In the late 1980s and early 1990s, production processes resulted in much more accurate castings. The result was head castings that had far more effective ports as received from the head manufacturer. This was the start of what can truly be described as the golden age of cylinder heads for the V-8 performance community and head porters alike. In this chapter, I list manufacturers that produce easy to port head castings. All the castings I refer to are best described as having port and chamber forms nicely roughed out, requiring little more than a finishing job.
This Tech Tip is From the Full Book, DAVID VIZARD’S HOW TO PORT & FLOW TEST CYLINDER HEADS. For a comprehensive guide on this entire subject you can visit this link:
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Getting pro results from these heads is about as simple as it can get. If you have average dexterity, a cheap die grinder, and a porting kit you are in business. For the most part, you do not even need a flow bench except to check your results. Even then, if you follow my porting recommendations, a flow bench really only determines if you have done a good job or a really good job.
All of the heads I discuss here work very well in the as-cast form, but about 12 to 30 hours of porting work (depending mostly on whether it’s a small or big-block) turns them into heads that, even as recently as the mid 1990s, are considered “race grade” hardware. Indeed, after being home ported, most of these heads can produce results close to or about as good as their much-more-expensive CNC equivalents. Throughout this book, I perform a basic porting job to the heads, which entails narrowing the guide bosses, blending the machined part of the short-side turn into the cast part around the main body of the port, and blending the bowls into the rest of the port and the bottom cuts of the valve seats. From here on, finishing involves blending the cast finish with a 60or 80-grit abrasive cartridge roll.
Now that you know your role as a porter, let’s look at the heads that are included in this easy porting scenario.
Air Flow Research
Air Flow Research (AFR) is a company that has been around since the early 1970s. It has been used by many of NASCAR’s top teams. Among the earliest of companies outside of General Motors to produce aluminum heads, this is a brand that I have had a very long association with. AFR has, over the years, pioneered many aspects of cylinder head design and development that we tend to take for granted these days.
As an early producer of CNC-style ported heads (in the mid 1970s with tape-controlled machines) this company has experienced much change. When net porting was in its early days, AFR looked at ways to speed up CNC porting, so it could offer such heads for little more money than as-cast heads. The company was largely successful in doing this, and the result is that small-block Ford and Chevy heads are coarse-step CNC ported. They produce excellent results right out of the box and leave little on the table for the home porter to do.
But “little” does not mean “nothing,” so if you choose to use a Street Eliminator–spec AFR head as your starting point, you can pull a few more horsepower for relatively minimal effort in the porting department. I have done this in the past because the ports that AFR
develop are well sorted, and some simple moves on these heads can make them more application specific without a huge investment in time. As for the full fine-feed CNCported AFR heads, I have had some very positive results right out of the box and can really recommend them if you don’t have time to port a set of heads yourself.
AFR Big-Block Heads
If you want a set of as-cast big block heads, the AFR offerings are really top notch. The chambers come already fully machined and the valve throats (bowls) are already cut to near-net shape. This means all you need do is finish the ports and do just the mildest amount of bowl work, and the job is done. Dyno results are outstanding.
This company produces a wide range of heads for both Chevrolet and Ford. At some time or other, I have ported at least one set of its popular-application as-cast heads. In the small-block Chevy 23-degree range of heads, Dart produces highly effective heads in both iron and aluminum. At the time of this writing, the cheapest bare Chevy Iron Eagles cost well under $300 each.
Iron Eagles can be had with intake port volumes of 165, 180, 200, 215, and 230 cc. All work well right out of the box, and all port up really well, such as the example shown in the following chart.
I have done basic port jobs on 165 and 180-cc heads for 350s and 383s intended to make good torque right off idle. A short hydraulic flat-tappet cam of around 265 to 270 degrees at lash (0.006 tappet lift) with a high lobe lift and 1.6 rockers all around gets the job done. For the cam lobe centerline angles (LCAs): for a 350, use a 108 LCA; for the 383, a 106. For a racy spec of 350, the 200-cc heads work well; for a 383, the basic ported 215 (as shown on page 49) zips right by the 600-hp mark given a 12:1-plus CR and a cam of 250 degrees at 0.050 tappet lift.
