Gday guys.Well i got the XK pre-crossflow 6 with blowthrough carb started but ive run in to a problem. Its running a VL turbo fuel pump to the Barry Grant 575 carb and a Barry Grant fuel regulator with return to tank.My problem is right from when i turn the pump on,before i start the engine the fuel pressure jumps up and down non stop.Any idea's greatly appreciated.

Arent you supposed to run a low pressure pump with a carby?

Im not sure what the go is with boost and carby's but usually you need a low pressure pump to feed into carb. The VL one is high pressure. The reg probably cant bypass enough fuel.

is the carby a proper blow through carby or are you using a normal style carb?

because if your using a normal one the fuel will blow back from the boost causing silly fuel pressure.

fuel for thought.

I assume you are using high pressure fuel reg to a low pressure [8Lb]boost referenced fuel reg ??
So boost doesn't push fuel back through carb ??
You'll need to replace the fuel floats with solid foam etc or they will deform on boost..
Check my second fav tech forum http://www.theturboforums.com/smf/index.php?board=13.0