Two-Valve 4.6 Head, Cam, and Intake Upgrade - Twisted Deuce

There’s no doubt that when Ford added the modular engine to the Mustang lineup in 1996, it was a significant technological advancement over existing pushrod engine designs. However, it also definitely had its limitationsprimarily the inability to breathe properly in high-horsepower applications.

To put it bluntly, the Mustang GT cylinder heads just weren’t up to par. Ford made improvements with the Performance Improved heads beginning in the ’99 model year, but the real power gains weren’t made until the Three-Valve cylinder heads were introduced, allowing the 4.6-liter engine to ingest some serious air.

The Two-, Three-, and Four-Valve heads all bolt to the same block, but switching to the better performing Three- and Four-Valve cylinder heads also requires new camshafts, timing chains, a front cover, and more. And as you can guess, all those extra parts quickly add up to lots of extra money. Or there’s the option of having the stock Two-Valve heads ported, but we don’t have to tell you the cost typically involved in that.

Now Two-Valve Mustang owners have a new option that makes great power gains without breaking the bank. We’ve gone years without an aftermarket Two-Valve cylinder head option, but Trick Flow has changed all that with the introduction of its Twisted Wedge Street/Strip Two-Valve aluminum heads.

The Trick Flow heads are no small change from the stock Ford heads. In case you haven’t seen our other tests, the main feature is a revised intake valve location that puts the valve on the opposite side of the camshaft. Having the valve in the correct orientation with the intake port not only helps greatly improve flow, it also improves clearance between the valve and both the piston and the cylinder bore. This allows a larger intake valve (hence, even more flow) without having to cut large valve pockets in the pistons or boring out the cylinder block.

Despite the revised valve location, Trick Flow’s Twisted Wedge heads practically bolt right up to all the Modular engine’s stock components. So, if money is tight, you can reuse the stock timing chains, tensioners, camshafts, intake, exhaust, followers, lash adjusters, and even the valve covers. By not having to replace all the other odds and ends that are usually part of a head swap, it helps make the economics of bolting up a new set of these heads a lot more palatable.

Like you, we wanted to know just what was possible with these heads when they are part of a well-thought-out package. What if we added a pair of cams that have been ground to take advantage of the extra airflow with these heads? And, of course, we’d need a good set of headers to take the burnt gasses back out.

We hit the jackpot when Dale Sciranko of Custom Performance told us he had just such a project going together. The car is a ’99 GT already equipped with a cold-air kit, short-tube headers, H-pipe, and an underdrive pulley kit. As soon as the car arrived in the shop, Dale put it up on the chassis dyno for a baseline. The results were 263.5 hp at 5,100 rpm and 299.9 lb-ft of torque at 4,000 rpm. From there, it was time to tear into the car and get going.

Thankfully, the entire project was a bolt-on affair. You will notice we dropped the engine and K-member out of the car, which makes working on the engine and getting good photography easier, but it isn’t necessary. Everything except for the dyno tuning which is necessary because of the engine’s greatly increased ability to ingest air, can be done in your driveway. If you have all of your parts on hand, a skilled mechanic can perform the swap in a day, but the rest of us will need to allow a weekend to get everything done.

On the Dyno

On the dyno the new combination moves peak power up to 6,300 rpm and bumps it up over 80 hp. Where the power flat-lined before at 4,500 rpm before because the stock heads simply ran out of breath, now the power keeps climbing right up to 6,000 and beyond. The peak torque number is only improved by 18, but it’s what this combination does to the torque curve that’s impressive. Torque is better than the stock configuration from 4,000 rpm onsometimes by as much as 80 lb-ft.