Muscle Mustangs & Fast FordsHow To Engine
Engine Masters Insider
Inside an Engine Masters 410 stroker.
If you take a look at many of our tech articles for MM&FF, it should beapparent that we're big fans of horsepower graphs. We should probablyrephrase that statement by saying we're not so much fans of graphs aswe are fans of the big picture.
By this, we mean the entire power curve.In our recent comparison between the four different forms of forcedinduction ("Boost Bash, Part 1," Dec. '04, p. 125), we made sure tostart the power pulls as low as possible (in this case, 2,500 rpm) inorder to fully demonstrate the power potential offered by each form fromas low as possible all the way out to our self-imposed redline of 6,600rpm.
Running such a long sweep on the SuperFlow engine dyno was no easytask, but only by showing the power production offered throughout theentire rev range can the merits (and limitations) properly be addressed.The importance of the overall power curve was instilled in parts 1 and 2of the "Ultimate Guide to Cylinder Heads" (Aug. and Sept. '03) as well,where we compared the many 5-liter heads to the stock E7TE castings onthe airflow bench and on the dyno. Only by running them down to 2,500rpm would we know what kind of power gain (or loss) was availablethroughout the rev range.
Why is it so important to know the powerproduction throughout the rev range? The shape (or change) of the powercurve determines not only the accelerative capa-bility, but also theoverall character of the motor. The often-quoted peak power numbers tellas much about the motor as a single snapshot in your photo album does ofyour personality. Imagine the opinion someone might get having only seenthat photo of you dressed up as Elvira for Halloween.
Just as yourMistress of the Darkness costume might not tell the whole story (thoughit tells us more than we wanted to know), the peak power rating providesonly a glimpse into the character of the motor. Think about it--will a400hp 5.0 offer the same performance or manners as a 400hp 408? Nothardly, as despite the similar peak power numbers, the larger 408 willalways offer much more low-speed torque--something that will make yourstreet Stang much more fun to drive and likely out-accelerate thelike-powered 5-liter version.
With such an affinity for average powerproduction (especially for street buildups), is it any wonder we wereexcited when sister publication Popular Hot Rodding introduced theEngine Masters Challenge? The EMC is a unique engine-buildingcompetition that helps stress the importance of the overall power curvefor street motors by rewarding the builder who produces not the mostpeak horsepower (or torque), but the highest average power and torqueover a specific range. In this, its third year, the EMC pitted the top50 engine builders from across the country to put together small-blockstroker motors displacing no more than 410 ci.
The previous two yearsincluded 366-inch small-blocks and 470-inch big-block buildups. (Checkout enginemaster.com for full details on the rules). But, racers beingracers, it was necessary to spell out the rules in black and white, lestsome savvy individuals find those all-important gray areas that lead toimproved performance. Case in point: The rules stated that anyone usingCleveland blocks must run a 9.2-inch deck height and not the 9.5-inchheight of the Windsor. Jon Kaase read the rules that stated head gasketswere unlimited, so he built a set of 0.300-inch-thick copper headgaskets to effectively produce a 9.5-inch deck height on his 9.2 deckCleveland. Pretty trick stuff, Jon!
Basically, the rules limitedcylinder head, intake, and header choices to as-cast, street-orientedpieces. The motors were required to run from 2,500 rpm to 6,500 rpm on92-octane pump gas. The winner was declared by the combination of theaverage horsepower and average torque produced throughout this revrange. Each contestant was required to make three consecutive runs, theaverage of which would be their final score.
Having spent every wakinghour on the dyno in an attempt to stress the importance of the averagepower production for the past 10 years or so, it was only fitting thatMM&FF throw its hat into the ring. While we in no way consideredourselves the engine-building equal of guys with names such as Shaver,Sherma or Kaase, we were hoping to find out if all those years spent onthe dyno have actually paid off. The EMC was interesting in that, forthe first time, we were never really con-cerned about the peak poweroutput of the motor. In fact, during testing, we even reduced the peakpower by nearly 50 hp in our quest for the all-important average powernumber. Were we building the same combination for a drag racer, we wouldnot have replaced the single-plane intake with the dual-plane. But weweren't interested in the power production from 4,000 rpm to 6,500 rpm.We were interested in the power production from 2,500 rpm to 6,500rpm--and the Performer RPM Air Gap produced the highest average power inthat range.
While suspecting we were no match for the big guns in thecontest, we had at least one ace up our proverbial sleeves. Even if wecouldn't hit the combination on the head on the first try, we certainlyhad the ability to find it with testing. The Westech boys were kindenough to offer some much-needed dyno time after hours and--believeus--we put it to good use.
