fuel pump trap door clearance

[paxton350]

ok, just got my walbro 255 fuel pump, ive seen several pages on how to cut a trap door and access the fuel pump... this is how i plan on doing this fuel pump, however a few things that are a needle in the back of my mind, i plan on using a dremel, but what is the clearance to the fuel lines, i mean if i make a wrong cut am i going to cut right into the fuel lines!? or do i have an inch or so of clearnace? this is the page im geting my info from....http://www.worldisround.com/articles/12533/, thanks!!

-chris

[xxRillixx]

Man, im kinda "P-Oed"... i cant find the link i used. The lines are pretty close 1/4-1/2 inch away. But the metal is like 1/8 thick, so you really wont need to go that deep. The Lines are more to the right (if i remember correctly). Ill keep looking for the link i used. Just make sure ur careful with the sparks! lay some towels to make sure they dont get anywhere and watch the direction they are flying. Good Luck!

------added------

Found it: Fuel pump

[Injuneer]

Don't know if you've seen this page..... a buddy of mine. He used tin snips.

http://camaroz28.cardomain.com/memberpage/348183/9

You're going to be "OK" with the Dremel on the sides and the back. Its the front cut that you have to be careful with. Its very close, as indicated in the post above. If you use a Dremel, you need to hold the cutoff wheel so it barely makes it through the sheet metal. Mabe do 3 sides with the Dremel and consider snips for the front cut.

If I was doing it, I would not cut sharp "corners".... they will concentrate any stress that the body has to carry. Try and round the corners off, rather than making them square.

[imwlw83]

I am with Injuneer, i was thinking round corners myself. If i had to do mine that looks like the way to go. The process is very documented.

[Injuneer]

I even "rounded the corners" when I opened up my SLP airbox, sharp corners are what make things crack......

[raroZ28]

Good luck with that walbro. Mine sucks. When I hit the key, it will fire up and run for a few seconds like it should (the pump). Sometimes, though, it will groan all funky, like it's dying for power. Hard starting if I don't prime it sometimes too. Mine is a couple months old. It only has a 60 day warranty too.

[paxton350]

thanks for all the info, ill probably use a pair of snips instead, however, i just installed my 30# injectors, i had my pcm tuned for timing and the injectors as well as the MAP for the supercharger, could i try to see how my stock pump runs with the new setup first, then go through the hassle of cutting the trap door and installing the pump etc, ive heard a few other ppl having problems with the walbro too any suggestions would be appreciated, thanks

-chris

[xxRillixx]

Good luck with that walbro. Mine sucks. When I hit the key, it will fire up and run for a few seconds like it should (the pump). Sometimes, though, it will groan all funky, like it's dying for power. Hard starting if I don't prime it sometimes too. Mine is a couple months old. It only has a 60 day warranty too.

60 day? Funny.... they told me mine didnt come with one when i got it and it only woked for the first day. But hey... they "Let" me buy the second one 'at cost'... Thanks.

[Injuneer]

There's a lot to be said in favor of the Bosch "984" 205 LPH pump. It will support 500HP. I run a pair of them in parallel. One is installed in the tank, in place of the stock pump, and does require some adapter fittings. And I don't know the details of the install, because Second Street did that little bit of work while I was working in Italy. The second pump is "outboard", off a connection at the back/bottom of the fuel tank. It is now 10 years old, originally supplied as the inline booster pump with my NOS 5176 dry kit that I installed in early 1995.

Second Street prefers the Bosch pump, and I've seen them use a bank of 4 of them to supply fuel to a slant-nose Porsche twin turbo, running almost 30# of boost.

It concerns me that the Walbro seems to have so many problems, and apparently has a very limited (if any) warranty.

[jerrysta]

Fred, is that 500RWHP or 500FWHP?

I think I will be a little above that flywheel but I need a new fuel pump for my 388 and have heard a lot of negative things about the Walbro.

