47-55.1 Those running LS and S10 frames- Help me understand this???

[65blackfleetside]

So i have been a habitual follower here on so many builds as I build my own 1951 LS /S10 frame. I could not done this build without the godfathers of this forum!! I am forever greatful of this forum!

AFTER 10 MONTHS First crank today on my LS 3 today. i was excited to hear it run. However the walboro pump was very noisy AND SQUEALING. I mounted it ON the top of the frame just below the cab. I used the corvette style filter and walboro pump like so many of you recommended.; However i dont think its lower than the feed on the stock S10 fuel tank. (LS3 5.3 is 2004 1 fuel line). Should the pump be mounted lower than the tank?

WHAT AM I MISSING HERE? I feel like the pump is starving for fuel.

[mongocanfly]

It doesnt matter. Mine Is mounted over the tank and I have no issues with pump noise...did the engine crank and run...how did you plumb in the pump and vett filter?

[joedoh]

sometimes its tough to run an external pump without some kind of low pressure priming pump in the tank, that noise and squealing could be cavitation, in which case you could find either the line to the pump is too small or is too long.

I like in tank pumps wherever possible, no suction problems. I realize you already have an external, I dont have a lot of experience with them other than the theory (I did do a scirocco with a low pressure prime and high pressure external but that was years ago), so I will leave that kind of diagnosis to the guys with more experience. but if you happen to burn up the external, its not a terrible job to modify just about any in tank setup to fit various depth tanks, with a little research.

[65blackfleetside]

I am using the 2 OEM fuel lines running out of the top of the S10 tank into the corvette style filter/regulator. I am then running a single braided hose with AN fittings into the pump. Then pump goes to Fuel rail with single 3/8" AN fittings and braided high pressure hose. about a 30" run. No leaks. Truck fired right up! I am getting a code but have not attempted to read it yet. Engine stumbles when I give it throttle. Fuel Pump Squeals on and off like a screaming pig! Most likely sucking air?

I ordered a fuel pressure gauge to see if I am getting the 58lbs needed at the rails? :-/

[mongocanfly]

OK...youve got it hooked up backwards...
You need to run to the pump first...then into the vett filter/reg....keep in mind the inlet into the reg is the angled fitting ...not the center...

[65blackfleetside]

oh well than that would make since. I plumbed this about 4 months ago so I will have to look again but I am pretty sure I put the filter first. Hopefully I didn't damage anything? I only ran the engine yesterday for two 1-3 min segments for the first start up. I knew that pump should not be that loud!

I have been reading every post on here daily - you all have been life savers for this 10 month build! I will get some pictures uploaded soon.

[65blackfleetside]

This afternoon I made up some new AN lines and switched the filter and pump around So now it goes : Tank,then Pump then Filter then return back to tank. Thanks Mongo for pointing that out. My fuel pressure gauge arrived today and I have 50+ PSI at the fuel rail. Engine runs much smoother. The pump is still quite audible. I am running a pretty aggressive borla muffler, No cats and shorty headers and you can still hear the whine of that external pump at idle.

[mongocanfly]

I'm running dynamax knockoffs on mine...headers with muffs dumping in front of axle...not super loud ,but not quite either...i can barely hear my pump at idle...even when I crawl under the truck....my pump is on top of the tank right at the back of the cab....

[65blackfleetside]

Update :I contacted Speedway about this walbro external fuel pump being extremely loud and they are going to send me a new one.

There are a few youtube videos of the Walbro GS 392 - and they are quiet.
I also noticed that the Walbro 392 is called a "racing pump" its rated to 500HP and good for turbo's superchargers too. I am wandering if a smaller walbro would be quieter? If i can't get a quieter external pump I am switching to in tank pump.

Joedoe What in tank pump do you run with an S10 tank and what supplier do you use?

