Tom Wilson
March 1, 2005
Photos By: Courtesy John Tymensky

Horse Sense:
Cutting-edge engines like this don't happen without plenty of help. John Tymensky would like to thank all those inside Ford and Roush who've helped with information and parts.

Ain't no replacement for displacement," goes the truest, if not most grammatically correct, saying in all motorsports. And as if to prove the point, you can't step off a curb these days without tripping over a 5.0 stroker kit, and the modular crowd is catching up now that inexpensive, Chinese stroker crankshafts have landed on our beaches. Pretty soon, we'll have to specify which 5.0 we're talking about-pushrod or modular.

For real cutting-edge displacements, however, it pays to hang around drag racers. And for modulars, the father and son team of John and Mike Tymensky are the drag racers with the mostest. Originally found pedaling a 460-powered T-Bird, the Tymenskys have moved on to modulars, enough so to service the overhead cam crowd via their Modular Performance Web site and parts outlet.

No doubt the thundering 460 gave the Tymenskys a taste for displacement, which may explain their Big Bore Process for 4.6 drag engines. Running in NMRA Hot Street and Fun Ford Street Bandit drag classes, however, the Tymenskys have been looking for more thrust, so they're developing the largest practical big-inch modular engine possible.

To answer your next question, that would be 358 cubic inches.

To reach 5.8 liters in a modular, takes the newest, most expansive, Ford block-the aluminum unit from the GT exoticar. This, in turn, leads to a host of detail changes in order to use the rather unique GT block in something as mainstream as the '01 Mustang and Performance Automatic C4 automatic combination the Tymenskys are campaigning.

Special details of the GT block are numerous. It is massive, since it's aluminum, and designed for supercharged-duty. That means more numerous and thicker bulkheads-especially across the front and rear of the block-a thicker deck, thick pan rails and so on. The GT engine is dry-sumped, so the oil pan is really just a tray the dry-sump pump immediately sucks oil out of. So the GT oil pan is quite shallow, and oil drain back passages are cast vertically into the block, to lead oil from the cylinder heads directly to the pan, without having to pass the whirling crank and rods. A cast-aluminum windage tray and main bearing stud reinforcement (girdle) are also used.

Now that we've gotten used to Windsor and Romeo modular main bearing retention, now we also find there is the GT arrangement. It's simply steel main bearing caps, tightly fitted to the aluminum bulkheads. They are retained by four vertical studs and two side bolts per cap.

Because it is dry-sumped, the GT block has no drilled or tapped holes for the oil pump. The GT mounts its starter motor on the bellhousing, so there is no starter motor pocket in the GT block.

Then there is the minor matter of obtaining GT blocks. Until now, that would have been impossible for anyone outside of Ford, but John is a Ford engineer-he specializes in powertrain systems and has worked on some rather cool V-10 Mustang projects during his day job. He had his son, Mike, draft a proposal letter that John hand delivered to the Executive Director of Ford Performance Group and to the Director of SVT. To make a long story short, Mike obtained two prototype GT blocks late in the spring of '03. So, the block we're looking at in the photos is not only a fairly rare GT block, it's one of a handful of prototype units. That means large, threaded core plug openings, among other things, but nothing meaningful when it comes to duplicating this engine using a standard GT block.

We're covering the interesting details of working with the GT block in the photos, but for now, we'll note the bore has been resleeved to 3.700 inches, the maximum diameter in performance modular engines. Combined with a stock 5.4 Navigator crankshaft's 4.17-in. stroke, that works out to 358ci. More stroke is physically possible inside the GT crankcase, but we assure you, piston speed is already something X-15 pilots can relate to. In fact, piston speed is the limiting factor in this engine, enough so to relegate it to sprint use at the drag strip with the 9,300 rpm Mike is running.

Other notables of this combination are the original FR500 Four-Valve heads the Tymenskys have run the last four years. They sport 2mm larger exhaust valves, dual springs with dampers (heads modified to accept these), and extensive porting, which includes welding and more grinding. Custom camshafts are also in place, plus a Sullivan carbureted single plane intake manifold that hasn't been port matched well to the cylinder heads. The Tymenskys aren't bothering to match the current heads and intake since the plan is to move to GT heads, which are really '00 Cobra R heads, with a bit more coolant flow around the exhaust port. When those heads go on, the port matching will be spot on.

The engine is wet-sumped, using an Aviad external oil pump, and a real anomaly is the MSD distributor, belt-driven off the front, passenger side of the engine. That, and an 850 Gold Pro Systems carburetor, give a vintage look to what is an otherwise modern hardware package.

At press time, the engine had only seen the Joliet quarter-mile during NMRA action last July. In Mike's 2,850-lb Mustang, it ran 9.57 seconds at 146 mph, right off the trailer. A real wailer, John says the shift light comes on at 8,800 rpm and it goes through the traps at 9,300 rpm. Torque is rated at 560 lb-ft, and the horsepower-well, John would like to get it higher before quoting a figure. When he does, it will be 800-plus.

The real power will come with the GT cylinder heads. Another issue is oiling; the GT drain-back system is limited at these elevated engine speeds, so improvement is taking place there, too. In the meantime, we can all appreciate a tour through this most exotic modular.

Biggest Modular Ever?
After years of dealing with Windsors and 5.0s, we'll admit we have to remind ourselves occasionally, that the Mustang modulars are just 281 cubic inches. Then along come the Tymenskys with their 358-inch modular and we have to remind ourselves that it's a lot bigger than 281 or even 330 cubes. Which got us thinking, is the Tymensky 358-inch modular the largest modular V-8 ever built, or could be built?

No, says John. Randy Haywood, of Super Street Outlaw fame, built a modular measuring 372ci using a 4.400-inch stroke and a 3.572-inch bore, but the combination proved troublesome and isn't running. John also reports the word from modular engine people inside Ford is 385ci is the modular's absolute theoretical maximum displacement. That would be in a 3.700-in. bore aluminum-block with the rods just barely clearing the crankcase, while swinging on a 4.470-inch stroke.

Sounds like Windsors are still safe as the displacement kings of reasonably sized and weighted Ford V-8s.