While the Popular Hot Rodding gang would haveyou believe the EMC competition is all about street motors, the simplefact that they are required to run on 92 octane does not a street enginemake. With few exceptions, none of the EMC entries were destined foractual street use. All of them were built to run right on the raggededge of detonation, something surely not desirable for a street motor.Such things as low-tension ring packages that improve power by reducingfriction are not really designed for high-mileage street use. Asexpected of any serious competition (did we mention the winner receiveda cool $100,000 in contingency cash?), the EMC mills were built with aspecific purpose--to make as much average power as possible throughoutthe test-rpm range without detonating themselves to death in theprocess. The fact that the power curves would be a welcome addition tomost any street (actually, strip, given the 650-700 hp and more than 600lb-ft of torque) machine was actually more of a byproduct.
It shouldalso be mentioned that these EMC powerplants were all a tad on thepricey side. Such things as Dart blocks, custom forged-steel (or billet)cranks, and rods and pistons all begin to add up. Throw in the alwaysnecessary custom machining, the multitude of test components, and thedyno time, and you're into a serious engine for something in theneighborhood of 25 large.
Despite the single-purpose use of the EMCmotors, we were excited about a venue that promoted the average powerproduction across such a broad range. We began to gather the necessaryparts from our con-glomeration of test pieces. In the stash were anumber of the required components, including a Dart four-bolt Windsorblock, a set of Air Flow Research 225 cylinder heads, and a variety ofdifferent intake manifolds (including our secret weapon in the form ofan Edelbrock Super Victor ported by none other than famed inductionexpert Keith Wilson). After thumbing through the catalog, we went toComp Cams for additional cam advice to narrow down our choices.
Fromthere, we went to Coast High Performance for our reciprocating assemblyneeds. CHP filled the block with a Scat 4340 forged steel crank thatfeatured a 3.825-inch stroke. The stroke was all but dictated by the4.125 bores in the Dart Windsor block. The crank was further tuned(knife-edged and lightened) by the experts at Castillo CrankshaftSpecialists. CHP also supplied a set of 6.0-inch forged connecting rods(small Chevy journals) and forged-aluminum Probe pistons. The piston(dish) design was finalized after digitizing the AFR 225 com-bustionchamber.
We would eventually further reduce the static compression bymachining the piston dishes, but we started out with a staticcompression of 12.6:1. The CHP/Dart short-block was topped off with aset of out-of-the-box AFR 225 heads and the Keith Wilson Super Victorintake. We installed a Tony Jones SS1 carb (modified Holley Dominator)and a Comp cam that offered 0.688 lift and a 249/253 duration split (at0.050). A set of Hooker Super Comp (5.0 Mustang) headers were added, aswell as a CSI electric water pump, an MSD ignition, and a CHPFox-chassis oil pan.
The 410ci motor was broken-in on the dyno and ranfrom 2,500 rpm to 6,500 rpm on the first of what would be 400-plus dynopulls! After tuning with jets and timing, the 410 eventually producedmore than 650 hp and 585 lb-ft of torque, but more importantly, anaverage score of 961.7 points (average horsepower plus average torquefrom 2,500 rpm to 6,500 rpm). Given that the calculations from theprevious two years told us we needed a score close to 1,020 points, westill had a long way to go.
Dropping down in cam duration to a 242/246split resulted in an additional 6.1 points, while adjusting the Jeselbeltdrive was worth another 5.7 points. Replacing the 320-pound (seatpressure) valvesprings with 170-pound Comp Beehive springs was worth 8.7points, and installing a Milodon oil pan and windage tray added 13.7points, bringing the new total up to 996.1 points. We were gettingcloser. More out of curiosity than anything else, we swapped out theSuper Victor for an out-of-the-box Edelbrock Performer RPM Air Gap. Thepeak power dropped by almost 50 hp, but the average power was up by 9.1points. Since the Air Gap was designed for a 351, we knew porting wouldyield big dividends. Extrude Hone porting the RPM intake added awhopping 14.7 points, while adding a 4150-4500 carb spacer added another14.2 points. Fabricating a divider in the open carb spacer was worth 3.2points, and a small notch in the divider added another 1.7 points. Astack of open (Dominator) gas-kets was worth 4.8 points. Now the totalwas up to an amazing 1,043.8 points.
It took endless hours on the dynoscratching to find every last bit of horse-power, but the EMC 410 wasfinally looking like a contender. Naturally, the testing pro-cess wasconsiderably more difficult than the simple points progression wouldhave us believe, as every test was run at 160 degrees water and 190degrees oil. Each combination required running different timing sweepsand may have required changes in jetting to the Tony Jones SS1 carb.
