I have learned to be cautiously pessimistic about dyno results. It is human nature, especially in this hobby, to make predictions about what sort of power your car is going to put down on the dyno. Yet having been dissapointed by the big red rollers more often than not, I have trained myself to guess low, and therefore leave the shop with, hopefully, better than expected numbers. It's pathetic, but it spares a lot of heartbreak when you make 50 horse less than you boasted to your buddies!

When it came time to get our 5.0L, ala AFR 165 heads, to the dyno, I played the same mind game on myself. However before I reveal my predictions, let's go over what got us to this point.

A while back we reviewed and flow tested AFRs 165cc small block Ford (SBF) cylinder heads. These were actually one of the few heads we were not able to test a few years back when we performed our major show down of SBF heads. As anticipated the AFR heads were serious contenders. If one discounts the Trick Flow head's larger intake runner and valve, and revised valve angles, the AFR head is the clear king of the street-head mountain, at least in the cfm category. At .500" lift the heads flowed 238 cfm on the intake side and 182 cfm through the exhaust. However in typical FM fashion we're after true gains on real world Ford muscle cars. The meant an obligatory dyno test with the heads installed on a test vehicle.

We decided to put the heads on a relatively stock 5.0L engine. FordMuscle has a new project car in the stable, the authors own 1993

FM's latest project car will receive the AFR heads.
Cobra (see '93 SVT Cobra in the Project Cars section.) The rare first year SVT snake was procured in bone-stock form, with 82,000 ticks on the odometer. The 5.0L Cobra motor is a about a 25 horsepower bump up from the stock 5.0L HO Mustang motor. The gains are largely attributed to the iron GT40 cylinder heads. Ford also modified the cam, used 1.7:1 rocker arms, and tweaked the air-fuel delivery to match. In stock form these cars put out roughly 220 horsepower at the rear-wheels. The challenge then would be to bolt on nothing but the AFR 165 heads and see what results.

To get a true understanding of the capabilities of these well touted heads, we installed the heads with the stock '93 Cobra camshaft. The

A ported Cobra lower intake was sought out to help match the larger intake runners of the AFR 165cc heads.
cam specs are roughly 210 degrees duration and .479" lift with the factory 1.7:1 Cobra roller rockers. We did retard the cam four degrees to move the power band up slightly and take advantage of the high-lift flow potential in these heads. The other changes to the engine are a ported Cobra lower intake manifold, underdrive pullies, and a larger mass air and throttle body. The exhaust on the car consists of shorty headers and a Mac Prochamber h-pipe running through the stock mufflers.

We installed the heads over a weekend without any major glitches. The AFR heads, in addition to being well designed, are truely a bolt-on head. We had no intake or exhaust manifold alignment issues. All that was required were a set of new, hardened, pushrods in the stock length. A couple weeks later we had the car to the dyno.
(Dyno Results)
In This Article:
With the AFR 165 heads proving themselves on the flow bench, we decided to install the heads on a 1993 Mustang Cobra motor, with no other major changes. The car is then tested on a chassis dyno.

Also See:
Part One: Flow Testing AFR's 165cc Head

Our AFR 165cc heads are set up with 1.90"/1.60" valves, 59cc combustion chambers, dual springs, and 7/16" studs.

The stock '93 Cobra GT40 heads are removed, note the factory equipped 1.7:1 pedestal mount rockers.

The heads are torqued down, and new Crane 1.7:1 stud mount rockers are installed with hardened pushrods.

The stock Cobra cam is left in place but retarded 4 degrees. The lower intake is ported to match the FelPro 1250 gaskets.

Hedman shorty headers replace the restrictive stockers.

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