Words and Photos: Richard Holdener
When it comes to coaxing more power from your combination, there are a number of different avenues. Bolt-ons are a time-honored tradition, as bolting on the right set of heads, cam, and/or intake can yield substantial results. Of course, there is always boost, and everyone knows that all motors, including our Ford stroker, work well with blowers or turbos. The final route to increased performance is displacement. All things being equal, bigger motors simply make more power than smaller ones.
The reasoning behind building a stroker motor is that, for any given power goal, it is easier to reach that level with a bigger motor. Of course, the ideal situation is the combination of multiple avenues in one build up, meaning a large-displacement stroker with a bevy of bolt-ons, then further augmented with boost. Obviously, such a combo would be powerful, and expensive. Unfortunately, build ups are usually dictated by the budget, but so too must they be a function of the intended application.
Starting with the intended application, this Ford build up was slated for an early street Stang. Drag racing was nowhere on the list, nor was a cantankerous, over-cammed monster that required high-RPM running just to be happy. Such a motor might work wonders at the track, but hardly provides acceptable behavior for a dedicated driver, even one not used for daily transportation. This automatically eliminated things like wild cam timing and high-RPM, single-plane intakes, but not necessarily free flowing cylinder heads. This is something the OEMs found out a while ago, as high-flow heads do not detract from things like idle and drivability, but they do improve power production.
To further improve power, we elected to go with both increased displacement and your basic bolt-ons, as displacement not only enhanced torque production, but also improved drivability. Since the added displacement also required additional flow, we stepped up the heads, cam, and intake on our big-inch 351W build, as well.
Having decided on the basics, it was time to fill to select the specific components. Though a 351W would certainly make acceptable power, we first improved power production by upping the displacement an additional 57 cubic inches. The stroked portion of our Windsor came from a 4.0-inch stroker crank (stock was 3.50-inches) from Speedmaster. In addition to the added stroke, the combo was also poked, meaning the cylinders were bored .030 over then stuffed with Wiseco forged, flat-top pistons. The stroked and poked components were joined by a set of 6.20-inch forged rods, also from Speedmaster.
A little math tells us that even at a specific output of just 1 HP per cubic inch, the displacement could add an additional 57 hp. Given the heads, cam, and intake we had planned, the gains would be even higher from the displacement, as the specific output of any combination with our chosen components would certainly exceed 1 HP per cube.
With our displacement and short block set, it was time for some enhanced efficiency. First up was a cam designed specifically for a stroker application. The XFI profiles from COMP Cams were designed specifically with stroker Fords in mind. Since this 408 was a street motor, we selected the smaller of the two shelf XFI grinds, the XFI236HR-14. This cam featured plenty of lift, with both the intake and exhaust checking in at .579. The 236/248-degree duration figures were also plenty powerful, but offered acceptable drivability for the displacement.
The XFI stroker cam was teamed a set of TFS Twisted Wedge 11R cylinder heads. The 11R heads featured healthy 205cc intake ports that offered peak flow numbers exceeding 320 cfm. The heads were offered in two chamber sizes, but we selected the 66cc combustion chambers for our big-inch stroker. The heads also featured full CNC porting, 66cc exhaust ports and a hydraulic roller valve spring package designed for cams up to .600 lift. The heads were installed using Fel Pro 1011-2 head gaskets and ½-inch ARP head bolts.
Finishing up the induction system was an Edelbrock Performer RPM Air Gap intake. Once again, we selected an intake based on the intended application, as a single plane would certainly make more power (we tested one that added over 20 HP), but the dual plane offered the best combination of power, torque, and throttle response.
With the major players all accounted for, we finished up the stroker with a 950 cfm carb, 1 ¾-inch, long tube headers and a suitable ignition system. Because we wanted a bullet-proof oiling system, we installed a compete system from Milodon that included a road-race pan, windage tray, and high-volume oil pump. What good is an XFI cam, ported heads, and top-flight induction system if your oiling system isn’t up to snuff?
Finishing touches included a set of 1.6-ratio, COMP Cams Ultra-Gold ARC roller rockers and hardened 8.40-inch pushrods tucked under a set of TFS cast aluminum valve covers. After assembly, it was time to hit the dyno and see if all our hard work paid off. Prior to start up, we primed the oiling system with a drill to ensure adequate lubrication to all the internal components. The stroker was then treated to multiple break-in cycles before making any full-throttle runs.
After adjusting both jetting and timing, we were eventually rewarded with a peak power output of 534 HP at 5,900 RPM, but we were much more interested in the torque numbers. The 408 not only produced 543 lb-ft of torque at 4,200 RPM, but the massive torque curve exceeded 500 lb-ft from 3,200 to 5,500 RPM! It might have been built as a driver, but this curve will make it the Torque of the Town!
Graph 1: 408 XFI Street Stroker
The whole reason behind building a stroker is torque production, and this 408 Ford was packing plenty. Thanks to the right components, including the powerful XFI cam, the 408 Street Stroker thumped out 534 HP and 543 lb-ft of torque. More than just a big peak number, torque production from the stroker exceeded 500 lb-ft from 3,200 to 5,500 RPM. One thing for sure, you would never be at a loss for power in this baby!