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Small Heads Keep Power Where We Like It

PT.03-572 lb-ft torque and 515 hp raises the bar.

We're sticking to a set formula with Major Mouse. And that formula is: Test only one part at a time to see what kind of effect it has on power. This way, we can find out if there's a hidden power producer lying around out there, or if the claims of ultimate power made by some manufacturers are just bunk. And since they're such a hugely controversial product today, we've tested yet another set of aluminum cylinder heads for Major Mouse (MM) Part 03-Test 03.

MAJOR PARTS SWAP
As is our usual way we swapped heads and then bolted MM back onto Speed-O-Motive's DTS dyno to flog the you-know-what out of them. We once again broke into little bro Danger Mouse's treasure chest of booty and stole the old set of Dart Pro 180s we'd tested on DM before. We made no other changes at all and plugged it back into the dyno. After warming up the Major and making sure timing was set the same as last month--32 degrees--we started our first series of dyno pulls.

DYNO POWER
The Major didn't respond all that well to the relatively small Dart heads and we don't exactly know why. When we'd last tested this set of heads ("DM31," SC March '05), it was on a stand-in engine we called "the Imposter" because Danger Mouse was on the disabled list. Although, that engine was built almost identically to DM, so we felt it was a suitable test subject. The Dart Pro 180 heads on "the Imposter" produced some good numbers. Even higher peak and average HP figures than some of the past's best heads, so we thought their performance advantage would cross over to the larger Major Mouse--but, it didn't. When compared to the peak and average numbers of the last two month's tests, we see that the Dart Pro 180's might not be the best choice for this large small-block. That's not to say they're a bad head. To the contrary, we've proven that they're a formidable power producer when used on a smaller displacement engine. And if your mind is already made up that your next set of heads will be from Dart, we're sure that you would not be unsatisfied with the power they're able to produce on any engine. This just further proves our point that making power is all about properly matching components. And that's why we're taking the time and spending the money doing all this stuff. So you will be able to make the best decisions on your next engine.

MAJOR MOUSE SPECS FOR PART 03 - TEST 03:
As in our usual format, we left everything else the same and only changed cylinder heads this month. All other items in this test--i.e. timing, jetting, cam installed position, etc.--were duplicated from last month.427 cid, 11.0:1 cr, 4.125-inch bore Mowtown iron four-bolt block, 4.00-inch stroke Lunati crank, 5.850-inch Lunati rods, Lunati pistons (14cc dish) installed @ "0" deck, Lunati Moly rings, Dart Pro 180 heads (64cc chambers, 180cc intake ports, 74cc exhaust ports, 2.02-inch intake valves, 1.60-inch exhaust valves, angle plugs), Edelbrock Performer RPM Air Gap intake manifold, Edelbrock Performer RPM hydraulic roller camshaft installed at 108-degree intake CL (234/238 @ .050, 296/300 adv, .574/.584 lift w/ COMP 1.6:1 rockers, 112 LS), Demon 750 carb, 32 degrees total advance, "0" degree Crank Angle Offset (C.A.O.)*, 91-octane Shell gasoline. Tested on Speed-O-Motive's DTS dyno.*C.A.O. refers to the setting on the Pertronix "Second Strike" ignition box. It re-fires the spark plug after its initial firing, such as 32 degrees BTDC on the first strike, and then maybe once again at 30 degrees BTDC. In this case, as was the same last month, Major Mouse responded best to a C.A.O. of "0" degrees, meaning there was actually no second strike of the spark plug. In the past on some other engines we've found extra power by re-firing the plug around 2-3 degrees later, but not this time.

MAJOR MOUSE COMPONENTS FOR PART 03-TEST 03
CAM EDELBROCK HYDRAULIC ROLLER (PN 2201)
CARB SPEED DEMON 750
FASTENERS ARP
GASKETS CORTECO
HEADS DART PRO 180CC (PN 11111112)
IGNITION PERTRONIX DISTRIBUTOR, "SECOND STRIKE" IGNITION BOX*
LIFTERS COMP HYDRAULIC ROLLER (PN885-16)
MANIFOLD EDELBROCK PERF RPM AIR GAP (PN 7516)
OIL SYSTEM MOROSO
PISTONS LUNATI DISHED FORGINGS
ROCKERS COMP CAMS 1.6:1 PRO MAGNUM (PN 1302-16)
SPARK PLUGS ­p; ACCEL (PN 8191)

MM03-T03
RPM TQ HP
2600 491 243
2800 519 277
3000 536 306
3200 535 326
3400 532 344
3600 540 370
3800 555 401
4000 564 429
4200 567 453
4400 563 472
4600 553 484
4800 544 497
5000 529 503
5200 511 506
5400 487 500
5600 461 491
5800 434 480
6000 412 471
     
Max 567 506
Avg 519 420

DART PRO 1 (180cc) FLOW NUMBERS
When shopping for cylinder heads there's lots of choices to consider and not every one of them will work best in every situation. So it's important to collect as much data as possible and then make your decision on what you've learned. When comparing cylinder heads, it's important to look at other figures besides just airflow. Port volumes, chamber shape and size, valve sizes, angle and locations, how much spring/lift they can take, and will it match your camshaft? These are just a few of the items that you should base your decision on, not just the power they produced in some magazine story. I also personally feel that a good indicator of how well a cylinder head will work is it's ratio of intake to exhaust flow, listed as "I/E flow" in this chart. Although this is not the "Holy Grail" of horsepower, it does indicate a head's potential to move air into and out of the cylinders effectively. A head with a ratio of less than 60 percent is not a very effective air mover, particularly since it indicates that it can move air in, but not out of the cylinders. A head with a ratio of over 90 percent, although rare, is capable of extremely good power numbers so keep an eye out for it. Check out the very high 85-percent I/E flow at .200-lift of the Dart Pro 180. This is an area of critical performance for any head, but particularly a street head that won't be run with much lift. Since the valve will see this area twice during every cycle, once on the way up and then again on the way down--as opposed to seeing max lift only once in every cycle--low-lift flow figures are often overlooked, but very critical to making the best power.

Intake port: 180cc, 2.02-inch valve · Exhaust port: 74cc, 1.60-inch valve
*Figures shown at 28 inches water depression
 
Valve Lift Int CFM* Ex CFM* I/E flow Ratio
.200 134 114 85%
.300 187 145 78%
.400 231 164 71%
.500 257 172 67%
.600 261 174 67%
.700 264 175 66%
  Average 72%  
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