bowl end view and seat angles later...<P> Image <P><BR>cont'd-> <HR></BLOCKQUOTE>

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David Coleman
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July 24 2002, 1:06 AM
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Post Re: FAQ: Headwork
<BLOCKQUOTE><font size="1" face="Verdana, Arial">quote:</font><HR><I>Originally posted by Tuan </I><BR><B>B. INTAKE PORT </B><P>DPR GSR Straight Shot Intake Port<P> Image <P> Image <P><BR>Endyn D-Shaped Intake Port With Injector Slot Turbulators and Minimal Roof Work<P> Image <P>A Better View of the "funny looking" Dimples (Turbulators):"the Endyn- pioneered "dimples" in the injector slot aid fuel atomization dramatically".<P> Image <P>Here they are again on the GSR head for a B20:" Note that the "huge" GSR injector slots have been filled and re-contoured with dimples..."<BR> <BR> Image <P>Remember dimples are on golf balls.....<P>cont'd-><P> <HR></BLOCKQUOTE>

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David Coleman
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July 24 2002, 1:07 AM
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Post Re: FAQ: Headwork
<BLOCKQUOTE><font size="1" face="Verdana, Arial">quote:</font><HR><I>Originally posted by Tuan </I><BR><B>A Brief Intermission: Wake Up!!!</B><P>....okay back to headporting.....BTW racing motorcycle headporters do very good work on import heads as well...if you don't have a local import porting shop, you may want to look into using a local motorcycle porting shop: same ideas -> small displacement, high revving engines....better than going to a domestic V8 porting shop.<P><B>C. EXHAUST PORT</B><P>DPR Exhaust Port<P> Image <P> Image <P>Endyn Exhaust Port <P>showing " small, high velocity ports, their tapered guides, and flattened floors. Of special note are the casting parting lines that remain behind the guides in the port bowls. Were these "imperfections" removed in the porting process, the flow would "die". One more instance, where looks and performance don't go hand in hand."<P> Image <P>Endyn B22 Race D-shaped Exhaust Port<BR> Image <P><B>D. COMBUSTION CHAMBERS </B><P>DPR Stage V Combustion Chamber (Non-Cloverleaf)<P> Image <P>Endyn Steep Quench Area Combustion Chamber (Non-Cloverleaf)<P> Image <P>cont'd -> <HR></BLOCKQUOTE>

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David Coleman
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July 24 2002, 1:08 AM
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<BLOCKQUOTE><font size="1" face="Verdana, Arial">quote:</font><HR><BR>Famous Endyn Steep "Anti-Reversion" Last Concentric Valve Seat Angle <BR> Image <P>Endyn GSR head combustion chamber for a B20<BR> Image <P>Here is a "Spot Faced" chamber for those of you interested in increasing your bore to get more displacement. The head chamber must have the same bore so you spot-face it whereby the quench area and bore are enlarged and matched to the block<P> Image <BR><HR></BLOCKQUOTE>

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David Coleman
I used to know alot about MX-3's, but not so much anymore. Oh well.


July 24 2002, 1:09 AM
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<BLOCKQUOTE><font size="1" face="Verdana, Arial">quote:</font><HR><I>Originally posted by Tuan </I><BR><B>6. Prepping Your Head for Shipping to The Headporter</B><P>Here is a nice summary of how you should pack the head before sending it out (with or without the TB, intake manifold, and header for portmatching)<BR> <A HREF="http://www.dpr-racing.com/content/shiphead.html" TARGET=_blank>http://www.dpr-racing.com/content/shiphead.html</A> <P>Lost Motion Devices: When you send off the head to the porter, please check if these are all there. I hear a lot heads get sent for work and then when they are returned there's complaints of a rattling noise when VTEC is engaged. Either the LMD's fell off after work or were never replaced when they arrived to the shop.<P><B>7. Wrap-Up</B><P>There is a statement by Endyn that the main gains in head porting are made in the seat angles, deshrouding the valves, and improving quench area. NOT AT THE PORTS. Larry said that the main porting done by Honda's top porters on the ITR head straight out of the factory is mainly at the bowl area around the valve seat. So basically an ITR head is just a mildly ported B16A head from Honda. That tells you where the main target gains are at.<P>Remember when you're getting head(work) ;) , you must consider improving both <B>flow quantity</B> AND <B>flow quality</B> over a specific powerband location...don't be swayed by pure flowbench numbers comparing cfm to valve lift at a fixed vacuum.<P><HR></BLOCKQUOTE><p>[ July 24, 2002: Message edited by: David Coleman ]

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David Coleman
I used to know alot about MX-3's, but not so much anymore. Oh well.


July 24 2002, 1:09 AM
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