[Dapper_Dan]

i think im gonna try this mod until i get my double pumper set up....

Originally Posted by FullBlown

I get alot of people who ask me how to modify a walbro fuel pump to hold pressure. There are alot of guys now that are running their dual pumps past 75psi since they are running 40+psi of boost. Well heres the story on how I accidently found out how the modified ones work.
Back last year when I sent our Dual Pump setup in to RC ENG to get flowed, I got the flow chart back and it said on the bottom of the page that the "Bypass Valve opens at 75 psi" When I saw that I was like wtf!! So I went and found the flow chart for the "Modified Walbro" and what do ya know.. at 70-75 psi the modified walbro kicks the non modified's ass. At that point I knew that the bypass was the only reason why the modified walbros outflowed the non, but i never got around to messing wit it.
Then, about 6 months ago I got in a shipment of walbros and 2 of them were damaged and UPS was being pricks about it so I just decided to keep it incase i needed them to mock up any new projects. Well.. today i was at work and just just got done wrapping up a customers car and had some free time to play with the pumps. Here is what I found.. I suck at explaining things so Ill let the pictures help.

WARNING!! I DO NOT RECOMMEND THIS MOD, WALBRO WILL VOID THE WARRANTY OF YOUR PUMP FOR SURE IF YOU DO THIS TO THE PUMP. THERE IS A REASON WHY WALBRO CHOSE TO PUT IN A RELIEF VALVE. PLEASE DO THIS AT YOUR OWN RISK
Here is a ghetto drawing of a non modified walbro ( i know i spelled hole wrong)

Heres the pump all take apart

Here is a shot of the bottom of the bypass valve

Heres a shot of the top

Befor we go on please be careful and wear goggles and a pair of gloves. You might want to have a friend help you. :D
Take a punch, I forgot the size of the punch but just size one up that fits and line it up and give it a few good wacks jk all you need to do is tap it a few times until it bottoms out.


BAM!!! Thats it youre all done, now go have a :beer: and paypal donations to Fullblown@tmail.com {thumbup}
Here is a drawing of the modified walbro and befor and after pics of the plug

Before

After

[Bonestock!]

I remember the big thread on EVOm about this mod and Buschur's modded Walbro pump. Walbro said this was a very bad idea and could cause the pump to short or something like that IIRC.

[Dapper_Dan]

Originally Posted by Bonestock!

I remember the big thread on EVOm about this mod and Buschur's modded Walbro pump. Walbro said this was a very bad idea and could cause the pump to short or something like that IIRC.

yeah ive read over alotof pages, and walbros arnt very reliable anyways...i didnt read about anyone having problems after doing this mod....i might try it.

[Bonestock!]

Couldnt hurt, they are fairly cheap. That being said, I have never had one go bad on me..... yet.

[Dapper_Dan]

Originally Posted by Bonestock!

Couldnt hurt, they are fairly cheap. That being said, I have never had one go bad on me..... yet.

yeah ive never had one go bad either but i know a few peope that have.

[WRX_Chris]

Mines running strong.

[blackedoutdsm]

ive never had one go bad i dont have currently but i have ran the 255's...seems like they might actually use a dif spring instead of just "preloading' it

[dnhieu]

of course walbro is going to say "DONT DO THIS". this is how they make money. i have also herd that they are not reliable but i have had mine for almost 3 years now and i have NEVER had a problem...