[RyanB58]

I did the trap door method about 8 months ago. At the time I did not think about doing round corners, but that would have been a nice touch. I used an angle grinder on my compressor and was just very careful as to how deep I went at the front portion. I also used the Racetronix kit which I believe uses the Walbro 255 pump, correct? Well, the car runs great and no complaints yet with its performance.

[Injuneer]

Fred, is that 500RWHP or 500FWHP?

I think I will be a little above that flywheel but I need a new fuel pump for my 388 and have heard a lot of negative things about the Walbro.

Fuel consumption is a function of flywheel HP. Doesn't matter whether you're running that power through a high (12% loss) efficiency manual, or a low (25% loss) efficiency automatic drive train - the engine needs the fuel based on flywheel HP.

You can estimate the fuel needs based on flywheel HP and brake specific fuel consumption (BSFC). For an NA setup, 0.50 #/Hr/HP is usually used, and that's very conservative. A well-tuned NA engine with efficient heads can run 0.45 #/Hr/HP.

500 flywheel HP x 0.50 #/Hr/HP = 250 #/Hr

Gasoline weighs approx 6 #/gallon, so you need 41.7 gallons/Hr = 158 liters/hour. Add 20% for return flow in a recirculated system, and you get 189 liters/Hr.

For a blower or nitrous application, use 0.55-0.60 #/Hr/HP.

Several people relabel the Bosch pump, and sell it as their own brand, including Accel.... they call it a "750HP" pump, but it isn't.

Also note that a pump's flow capacity is a function of discharge pressure. As the fuel system pressure increases, the flow drops off. If you run your fuel system at higher than 43.5psi, like the LS1 engine does (58psi), the pump will not flow as much. Just to put the Bosch pump in perspective, it will still support 500HP at 58psi. I run my fuel system at 58psi, and the engine makes just about 500 flywheel HP NA.

[Kevin - Blown 95 TA]

Just drill some holes where you want the corners to be - use a drill stop or collar set shallow to keep you from punching through. I cut the whole thing out using a 4" grinder with a cutoff blade - it took about 10 minutes from start to finish. Then I drilled and threaded a bunch of holes to hold the cover plate in, using my pre-drilled cover plate as a template. I can't imagine how long it would take to cut out with a dremel, although if you could get some of the larger & tougher fiber disks, then it wouldn't be as bad as if you try to use those fragile 1" disks that they give you in all the kits.

I think the hardest part of the whole install is getting the fuel lines undone and getting the pump/sender in & out of the tank.

[Racetronix]

Opening a trap door is not recommended. Always drop the tank and clean it (and the bucket) properly before installing a new pump. The trap-door install has caused many pre-mature pump failures due to contamination and is one of the contributing factors to Walbro canceling all warranty on HP pumps as of March '04!

If you are adamant in this approach do not use any method which will generate sparks. There have been a few fires because the vapor seal on some older cars was not 100%. Gas fumes may be sitting around the top of the tank. An air nibbler would be a much better idea. Snips or cutting wheels may damage the plastic fuel tubes and / or wires sitting on top of the tank.

[Kevin - Blown 95 TA]

Opening a trap door is not recommended. Always drop the tank and clean it (and the bucket) properly before installing a new pump. The trap-door install has caused many pre-mature pump failures due to contamination and is one of the contributing factors to Walbro canceling all warranty on HP pumps as of March '04!

If you are adamant in this approach do not use any method which will generate sparks. There have been a few fires because the vapor seal on some older cars was not 100%. Gas fumes may be sitting around the top of the tank. An air nibbler would be a much better idea. Snips or cutting wheels may damage the plastic fuel tubes and / or wires sitting on top of the tank.

You guys didn't even send any instructions with the pump or the overpriced wiring harness and the ones on the website are inconvenient, and the pump doesn't fit worth a crap in the bucket because the inlet to the Walbro pump is in the middle, not on the side as the stock pump is, no one was there to answer the phone for tech advise, so your opinion on how to do it doesn't mean much to me.

Keeping the sparks away from gas fumes is good advice in any case, though.