I_clutch

Looking for some input on the setup I've been piecing together. The goal is to unrestrict the engine and install supporting parts for the cam I have. This engine will see high rpm's often at the track. There are no plans to do any machine work at this time. Most of the parts are from what I found searching on the forums here. This is the most I've done engine wise so learning as I go.

Engine: 5.3 LM7 103K Miles 706 Heads
I may change to different OEM Heads

Vehicle:
91 300ZX 2+0 5 SPD Race Car Build
RS5R30A Nissan Transmission
LOJ intermediate kit

Parts List:

COMP Cams (26925-16) 1.320" O.D. Dual Valve Spring
Melling 10296 Oil Pump
HINSON C5R LSx Timing Chain
HINSON Red Truck/SUV Performance Spark Plug Wire Set
Gates 45011 Water Pump
Oil Pan (6.5qt* Capacity, Road Race Baffling, Anti-Slosh Baffling)
Comp Cam 223/239 .610/.624
Professional Products 80033 7.5" Damper for LS-1/LS-6 Corvette
COMP Cams 7639-16 5/16" Diameter 7.450" Length Magnum Pushrod
12573572 LS6 Intake W/ OEM Injectors, Rails, OEM TB DBW
Stainless Shorty Chevrolet Engine Swap Headers

Build Goal:
Mid/ High Power Range
Road Racing/ Weekend Mountain Cruiser

KCS

iTrader: (20)

Define "high RPM". The small valve 706 heads, long runner LS6 intake; and skinny 5/16" diameter pushrods aren't really in your best interest for power in the upper RPM range.

I_clutch

High RPM: Where I'll likely get peak HP over 4,500 RPM
The heads are a concern and I'm considering swapping those. When you say "best interest" what symptoms are you predicting? Bottleneck maybe? I don't necessarily want crazy power but mods for a balanced reliable engine at higher rpm is my goal currently.

JoeNova

The stock engine peaks above 4500 RPM...

KCS

iTrader: (20)

Exactly. Peak torque is usually above 4500RPM too.

Long runner intakes are fine for engines with a power band in the 4500-6500RPM range. After that, the harmonics hurt more than they help. Carb manifolds are a cheap option to get a shorter runner, but expect to lose a little power in the midrange.

5/16" pushrods just suck for most performance LS applications. If you're going to spend most of your time above 4500, you should be looking at a 3/8" pushrod at least.

Small valves suck for most performance applications as well. It doesn't matter if it's for low RPM or high RPM, larger valves almost always make more power. The 706 and 862 heads are good in that they have small chambers so it's easier to get compression with a teeny tiny engine like a 5.3L, but they have small 1.89" intake valves which hurt flow at any lift. You can swap to a 243/799 casting, which has bigger 2.00" intake valves and an arguably better port, but the chambers are also a little bit bigger. You can also have your 706 heads machined for 2.00" valves for about the same amount of money as swapping to used 243/799 heads.