Latest pictures from 2018 SEMA of the 1973 Laguna featuring the new 750hp LT5. Even though this version looks to be a couple inches taller than the LT4, they still got it in. With superchargers these are very tall engines and present a problem trying to retro-fit them into 60’s Muscle cars. It appears that GM has learned from the overheating issues the very first LT4’s had and have incorporated substantially more cooling capability. The internal supercharger intercoolers are at the very top of the engine on both sides right under the lettering that says “Corvette LT5.” You can see two complete sets of intercooler lines coming in and out of the top of the engine, the LT4 only has one set. The ZR1 Corvette, which uses this engine has 13 total intercoolers. More on the car here:
The LT5 features a specific, larger-capacity Eaton R2650 supercharger than the LT4 and has unique rotor profiles and larger heat exchangers within the intercooling system for approximately double the cooling capacity. This larger-displacement supercharger also expands the engine’s power band, which in turn enhances low-rpm power response and sustains horsepower through the upper rpm range. The engine also utilizes a unique 95mm throttle body and electronic bypass control for greater boost pressure control and torque management among other engine upgrades.
A dual fuel system features a primary direct injection system and a supplemental port-injection system for higher engine loads. Dual engine controllers are also utilized, one for each injection system.
The directions from GM include a drawing with the appropriate resistor values to make the tap switch function. They are correct as mine works perfectly. I had a large box of resistors and was able to come up with almost the exact values that GM asked for, I used 1/4 watt. GM’s drawing uses two single pole, single throw switches. I made up a diagram using one mini switch which is a DPDT (double pole, double throw). It is momentary and is a center off switch. It cost a couple of bucks on eBay. I mounted it on my dash where I can reach it easily. I simply reach up and tap the switch lever up or down, it’s small and hardly noticeable.
My tap switch wire was in the harness near the bulkhead connector. It was labeled as “tap switch”. I just added more wire and ran it inside the car and under the dash.
After building the car in 2015 I decided to swap out the cam, upgrade the rockers, valve springs and lifters from Comp Cams. In Reno last year I saw the new “Sheet Metal Fabricated Intakes” and decided they would look pretty good. This is the low rise model and uses the 92 mm opening instead of the 102mm. The Holley engineers explained that it doesn’t matter what size the opening is if you use the stock 90 MM throttle body. The serpentine system is from CVF racing.
We’ve been conferring for awhile now hoping to get his build together and ready to show to his buddies and the Whidby Island Cruizers. Harry invited Bud and I to take part in the festivities today, see his shop, meet his buddies (his neighbor brought over a 1918 Pierce Arrow) and check out the build.
We can’t confirm for sure but since it doesn’t have any window cranks in the rear, we think it might be a ’55 Utility Sedan rather than a 150. It came with a Nomad interior, so Harry found a wagon bench seat and turned it into a fold down rear where he’s hidden all the audio gear. I’ve never seen one before, but he tells me the vacuum brake system is run by a small electric system with a can hidden under the body down by the transmission. On the right side of the fire wall you can see the TCU (Transmission controller) that hooks us with the E92 ECM on the left side (runs small countries when the cloud fails). Harry opted for the Drive Junky serpentine system to add hydraulic power steering. As you can see everything is neat and tidy, really a very professional installation.
Harry’s old school so he added a ’57 vette grill and replaced the water cooled oil radiator with an air cooled version along with a similar stacked plate cooler for the transmission. He’s quite the character and has a reputation among his peers as the wizard that can make anything run. I hope when I turn 77 I’m building state of the art cars with the latest stuff, way to go Harry. Please direct you comments to him at: firstname.lastname@example.org
Watch closely at the 0:40 second mark when the transmission shifts down 4 gears from 8th gear to 4th gear, the direct injected engine revs almost instantly. Same bottom end as the LT4, just a bigger supercharger gets you another 100 hp. Ligenfelter has pushed the LT4 engine up to 1,400hp with the stock bottom end.