5.0 Mustang & Super FordsHow To Engine
Dart 195 As-Cast Cylinder Heads - Sharp Darts
Dart's As-Cast Cylinder Heads Don't Suffer From Porting Envy-They Just Set A New Power Record On Our 347 Dyno Mule
Dart says its As-Cast heads are "...for the commodity kind of guy, who wants to make between 500 and 800 hp, depending on displacement or power adder." The two new heads are known as the 170 As-Cast and the 195 As-Cast, because no CNC porting is required
We smiled to ourselves when Richard Maskins, prin-cipal at Dart Machinery, told us he couldn't figure on building yet another cylinder head several years ago. By his count, there were already 52 small-block Ford heads for sale in the magazines. So he built something no one else had-a block.
That Richard's company could even produce a block speaks volumes about its extensive engineering and manufacturing capability. Dart keeps all manufacturing steps in-house, save for the foundry work, and even there Richard has longtime employees working for him now so his ties to the foundry are excellent. This allows Dart to precisely understand the foundry's capabilities. It has also given Dart direct and immediate feedback on how to design heads and blocks from a casting standpoint.
Once past casting, Richard says Dart has more high-end machining capability than the rest of the industry combined. In real terms, that's 24 Makino CNC-machining centers, an impressive array by any accounting.
After the Ford block project was completed, Dart was back to the small-block Ford cylinder head, and the company produced a pair of aluminum castings. Designed as either the last word in street engine heads or-more reasonably-as race heads, these castings were fitted with Texas-sized intake valves and equally voluminous CNC-cut ports.
Those heads, the 210 CNC and the 225 CNC, have been on the market for a couple years and have been well received. Now Dart has released two more versions of this head design, this time aimed at the hot street and general high-performance market. As expected, to promote street-friendly port velocities, these heads use smaller intake valves and ports, 170 cc and 195 cc, respectively.
What's more, Richard says that thanks to Dart's understanding of the casting process and the company's ability to machine casting cores as well as castings, Dart is now able to cast heads with port shapes accurate enough, at least at this level, that CNC porting is not mandatory to achieve class-leading power output. Therefore, the two new heads are known as the 170 As-Cast and the 195 As-Cast, because no CNC porting is required. These heads are also known as Pro 1 heads.
All this would be for naught should the As-Cast ports not promote power, but there Dart has its drag-racing experience. We're not talking about bracket engines and the odd Outlaw car, either. Dart concentrates its cutting-edge cylinder-head flow work in Pro Stock racing, a tough head to port by any measure.
For such demanding head development, Dart has worked hard at improving wet-flow head testing. As the name implies, a wet-flow bench flows both air and fluid through the ports, the better to mimic the real-world air/fuel mixture. Richard says this wet flow is totally different from the dry flow that's the industry standard, and is absolutely vital to making power.
To that end, Dart has a custom-built wet-flow bench capable of drawing 800 cfm of wet flow at 55 inches of water-big numbers for a bench, we assure you. No Ford cylinder head can flow those figures, so the bench is hardly stressed when working at half those values, as it does with a small-block Ford head.
What's so important about wet flow, says Richard, is the heavy air/fuel mixture does not act anything like dry air, and so heads developed strictly on a dry-flow bench can miss big parts of the picture. "We can see things that no one has ever seen before," he says. "Wet [flow] is where the power comes from ... Moving atomized fuel into the cylinder and using the chamber and the port to carry it there..." is where Richard concentrates his development time. It makes intuitive sense, and the growth of Pro Stock horsepower puts empirical horsepower behind the statements. "Our Pro Stock stuff from 1997 to 2004... we're up 80 hp for the same displacement and valve size. We're now aver-aging 1,300 hp."
Concerning the evolutionary process of developing cylinder head ports, Richard says, "We've been doing a good job of spoke-tightening." That technology-the port shape, the casting techniques, the post-casting machining-are all found in the current crop of Dart cylinder heads. For as the technology improves, it goes into the next batch of castings.
So, don't expect to see any flashing neon over the hot new trick in the 195 As-Cast Dart head we're reviewing here. In a spec-box sort of way, it resembles many other bolt-on small-block heads currently on the market. But, as our dyno showed, it runs better than other heads it-at least superficially-resembles.
To see what the new heads were like, we obtained a set of 195 As-Casts and had them prepped by Panhandle Performance in Panama City, Florida.
An experienced supplier of street and race cylinder heads to the Ford performance market, Panhandle prepped our castings by working with the valves but leaving the castings raw so we could all see what the basic Dart head was capable of-in other words, the way many cylinder heads are installed on engines, with a valve job, good valves, and good springs, but unported.
