For any application where...
For any application where over-the-nose spring forces are below 350 pounds, the Comp Cams Magnum roller-tipped rockers are a reliable and cost-effective choice.
This being the case, we will have to perform a fix that will allow the stock lifters to do the job of opening and closing the valves without suffering any collapse. The technique here is to turn the stock hydraulic roller lifter into a hybrid solid/hydraulic or a "solidraulic" lifter. The first move is to strip each lifter separately so as not to get the plungers mixed. Once stripped, discard the lifter's preload spring. Also, you will not be using the stock wire retaining clip. Instead replace this with a snap ring (NAPA has these). Next, find some washers (32) that have an outside diameter (OD) less than the body but that fit over the smaller central diameter. Also, the thickness of the washers needs to be such that you can make up a stack between0.100 and 0.110 inch thick. When the lifter is reassembled, it will have a stroke of only 0.010-0.020 inch. This will limit the amount of collapse that can take place. Do not fill the lifters with oil as this will make adjustments more difficult to do later.
The first operation towards...
The first operation towards making something of the GT-40 intake is to weld up the casting over the top corners of the runners as seen here. This allows the runners to be ported to a much more efficient shape for flow.
Cylinder Heads
We-the University of North Carolina at Charlotte (UNCC) students and your author-scoured various sources of ads for a set of used heads, and though we have seen them advertised in the past, nothing came up when we needed them. This meant going with a new set, and a pair of Edelbrock Performer RPM heads were acquired.
If you're following this build, you will realize that for a low-buck team, this is a big chunk of change even at the discounted price of $1,080 from Jegs. But even in "out of the box" form, our past tests have shown they represent a potentially large chunk of power for the money invested. Featuring 2.02/1.60 valve diameters, 170cc intake ports and 60cc chambers, these heads represent a large increase in airflow over even the pocket ported heads we had for Part 1 of our budget build series.
The only aspect that is not quite where we want it is the compression ratio. With the valve cutouts and the 60cc chambers, our project engine's compression ratio (CR) works out at 9.1:1. This means we can probably run intermediate-grade fuel even while racing. We didn't intend to sweat the issue of a slightly lower CR because Phase 2 for this motor was to port the heads (they port out easily, with excellent results) and use a set of higher-compression pistons. What these heads offer is not only plenty of flow for 302 inches, but also good port velocity and some way-better-than-average swirl.
Just by skinnying down the...
Just by skinnying down the throttle shaft and knife-edging the butterfly, the flow of the factory throttle body climbed from 495 cfm to 520.
Valvetrain Potential
There's little point in having a good set of heads if the valvetrain is severely lacking in capability. In the past, a cost-effective choice with which to replace the stock rockers has been Comp Cams' stainless Magnum roller rockers. Not only are they near bulletproof, but they also have shown respectable power increases over the stock items. On an engine with mildly ported heads and a slightly hotter-than-stock cam, our dyno tests have shown an 8hp increase at peak and as much as a 16 hp increase at about 700 rpm past peak. These past performances and the low price made the choice of rockers an easy one.
Induction System
The system we ended up with on our engine was the Ford Racing Performance Parts GT-40 setup. Fortunately for us, the guy we bought it from was unimpressed with it and used it for only a week before replacing it with a more effective intake. That's how we got it (plus some other minor bits and pieces) in nearly new condition for $380.
Here is how the finished runners...
Here is how the finished runners looked. Flow capability was improved measurably even for the straighter runners as seen here.
The EGR spacer was modified...
The EGR spacer was modified so that its only function was to be a spacer as opposed to an EGR exhaust passage to the intake. We used epoxy to plug all the unwanted holes/passages (arrow).
Here's the engine so far....
Here's the engine so far. The intake is installed and valve covers are on. Be aware that valve covers for carbureted engines have an oil-filler cap that gets in the way of the GT-40 intake plenum. Stock valve covers will work.