Dart’s aluminum Platinum Pro 1 heads have basically the same ports as their iron siblings. These heads cost more, but the advantages are faster porting and a finished head that is half the weight of an Iron Eagle. For what it’s worth, my favorite move with Dart heads is to port the 200-cc heads and install the 2.08 valve normally used in 230-cc Darts. This does involve having the intake seat cut by someone who knows how to cut a high-flow seat, but the results are well worth the minimal extra effort. My 383 with 10.5:1 compression with a cam of no more than 242 degrees at 0.050 (280 advertised) regularly cracked the 605-hp mark and produced torque figures in the low 530 ft-lbs. And it was still street-able.
Dart offers two big-block Iron Eagles, one at 308 cc for the intake port and one at 345 cc. I have worked with both. They work well as cast, but because big-block Chevys are so starved for air I port them for any build requiring iron heads. The results are far and away worth the effort. I have used both the small land big-port variants. On smaller engines (454 to about 500 ci), my favorite move is to port the 308 heads and install the larger 2.3 valve used in the 345-cc heads. With the small port heads done in this fashion, it is entirely possible to approach the 700-hp mark from a relatively low budget 482 (1/8-inch overbore on a sonic-tested thick-wall 454 block).
In much the same way as with Dart’s small-block offerings, the 24degree aluminum heads share the designs used for the Iron Eagles. The Pro 1 aluminum heads are available in 275-, 310-, 325-, and 345-cc ports. I have not used the 275-cc option but have ported the other three to good effect. My favorite combo here is the 325 with a 2.3-inch intake. I have made street-able 540s that have cracked the 800-hp mark on pump gas.
Dart’s Windsor small-block Ford heads can be had as an Iron Eagle (165-cc port) or as an aluminum casting with either a 170or 195-cc port. I have had top-notch results with all of these heads. As I write this, my latest effort using the 170-cc aluminum heads, ported and equipped with a 2.08/1.6-valve combo, gave my 280-degree (advertised) cammed 347-ci stroker 5.0L with 10.5:1 compression some really respectable results. Using a Parker single-plane intake, this combo cranked out 562 hp and 472 ft-lbs on pump gas.
When I swapped the Parker race intake for an Edelbrock Performer RPM Air Gap two-plane intake, the torque below about 3,500 rpm picked up to the tune of 30 to 40 ft-lbs. Peak torque stayed about the same. At about 4,500 rpm, both manifolds produce the same output, but above that the two-plane started to show the signs of its lesser breathing capability. Even with the two-plane intake and its superior street drivability, peak power was still a very respectable 531 hp.
Edelbrock offers a variety of high-tech aluminum heads for most American V-8 engines. These heads feature efficient ports and cutting-edge chamber design, but for how good these cylinder heads are out of the box, they certainly can be improved with some work.
Again, I begin with heads for the small-block Chevy. Edelbrock lists an extensive range of heads for this engine, which numbers almost to the point of confusion. I have heard good stuff, from reputable engine shops that dyno everything they build, about most of Edelbrock’s small-block Chevy heads. But my experience is with the three least expensive categories: the E-Street, the Performer, and the Performer RPM E-Tec range of heads.
E-Street: These are a 185-cc intake port casting and can be had with 64or 70-cc chambers. I have only had experience with the 64-cc heads because I am a believer in compression. The main aspect favoring these heads is that, although they are American made, they rival the price of lesser-quality off shore made heads. Although they work well right out of the box using the basic porting techniques I describe, these heads can be made to produce output results that are really satisfying. A nicely built 10:1-CR 350, utilizing an aggressive hydraulic flat-tappet cam of around 270 (advertised) on a 108 LCA, goes 440-plus ft-lbs and comfortably breaks the 450-hp mark.
Performer: Moving on, what I see here is heads that are close to identical and consequently port up about like the E-Street heads. The difference is that the Performers have upgraded hardware if you are buying them in complete, rather than bare, form. If you get these heads bare, figure in the cost of a valve job.