For the record, the spring package followed conventional practice using the following values.
|Coil Bind||1.118 in|
Ferrera F6101 and F6100 valves were selected using the stock 2.02x1.60-inch diameters. In the intake flow tests below, the first value is for the stock valve and the second is with Panhandle's custom backcut machined into the valve face.
|LIFT||TEST 1||TEST 2|
On The Dyno
As Richard says, all that really matters is what the dyno shows, and to check what that was involved a simple reading out of the 195's performance, thanks to having the heads well prepped by Panhandle Performance. Our 347 dyno mule from Coast High Performance was hoisted onto the SuperFlow water brake at our usual test site, Westech. Then, the Ford Racing Performance Parts Z304 cylinder heads on it were swapped to the Pro 1s. Our usual Edelbrock Performer RPM intake manifold and 650 Mighty Demon carburetor were reinstalled, and we were ready to make hot water.
The thumpity Comp 284 Extreme Energy hydraulic-roller cam already in the engine seemed a good match for the new heads, so we left it in. As the Z304 cylinder heads use a tall valve and consequently long pushrods, Steve Brule at Westech set us up with a set of 6.400-inch-long Comp pushrods for the 195 heads. We installed our usual 1.6 stainless steel Comp rocker arms and the in-house "court jester" valve cover set-that's a one blue, one red set of Comp polymer valve covers that have seen more than their share of dyno duty.Duct tape and Devcon keep these veterans going.
From the first, the combination was an easy starter, and it produced a fairly lumpy, 950-rpm idle with 10 inches of vacuum-good for a Saturday-night shaker or Sunday-afternoon bracket beast. The fuel, air, and temperatures all looked good, so we got right to fiddling with the ignition timing. As is typical with the current crop of good small-block heads, 32 degrees is all the timing the engine wanted, and the 195s were making 437 hp.
Next, it was time to optimize the air/fuel mixture. We ended up with 77/88 jets in the Demon, along with 453 hp. This is 1 hp better than this short-block had ever made, so with the 195 Pro 1 heads, right away things were looking up.
Examining the power curves, we noted the small dip at the power peak. It's an interesting-or should we say maddening-shape, as that curve should round out nicely right where it has that little dip. Timing and fuel did not tune it out, and we ended up figuring it was possibly the valvesprings beginning to lose control of the valve event. In any case, we had found the reasonable bolt-on limit of the Pro 1 heads, and it's likely further optimization would bump up the small dip to give these heads even more bragging rights.
Although it was reasonable to assume the standard Performer RPM on the engine would deliver everything reasonably possible, we had a Performer RPM Air Gap intake and elected to give it a go. We didn't expect much of a change, as the Air Gap's advantages are subtle and more likely to reveal themselves in a real-world, underhood installation. And not much of a change is exactly what we got-call it maybe 1 hp, not quite enough direction to say there was a change. After closely reviewing the Air Gap versus non-Air Gap data, we did note an airflow increase from the midrange on up using the Air Gap, but no power came of it.
When nothing else seems to be working-often because the combination is optimized-it's time to try "small" tuning tricks such as carb spacers. Stone-simple and easy to install, a carb spacer can make a real difference as it increases the intake manifold's plenum volume. Theory says this can soften throttle response and power at lower rpm, but aid the top-end punch.
We had a typical, open-center, 1-inch spacer built by Wilson Manifolds, so we installed it and hit the throttle. For once, reality and theory played out as the spacer traded some bottom end for top end. The crossover was at 4,800 rpm, with the power lying down eventually at the end of the run, as breathing in general gave up.
Does the top-end gain offset the torque loss? Probably not. By averaging the power output from 3,100 to 6,000 rpm, the average was a bare 1 lb-ft and 1 hp better without the spacer. But the top end was definitely better, so if the car was steeply geared and the engine kept in the top of the powerband-sounds like drag racing to us, or a fast road course-then the spacer would help.
The bottom line is, with the carb spacer and Air Gap intake, the 195 As-Cast cylinder heads produced a nice, round 460 hp. This is a new high point for our 347 dyno mule, and reason enough to consider the Dart heads for projects to come.
|As-Cast Pro 1|
|Description||Bolt-on street head|
|Material||355 T6 aluminum|
|Valve Package||2.02 in x 1.60 in|
|Intake Port Volume||195cc exhaust port|
|Volume||75cc exhaust port|
|Location||Raised 0.135 in,|
|std 2.00-in bolt centers|
|Intake Gasket||Fel-Pro PN 1262|
|Exhaust Gasket||Fel-Pro PN 1487|
|Head Bolts||11/42 in|
|Spark Plug||0.750-in reach, gasketed|
|Spring Pocket||1.550-in diameter|
|Valve Seats||Ductile iron, hardened|
|Piston Requirements||Most 20-degree|
|Dart Small-Block Ford Cylinder Heads|
|MODEL||INT VOL||VALVE PACKAGE||DESCRIPTION|
|170 As-Cast||170 cc||1.94x1.60||Mild street performance|
|195 As-Cast||195 cc||2.02x1.60||Maximum street performance,|
|210 CNC||210 cc||2.05x1.60||Street perf., oval track, brackets,|
|6,500 rpm, 302-351 ci|
|225 CNC||225 cc||2.08x1.60||Serious street, oval track, brackets,|
|7,000 rpm, 337-400 ci|
|Dart Pro 1 Heads|
|Dart Pro 1 Heads||w/Performer RPM intake|
|w/Performer RPM intake||and Carb Spacer|