help please sc14 with no boost

[dale30]

Hi All

Well the project has taken a huge turn for the worse and im stumped.. and we race in six days.!!!

Heres a quick run down..

18RGEU with a SC14 plummed into the efi manifold with a 350 holly sitting on top the sc14. I forget the amount of overdrive but its about 1.3.
So if engine requires 1ltr of air per rev and sc14 produces 1.4+ it must be at boost from idle up.
It starts ,idles , and revs great.BUT
Ive hooked up the boost guage and it idles at 50 metric VACUUM things.??
when you blip the throttle it goes up to 0.5 bar ( about 7psi ) but its just like a tacho, it goes up and down with the revs.
But when you build up the revs and hold it at any revs even 7000 there is no boost,actually its in vacuum most of the time.

Now for what ive tried.
checked pully clutch, then tack welded it solid. no change
Taken of the air cleaner. no change
Tightened up belt..bloody tight.no change.
Also i have even put a piece of heater hose onto the inlet manifold so i could check the guage. It reacts just like the boost guage,,,sucks in on vacuum ..blows up on boost...

What have i missed.??????

[bassy]

at what revs does it stop getting boost? is there boost on idle? how much? check the location of the boost guage sender.

bassy

[dale30]

at what revs does it stop getting boost? is there boost on idle? how much? check the location of the boost guage sender.

bassy

It only gets boost while the revs are on the way up( while your actually reving)
NO boost at any constant revs.
No boost at idle..But vacuum
gauge is plugged straight into one of the old vacuum pipes on the inlet manifold.

[Grant]

1) You won't get constant boost unless the car is actually being driven and is under load. The short blip of boost when you rev the engine engine is normal.

2) Constant revs = engine under vacuum.

3) No boost at idle is normal.

[dale30]

Do these superchargers have some sort of internal BOV or something similar.???

[dale30]

1) You won't get constant boost unless the car is actually being driven and is under load. The short blip of boost when you rev the engine engine is normal.

2) Constant revs = engine under vacuum.

3) No boost at idle is normal.

Sorry i was typing while you was...

I think the penny has dropped.

Throttle position at flight revs is not enough to allow enough volume of air through to produce boost.
Hench why it boosts when i blip the throttle wide open...

I must be getting to old...the brain is slowing down..