Performer RPM: These heads are available with a 170or a 200-cc intake port. Edelbrock claims one of the design advantages of the E-Tec heads is that the spark plug is in a more favorable position than on most other heads. This may or may not be the case, but results on the dyno certainly suggest something is working for these heads. When given a basic porting job, the flow of either port-size head is good but not exceptional. The same goes for the swirl; good but not exceptional. If we add port velocity and velocity distribution, the same applies.
On the dyno, these heads deliver more than the individual numbers indicate, so what they deliver is a good working combo. For this reason, I suggest that unless you really know what you are doing do not do any major reworking of anything. Just clean up the ports, skinny the guide bosses, and blend the ports and chambers into the valve seats. With these heads that proves to be a simple recipe for some very positive results.
Much like Edelbrock’s small block heads, the big-block heads we are going to look at fall into the same three categories: E-Street, Performer, and Performer RPM.
E-Street: This entry-level head represents great value for the money. Not only is low cost a positive, but also the fact that this head sports a smallerthan-usual, 110-cc combustion chamber. On the negative side is the fact it has a 2.190 intake valve instead of the more normal 2.25or 2.3-inch valve. At the time of this writing, I have only personally had one set of these heads. They were used on a 496-ci street big-block intended for a high performance truck that still had to be capable of carrying out normal truck duties. Dyno tested on Terry Walters Precision Engines’ dyno my 9.5:1 engine made 524 street-able hp and a torque curve starting right off idle and peaking at a solid 620 ft-lbs. Not bad for what was essentially a low-buck, two-bolt block and cast-steel crank (Scat) build.
I have ported only one set of E-Street heads. Even the basic porting (as detailed in my book How to Build Max-Performance Chevy Big Blocks on a Budget) I did “woke up” these heads. After just about 10 hours work, they flowed 352 cfm on the intake (which is good for a port still under the 300-cc mark) and 270 on the exhaust. The bottom line is that these 290-cc-port heads are easy to rework and produce better results than Edelbrock claims.
One aspect, though, that you seriously need to take into account is the fact that these smaller valve heads need to have a cam with an LCA 1 or 2 degrees tighter than their bigger valved counterparts. I suggest you read my book on big-block Chevys (How to Build Max-Performance Chevy Big-Blocks on a Budget), which goes into great detail on the matter of cam event requirements for this engine.
Performer and Performer RPM: These heads are offered in two configurations. One has combustion chambers with 110-cc volume. The other (basically the same head but called The Performer RPM series) is offered as a 290-cc oval-port version with a 110-cc combustion chamber (same as E-Street and regular Performer) or a 118-cc-chamber casting with a 315-cc runner. Both these castings port up well, but the rectangular-port head, when reworked, really deserves a bigger intake valve.
RPM Xtreme: Not originally on the list, but I want to mention them because these heads are about as fast to port as it gets. Although they cost more because the chambers and much of the ports are CNC machined, there is still a useful amount left on the table, and therefore you can gain a significant amount of performance. If you use the big-block porting guide in my big-block Chevy book, you will be in business with some 400-plus cfm on the intake and 290-plus on the exhaust. All this can be had for about 4 to 6 hours of work and the result, for a 13:1 496, is a relatively low-cost engine that easily exceeds 800 hp when used with a suitable cam and induction system.
Again, we have the Edelbrock identification tags of E-Street, Performer, and Performer RPM to look at. This time I am going to lump them all together because the primary difference between them seems to be the cost of the associated hardware. The E-Street castings are low cost, that’s for sure. As for the performance capability of these heads—the power and torque figures Edelbrock quotes are not even close to reality.
I did a quick cleanup on a set of Performers with the 1.9-inch intake valve (fits stock valve cutouts). My then-11-year-old daughter Jacque used them to build a 0.030 over-bored 302. She did all the assembly other than timing in the cam, lifting in the crank, and torqueing up the mains, big end, and head bolts. Using an Air Gap Performer intake, a 650cfm carb, and a flat-tappet hydraulic cam of 280 degrees at lash, that engine made 381 ft-lbs and 406 hp. A 2.02-inch-intake-valve version of this head would have gone about 10 to 15 hp more.
