Over Labor Day Weekend, the NHRA’s traditional stop in Indianapolis saw a new combination this year in the series’ Factory Showdown event. The Factory Stock Showdown is run at four events throughout the course of the season. There are stops at Gainesville, Indianapolis, Maple Grove, and Las Vegas, with the goal to showcase the three major manufacturers’ latest and greatest racing engines in their latest chassis platforms.
This year, Ford Racing Parts stepped up to the plate with an all-new program aimed at powering their Cobra Jet racers in the FS/B naturally-aspirated class. FS/B has very specific rules – the engine must measure between no more than 430 cubic inches, carry a minimum weight of 3,350 pounds, and has an index of 10.35. Engines smaller than 400 cubic inches carry a minimum weight of 3,250 pounds – and that’s about it. The Cobra Jet Mustangs in this instance race against COPO Camaros and Drag Pack Challengers.
The Ford Racing program, run in conjunction with legendary Michigan-based engine builder Chris Holbrook, is based on an all-new engine combination developed specifically for this class. The engine specs out at 429 cubic inches, and is designated “Ninja” by the Ford Racing team. With David Barton running impressive times in his 426-powered Drag Pack Challenger, and Chevrolet getting serious about the Factory Stock program with the LSX-R-headed engine in the COPO Camaro, Ford had their work cut out for them during the development phase of the engine.
Providing The Solid Base
Previously, the Fords were competing in this arena with the naturally-aspirated 428 Cobra Jet engine wearing a set of Ford’s Z-series aluminum small block heads. The platform was maxed out – especially the cylinder heads – thus the reason for development of the new program. The new engine platform is based on the previous design with some tweaks to make it more competitive.
“We kept the same stroke and slightly different bore but otherwise the short block is very similar. Obviously the pistons are different to accommodate the D3 style heads. On the top end the heads and intake manifold are completely different. We were forced into a situation where the Z head on the 428 could not get the numbers we needed to compete. We looked at going with a completely new head but instead decided to take what we had on the shelf and tweak it to work,” says Ford Racing Parts’ Jesse Kershaw.
The new engines were built entirely at Holbrook Racing Engines in Livonia, Michigan, using one of Ford Racing’s Z351 aluminum engine blocks to create a solid base.
A Callies crankshaft and connecting rods are inside, swinging a set of eight Diamond pistons. With the idea of more airflow at the forefront of the project, Ford Racing went into their catalog and selected the proven D3 NASCAR cylinder head to sit on top.
An LSM camshaft with undisclosed specifications was used to maximize horsepower potential under the given ruleset.
Given the cylinder head’s NASCAR heritage, major changes had to be instituted for it to excel in this application.
“The head had major changes made to it to accommodate the relatively low valve lift and the CID of the engine. NASCAR engines were over 1-inch lift and 358cid, we were at .650-inch lift and roughly 440cid with legal overbore. During development I didn’t let the cylinder head guy give me flow numbers at anything over .700-inch lift because I didn’t care what they were. The goal was to get max air through at the lift we were working with,” says Kershaw.
Factory Technology To The Rescue
The real star of the show is the all-new Ninja intake manifold, initially developed through the use of 3D printing in the Ford Rapid Prototyping lab.
“It was critical that for the manifold it had to look like a production piece and that the throttle body had to be off-the-shelf. We decided to model it after the 5.0 Coyote Cobra Jet intake using the common GT500 throttle body bolt pattern. It allowed us to use the technology we have developed for newer intakes on an engine platform that traditionally did not have an intake like that. Even though this generation Mustang never had a pushrod engine we wanted it to look as OE as possible,” Kershaw explains.
“We machined the block here, and put roller camshaft bearings in it to reduce friction. They were blueprinted here during the assembly process, we wrapped them up and delivered them to the customers. Neither one of them had any time to really go do any testing, so we were guessing at the transmission ratios, the torque converter, and the car setup,” says Holbrook.
Both vehicles use BigStuff3 fuel injection that was calibrated in-house at Holbrook Racing Engines by Holbrook himself. The engines were delivered to Ford Racing customers Bo Butner and the Cook Brothers Racing team (car driven by Ken Miele), who used them during the event last week to get into the second round, Butner losing to Dave Connolly and Miele going down to eventual runner-up Kevin Helms.
The Factory Stock Showdown is unique for the NHRA in that there is an index, but the races are run with no threat of weight penalty if the racer runs extremely well. In addition, these cylinder heads are legal for other types of NHRA competition.
“While our goal was to be competitive heads-up in Factory Stock Showdown this combination is completely legal for Stock and Super Stock to be raced in the Eliminator. I expect the work we’ve done will make D3’s more acceptable in other drag racing as well,” explains Kershaw.
As an aside, Holbrook won the whole event in his own supercharged FS/A Cobra Jet, earning a back-to-back title in one of the NHRA’s most difficult classes with a win over Helms in the final round.