http://www.theoldone.com/articles/regulator/

i have a walboro 255 fuel pump. Without the installation of a fuel pressure regulator will cause my engine to run excessively rich due to the increase of fuel pressure across the board. now i have a B&M FPR and i'd like to do the drilling trick.

has anyone done this? i don't have a .035" drill bit but a 1/16" (.0625") bit. i'd think that the bigger the relieve hole the bigger the adjustability?

please let me know.
thanks
chris

 

What was your fuel pressure before the walbro install? Pressure after the walbro install?
Get a 1/32" bit if you're gonna do it.

<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by c17r15 &raquo;</TD></TR><TR><TD CLASS="quote">i'd think that the bigger the relieve hole the bigger the adjustability?</TD></TR></TABLE>

It will lower fuel pressure at idle and do nothing at WOT. I don't think it has anything to do with adjustability. I haven't done this yet. I asked my tuner about this and he said it wasn't necessary unless you're having idle problems. Please note fuel pressure at idle before and after.
I'm installing itr im this week and that would be the perfect time to do it.

 

I just did this trick last week. It totally fucked up my FPR. Yes, it will lower pressures at idle, but it will also decrease the ability of your FPR to regulate fuel pressure. At the dyno, we would start a pull and it would suddenly lean out under boost. The tuner had no clue what was going on, until we mentioned that we had drilled out the FPR. It was replaced with a B&M unit with a non-drilled stock bottom end and suddenly my car started running correctly.

I'll be honest and say that I drilled out hole a lot more than 0.035". However, the tuner said that a hole of any size in there will cause the problems I was having. In the end, it cost me more money in dyno time and to replace it than it would have to buy a more adjustable unit. Live and learn I guess. Hopefully you can learn a little from my mistakes, though. Good luck.

Josh

 

I drilled my fpr. I messed up the first one and broke three bits. I let the machine shop do it the second time. If you want to do it yourself, you need cutting fluid, a vise, 1/32" (.031") cobalt drill bits. Drill at slow speed. My pressures before were 48 wot/ 44 idle. After 50 wot/ 40 idle. Pressure at idle is a bit high still, but it's within spec.

 

As long as you dont drill the hole too big,you should be able to lower you fuel pressure at idle.
Drilling too big will cause too much of a pressure drop and lead to insufficient fuel pressures.
If you drill a SMALL hole it will not affect your WOT fuel pressures in a negative way. The walbro 255LPH pump pumps enough volume to make up for it.