Home 1968 Shelby Cobra GT350, GT500 & GT500KR My 1968 Shelby Cobra GT350 Edelbrock E-Street Aluminum Heads Six Small Ford Small-Block Heads that Work HotRod – 6 Small Block Cylinder Heads that Work

HotRod – 6 Small Block Cylinder Heads that Work

Bolt-on Horse Power for less than $1,350

By Jeff Smith – writer Feb 1 2013

(This page is a copy of HotRod’s original article by Jeff Smith. I put it here only because the info is extremely valuable and I have linked to many pages on the web that eventually disappeared. Subscribe to MotorTrend’s cable channel and the MotorTrend YouTube channel.)

Today’s small block Ford street engine builder has it easy. Not all that long ago, the small block fan’s only choice for Ford cylinder heads was the classic 351W Ford heads swap on a 302. Today, the aftermarket lineup of Ford cylinder heads has plenty of castings from which to choose. We’d love to test ’em all, but we decided to line up as many performance small block Windsor Ford heads as we could find, as long as they were available complete for less than $1,350 for the pair. These Ford cylinder heads all feature between 170 and 180cc intake port volumes and offer excellent performance potential over even the best production iron 5.0L heads. To pull this off, we needed a durable mule, so we chose Ford Racing’s Boss 302 345hp crate engine that comes with a set of aluminum heads and actuated by a 0.480-inch lift B303 hydraulic roller cam, and 9.0:1 compression. To complete the Boss, we added an Edelbrock Performer RPM intake, a Holley 750 cfm mechanical secondary HP carb, MSD distributor, and a set of open exhaust dyno headers, and we were ready to rumble.

It’s also worth mentioning that due to deadline pressures, Dart and Pro Comp Electronics also offer small block Ford heads that fit within our price prerequisite, but for a variety of scheduling reasons, they didn’t make the test. The Dart castings would have been the Iron Eagle versions while the Pro Comp’s are affordable in aluminum.

As with our small-block Chevy head test published in the Sept. ’12 issue, we will evaluate each of these small block Ford cylinder heads using several different categories in addition to peak torque and horsepower. We evaluated each head on the flow bench, average overall power, and we calculated average horsepower-per-dollar. We’ll squeeze all of this into these few short pages, which means we have a long way to go and a short time to get there. So get comfortable, slip on your Ford-colored glasses, and hang on

Edelbrock Heads: E-Street Ford Cylinder Heads
This made-in-the-USA head is Edelbrock’s value leader. Edelbrock heads are available in two different versions with either 1.94- or 2.02-inch intake valves. Our test heads came with the larger intakes that clearly contributed to these heads’ strong showing. The E-street came in second in peak horsepower and a very close third in average horsepower and torque. The Edelbrock heads showed a little weakness in the midrange, something that could probably be rectified by adding a 30-degree back cut to the intake valve. At less than $950 for the pair, these Edelbrock heads may be the best bang-for-the-buck investment of all the Ford heads in this test. Combine Edelbrock quality with excellent power and a highly competitive price, and the E-Street Edelbrock heads strike us as an excellent choice.

Ford heads: Edelbrock E-Street 170cc
PN 5025, $935.95

Peak HP371
Peak TQ346
Valve Sizes2.02/1.60
Intake Port170cc
Valvesprings1.250-inch single, max lift 0.550

The first thing we did was bolt each head to the Superflow 600 flow bench at Jim Grubbs Motorsports to evaluate the flow characteristics.

Ford Racing X307

The Ford Racing X307 head is not the casting that comes on the Boss 302 crate engine, but its affordable price made it a natural choice for this test. It’s important to note that this was the only head in our test that required its own separate valvetrain. The Ford head uses a net-lash design that makes the valvetrain non-adjustable. The Ford roller rockers use a fulcrum base and a 5/16-inch bolt to attach the rockers to the head. We used Comp roller rockers for the remaining heads to level the playing field, but if you are considering a set of these heads, be aware that the rockers and fulcrums need to be considered as well. The Ford heads did well during the testing, making a peak of 362 hp. Much of this gain over the stock 345-hp Boss 302 rating can be attributed to Westech’s lower 140-degree engine coolant test procedure and open dyno headers. These Ford heads tied with the Edelbrock heads for third place in average torque and were extremely close to the RHS head’s second-place power level.