Any of these heads, given a serious but still straightforward porting job, flows enough air for a 10.5:1 302 to pass the 500-hp mark.
Engine Quest (EQ) is primarily in business to supply the engine recon community with new parts for rebuilt engines. Part of its program was to produce new stock-replacement high-grade, cast-iron cylinder heads at a price that made reconditioning worn-out and often fragile factory heads less than worthwhile. With this part of its business established, EQ took a look at the cast-iron performance segment and decided it could produce a head that was both performance and cost effective. The company met that goal very well and has a stack of circle-track championships as proof.
EQ’s small-block Chevy heads work very well in the as-cast form and even better when given just a basic porting job. Since these heads are only available in cast iron, they do take a little longer to port than aluminum counterparts from other manufacturers. The porting, though, is about as simple as it gets and speed of porting cast iron is, in this case, partly made up for by the minimal amount of metal removal. As can be seen from the flow numbers in Figure 5.14 the EQ heads acquitted themselves very well. The flow figures delivered in test number-4 are more than enough to make a 12.5:1 350 small-block Chevy deliver in excess of 600 hp and 465 ft-lbs without requiring a massive budget. All that is needed is a good block to contain the loads generated and a strong rotating assembly.
There is not a lot else I can say about these heads other than I have used a half-dozen sets myself and have been involved in at least another four or five builds where I was called in to spec the build. In every instance the results were outstanding.
Racing Head Service
Although I have done a couple of sets of Racing Head Service’s (RHS’) Pro Action small-block heads in both iron and aluminum, most of my experience is with small-block Fords and big-block Chevys. For ease of porting, the Pro Action series is really good. In most instances, it’s a case of skinnying the guide bosses and blending the rest of the port to be in business grand style with any of these heads, Chevrolet or Ford and bigor small-block. As good as the small-block Chevy heads are, I want to give extra kudos to the small-block Ford and big-block Chevy heads in iron or aluminum.
First the Pro Action small-block Ford heads from RHS—these are an excellent choice for a first-time porter. One of my students ported a set of these when I was teaching at the university in Charlotte, North Carolina. He produced, over a weekend, a set of ported 215-cc aluminum heads. When used on a hydraulic roller-cammed 415-inch bottom end, these heads produced a very creditable 562 ft-lbs of torque and 628 hp. All this on pump gas!
At the other end of the scale, I have used several sets of 160-cc port runner small-block Ford heads on 302s, 331s, and 347s. Even ported and sporting no more than a 170-cc port, these heads crack the 300-cfm mark at less than 0.600 valve lift. All this big intake flow comes with the complementary amount of exhaust flow. In all, these RHS Ford heads get my top marks for easy porting and great results.
Similarly, I have found that the RHS big-block heads deliver well. A first-time porter following the basics needed for big-block heads can pass the 400-cfm mark with relative ease even on the smaller 320-cc variant. With the 360 port heads, the flow at 0.750 to 0.800 valve lift can approach 420 cfm without reference to a flow bench.
Trick Flow Specialties
Trick Flow Specialties or TFS, as they are commonly known, made a big impression in the hot rod scene when it introduced its “Twisted Wedge” small-block Chevy head in the 1980s. The company have been in the forefront ever since.
TFS is well known for its Twisted Wedge small-block heads for Ford and Chevrolet. The advantage of the Twisted Wedge concept is that it is possible to get a lot of compression without the need for big valve cutouts. I have experience on each of the small-block Chevy and Ford heads, and they work well. However, they take a little longer to port, but the effort-to-return ratio is still good.
TFS also sells a nice line of conventional small-block Chevy and Ford heads. However, to date, I have no hands-on experience porting them but they look like they deliver easy results.
For the TFS big-block heads, let me start off with a possible negative. These heads come with a claimed 122-cc combustion chamber, but by the time they are cleaned up and blended into the seats they are nearer 130 cc. This means that they either need to be milled, or that you use them on a big-inch engine that does not have that high a CR.
