If you followed last month's basic rebuild, you would've seen how we got to a fully rebuilt long-block for $394. This month, the plan is to build a twin of that long-block. The stock components we intend to change are the heads, the intake manifold, the cam, and the rockers.
The cam we intended to use was one of Comp Cam's XE 270 HR Extreme Energy hydraulic rollers. This cam normally comes on a 112 lobe centerline angle (LCA) and is usually run in conjunction with 1.7:1 rockers. In this instance, it was planned that the stock rockers be changed for a set of Comp's budget nonrail 1.6:1 Magnum rockers (PN 1442-16). Because they're a lower ratio, the cam can use a tighter LCA, so our cam was ground on 110 degrees. Why did we use the 1.6:1 Magnums? The fact that our head choice did not accommodate rail rockers was the prime issue, but additionally, we had some left over from a previous dyno test, and that clinched the deal.
The first move for our power...
The first move for our power upgrade was to strip the previously rebuilt engine down to the short-block; then remove the stock cam in readiness for the Comp Cams cam.
The Extreme Energy cam in conjunction with the 1.6 Magnums does not have so much lift that the depth of the valve notches in the stock pistons cannot be accommodated, but we are making a head change here as well. The heads we intended to use were Edelbrock's Performer RPMs (PN 60259). These have 2.02/1.60-inch valves, and that's a fair amount bigger than the stock valves. As such, the edge of the valve hits the edge of the piston notch, so a fix is needed-other than new pistons. This is where our partner in crime, Dale Sciranko of Custom Performance, comes in. A big part of his business is bolting on parts that make things happen faster for a Mustang.
Sciranko installs big-valve heads onto stock 5.0 bottom ends on a regular basis. To resolve valve clearance issues, he uses a partial cylinder head and a special piston-notching tool that is located in the guides of the partial head. Once the engine is down to the short-block, he can cut suitable valve pockets in less than an hour, even if the engine is still in the car. This was the procedure used here.
Here, University of North...
Here, University of North Carolina at Charlotte student Nathan Bornitz times in the new cam. Because of the near-stock compression ratio, a relatively short duration high-lift profile was chosen. This maintained cylinder pressure.
After our engine was stripped to the short-block, the stock cam was removed and the Comp grind installed. At this point, a timing check was done. Here we made the decision that if the cam was within +/- 1 degree, we would run with it "as is" because our stock (and nonadjustable) timing-chain assembly was in perfect condition. As events would have it, the cam, which should have gone in with the intake centerline at 106, actually delivered 105, so we were good to go.
Using masking tape, grease, and a vacuum cleaner, Sciranko got the job done without getting metal shavings into the rest of the engine. Once the valve notches were done, the timing cover and pan were installed, and we were ready to deal with the next valvetrain issue.
Lifters
Anyone who has tried to extract the most power from a near-stock Mustang valvetrain will have undoubtedly fallen foul to the effects of stock roller-lifter collapse. It would be nice to replace the lifters with some high-performance items, but the budget has already gone for a roller cam.
From this view, the size of...
From this view, the size of the newly cut intake-valve notch can be seen. Custom Performance charges $100 to do this operation-with the engine in or out of the car.
Our tests showed excellent...
Our tests showed excellent out-of-the-box flow for a 170cc port head. Along with that, the swirl was far better than is typically seen with replacement-style Ford heads.
At this point, the timing...
At this point, the timing cover and pan have been reinstalled and the short-block is ready for cylinder heads.
With the Edelbrock heads installed,...
With the Edelbrock heads installed, it was time to address some of the issues the stock valvetrain has when heavier-than-stock springs and more rpm are involved.
The Edelbrock Performer RPM...
The Edelbrock Performer RPM heads exhibit good swirl, which may in part be the result of the chamber shape used.
To turn our street lifters...
To turn our street lifters into race lifters, we modified them to limit the amount of hydraulic travel. This involved removing the return spring and replacing it with appropriate-size washers (arrow). To ensure all this stayed together at high rpm, the wire retainer was replaced with a heavy-duty snap ring.