The new Dart Pro 1 aluminum heads come in both 170cc and 195ccintake-port configurations. While making good power, you can also get apair of these heads, assembled and ready to bolt on, for less than $925.
We don't have to tell you that other than a nitrous kit, the best bangfor your horsepower buck will always be with a set of good cylinderheads. Dart recently upgraded its lineup of aluminum Pro 1 Ford castingswith two sets of redesigned Pro 1 heads that have benefited from Dart'swork with a very sophisticated wet flowbench.
This bench has allowed Dart to massage the ports to improve wet-flowperformance, which means that the company now takes into considerationnot just how the air flows through the intake ports and into thecombustion chambers, but also how the heavier fuel is transported intothe chambers. The theory is that by tweaking the intake ports and thechambers, these heads will make more power. It sounded good to us, so wedecided to test the idea on a conservative little 0.030-over 302 WindsorFord we put together for "Build Your First Engine" in the July '04issue.
The only significant change we made to the engine was to swap in alarger cam to take better advantage of these new Pro 1 heads. Rightabout now, you're probably thinking that while these heads made greatpower, they're also probably close to $900 each. Would you change yourmind if we told you these heads sell through Summit Racing for $456each, complete and ready to bolt on? That's just a touch over $900 forthe pair.
The 62cc chambers fit either 2.02/1.60-inch valves for the larger 195heads, or 1.94/1.60-inch valves for the smaller 170cc-intake-port heads.These small chambers will give you just under 9:1 compression with aflattop piston, a 0.042-inch gasket, and a zero deck.
Head Games
Dart offers two new Pro 1 wet-flow aluminum heads for the WindsorFord--a 170cc intake port and a 195cc version. The smaller heads comewith 1.94/1.60-inch valves. The larger heads are blessed with a bigger,2.02-inch intake valve, while the exhaust remains at 1.60. Both headsfeature 62cc chambers with a modern, kidney-shaped configuration toimprove combustion efficiency. The heads lock into the standard Ford20-degree valve angle and intake-face configuration, but to improve theexhaust side, Dart raised the exhaust ports 0.135 inch, although thestock header-flange bolt spacing remains. This means there may be someclearance issues between the chassis and headers in some applications.
The heads were assembled with 1.437-inch-diameter springs set up with130pounds of seat pressure at an installed height of 1.800 inches. If youdesire bigger springs, Dart can also equip either of these heads with1.550-inch-diameter springs that pump up the seat pressure to a stout195 pounds at a 1.900-inch installed height for more valve-liftclearance for the valve-stem seals.
The exhaust port on the smaller Dart head measures 65cc while its largercousin measures in at 75cc. In an effort to improve port flow, thestandard Ford port spacing remains the same, but the ports on both headshave been raised 0.135 inch.
Test Configuration
To complete our 306ci little-block, engine guru Ed Taylor bolted in amore aggressive Comp Cams Xtreme Energy 274 camshaft (see "Cam Specs"sidebar). While hardly a daily driver kind of cam, if you're going tobuild a serious small-block Ford, you have to screw a little camshaftinto the engine. At a touch over 0.500-inch lift for the intake andexhaust, this cam and its longer duration seemed to be a good match forthe Dart heads.
To complete the induction side, we retained the Edelbrock Performer RPMAir Gap intake manifold but added a larger Holley 750-cfm, 0-4779mechanical- secondary fuel mixer to ensure the induction side would notpresent a restriction. We could have converted to a single-plane like anEdelbrock Victor Jr. 302 to pump up the top-end power, but we felt thatthe midrange torque advantages of the RPM Air Gap were well worth thesmall sacrifice.
By the Numbers Test 1: Stock iron 5.0 heads with 1 5/8-inch headers, Flowmaster 2 1/2-inch exhaust, 750-cfm carburetor, and Comp Cams XE274 hydraulic flat-tappet cam Test 2: Same as above with Dart 170cc Wet Flow heads Test 3: Same as above with Dart 195cc Wet Flow heads TEST 1 TEST 2 TEST 3 DIFF RPM TQ HP TQ HP TQ HP TQ HP 2,200 276 116 266 112 271 113 -5 -3 2,400 275 125 262 119 280 128 -5 -3 2,600 282 140 277 137 292 145 10 -5 2,800 292 156 295 158 305 163 13 -7 3,000 303 173 311 178 317 181 14 -8 3,200 312 190 323 196 327 199 15 -9 3,400 321 207 331 213 336 217 15 10 3,600 328 224 337 231 342 235 14 11 3,800 330 240 343 248 347 251 17 11 4,000 334 255 348 266 350 267 16 12 4,200 334 268 352 282 351 281 17 13 4,400 332 278 354 296 351 294 19 16 4,600 327 287 353 309 350 306 23 19 4,800 321 293 350 319 348 318 27 25 5,000 314 299 346 329 345 329 31 30 5,200 307 304 341 338 343 340 36 36 5,400 300 309 337 347 339 350 39 41 5,600 293 312 334 356 335 358 42 46 5,800 284 313 328 362 329 363 45 50 6,000 271 310 317 362 320 365 49 55 6,200 256 302 301 356 308 364 52 62 6,400 242 295 291 355 298 364 56 69
Avg 303 246 324 268 328 270 24.5 24.0 Peaks 334 313 354 362 351 365 Note: The DIFF column calculates the power difference between Test 1 and 3. The average power numbers were generated from data taken every 100 rpm, while we limited this chart to every 200 rpm.
