You should really have an idea of where things are at with this, using pressure numbers. Is your system regulated? Also, what is the plumbing like coming out of the fuel pump. I've seen some people using sharp 90's coming out of their pumps. It sounds like you're likely at a power level about towards the max for this pump. I had one of the 550's and ended up selling it to moleary and will be going with the 1100 pump and a regulator.
Andy, Mechanical pumps do not like a filter on the suction side of the pump. Take the filter out. Put it between the pump and carburetor. That is most likely your problem.
Larry, I have the McRobb 560 pump with the optional cover(supposed to be good for 600+ HP). I have a semi Diesel truck pre-filter with no bad effects.I think you can have a mechanical pump sucking through a filter if the filter is big enough(and the pickup and line are of a size to pose little restriction).I have a mild Stage 2 motor with this setup .It has been to the strip only once. All others there were running .4 off their usual.Mine went 12.2 at 112.47 with 3.08 gears.It doesn't seem to be starving for fuel too badly. Rod
It's possible Rod, but the general rule is to not to put a filter on the suction side of a mechanical pump. It is much better to put it on the pressure side between the pump and carburetor.
I don't use a regulator. Check above for my plumbing after the pump. The pressure side is a lot more forgiving so I don't think there's a problem with my setup but I could be wrong. Maybe the 550HP isn't enough, I'm just going on published info. I agree Larry. Again, the NAPA filter was temporary. I've been planning on going with Robb's advice and installing a 100 micron pre-filter. While this will still be before the pump(pre-filter), the 100 micron rating is more like a screen and should not be restrictive. We'll see. Here's what Robb said in a PM when I first had my problem..."Hi Andy, First, if you haven't already, remove the sock filter from the tank and add an inline 100 micron prefilter that you can service. Then make sure the stock line is not kinked anywhere. Replace all the short factory rubber lines where they join the hard lines (coming out of the tank, etc) as if they get hard they tend to allow air to be sucked into the line. If your car is under 450 hp, and the 3/8" line is not kinked or sucking air, and the sock is removed from the tank, the fuel pressure should not drop below 4.5 psi. If you are above 450 hp, you can either switch to 1/2" line or add a pusher pump at the rear of the car. Use a low pressure pump (around 6 to 8 psi) such as a Mallory 110. Robb"