With that out of the way, all else with these heads appears to be a plus. They are as easy to port as most of the others I mention in this chapter. If you are intent on building a big-inch, all-street torque monster, the small 280-cc-port TFS heads work just fine and still make big horsepower numbers upstairs. The bigger port variants (320 and 360) also port up well and produce flow numbers close to the top of my list of easy-toport heads. I have dyno tested the 320 but not the 360 heads. The 320s I did test produced top-of-the-line results (over 800 hp and 730 ft-lbs) on a 10:1-CR 525-inch dyno mule.
Ford Mod Motor
Right from the get-go, I have never been very impressed with the two-valve heads used on Ford’s 4.6and 5.4-liter Modular (Mod) engines. In fact, I was not that impressed with the first of the four-valve heads either, but that’s another story. When these externally large, small-cubic-inch engines were first introduced, I could see no endearing virtues whatsoever. They looked larger than a big-block Chevy on the outside but displaced a mere 4.6 liters on the inside. Early on, I modified a set of the factory heads and I was well short of happy with the results. Then Ford introduced a few special versions that were better. But still, even after a makeover, they were nothing to shout about.
After spending quite a few hours porting a set of limited-production SVO heads, I got to take a look at the new (2009) Trick Flow Mod Motor heads. Somebody thought this one through really well. The intake valve was inclined at the opposite angle from vertical that was used on the stock head. This had the effect of straightening the port by more than 30 degrees. This resulted in a downdraft angle about as steep as a serious race head and its effect on flow was dramatic.
This head looked so promising that I was eager to go through a couple of builds to test it. At the time, I was no big expert on Ford’s Modular engine, so I teamed up with Chris Harrington of Harrington Racing Engines (a well-known engine machine shop having top NASCAR stature) and Andy Wood, who has built many a fast Mod motor.
The first time around it was an out-of-the-box deal, in terms of intake, etc., on a conventionally modified 4.6L. With what is truly a street cam, this engine was treated to a set of TFS Street Heat heads after chassis dyno testing, with a set of nicely prepped but otherwise stock heads. Figure 5.23 shows the dramatic improvement these heads delivered.
Mod Motor: Round-2
After the preceding dyno tests, a comparison was made of the 2004 two-valve engine in its final TFS equipped form with a stock three-valve 2005 GT. The good news is that the TFS two-valver won out everywhere over a stock three-valve equipped engine. Basically, it was up 20 hp and 20 ft-lbs more than its newer three-valve sibling. However, my thoughts led me to look further into these TFS heads. The problem as seen at this point was that a stock or stock-like intake was not the best for flow and could be seriously holding these heads back. So I started a brand new engine build with the intent of using the Edelbrock 4-barrel-carb intake because this had already shown better than 50 hp more than the stock fuel-injected intake.
With Chris Harrington doing all the machine work and balancing, etc., the new engine shaped up over a couple of months. Good results were expected so a very real effort was made to upgrade critical parts. Stock rods break, so they were replaced with Scat rods. D.S.S. Racing responded to the piston issues with a set of the race pistons. Finally, I decided to put some compression into this engine and use E85 pump gas-station fuel.
As for a cam, well, this was to be one of my computer-spec’d items. This cam only had 236 degrees at 0.050 lift at the follower, so it was more of a moderately stout street cam than a race cam (a race cam for this application is more in the range of 260 to 265 degrees). The exhaust was dumped through an Edelbrockbuilt set of headers, which from the dyno testing seen so far work just fine.
As you can see from the chassis dyno results in Figure 5.29, our 4.6 Mod Motor made some really healthy numbers. At the time of this writing, all I can say about porting these heads is that they are about as easy as it gets. On my bench, the 1.84 intake version flowed about 258 cfm at 0.600 lift. After a basic porting job, this rose to a little more than 270. Given a 12.5:1 CR and a suitable cam, that’s enough air to make about 550 normally aspirated horsepower from a 4.6-ci motor.
At the time of this writing, I am experimenting with a 1.9-inch intake version of this head. So far, with a very special seat design, I have seen some really encouraging results but reporting on that has to wait until a later date. To sum up these TFS heads, I have to say that they are about the best thing that ever happened for the two-valve-per-cylinder Mod Motor community.
Written by David Vizard and Posted with Permission of CarTechBooks