Testing engines is like running a marathon. There are some spots where you're way behind and there are others where you're pulling ahead. But, the race is almost never done.

The race to make more from less with normal pump-gas engines is becoming increasingly harder to run. A lot of the difficulties come from finding a set of cylinder heads that'll make power but not break the bank. For ideas, we dove into our ever-enlarging pile of readers' letters to find out which set of heads they'd most like to see bolted on next. The clear winner in the iron head category was GM's Vortec, receiving more than 10 percent of the total votes. We know that the Vortec is a good head design, and it didn't take us long to make our decision.

GM has really hit the nail on the head with its iron Vortecs. But unlike so many other replacement cylinder heads on the market today, the Vortecs require some different parts to bolt them on. It would seem at first glance that for the power they make, the Vortecs might be the best set of heads on the market. And that's not too far off the mark, except there's a catch, and like most good things in life, the extra power isn't free. While it's true that the Vortec castings will bolt right onto your favorite old small-block, just about everything else connected to them will have to be changed to make the engine run again. And the cost of all those changes can quickly add up. Basically, if you're building a new engine and don't have any top-end components yet, then the Vortec heads and all of their related components will be well worth the investment.

Starting from the top and working our way down, the Vortec heads require a different intake manifold, intake gaskets, intake bolts, valve covers, gaskets, and bolts, unless you already had center-bolt valve covers. The Vortec heads will also require new rocker arms, unless you were already using the self-aligning-style arms, and chances are really good that your old spark plugs won't fit either, so you'll have to buy a new set of those, too. The good news is that your exhaust should bolt up without a problem and you can reuse your same distributor. If you're running a Q-jet carb, it may also have to go depending on which intake manifold you choose to run. The Edelbrock RPM Air Gap Vortec manifold we ran is only offered in a square-flange design. Edelbrock offers its Performer Vortec intake with a Q-Jet pattern, but that manifold might not produce the same power we saw in our tests.

Then there's the matter of choosing the proper set of Vortec heads for your application. GM actually offers only one set: PN 12558060 (Scoggin-Dickey Performance Center-SDPC), so you'd think selecting the proper heads would be quite easy, but GM's ready-to-run assemblies will only take a cam up to about .460 lift before you run into trouble. If you want to run a cam with more lift (as we did), you'll have to machine the spring pockets in the heads, cut down the valve guide bosses, and install larger springs. The set of heads we installed from SDPC (PN SD8060A) came with bigger springs and all the required modifications and can safely take cams up to .550 lift.

So, add it all up and there's no denying the power potential of the complete package once you've bolted those Vortec heads in place.

Vortec heads PN SD8060A: (Two needed)

Edelbrock manifold PN 7516

Valve cover gaskets PN 10046089 (Two needed)

Center-bolt valve covers PN 12555270, 12555271:(One each)

Valve cover bolts PN 12338092 (Eight needed)

Oil fill cap PN 10108650 (One needed)

Intake gaskets PN 12529094 (One needed)

Comp Cams 1.5:1 rocker arms PN 1417-16 (One needed)

Intake bolts 5/16-18 x 1 1/2-inch: (Eight needed)