Picking a cylinder head for...
Picking a cylinder head for your latest project motor really is a tough, somewhat confusing situation. With prices ranging from hundreds to thousands of dollars, slick advertising talk skewing the facts, and little to no reliable independent testing, it is no surprise that people end up with some pretty wacky combinations.
With head technology constantly evolving and a fiercely competitive market always pushing development, it is time we sat down, built a nice short-block, and put them to the test. It is important to note that, while tempting to name a winner, each head in this particular test has its advantages and disadvantages. While peak horsepower is important, we recommend you also look at your specific goals, budget, and future modifications before picking a cylinder head. Much like life, it is important to figure out what is best for you and go from there.
The Test
For this test, we turned to our friends at Golen Engine Service in Hudson, NH, to help us build and dyno each combination. Based on what most people would build, we assembled a mild 383 LT1 capable of making good, streetable power on pump gas. With a target compression of 11:1 we had each head decked to 54-55 cc combustion chambers. Since this was going to be a street engine, Comp Cams sent us a very mild 280XFI camshaft, which features 230/236 degrees of duration, 0.576/0.570-inch lift with 1.6 ratio rocker arms on a lumpy 113 LSA. We felt that most of these heads would do quite well with this camshaft, and with a group average of 495.4 hp, we were quite impressed. All of the heads, except for the Edelbrock RPM Xtreme LT4, were tested using a hand-ported LT1 intake manifold. Chad Golen has perfected the art of the LT1 manifold and feels it offers a great upgrade to any performance LT1 build. The Edelbrock heads were tested using the excellent Air-Gap LT4 manifold, since they ship port-matched to the much larger raised-runner LT4 race port intake manifold gasket. To make all of this happen, you need a lot of gaskets and we thank Fel-Pro for coming through with five sets of head and intake manifold gaskets. Without these, we would never have been able to complete such a test. With the engine assembled and bolted to the dyno, we will let the heads do the rest of the talking.
All testing was done with 38 degrees of timing, 43.5 lbs of fuel pressure, Standard correction, and a consistent 12.5-13.0:1 air/fuel ratio. Had we chosen to adjust timing for the differences in each head, most likely we could have increased peak outputs, but would run the risk of human error. A variable we, instead, chose to keep constant.
The engine for this test is...
The engine for this test is an 11.1:1- compression, mildly cammed, 383-cubic-inch LT1 built by Golen Engine Service. A Comp Cams 230/236 duration, 0.576/0.570- inch lift, 113 LSA camshaft is our constant, with each head acting as the sole variable.
The Edelbrock LT4-style intake...
The Edelbrock LT4-style intake (PN 7109) was only used on the Edelbrock heads due to the large LT4 race port gasket matching provided by Edelbrock. Out of the box, this is an excellent intake, which is nicely finished and ready to bolt right on. And it sure beats spending over a grand on eBay for the now out-of-production GM LT4 intake.
Starting with a stock LT1...
Starting with a stock LT1 intake manifold, the masters at Golen Engine Service have several tricks to porting these units.
Using a Bridgeport, they first...
Using a Bridgeport, they first enlarge the throttle body inlet holes. After machining, they spend a ton of time hand smoothing and porting the manifold for good, even flow.
We exclusively used Fel-Pro...
We exclusively used Fel-Pro gaskets for both the cylinder heads and intake manifold. While they may seem like a small part of the build, having a quality gasket is key to making clean, consistent horsepower.
All testing was done on Golen's...
All testing was done on Golen's Land and Sea Dyno-Max 2000 "Pro" engine dyno and Big Stuff 3 engine management. This allowed us to test with accuracy and consistency.