juanpablo046

Hi,
I have a C6 Z06 with some issues.
The car has the Edelbrock supercharger kit with some extra mods:

• LONG TUBE HEADERS

• ID-1050X 1260 CC AT 4 BAR GM SHORTY# 1XCN,856,961,862,1XC0,
• 263,130,238,116,265
• 3.00" EDELBROCK SUPERCHARGER PULLEY
• JMS FUEL PUMP VOLTAGE BOOSTER
• LS7 CAM PACKAGE, 228/240, .635"/.635", 114 LSA,110 ICL, 7.750
• CHROME MOLLY PUSH RODS, .660 DUAL VALVE SPRING &
• RETAINER KIT INCLUDES ,SEALS . LS7 CAM GASKET & BOLT
• PACKAGE. DRY SUMP HARMONIC BALANCER BOLT KIT LS7.
• WATER PUMP GASKETS. FRONT CRANK SEAL & TIMING COVER
• GASKET.
• NGK-3346 8 4.95 NGK SPARK PLUG BR7EF 39.60T

With this setup we hope to see around 10 psi but we only see under 7psi on the logs and on the gauge.
We have already checked:
- Tensioner and belt (we installed the updated Edelbrock part number)
- Leaks (SC unit has around 30.000miles already, we eliminated several minor leaks)
- Crank pulley not spinning

But we do notice the following:
- The inner side of the cover of the supercharger has been rubbing with part of the spinning parts of the supercharger. Can a minor wear mean the SC unit can't produce that much boost?
- When we use pressured air into the SC it can hold over 15psi and then slowly drops, which we understand as normal due to the valvetrain position.

Any idea of how to check the SC unit condition?
Could the mods be affecting by any reason?

CI GS

On a 427 cid engine with those cam specs, it’s possible that you might not be able to make 10 psi with a 3” pulley and a stock-sized balancer. You say you were hoping to see 10 psi? Is that based on experience/research, or just wishful thinking? I would also think it should make more than 7 psi, but no one knows for sure how much boost a blower setup will make on any custom engine combo, unless they’re comparing it to an identical setup. There’s also the possibility that the cam isn’t ground or aligned properly, which could affect boost and, more importantly, power.
How are you pressure testing the blower? The only how I can think of to do that with the blower on the car would be to take the rockers off so that the valves are closed and the spark plugs out, so that if you have one or more of the valves leaking, you can detect it.
Have you checked the bypass valve to make sure it’s working properly? If the linkage is bent or misadjusted, it can bleed boost.
BTW: There is no way that any spinning part of the blower (especially the rotors) should be anywhere near touching, let alone rubbing, on the inside of the lid. Or are you talking about the inside of the rotor housing, where the rotors are spinning? These blowers are designed to run for 100,000+ miles, so they should wear out by 30,000. Unless someone was running it in dusty conditions without an air filter or something stupid like that.

Garymorris

What is the altitude where you live? If you are significantly above sea level you will see less boost. I live at about 4600 feet and I gain 2psi when I drive to the coast and sea level with my maggie.

Unreal

Cam and headers will both lower boost. Why are you targeting 10psi? What power does it make? It it making the power a 3" pulley should make, and running good? If so don't worry about boost. If you want to see 10psi, put a small cam in it so it is more restrictive and boost goes up. Boost is just a measure of restriction. When you remove restrictions with cam/headers/port heads/etc you lose boost even though the airflow is the same or greater. Charts and guides saying what a pulley or blower should make assume a bone stock car, at sealevel, on a nice day. So unless you are stock besides the blower, at sealevel, and on a nice weather day, you won't see the advertised boost.

juanpablo046

It’s a setup already tested by Ted Jannetty.
He is the one pointing to an issue in the car

You’ll see that there’s several cars with this setup with that kind of boost. We almost as low as the stock pulley boost.

We are 600m above sea level.

CI GS

I thought stock pulley (96mm) boost for a Heartbeat on a stock LS7 was ~5.5psi?
Would think the Edelbrock kit would aim for about the same boost...

old motorhead

Stock pulley on the Stage 1 Eforce for LS7 is 3.875" or 98.4 mm.

juanpablo046

Please keep in mind this car has 3.00" sc pulley, not the stock one, crank is stock diameter.