LT1 - High Mileage - Old School

Comp Cams 1.6 Rocker 1418-16...        read full caption Comp Cams 1.6 Rocker 1418-16 $186

Comp Cams Timing Chain, Pushrods,...        read full caption Comp Cams Timing Chain, Pushrods, Valve Springs/Retainers/Locks 3206, 7940, 983-KIT $469, $124, $120

MSD Blaster Coil, Super Conductor...        read full caption MSD Blaster Coil, Super Conductor Wires 8226, 32143 $44, $76

LT1 F-bodies have good looks, great performance, and huge potential. And lately, they're getting damn cheap, too. Look on some of the big trader Web sites and you can find a running example for under three-grand! So if you're in the market for a high-mileage Z or 'Bird, or have one already sitting at home, lucky you.

Of course, most of the low-ducat rides out there have between 80,000 and 170,000 miles on them. That means some of the car's original components will, by this time, be in sorry shape. Along with those low prices comes a catch: the LT1 engine was the bridge between the archaic GM small-block and the futuristic Gen III/IV. This torquey work-in-progress produced good power, but was more complex than it had to be, and suffered because of it. Oftentimes, newbies find themselves way over their heads when something goes wrong.

GMHTP wanted to update and enhance an LT1, and 83-year-old speed demon King Rhiley offered up a 119,000-mile Z28 that was so near factory it was sick. It's go-time.

We approached Chatsworth, California-based Los Angeles Performance Division to do the work. This crew, which works out of an enormous Canoga Avenue shop with several lifts and a Dynojet, specializes in Gen III Corvette performance. However, they were still willing to tear into the LT1 motor in the name of science.

The plan was to baseline the car on LAPD's dyno, replace the worn-out OEM stuff, then bolt up some high-quality speed parts. Wearing only an airfoil and air intake, 236 horses and 280 lb-ft of torque showed at the rear wheels. The baseline dyno was without incident, but due to the LT1's age and complexity, we hit a few bumps later on. Read on to see what happened--and learn how to make aging LT1 upgrades hassle-free.

Dynotech Dynaspark Distributor...        read full caption Dynotech Dynaspark Distributor Gen I $599	Kooks 1.75x3 Race Headers...        read full caption Kooks 1.75x3 Race Headers 6400RHS $864	PCMFORLESS Custom Tuning '94-95...        read full caption PCMFORLESS Custom Tuning '94-95 OBD-I $99
Borla Single-Cat Exhaust 14464...        read full caption Borla Single-Cat Exhaust 14464 $884	Here's the test subject: a...        read full caption Here's the test subject: a 119,000-mile, nearly untouched LT1. It runs better than it looks, putting down 236/280 on the dyno.	Los Angeles Performance Division,...        read full caption Los Angeles Performance Division, located in Chatsworth, California, offers SoCal flatfoots performance parts, in-house installation services, and Dynojet tuning. C5s, C5 Z06s, and C6s are LAPD's specialties, but it also service new GTOs, CTS-Vs, LS1 F-bodies, as well as all other LS-powered vehicles. These guys gladly accepted our aging LT1 F-body into the fold for some much-needed service.
The LAPD techs start by disconnecting...        read full caption The LAPD techs start by disconnecting the negative battery cable and removing the OEM intake assembly from the top. The Z is lifted to unhook the intake nose from the bottom.	From underneath, the cooling...        read full caption From underneath, the cooling fan's connector is unplugged. The fans are removed as a unit to get more room to work on the front of the engine.	They disconnect the coolant...        read full caption They disconnect the coolant temp sensor on the water pump, then loosen the coolant petcock to drain the coolant. An LT1 shortcoming is the lack of a crank key. Many LT1 balancers aren't weighted but some are (see the 2 o'clock position in photo). Either way, we prefer to reinstall the exact way it came off, for safety's sake. Note the arrow on your balancer--if you pull the #1 spark plug and bring the motor to TDC, the arrow should be pointing straight up. You can do this now and make a mark, or perform the TDC procedure when it's time to reinstall.
The belt tensioner is loosened...        read full caption The belt tensioner is loosened with a 13mm wrench; a 16mm, six-point impact socket removes the harmonic balancer bolts. Keep the belt on for tension if you use the breaker bar approach. After many years, the balancer may be frozen on; use a penetrant spray and a rub-ber hammer to loosen it, and then use a puller (GM PN 39046 or equivalent).	The crankshaft hub will probably...        read full caption The crankshaft hub will probably be rusted by now; remove its bolt and washer, then use the same J-tool to pull the hub.	Remove the spark-plug wires...        read full caption Remove the spark-plug wires from the distributor and plug sides.
Remove the water pump and...        read full caption Remove the water pump and the nuts holding the air-injector pump/bracket; move air pump out of the way slightly to remove Optispark.	To pull the front cover, lower...        read full caption To pull the front cover, lower the oil pan about 2 inches (don't rip the pan gasket). Remove the timing chain sprocket from the camshaft and the chain.	Pull the crank sprocket with...        read full caption Pull the crank sprocket with puller J 5825-A or equivalent (don't turn crankshaft with the timing set removed as engine damage can result).