Ford Racing 178cc

  • PN M-6049-X307, $1119.90
Peak HP362
Peak TQ346
Valve Sizes1.94/1.54
Intake Port178cc

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Speedway Motors/Flo-Tek

The most notable thing about the Flo-Tek heads available through Speedway Motors is the price—that’s $739.98 for a complete, ready-to-bolt-on pair of aluminum heads for a small-block Ford. Though the average power was down compared to the TFS, RHS, and Edelbrock heads, the power is still acceptable, especially if you are more interested in getting a nice pair of aluminum heads than ultimate power. Peak power was good, at 349 hp, and torque is also reasonable. These are certainly worthy of attention at this excellent price.

Flo-Tek 180cc, Speedway Motors

  • PN 7223000, $739.98
Peak HP349
Peak TQ347
Valve Sizes1.94/1.60
Intake Port180cc

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Racing Head Service (RHS)

The RHS heads come out of the box with a very nice-looking casting, and back that image up with respectable performance. The heads offered an excellent midrange power curve, behind only the Twisted Wedge casting between 4,000 and 5,500 rpm. RHS shipped the heads with what should have been a sufficient single 1.460-inch-diameter valvespring, but the horsepower graph reveals that above 5,800 rpm the power trailed off, leading us to think that perhaps with a better spring this head could have carried the power out beyond 6,000 rpm, which would have improved its peak horsepower number. Nevertheless, for a street engine, this head delivers excellent midrange power. Its biggest weakness may be the price. It was the most expensive of all the heads we tested.

RHS 180cc

  • PN 35011-01, $1,326
Peak HP364
Peak TQ352
Valve Sizes2.02/1.60
Intake Port180cc

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TFS Twisted Wedge 180

The TFS heads appeared to be the big dog in the room when it came time for testing. We were smart enough to test-fit the heads on the Boss 302 block before testing began and discovered these heads are designed to be used with 7/16-inch head bolts, with restrictors in the head-bolt holes. This was a simple fix, using a drill press to open up the restrictors before we could use the 1/2-inch ARP head bolts. The heads also required custom-length Comp Cams pushrods to compensate for the relocated valves. Once those two tasks were completed, the heads delivered the best peak horsepower and torque numbers of the entire test, knocking down an excellent 380 hp at 6,000 rpm. The Twisted Wedge heads also had the strongest horsepower curve above 4,000 rpm of all the heads tested. The only caveat to all this is that the Twisted Wedge heads do limit valve lift (0.600 inch) and duration on stock pistons due to their repositioned intake valve—just so you know.

TFS 180cc

  • PN 51410004 M58 / $1,099.96
Peak HP380
Peak TQ357
Valve Sizes2.02/1.60
Intake Port180cc

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Exhaust Port Flow (CFM)

World Products Windsor, Jr.

World contributed the lone cast-iron head to our Ford small-block test. This head is intended for a flat-tappet camshaft, so it was outfitted with a small-diameter spring that might have limited its performance in the midrange slightly. If we were going to use these heads on a street engine, we’d disassemble them and spend the extra bucks to add a 30-degree back-cut to the intake and exhaust valves to improve their overall flow. This minor tune-up would really improve the flow curve and add a measurable amount of torque. If weight is a consideration, keep in mind that these iron castings weigh considerably more than the rest of the aluminum heads. If you are looking for a set of World aluminum heads, you can find them at Bill Mitchell Products.

World Products 180cc

  • PN 053030-1 / $1,183.90
Peak HP352
Peak TQ342
Valve Sizes1.94/1.60
Intake Port180cc

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Peaks And Averages

We should stress that during testing we optimized each set of heads for timing and jetting and then ran the engine for two near identical runs, which were then averaged to come up with the final power numbers. Though peak horsepower is a quick reference point for evaluation, we prefer to use average power in these comparisons because it always produces a better picture of overall performance. But as we’ve seen before, the heads that produce the best peak power also tend to do so throughout the entire rpm band. That’s what the TFS Twisted Wedge heads did here. Not only did the TFS heads produce the most peak power, they also logged the best average torque and horsepower. The RHS heads produced the next-closest average horsepower and torque, with the Edelbrock and Ford heads very close behind. The power numbers are so close that if we had tested these heads in a typical street car, it’s doubtful we would have seen much of a difference in performance among the middle four heads. Throw a blue oval flag over the RHS, Edelbrock, and Ford heads, and the performance is very similar.

We certainly don’t want to ignore the peak numbers, and that’s where the TFS Twisted Wedge heads really earned the spotlight. The TFS heads made an honest 380 hp, but what we found surprising was how well the Edelbrock E-Street head did, with a peak of 371, substantially better than Ford Racing’s 362-hp third-place finish. The finishing order for peak torque realigned slightly, with TFS out front, RHS coming in a strong second, and Edelbrock and Ford tied for third.

