Gee what's that knocking noise?. The motor blew right at the finish line of an autocross event in the middle of nowhere Michigan. Of course right at the height of race season and one day after I had just spent big bucks on 4.09 gears. I broke my vette and Al Murrel, a fellow competitor, hauled me home. Thanks Al! You have an invitation to co-drive my car! Also, I owe thanks to John & Debbie Fessler, and Paul Wines for hauling my tire trailer home.

A word of warning, 6200 RPM is the Limit for a stock LT1. I set my rev limiter to 6400 RPM against the advice of Justin Vandersall (Superman Vette Mechanic). The motor lasted for maybe 10 revs at that limit. The LT1 rod caps can not take high RPMs. The cap on the number six cylinder stretched. The piston began to slap against the head when down revving. As soon as the engine cooled the bearing spun.

More displacement means mores mass airflow, which means more power. A 383 is made from a 350 by boring the cylinders over 30 thousandths (4.030") and upsizing the crank stroke from 3.5" to 3.75". The result is massive torque across the RPM range. Perfect for autocrossing and helpful for drag racing.

Here are the parts I used.

• Cola 3.75 4340 forged steel crankshaft
• Lunati Pro Mod Rods 5.7"
• Wiseco Pro tru pistons, tops ceramic coated, skirts teflon coated.
• 11 to 1 Compression Ratio
• Fed Mog main & rod bearings (Molybdenum coated)
• Oil Pump, Std Volume, High Pressure
• Competition Cams 220/230 540 lift roller cam
• Balanced and blueprinted to 1/10,000 inch.
• CNC Cylinder Heads, ported & polishied, 2.02/1.6 valves, three angle valve job.
• Very very stiff valve springs
• Felpro 0.039 thousandths head gasket.
• 7 Quart oil pan with baffles, windage, and trap door for heavy duty cornering.
• Camaro flywheel, single mass
• Centerforce Dual Friction Clutch
• TPIS 1 3/4" Long Headers, 3" collectors.
• Hypertech Special Program

This motor turns 7000 RPM.  Altogether this motor makes over 530 ft-lbs of torque and 500 horsepower at the flywheel.  Click to see the estimated dynocurve.

The stock rod length for a 350 is 5.7". The rod to stroke ratio is important because it effects the amount of side wall force the piston exerts on the cylinder wall. It also affects the piston velocity near TDC and the amount of squish time during combustion. Longer rods such as 5.875" or 6.0" result in lower sidewall forces, more squish time, but less TDC velocity. According to CNC Cylinder Heads flow testing on the LT1 has shown that staying with 5.7" rods results in the best horsepower. This is due to higher piston velocities near TDC. However, higher sidewall forces will result. To help compensate for this I had the piston skirts teflon coated.

Material science has developed along ways since the days of the 60s muscle car. Developments in specialized coatings have increased the performance of the internal combustion engine in several ways.

First, I had the piston tops ceramic coated. Ceramic is an excellent insulator, reducing heat conduction through the piston. The result is a higher combustion temperature increasing the thermodynamic efficiency of the motor. That is the motor can get more power out of the fuel. This also helps to reduce temperatures in the lower portion of the block leading to more consistent bearing tolerances and longer oil life.

Cam shafts are the heart of it all.  Along with the shape of the cylinder head intake port this is probably the most important part of the engine affecting torque and horsepower.  

Selecting a camshaft depends greatly on how you're going to drive your car. If your racing and your car is above 5000 rpm most of the time then a higher duration camshaft for high end power would be your best bet. I however, prefer mid-range torque and want to stay away from 7000+ rpms. 

Back when the engine was still a 350 after talking with Lingenfelter racing I selected a cam with 213/219 duration and 462/470 lift. The lift wasn't a whole lot more than stock (450/460) so I went with 1.6 Ratio rockers that extended the lift to 493/502. The cam is supposed to be good for 20 hp and the rockers and additional 10 hp. Along with the camshaft I purchased stiffer springs, hardened push rods, hardened guide plates, and new valve seals.  This cam idles smooth and comes alive above 4000 RPM.