Itwas about this time that we ran into fellow competitor Andy Dunn whilehe was testing his (similar) 410-inch Ford combination at Westech.Unfortunately for Dunn, a rather elevated static compression ratioresulted in damage to a couple of pistons while testing on pump gas.This worried us because we had yet to run any tests on pump gas. Ourthinking was to test everything on race fuel, then slowly dial in thetotal timing to sneak up on the possibility of detonation afterfinalizing the combination. The detonation experienced by Dunn concernedus to the point of disassembling the motor and lowering the staticcompression from 12.60:1 to 11.82:1. While out, the piston tops werecoated with a thermal barrier coating and the sides with an antifrictioncoating. We also took the liberty of coating the Edelbrock Performer RPMAir Gap intake manifold.
As expected, the drop in compression had anegative effect on the power production, and the average score droppedfrom 1,043.8 to 1,025.3 points. Though we were disappointed to losenearly 20 average points, they would be useless if the motor would notrun on the 92-octane spec pump gas. Not only would detonation hurtpower, but it also might kill what was beginning to be a highlyexpensive Windsor.
We suspected the score of 1,025.3 was going to befairly respectable. We also knew that guys such as Jon Kaase take thiscompetition quite seriously and would be looking for every last point.Back on the dyno, we tried changing the rocker ratios in everycombination, eventually settling on a 1.7 ratio for the intake and 1.6for the exhaust. All the rocker swapping was worth just 1.2 points. Theguys from Kooks headers shipped us a set of their 13/4-17/8-inch stepheaders complete with merge collectors. We were a little disappointedafter letting Dunn test them on his motor, as they showed no gain overthe Hooker Super Comps (just like ours). Since the combinations weredifferent, we decided to give them a try nonetheless. Good thing we did,as the Kooks headers were worth an extra 6.1 points.
This next test hadto be run several times before we were convinced, but increasing thespeed of the CSI electric water pump was worth 3.9 points (three timesin a row). A large shield to isolate the carburetor from the radiantheat generated by the (uncoated) headers and the motor was worth another2.1 points, bringing the final tally to 1,038.6 points.
The final testperformed on the 410 stroker was to run pump gas. The timing was backeddown to 21 degrees (from the best setting of 31 degrees total) forsafety, and the 410 was run from 2,500 rpm to 6,500 rpm. Run with 21degrees of timing, the 410 produced 998.9 points. The timing wasincreased in 2-degree increments until we were able to successfully run31 degrees of timing on pump gas, where the 1,038 score was once againrepeated.
We then ran three consecutive runs to mimic the EMCcompetition, with excellent results. The average score dropped by lessthan 1 point across the three runs. A post-test leakdown showed allcylinders were in the 2-3 percent range. The motor was ready to beshipped to the competition.
Unfortunately, this is where things began togo wrong. After hooking up the motor to the DTS dyno, the power andground feeds to the MSD were crossed--the MSD 6A was toast. The waterlines to and from the motor were shut while locating a suitablereplacement for the fried MSD. After finding one, the motor was refiredand warmed up under load only to discover the water to the motor wasnever turned back on. The motor overheated badly (steam shooting out ofthe thermostat housing is bad sign).
The water valves were reopened, butthe damage was apparently already done as evidenced by the first powerpull. No amount of tuning could stop the ever-decreasing powerproduction. We managed to make the final six with a score of 991.6points and finished sixth overall with just 971.4 points. On thepositive side, we did manage to make the finals in our first attempt andproved we could compete in this arena. It's just a bummer the motor wasnever given the opportunity to show its true potential. A post-mortemleakdown showednumbers as high as 26 percent on seven of the eight cylinders.
[Editorsnote: Initially we were concerned about the difference between theSuperFlow and DTS dynos, but we were relieved after seeing thepreliminary score posted by fellow Ford competitor Dunn. His motorrepeated the score achieved during testing at the Westech dyno within1-2 points, so we were excited about running our motor, especially giventhe eventual winning scores.]
EMC 410 Stroker: Baseline Run vs. Final Combination Shipped toCompetition
The graph illustrates what can be achieved after roughly seven months oftuning on a particular combination. Though the peak power was down by asmuch as 50 hp (at 6,500 rpm), the all-important average power was upsignificantly (from 961 points to 1,038 points). A significant portionof the differences in the power curves can be attributed to the changein intake manifold from the single-plane Super Victor to the ExtrudeHone-ported Performer RPM Air Gap, but as much as half of the additionalpoints came by chipping away 1-2 points at a time. The drop incompression took away 20 points, but we were able to get back almost allof what we lost with additional testing. Unfortunately, the EMC 410buildup never got to produce this power curve during the competition.