To feed the engine and provide...
To feed the engine and provide some pretty decent fuel mileage to boot, Holley recommended a 570 cfm Street Avenger carb with an electric choke.
This month, however, we’re going to get our little LS engine prepped and the initial bolt-ons installed before its time to mate the engine to the trans and slip her in the ’68. Over the course of the next few months we’ll keep messing with the combo, whether it’s in the truck or not, to give ya’ll a look at what’s possible with today’s technology.
One thing to keep in mind, although we’re using a brand-new crate engine from Chevy Performance, nearly everything we cover can be done on a junkyard GM truck engine for pennies on the dollar, if that’s your thing. The only drawback is that you don’t know what you’re getting when you pull a used engine. But if rebuilding engines is something you enjoy, that would be a great way to put together a stump-pulling Chevy engine that runs like a clock, makes gobs of power, and accepts all the latest and greatest GM and the hot rod aftermarket have to offer. CCT
Although there’s probably...
Although there’s probably enough ground clearance on the C10 to run a full-length header, I really wanted to retain the same ground clearance and drivability characteristics the truck had when the original 307 was in place. That said, I wanted an exhaust that would sound good and tuck nice and high up in the frame so I opted to go with Hooker Header’s cast-iron exhaust manifolds in silver ceramic finish. Designed to work with all GM LS swaps with the exception of the LS7 and LS9, the high-silicon-moly ductile iron used to cast each manifold yields a mellower, quieter exhaust tone than traditional headers, which can have a “tinny” sound. The silver ceramic finish also helps to reduce underhood and operating temperatures.
Here’s a look at the OEM GM...
Here’s a look at the OEM GM truck coil packs mounted atop the factory bracket attached to the plug wires, which terminate under the Hooker manifolds. These coils are what’s commonly referred to as 3rd Gen LS coils and came in ’99-06 GM pickups and SUVs w/ 4.8, 5.3, 6.0, and 8.1L engines. That’s the coolant temperature sensor (CTS) at the left of cylinder number one’s exhaust port.
Wiring the engine is especially easy using a carb and GM’s factory coil harness, mated to MSD’s 6LS timing controller. The 6LS is a very versatile ignition controller in that it can be attached to the factory sensors and used with a carburetor (like we’ll be doing) or can be utilized to work in conjunction with a stock EFI application using an accessory harness from MSD (part number 88862). In both applications, the controller offers several programmable features that allow for RPM and timing adjustments via their supplied ProData+ software and a PC or with an optional hand-held programmer (part number 7550). Timing adjustments and selections can also be made with plug-in modules. Here, the main harness is attached to the controller (right), leaving a few wires disconnected. At the bottom of the photo, the black/gray wire should be run to a good engine ground source, while the pink wire is a switched 12V+ and the yellow wire is the tach signal. The connector at the upper right (pink and blue wires) is for a step retard for nitrous oxide applications and a two step signal to control two rev limits respectively.
At the engine end of the harness,...
At the engine end of the harness, things are nice and simple to connect, just like you’d expect them to be in the 21st century. You can see the two different coil connectors at either side of the intake, the cam sensor (where the distributor should be), and an optional MAP sensor connector (in my hand).
The harness also attaches...
The harness also attaches to the crank position sensor down behind the starter, arguably the most important as that’s how the controller determines timing and thus ignition.
And speaking of starters,...
And speaking of starters, we opted to try out MSD’s Advanced Power System or APS starter. Capable of cranking over the highest compression engines on a hot day in Death Valley, the APS starter is built from completely new components, including its 3hp motor. Reduced 4.4:1, the armature is balanced during assembly and guided by two ball bearings for a smooth engagement and thousands of starts. The smaller housing was designed with clearance issues in mind, but even features a billet mount that can be clocked in different positions to help in even the tightest applications.
Though not completely finished,...
Though not completely finished, the engine is dressed up to a long-block standard thanks to Holley coil covers and the same Classic Industries dual snorkel air cleaner that graced the 307 small-block.
It should be noted that the...
It should be noted that the truck coils (pictured a few shots back) won’t fit under the Holley coil covers, as they require the use of LS3-style coils and valve covers, shown here on an EROD LS3 engine.
And just to give you an idea...
And just to give you an idea what such an execution can look like under the hood of a truck, here’s Holley’s very own version in their ’67 Chevy built by So-Cal Speed Shop.