Tech Article: Mustang Power-Up!As featured in 2014 NZV8 magazine. Text by John Mincham & Todd Wylie. Photos by John Mincham
After selling a more powerful car, a near-stock 302 Windsor was never going to cut it for this Mustang’s owner.
The owner of this 1966 Mustang is a Ford man at heart, but he is also the first to admit that his old 350 Chev-powered Capri had a whole lot more power than his recently purchased Mustang.
When he bought the car, it came complete with a ready-to-run MSD distributor and Quickfuel Slayer carb mounted on an Edelbrock Performer RPM manifold. Even with these parts, the car still had very noticeable flat spots in its power delivery and generally wasn’t running right.
The first step in the path to automotive happiness for the owner was to get the car running properly, then see if this offered enough performance to satisfy him. With the parts already fitted, there was no reason for it to be running as it was — apart from a lack of tuning.
Thus, the team at Magnum Automotive was called upon, not only for its expertise, but also because of its in-house rolling-road dyno, which makes tuning a car under real-life driving conditions far simpler.
With the car strapped to the dyno, and a few baseline tests carried out, what the owner could feel was confirmed: power delivery was anything but linear.
Those noticeable holes in the vehicle’s power were simply caused by a lack of tuning. With some simple adjustments of the carburettor and adjustment of the timing to an optimal 32 degrees, the car not only ran smoothly but produced an almost respectable 202hp at the wheels at 4400rpm.
The owner took the car for a test drive and was happy with the smoothness of the engine, but unhappy with the overall performance. The car still needed more power!
With the MSD ignition, Slayer carb, and Edelbrock intake previously fitted, the decision was made to fit a set of CNC ported AFR185 heads. To make the most of the highflowing heads, a retrofit-style hydraulic roller cam would also be fitted.
While the heads chosen were a touch on the large side, with their 2.02-inch intake valves, 1.60-inch exhaust valves, and 58cc combustion chambers, the owner has made murmurs of a 347ci stroker build somewhere in the future, so the heads were decided to be a good overall compromise between now and later.
The car was once again dropped off to Magnum, and the engine was completely removed from the vehicle. This is not always required for a cam change, but, due to the fact that the heads were coming off, the block needed to be modified for the retrofit hydraulic roller lifters, and the torque convertor was going to get a rebuild at the same time, it was decided this would be the most costeffective way to approach things.
The engine was put on a stand and some basic checks were performed. With the rocker gear removed, the
engine was given a cylinder leakage test to check ringseal condition. Thankfully, it passed with flying colours.
The heads, front of the engine, sump, and camshaft were all removed from the engine block. The block was then carefully drilled to accept the hydraulic lifter plate, with great care taken to remove any metal filings. The new Comp Cams Xtreme Energy XR276RF cam was then installed and the cam timing checked and adjusted to the manufacturer’s specifications.
With the cam in, the team could focus on the heads, which were cleaned and checked before being dummy
assembled on the engine. With the new set of Comp Cams roller rockers fitted to the heads, the pushrod
length was determined (see ‘Calculating Pushrod Length’ sidebar), then the piston-to-valve clearance was checked. It was found that the exhaust valve had plenty of clearance, but the intake valve was in trouble, hitting the piston at the valve-relief eyebrow. This meant that the valve pocket had to be opened up to get the desired piston-to-valve clearance (see sidebar).
With the pistons returned with their newly modified tops, the piston-to-valve clearance was double-checked on all cylinders, just to be sure that there was now sufficient clearance. Once it was determined that the clearancing had worked, the heads were installed for the final time, using the
correct 7⁄16-inch to ½-inch washers and new ARP head bolts.
The rest of the engine could now be reassembled and fitted with the modified torque converter from
Auto Trans. While the converter could have been left alone, it made sense to get it modified at the same time. The new cam’s rev range is 2200rpm plus, so the converter has been set to lock at around that same rpm level.
After being plumbed up, the engine was started and taken through a minor break-in process. Although it is a roller cam set-up, it is still worth being careful with the first half-hour running and to change out the oil and filter almost straight away.
With the run-in procedure done, the oil was drained and filter cut open to check for any metal filings or signs of undue wear. All was well, so the car was refilled with oil and once again strapped to the dyno for tuning.
TECH-TIP: Calculating Pushrod Length
To check for proper pushrod length, all you really need is a black felt-tip marker and a few tools. Simply take off a valve cover and rotate the engine until the rocker arm of your choice is on the base circle of the lobe. Loosen and remove the rocker arm. Clean the top of the valve-stem tip and then paint the tip with the black marker. Place the rocker back over the stud and adjust to correct valve lash. Then rotate the engine two complete revolutions. The rocker will then have left a witness mark on top of the valve tip.
If the pushrod length is correct, the witness mark should be located on the inboard third of the valve-stem tip. If the witness mark is too close to
the intake side of the valve-stem tip, the pushrod is too short. If the witness mark is in the middle or towards the exhaust side of the valve-stem tip,
the pushrod is too long.
With the timing needing adjustments to suit the new camshaft, and the carburettor needing both air and
fuel adjustments, a final power run was conducted. The results were a major increase in power throughout the entire rev range, with an increase of 60hp at 4500rpm through to a peak of 279hp at 5800rpm. That’s a 40–per-cent increase in power from a simple head-and-cam swap, and one seriously happy Mustang owner!