460 Big-Block Build - Large And In Charge, Part 1

Chances are your 460 will be equipped with standard cylinder heads, but there are variations of the standard 429/460 heads that are more desirable than others when it comes to modifications. Though they can be made to thump out pretty decent torque, the later ’88-up EFI 460s should be avoided in favor of the early carbureted variety. Within the carbureted contingent, the early (pre-’72) engine (both 429 and 460s) featured cylinder heads with smaller (74- to 77cc’s) combustion chambers versus 90 cc’s for the later heads. Not surprisingly, the pre-’72 engines offered additional performance even in stock form thanks to higher compression ratios (10.5:1 versus 8.5:1). Early 460s were rated at 365 hp (remember the 429 Super Cobra Jet was rated only 10 hp higher), while the power output of the ’72 460 plummeted to just 212 hp. Some of the power difference between the ’70 and ’72 engines can be attributed to the change from gross to net power ratings. Gross ratings were derived in optimized configuration on the engine dyno before accessories, while net ratings were given in as-delivered tune with accessories (still flywheel rated). Regardless, the early engines with high compression will make more power and everything that follows about the build up of the 460 applies to its little brother, the 429.

The base heads (like ours) that you’ll find on an early 429 or 460 will likely feature rail rockers and screw-in rocker studs, along with a 2.07-inch/1.64-inch valve package. This compares to the 2.42-inch/1.72-inch valves used in the Cobra and Super Cobra Jet heads, and slightly smaller 2.19/1.66 in the Police Interceptor heads. A common upgrade for these base heads is to install the Cobra Jet-size valves. When combined with a little porting, these base heads can perform impressively, with 650-700 hp possible on the right combination. It should be noted that the smaller combustion chambers on these early heads make them less sensitive to detonation. Some sources claim that static compression ratios as high as 11.0:1 can be run on pump gas, but this would likely depend on the cam and ignition timing. Run with cold water in a marine application, we can certainly see this as a possibility, but we’d recommend keeping the compression near 10.5:1 for pump gas. The downside to the rail rockers mentioned previously is that they aren’t suited to performance use with higher-lift cams, but since the early heads are equipped with screw-in studs, aluminum roller rockers (and attending guideplates) are an easy swap. Later heads featured positive-stop pedestals for non-adjustable rockers.

All of the base 429 and 460 engines will be topped by a cast-iron intake manifold. Our 4V engine featured an Autolite carburetor, but there were two-barrel versions as well. If you’re going to change the intake and install a mild hydraulic flat-tappet cam, as we did in Part 1 of this 460 buildup, then it matters not which engine you start with as both offered the same compression and cylinder heads. The difference in power rating between the 2V and 4V versions of the 429 was 40 hp. According to our data, the early 460 (ours came from a ’68 Lincoln) was offered only in 4V configuration. The engine had obviously been rebuilt some time in its life, as the bores measured 0.060-over, but there was no work done to the cylinder heads (the valvesprings looked new, but no evidence of any port work).