Our test subject is a '99 GT that's had a few upgrades, mostly intake and exhaust mods, an
Horse Sense: Trick Flow is full service when it comes to gear. Not only does the company address modulars, but it now offers a line for the ever-popular Cleveland engine family.
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.
Here's the mandatory before photo. Other than a cold-air kit, short-tube headers, and an u
To make the process easier, Custom Performance drops the entire engine and K-member out of
After dropping the engine onto four jackstands, mechanic Jon Wilburn begins by removing th
With the cam covers out of the way, Wilburn does a quick check to make sure everything has
Before pulling the heads it's a good idea to remove the followers, and this is one instanc
Here's another look at getting the followers out. Once the tool has the valvespring compre
The next step to getting the heads off is to pull the front cover, but before you can do t
Jon pulls the tensioners and timing chains. If your engine is still relatively fresh, set
If you are going to reuse your camshafts, go ahead and pop the cam caps off and pull the c
Here's a look at the combustion chamber for the stock two-valve cylinder heads. Notice how
Now compare that to the Twisted Wedge combustion chamber. The intake valve has been moved
If you purchase the cylinder head assembled, it arrives with stainless steel valves and re
Trick Flow sends two identical cylinder heads. Here, Jon marks them for the left and right
You can see the NPT plug that has already been installed in the upper lefthand corner of t
This one isn't a necessity, but Jon has found it is easier to install headers on the cylin
Here, you can see that tight fit as Wilburn lowers the head into place. We're using BBK 1-
The head gasket is a multi-layer steel unit chosen for its superior sealing ability. We so
The stock head bolts are torque-to-yield and cannot be reused. You can get stock replaceme
New lash adjusters are soaked in oil before being dropped into place. The Trick Flow heads
The two-piece cam towers are made of powdered metal. The caps are numbered so when removin
We went to Comp Cams for a recommendation on the best cam profile to Match the Trick Flow
Starting at the center of the head and working out, the cam caps bolt back in place by tor
Again, since you have the motor opened up, it's probably a good idea to go ahead and repla
Setting the timing on a Two-Valve motor is relatively easy. The timing chain has two black
Here's the completed timing set with all the new pieces in place.
Installing the followers is a lot easier than removing them. Just place the follower under
With the followers in place, the valvetrain is complete.
Now that the valvetrain is finished, Jon dropped the valve covers back into place. To make
This customer chose to swap out the stock intake for a cast-aluminum intake from Professio
Here's the completed engine back in the engine bay. One final change is the addition of a
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.