With all this power potential, we knew we'd need a decent ignitionsystem, so we plugged in one of Pertronix's new billet plug-'n'-playvacuum-advance distributors along with a set of Pertronix 8mm wires. Theaddition of the vacuum advance will also help part-throttle performanceand also give a positive nudge to fuel economy, if you care about stufflike that. Then for the exhaust side, we bolted on a set of Hooker15/8-inch Super Competition coated headers and plumbed the 3-inchcollector into a 21/2-inch exhaust system using a pair of FlowmasterSuper 40 mufflers.
Testing, 1-2-3
The heads use standard Ford small-block valvetrain parts, and our headscame with 1.437-inch single springs, 10-degree retainers, 3/8-inchrocker studs, and Comp Cams guideplates.
To begin our test, we decided to use the base set of iron '89 5.0L headsalong with the Performer RPM intake, 750-cfm carb, headers, and exhaust.The engine spec'd out at 9.2:1 compression, running on paltry 92-octanepump gas. This would give us a solid baseline with the bigger Compcamshaft that we could use for our power evaluation. After carefullybreaking in the camshaft, the little 306ci small-block churned out 313hp at 5,800 with at 334 lb-ft at 4,000. Now it was time to bolt on thefirst of the Dart heads.
We decided to test the smaller, 170cc heads first. It was a simple taskto bolt on the heads on the Digilog dyno. We did not see a huge gain intorque--peak torque improved by 20 lb-ft--but it also moved up the rpmband from 4,000 to 4,400, which would explain part of the increase.Where these 170cc Pro 1 Dart heads really shine is in the horsepowerdepartment. From 4,400 rpm on up, the Dart heads were worth an averageof 43 hp, while peak power surged from 313 with the stock iron heads toan impressive 362, for a gain of 49 hp. Average horsepower throughoutthe entire rpm span also improved from 246 to 268, for an overallaverage horsepower gain of 22. Remember, all we did was bolt on a set ofheads.
We used a Comp Cams Xtreme Energy flat-tappet hydraulic cam for allthree tests on our gallant 306. Combined with the Comp Cams 1.6:1 rollerrockers, this pushes the valves open to 0.519- and 0.523-inch lift.
With this kind of gain, we were excited about testing the 195cc heads tosee what kind of power we would see with the larger intake. Weanticipated that the low and midrange power probably would not improve,since the 170cc Pro1 heads would have the velocity advantage over thelarger 195cc heads. The larger heads did perform better compared to thesmaller Dart heads in the midrange from 3,000 to 4,000 rpm, generatingmore torque than the smaller Dart heads. Had we spent more time ontuning the smaller heads, it's possible we could have made more torquein this range since the air/fuel ratio was a bit lean in the midrangearea with the 170cc heads.
Swapping heads was easy enough on the dyno using new Fel-Pro head andintake gaskets along with a set of ARP head bolts to keep everythingglued together.
Our little 306 really responded to bolting on the alloy Dart heads thatwere worth a solid 52 hp and a nice torque boost almost all the waythrough the power curve over the stock iron Ford heads.
Looking at the peak numbers, the 195cc heads cranked out a serious 365hpachievement at 6,000 rpm and continued to carry only a minor drop inpeak power all the way through 6,400 rpm, which told us that had webolted in a bigger cam or perhaps a set of 1.7:1 rockers, we might havemade even more power. But let's not downplay a solid 52hp increase overthe stock iron heads with these out-of-the-box Pro 1s. If we're allowedto play "what-if" games, it appears that the larger 195cc heads would dobetter yet with a larger camshaft and more valve lift to take advantageof their greater flow potential.
Evaluating either of the Dart Pro 1 heads against the iron baseline,it's obvious that Dart has scored again for the small-block Ford fanswith a great selection of heads. Anytime you can bolt on 50-plushorsepower with a pair of heads that cost less than $1,000, that's abull's-eye where we come from.
Parts List Item Source Type PN Price Camshaft Comp Cams XE 274 31-246-3 $105 Lifters Comp Cams Hydraulic flat 832-16 86 Rocker arms Comp Cams Aluminum rollers 1043-15 301 Pushrods Comp Cams Heavy duty 7831-16 28 Dart 170, Pro 1 Dart Aluminum 13100080 456 Dart 195, Pro 1 Dart Aluminum 13200010 456 Carburetor Holley 750 0-4779 398 Intake manifold Edelbrock RPM Air-Gap 7521 231 Valve Covers Ford Racing Black {{{M}}}-6582-F302 n/a Water Pump Edelbrock Aluminum 8840 145 Main studs ARP Stud kit 254-5501 58 Head-bolt kit ARP Black oxide, 6-pt. 154-3605 91 Engine-bolt kit ARP Black oxide 554-9801 117 Pulley set March Single V-groove 01614 n/a Headers, coated Hooker 15/8-inch 6222HKR 380 Mufflers Flowmaster Super 40 952546 {{{80}}} ea. Distributor Pertronix Billet plug 'n' play D130710 191 Plug wires Pertronix 8mm 808390 50 Note: All prices were pulled from www.summitracing.com so you have a realistic idea of what the parts cost.