Two popular cams for 350 LT1s and L98s are the LT4 Hot Cam by GM Performance Parts and the ZZ9 from TPIS.

With the 383 stroker the cam is now a Competition Cam 230/230 duration and 540 lift.  Idles real rough, just the way I like it.

1.6 Ratio Roller Rockers

Roller rockers reduce valvetrain friction. They are simply a superior design. The stock rocker arm ratio is 1.5 to 1. Increasing the ratio will get more lift out of the valves without having to replace the stock cam or is a good addition to performance cams. Also the increased rocker arm ratio will open and close the valves faster. According to Crane Cams the higher valve velocity makes the engine think the cam has an additional 2 to 4 degrees in duration (I don't understand why). The roller rockers will also reduce valve train friction, a source of horsepower loss. This modification would be good for 5-10 ft-lbs of torque.

I have seen some warnings about valve spring coil bind. That's when the valve spring compresses until the coils touch each other. Check with the rocker arm manufacture for your particular application. A valve spring replacement would probably be a good idea anyway and is a must with a new camshaft. Stiffer springs will allow higher engine RPMs.

With the LT1 too much lift (.500"+) could result in the valve retainers hitting the raised porting of the head around the valve. Some machining may be required. Check with your camshaft vendor.

I went with Competition Cams stainless steel roller rockers. These rockers won't fit under the stock LT1 valve covers without some minor grinding on the drip tabs.

Inertia robs horsepower. The faster the flywheel is accelerated the more horsepower is robbed. The effect is most profound in first gear. I weighed the stock dual mass flywheel and my new Camaro flywheel. The vette flywheel weighed 55 lbs. The Camaro flywheel weighed 35 lbs. For my car only this results in an effective horsepower gain of14 HP and a torque gain of 21.2 ft-lbs. In first gear only.

To calculate this you have to know how fast your vehicle accelerates in first gear. I used the Drag Strip Calculator program to calculate this. It's currently in beta testing but will be released for sale shortly. Without getting into full detail it is a complete dynamic model of a vehicle which computes velocity, acceleration, G-force, ET, horsepower, torque, forward thrust, RPM, and many other parameters for every foot of the 1320 feet in a drag strip run. The program can be used to completely optimize gear selection for the dynocurve of your motor. It predicted the ET and MPH within 0.5% for my car before the engine was even in it.

The Camaro flywheel has to be turned down 1/8" in order to fit. I bought the flywheel from DRM.

When your motor turns over 500 ft-lbs of torque you need a serious clutch. The Centerforce clutch has weights the spin out due to centrifugal force, which increase the pressure on the disk. I studied this clutch for quite awhile and I can't figure out how it works, but it does. The pedal is softer than the stock clutch. My disk has no springs in it. Combine this with a single mass flywheel that has no dampening springs in it either and you get major neutral gear rattle in the transmission. My transmission sounds like it is going to explode when idling with the clutch out. The solution, I don't let the car idle with the clutch out. It's really not a problem for me, just a minor inconvenience.

Gears work wonders with small block V8s. I went with 4.09 rear end gears. This really helps autocrossing and has my car finishing the quarter rapping out in 4^th gear (perfect). With the stock 3.45 gears I shifted into 4^th about 200 feet before the finish. 4.09s, in effect, has the engine at the peak horsepower rpm range one more time in the quarter mile. Fortunately, for everyday driving, I still have two more gears. Get this, if you had enough horsepower 4.09 gears would still go 225 mph in sixth gear at 6000 rpm, 5^th gear tops at145 mph, and 4^th gear tops at 112 mph. Heck, six speed Corvettes and Camaros should come with 4.09s in them.

Drag Strip Calculator predicts a 3 tenths of a second gain in the quarter going from 3.45s to 4.09s. Several others with LT1 Corvettes have verified this. I changed other components at the same time so couldn't perform an isolated comparison.

The bottom line is lower gears result in more torque multiplication, which leads to more forward thrust at the wheel and consequently higher vehicle acceleration. See the page on rear end gears for more.