[mongocanfly]

I'm running a walbro 255 on my truck....stock lq9

[joedoh]

I use the stock s10 pumps, AC Delco if I need a new one. I use primarily the 98-03 s10s with 4.3 so they have the high pressure fuel system (~50 psi) and could sustain an LS swap.

but for any kind of hop up power I would suggest using the 2.2 flex fuel pump. it has a similar returnless system to the corvette with the return line on the filter, and because the 2.2 flex uses a SFI (sequential fuel injection) system the injectors are actually larger and flow more than the CPI/MPI system of the 4.3/5.7.

a lot of people think that injectors fire when the valve opens, and only when the valve opens. the real truth is that the air bounces back and forth in the intake runners till the valve opens, so the injectors fire whenever they can, usually in two batches of half the cylinders, and twice per cam revolution (once per crank revolution). if the valve happens to be open at that time, so be it, if not, the atomized fuel bounces with the air in the runner until the valve opens. firing only when the valve is open is called sequential fuel injection and it takes a LOT of computer processing power to figure out exactly when and how long to fire. it also takes a huge injector with a big duty cycle to fit all that squirt in one shot, which is why sequential engines have such big injectors and why the 2.2 injectors need more pressure and volume from the pump. in a batch system, it has two squirts, evenly divided for every intake cycle, so the injectors can be smaller.

there is a diminishing return to sequential systems though, and almost every sequential system switches to batch over about 2500 rpm, because the bigger injector is still too small to fit all that squirt in a shorter and shorter (time wise, not duration wise) valve opening. direct injection engines (DI) for example use HUGE injectors at incredible pressure (200 bar! thats almost 3000 psi) and volume because the injector head is IN the combustion chamber, and injection cant be done in two batches, because half of it would end up in the exhaust. interestingly, extremely high rpm engines use a continuous injection system, sort of like a carburetor but with individual injectors, because at 16k rpm it might be easier just to use a bucket over the runners.

[layinrocker65]

There is no reason to run an external pump if you’re using the stock tank. They make drop in pumps that will support 600hp without issue. I have done several swaps and Walbro pumps are very noisy when I’ve used them. It’s a higher pitched noise.

[1project2many]

and because the 2.2 flex uses a SFI (sequential fuel injection) system the injectors are actually larger and flow more than the CPI/MPI system of the 4.3/5.7.

I spent a *lot* of time involved in 2.2 engines several years ago. The above claim seemed to be worth checking so I dug into reference information.

The injectors for the 2001 2.2 flex engine are 24 lbs/hr injectors, about 7 lbs/hr more than a gasoline only engine. The fuel pump average flow is listed at 21 GPH fuel at 59 psi. The 4.3 fuel pump for the same year is actually showing 24 GPH at a slightly higher 62 psi. Both pumps show the same max pressure at 109 psi. But the 2.2 fuel pump shows a lower current draw (due to lower OEM volume and pressure ratings) at approximately 7A.

For comparison, the fuel module for a Camaro with 6.2L engine is rated for 34 GPH at 58 psi.

Once upon a time a person could buy a Walbro high flow pump for the GM fuel modules, just like the ones in the S10. They are installed in the tank and usually quieter than externally mounted pumps.

[joedoh]

its been my experience that a 4.3/5.7 mpfi fuel injectors (the cpi upgrade in 03, retrofit for earlier) are 17lb and running pressure should be 57+ psi. it has also been my experience that a 2.2 flex truck would not start or run with less than 60psi.

your numbers for gph and psi are opposite of that. I dont have an explanation.

my original comment was that the injectors of a flex 2.2 are larger and flow more than the 4.3/5.7.

[1project2many]

Originally Posted by joedoh

its been my experience that a 4.3/5.7 mpfi fuel injectors (the cpi upgrade in 03, retrofit for earlier) are 17lb and running pressure should be 57+ psi. it has also been my experience that a 2.2 flex truck would not start or run with less than 60psi.

your numbers for gph and psi are opposite of that. I dont have an explanation.

my original comment was that the injectors of a flex 2.2 are larger and flow more than the 4.3/5.7.

It is an interesting question and that is why I looked up the pumps and injectors. It would seem like the larger injectors would dictate the matching pump should be required to deliver more fuel. But the total mass of fuel consumed at any time is determined by the engine VE and required AFR. Although the lower energy content of E85 requires a substantially lower AFR than gasoline, it appears as though the 60 hp difference at peak power actually requires a very slightly greater mass of fuel, hence the very small difference in pump volume.

Knowing the flex 2.2 injectors flow roughly the same as an LT1 injector, I will be on the lookout for them as an unexpected source for injectors for a mild V8. It is very disheartening for many V6 and V8 owners that GM opted to use the "spider" injectors rather than traditional injectors.