Most of the heads were equipped with Thermactor holes that are required for emissions-controlled engines. If you don’t need this exhaust outlet, you can purchase Thermactor plugs from several outlets, including Summit (PN TFS-5140026, $9.49 each).

Average Power

Avg. TQAvg. HP

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Power Chart

  • Test 1 (TQ1/HP1): World Windsor, Jr.
  • Test 2 (TQ2/HP2): Edelbrock E-Street
  • Test 3 (TQ3/HP3): Flo-Tek / Speedway Motors
  • Test 4 (TQ4/HP4): Ford Racing
  • Test 5 (TQ5/HP5): Racing Head Service
  • Test 6 (TQ6/HP6): Trick Flow Specialties Twisted Wedge

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Horsepower Graph

You’ll notice that we attenuated the horsepower graph to include just the power curve between 4,000 and 6,200 rpm. We did this to expand the scale to show the differences in power near peak horsepower. The TFS head looks much stronger than the Edelbrock version above 5,500 rpm, but the maximum differential is only 13 hp at 5,900 rpm. Though that’s significant, this is only reflective of a single point in the curve; it is more important to evaluate the entire length of this horsepower graph. When you do that, you can see that the TFS head did substantially better than all the other heads above about 4,400 rpm. You will certainly feel that in the car. We should also mention that although we didn’t test a stock iron casting, it should be clear that even the heads on the lower end of our test would still be an improvement over stock factory castings.

Cylinder HeadPeak HPPeak TQ
TFS380357 (1st)
Edelbrock371346 (tie 3rd)
RHS364352 (2nd)

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The Ford heads require these net lash rockers. These rockers use a fulcrum placed underneath the rocker and a 5⁄16-inch bolt to position them. This system is not adjustable, except through shims under the fulcrum and by pushrod length.


Peak power numbers are always fun to throw around, but car-crafters are also very astute at determining what all that power will cost. To minimize the grief of doing the math yourself, we averaged the horsepower between 3,000 and 6,000 rpm, then divided that into the cost of a pair of heads. The winner in this evaluation is almost always the least-expensive head just because of the way the math formula works. This particular evaluation only works, however, if lowest cost is the highest priority. If it is, then you know what you need to do. But for perhaps a majority of enthusiasts, this evaluation may be too simplistic. If this becomes a bit more subjective by adding in power (and why wouldn’t you?), then the second-least-expensive heads—the Edelbrock E-Street heads—really begin to stand out. If we’ve muddied the waters a bit, it’s only the result delivering more information on the way to a decision.

Average Dollar-Per-Horsepower

Flo-Tek / Speedway$2.61

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Parts List

Edelbrock E-Street5025Summit Racing$935.95
Ford Racing X307M-6049-X307Summit Racing1,119.90
Flo-Tek/Speedway7223000Speedway Motors739.98

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Intake Port Flow (CFM)

Ford Int.RHS Int.World IntFlo-Tek Int.Edel Int.TFS Int.

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Exhaust Port Flow (CFM)

Ford ExhRHS ExhWorld ExhFlo-Tek Exh.Edel Exh.TFS Exh.

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Like we said, if best power or least price is your only concern, then the decision is easy. But for the rest of us, choosing a cylinder head might be a complex algorithm of price, power, brand loyalty, ease of installation, head bolt size, and maybe even shoe size if you’re that compulsive. If ultimate power is not the most important point, then you could easily choose any of these heads and make a good decision. That may or may not make your ultimate choice any easier, but if so, you can thank us later.

Watch A Full Episode Of Engine Masters! Camshaft Specs Explained

Ever wonder what those camshaft specification numbers really mean and how they affect engine performance? On episode 19 of Engine MastersDavid Freiburger explains cam lift, duration, lobe separation angle, and installed centerline. Next, we test a low-rpm cam and a high-rpm cam in the same engine to demonstrate the power differences. Sign up for a free trial to MotorTrend+ today and start watching every episode of Engine Masters, plus much more!

(I am a big fan of Engine Masters. I have access to the MotorTrend channel on my Cable. I also am a subscriber to their YouTube Channel. Good info and they often make me laugh. My wife does not think they are funny though. Guess you need to be a MotorHead to appreciate these guys. Like Jay Leno said on his first Garage show. If you have to ask why we are doing this program, you probably don’t want to be here.