Two-Valve 4.6 Head, Cam, and Intake Upgrade - Twisted Deuce
Revving up a Two-Valve 4.6 with a head/cam/intake upgrade
From the June, 2011 issue of 5.0 Mustang & Super Fords
By Jeff Huneycutt
Our test subject is a '99...
Our test subject is a '99 GT that's had a few upgrades, mostly intake and exhaust mods, and produces peak horsepower and torque numbers of 263.5 and 299.9, respectively.
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...
Here's the mandatory before photo. Other than a cold-air kit, short-tube headers, and an underdrive pulley kit, everything is still stock (and dirty).
To make the process easier,...
To make the process easier, Custom Performance drops the entire engine and K-member out of the car. It's only a little more than an hour's worth of work to get to this point (and from our standpoint, it makes photography a lot better), but if you don't have the luxury of a lift, you can do everything you see here with the engine still in the car.
After dropping the engine...
After dropping the engine onto four jackstands, mechanic Jon Wilburn begins by removing the accessory drive system, intake manifold, and everything else that will get in the way of pulling the heads.
With the cam covers out of...
With the cam covers out of the way, Wilburn does a quick check to make sure everything has been running correctly without damage before removing the cam and followers. This is especially important if you will be reusing any of these components.
Before pulling the heads it's...
Before pulling the heads it's a good idea to remove the followers, and this is one instance where having the correct tool will definitely make your life easier. You can get by with a big screwdriver, but you're far more likely to end up gouging either a follower or a cam lobe or even hurting yourself. This is a valvespring compressor tool from Ford that makes the job a breeze.
Here's another look at getting...
Here's another look at getting the followers out. Once the tool has the valvespring compressed, the follower drops right out.
The next step to getting the...
The next step to getting the heads off is to pull the front cover, but before you can do that, you will have to get the harmonic damper off. This is one area where it's definitely nice to have the engine out of the car.
Jon pulls the tensioners and...
Jon pulls the tensioners and timing chains. If your engine is still relatively fresh, set these components aside for reinstallation later. But if they've already seen their share of miles, now is a good time to install new ones for peace of mind.
If you are going to reuse...
If you are going to reuse your camshafts, go ahead and pop the cam caps off and pull the cams. We're using all new valvetrain components, so Jon leaves the cams in place while removing both heads.
Here's a look at the combustion...
Here's a look at the combustion chamber for the stock two-valve cylinder heads. Notice how the intake and exhaust valves are in line and the chamber is relatively open.
Now compare that to the Twisted...
Now compare that to the Twisted Wedge combustion chamber. The intake valve has been moved to the opposite side of the chamber and is now oriented so that air flowing through the intake port has a straighter path into the cylinder. The new chamber design also allows for a large 1.840-inch intake valve without requiring a new piston or boring the cylinders. The exhaust valve is 1.450 inches. Finally, Trick Flow offers this head with two different combustion chamber sizes. This is the smaller 38 cc chamber, but if you plan to add a turbo or supercharger, you may want to consider the 44cc chambers.
If you purchase the cylinder...
If you purchase the cylinder head assembled, it arrives with stainless steel valves and retainers. The springs are 0.940 of an inch in diameter for the intakes and 1.050 for the exhausts, and can handle up to 0.600-inch lift.
Trick Flow sends two identical...
Trick Flow sends two identical cylinder heads. Here, Jon marks them for the left and right side of the engine. The recessed side of the head points forward on the left side, while the flat end of the head points forward on the right. Which side of the engine the head will wind up on determines where certain plugs need to be installed.
You can see the NPT plug that...
You can see the NPT plug that has already been installed in the upper lefthand corner of the deck. The heads also have an oil gallery to feed pressurized oil to the cam journals and requires the installation of six plugs to seal off.
This one isn't a necessity,...
This one isn't a necessity, but Jon has found it is easier to install headers on the cylinder heads before bolting them to the block because of the tight fit between the sides of the block and the upper K-member.
Here, you can see that tight...
Here, you can see that tight fit as Wilburn lowers the head into place. We're using BBK 1-5/8-inch longtube headers for this project. The headers will slide into place with the cylinder heads already bolted onto the block. Once they are there, it's really difficult to access and tighten the bolts on the header flange.
The head gasket is a multi-layer...
The head gasket is a multi-layer steel unit chosen for its superior sealing ability. We sourced this one directly from Ford Racing Performance Parts.
The stock head bolts are torque-to-yield...
The stock head bolts are torque-to-yield and cannot be reused. You can get stock replacement head bolts from Ford Racing Performance Parts or your local dealership, just make sure to follow the directions carefully. Usually the process is to torque all the bolts to 35 lb/ft, turn all the bolts 90 degrees, and then turn all the bolts 90 degrees again. If you plan to make more modifications to the engine and might be taking the heads off in the future, it's usually worthwhile to invest in a set of reusable head bolts from ARP.
New lash adjusters are soaked...
New lash adjusters are soaked in oil before being dropped into place. The Trick Flow heads maintain all the standard dimensions, so stock components work as they should without modification.
The two-piece cam towers are...
The two-piece cam towers are made of powdered metal. The caps are numbered so when removing and reinstalling them, make sure they always go back on the correct lower section. The cam cap sections are machined in matched sets, so switching them can affect cam clearance. Before installing the cams, coat the housing bores with assembly lube.
We went to Comp Cams for a...
We went to Comp Cams for a recommendation on the best cam profile to Match the Trick Flow heads, and this is what the company sent us. These cams feature 0.545 inches of total valve lift, 242/246 degrees of duration at 0.050-inch lift, and a 109-degree intake centerline.
Starting at the center of...
Starting at the center of the head and working out, the cam caps bolt back in place by torquing the fasteners to 150 in-lb. After the caps are torqued in place, the cams should still rotate freely.
Again, since you have the...
Again, since you have the motor opened up, it's probably a good idea to go ahead and replace a few select components if your engine has some miles on it. Wilburn takes advantage of the opportunity to replace the timing set with new components from Cloyes, including the timing chain guides and tensioners.
Setting the timing on a Two-Valve...
Setting the timing on a Two-Valve motor is relatively easy. The timing chain has two black links; when you line them up with the dots on the sprockets on the camshaft and crank, you know the cam is timed correctly. In this photo, the dot on the crank sprocket is pointed to the 6 o'clock position, while the cam sprocket is at 12.
Here's the completed timing...
Here's the completed timing set with all the new pieces in place.
Installing the followers is...
Installing the followers is a lot easier than removing them. Just place the follower underneath the cam lobe and use a large-bladed screwdriver to pull it into position.
With the followers in place,...
With the followers in place, the valvetrain is complete.
Now that the valvetrain is...
Now that the valvetrain is finished, Jon dropped the valve covers back into place. To make life easier, Trick Flow taps extra holes in these heads so that they will work with the valve covers from either Windsor- or Romeo-style modular engines.
This customer chose to swap...
This customer chose to swap out the stock intake for a cast-aluminum intake from Professional Products. We had hoped to compare both intakes on the dyno but ran out of time before it was time to deliver the finished car.
Here's the completed engine...
Here's the completed engine back in the engine bay. One final change is the addition of a cold-air intake. Also, sharp eyes may notice the Zex nitrous kit. Don't worry-we didn't cheat. The bottle wasn't attached for these dyno pulls.
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.