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.
PARTS FOR VORTEC POWER
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)
The Vortec heads require a...
The Vortec heads require a few different parts to bolt on. The Edelbrock intake manifold uses only eight intake bolts (5/16-18 x 1 1/2-inch long) and a unique gasket. Center-bolt valve covers and self-aligning rocker arms are also needed. Your old spark plugs may not fit either.
The Vortec heads have heart-shaped...
The Vortec heads have heart-shaped 64cc combustion chambers that have a cast-in hump above the spark plug. According to McKenzie's Cylinder Heads, this is a foundry reference point and can be radiused smoothly without hurting power if you're porting your heads.
The combustion chamber's shape...
The combustion chamber's shape and location, and the water jacket layout in the Vortec heads make them compatible with most blocks. Check with SDPC or your Nearest GM Performance Parts dealer (800/577-6888) before installing them on a 400 block.
SDPC machined the Vortec heads...
SDPC machined the Vortec heads to fit a larger valvespring so we could run cams up to .550-inch lift. Stock Vortec heads can only take about .460-inch lift.
Both Fel-Pro (PN 1255) and...
Both Fel-Pro (PN 1255) and GM (PN 12529094) make intake gaskets to fit the Vortec heads and we know for a fact that the GM gaskets are reusable because we've had the manifold on and off about 10 times without a leak from the same pair of gaskets.
We used a set of Mr. Gasket's...
We used a set of Mr. Gasket's MLS (Multi-Layered-Steel) head gaskets to seal the Vortec heads. So far, we're very satisfied with their performance.
Edelbrock offers both a Performer...
Edelbrock offers both a Performer Vortec (PN 2116) and a RPM Air Gap Vortec (PN7516) manifold, which is the intake we ran. It's important to note that while the Performer Vortec manifold will accept either a Q-jet or a square-flange carb, the Air Gap Vortec will only fit a square-flange.
The Vortec heads require self-aligning...
The Vortec heads require self-aligning rocker arms, so we installed a set of COMP Cams roller-tip Magnum rockers (1.6: ratio, PN 1418-16) for the test. Notice that we coated them with COMP's break-in lube so they'll be well oiled upon startup.
We also tried a set of 1.52:1...
We also tried a set of 1.52:1 Magnum roller tip rockers from COMP (PN 1417-16). This combination made a little less power.
There are several valve cover...
There are several valve cover options for the center-bolt style Vortec heads. These are the least expensive, factory-stamped-steel covers from GM. Not as good looking as the Proform covers you'll see in the lead photo of this story, but they're also less expensive.
For this dyno test we thought we could do a little better by installing a set of Vortec cylinder heads and trying COMP Cams Magnum roller tip rocker arms. Our 355-cid small-block clocked in at 422 peak hp and 452 lb/ft of torque. Average horsepower and torque were at 339 and 426, respectively.
GM four-bolt, 355-cid, 9.4:1 compression, GM Vortec iron heads (SDPC PN SD8060A, 64cc chambers, 170cc intake runner volume, 1.94/1.50 valves), COMP Cams 1.6:1 Magnum roller tip rockers (PN 1418-16), Edelbrock RPM Air Gap Vortec intake manifold (PN 7516), Speed Demon 750 carb, 1-inch open carb spacer, COMP Cams XE262H cam (262/270 adv duration, 218/224 duration at .050, .462/.469 valve lift, 110 lobe separation) straight up, 1 /34-inch Hooker headers, 91-octane Shell Unleaded fuel
|VORTEC POWER |
|355-cid VORTEC SPECS |
|Bore / Stroke / CID:||4.030 / 3.48 / 355 cid |
|Block:||GM factory four-bolt 350 |
|Crank:||SCAT cast-steel PN 1101-11133 |
|Pistons:||Probe forged (PN 130212334-030) |
|Rods:||Probe (PN 1201-10062) 5.7" |
|Rings:||Total Seal Moly |
|Gaskets:||Mr. Gasket and GMPP |
|Cam:||COMP Cams (XE262H) 218/224 at .050, .462/.469 lift, 110 LS |
|Lifters:||COMP (PN 858-16) |
|Chain:||COMP (PN 2100) |
|Pushrods:||COMP (PN 7372-16) |
|Rockers:||COMP 1.6:1 (PN 1418-16) |
|Heads:||GMPP Vortec (Scoggin-Dickey PN SD8060A) |
|Manifold:||Edelbrock Performer RPM Air Gap (PN 7516) |
|Carb:||Demon (PN 1402010VE) |
|Distributor:||Pertronix (PN D1000) |
|Spark Plugs:||Autolite AR103 |
|Oil System:||Milodon HV (pan PN 31505) |