Muscle Mustangs & Fast Fords
The Four-Valve Swap Power Struggle Upgrade Part 2
Our Quest For Reliable 9-Second Timeslips From Our Modular Powerplant Continues.
Last month we presented Part 1 of this Two-Valve to Four-Valve modular engine swap on our '01 Bullitt Mustang. Our quest for a reliable engine combination that can push our SN-95 Mustang into the 9-second zone culminated in swapping the Mustang's high-strung 5.0L Two-Valve stroker for a tamer but better prepared Four-Valve 4.6L engine.
We left off with the long-block sitting in the engine bay. This month, we put the finishing touches on the little cammer. There were many roadblocks along the way before we turned the key for the first time, mostly due to the fact that we had started with not only a Two-Valve car, but a Bullitt at that, which has a number of model-specific parts that we needed to either swap out or modify to work.
Giving us the room to work, the lift to raise, and the tools to tighten was HP Performance in Orange Park, Florida. Our subject car has spent its fair share of time turning the company's Dynojet rollers, and it would soon be turning them again once we fired up the new modular mill.
In preparing the new engine assembly for installation into the Mustang, we discovered the SFI flexplate shield, which fit perfectly with the BC Automotive 4R70W automatic and the Two-Valve, now had a clearance problem with the new Four-Valve motor. It interfered with the lower outside area of the driver-side head. Though not technically SFI approved, the shield was notched a bit to provide the needed clearance.
"We've discovered over many installations of the Two-Valve motor and fighting the head gasket issues that it is much easier to remove and reinstall the motor from the bottom of the car," says Watson, "especially with an automatic transmission attached." Watson's wife, Wendy, came up with the idea of wrapping the engine in bubble wrap before installation. If you've done some painting while the motor was out--whether it was the engine or the engine bay or both that you painted--the bubble wrap can keep things pretty with its early warning system. Anytime something gets close to touching, the bubble wrap pops; you can stop and figure out the clearance problem.
Fine-Tuning The Fitment
At the time of the install, we decided to eliminate the connection to the heater core to improve engine coolant flow and to make more room for the larger fuel lines needed to run at the back of the engine. We used a preformed 90-degree-bend heater hose attached to the water connection on the back of the passenger-side head, and then used a reducer to connect the hose directly to the valley water tube eliminating the heater core in the loop.
Many subscribe to the modular motor cooling mod--adding an additional connection on the rear of the driver-side head, and routing the coolant to either the front crossover or to the inlet of the heater core. Our engine builder, Al Papitto of Boss330 Racing, doesn't believe there's much advantage to this mod on a Four-Valve. Papitto says the cooling mod is probably more useful on Two-Valve motors, which are more prone to detonation and would benefit from the better cooling in the rear cylinders.
One of the main concerns with this swap was hood clearance, as the short-runner intake we were employing utilized a 1-inch spacer between the upper and lower intake manifolds to maintain plenum volume on the modified straight-runner intake. It was a great relief when we were able to close the stock Bullitt/GT hood over the installed intake manifold, but we did have a problem after installing the throttle-body bracket on top of it.
Normally there are two cables attached to this bracket: one for the throttle and one for the cruise control, whose position is higher on the bracket. The hood just touched the top of the bracket where the cruise-control cable normally attaches. We could have ground off some of the top of the bracket, but since we weren't going to use the cruise control anyway, we just removed the entire area. The bracket looked better without the unused hole anyway.