This may not be popular(concerns fuel flow)

[BillyGman]

Check this fuel requirement formula out...I think that the results will surprise you......

Holley offers a wide selection of both mechanical and electric fuel pumps for
a variety of street performance and race applications. Selecting the proper
fuel pump for your vehicle, however, begins with understanding your engine’s
fuel requirements.










FUEL REQUIREMENTS







Typically, at wide open throttle, full power, an engine requires 0.5 lbs. of fuel
per horsepower every hour. A gallon of gasoline weighs approximately 6 lbs.
Therefore an engine rated at 350 horsepower will require about 175 pounds
(29 gallons) of fuel every hour.










(350HP x .5 lbs = 175 lbs of fuel






175 lbs/6 lbs = 29 gallons per hour)










FUEL PRESSURE AND VOLUME







The relationship of pressure to volume is inversely proportional. That is, as
pressure increases the volume will decrease, everything else being equal. A
certain amount of fuel pressure is always required to maintain engine performance
by assuring that fuel is available on demand.

So by using the above formula (which happens to be on the website of a carburetor and fuel pump manufacturer) my 800 HP 632 cubic inch engine will only need 66 GPH of gasoline, and that's at WOT!!

Keep in mind that the Holley website isn't the only place where you can find this same formula for determining fuel requirements......

....here's a link to another site that will result in the same final numbers......

http://www.stealth316.com/2-air-fuel-flow.htm (http://www.stealth316.com/2-air-fuel-flow.htm)

and so all of that translates to the theory that I can run a mechanical fuel pump capable of merely 110 GPH and 7.5 PSI with a 3/8" diameter fuel line , and still feed a real big hungry beast. I know that this isn't going to be a popular theory, because the common practice is to throw as much fuel at your engine as your wallet can handle. I've heard of things like $1,000 gas tanks, and $300 electric fuel pumps running off -10AN lines ( about 5/8" diameter) which are capable of delivering 300+ GPH of gasoline and 20+ PSI of pressure even with carbureted engines.

The funny thing is, that once you go any higher than 8 PSI with carburetors, then you just have to run a regulator to limit the pressure to under 8 PSI anyway. Otherwise you'll be pushing the fuel past the needle and seat, and flood the carb. So I'm thinking that much of this fuel flow and high pressure fuel systems, is really overkill (at least for carbureted engines) and only stems from big companies like "Aeroquip" or "Aeromotive" striving to sell car nuts things that they don't really need.

What I'm thinking about doing is using a wideband device to measure the Air/fuel ratio that has a digital read-out and displays the A/F ratio changes immediately while the car is being driven, to make sure that a modest 110 GPH/7.5 PSI rated fuel pump will not be causing a lean condition. My thinking is, when I fire up the engine, I can first rev it to a high idle such as 2,000 RPM while watching the wideband digital read-out of the A/F ratio, and then if it looks okay, then I can take her out for a drive, and watch the readings, or have a passenger watch them as I proceed to give it a little bit more throttle each time I pull away from a traffic light or a stop sign, and as long as the A/F readings don't go leaner than about 13.0:1 or 13.5:1, I can then continue to open up the secondaries up a little bit more each time.

If at any time during the process, the A/F reading get too lean, then I'll know that I either need to re-jet the carb, or get a fuel pump that's capable of more volume than the 110 GPH that the one I plan on trying with this engine delivers. What do you guys think? Does that sound like a rational plan???? I invite everyone's input. Just please be willing to re-think some preconceived notions possibly steming from some sales pitches you might have heard concerning the need for giant fuel lines, and huge electric fuel pumps. That is unless you've done some significant experimentation with different fuel pumps on engines of your own in the past. Particularly big displacement carburated engines. ;)

[MM2004]

Can't see the text Billy. Font color change?

Mike.

[SergntMac]

I think you should keep working the numbers, Billy. Those could be formulas from an engine dyno and things will be a bit tougher in the real world at speed. Inertia will make the trip forward more of a chore.

One thing I noticed, was weight per gallon. I weighed a gallon of gas myself a while back, and got just shy of 8 pounds per gallon. Both of your resources may be using the same weight data, can't be hard to check out.

[BillyGman]

Can't see the text Billy. Font color change?

Mike.That must be because I used bold black in much of my post, and you've chosen that newer black backround as your default. I was going to change it to blue, but I don't know how I can change it at all w/out having to re-write much of that post (help!!)

[BillyGman]

I think you should keep working the numbers, Billy. Those could be formulas from an engine dyno and things will be a bit tougher in the real world at speed. Inertia will make the trip forward more of a chore.

One thing I noticed, was weight per gallon. I weighed a gallon of gas myself a while back, and got just shy of 8 pounds per gallon. Both of your resources may be using the same weight data, can't be hard to check out.

Hmmm, thanks for your input MAC...2 things come to mind.....first, I know that water weighs exactly 8 LBS per gallon, and gasoline is definately lighter than water. :confused:

Secondly, even if the wiehgt is a bit off, would that really change the results all that much??? Just curious.

[BillyGman]

Can't see the text Billy. Font color change?

Mike.Okay Mike...I just changed the colors. Hope that helps.

[looking97233]

Billy, water is 8.6lbs/gal.

I ran my Bronco off a mechanical pump for three years until I went to fuel injection. Only 482cu. in. though, somewhat smaller than yours. Although I run that motor up to 6500rpm. I never had a problem with it. In fact it ran better with the carb. than it does with the FI.

Rod.

[BillyGman]

Billy, water is 8.6lbs/gal.

I ran my Bronco off a mechanical pump for three years until I went to fuel injection. Only 482cu. in. though, somewhat smaller than yours. Although I run that motor up to 6500rpm. I never had a problem with it. In fact it ran better with the carb. than it does with the FI.

Rod.Thanks for that post Rod. I value things like that which have come from someones experimentation and experience. that isn't to say that I'm not open to others comments, but I just can't help but to expect that with this topic, all of us have been fed a big lie by many of the aftermarket companies due to their quest to boost sales. Look at the Nascar vehicles. Don't they have to run mechanical fuel pumps according to the rules? I know they still have to run carbs. And their engines are no slouches either.

I realize that whatever they do run for fuel pumps is likely real exotic stuff, but I don't think electric fuel pumps are indispensable in that application, as some aftermarket companies would have us believe with engine power levels being what they are in Nascar. But I'm not a big Nascar fan by any means, so please correct me if I'm wrong about that.

[looking97233]

Billy, my only other thought is at what RPM is the pump rated? It may not flow enough at lower speeds? I dunno but a thought that maybe you should look into befor trying it. Just thinking out loud trying to be helpful.

Rod.

[BillyGman]

Billy, my only other thought is at what RPM is the pump rated? It may not flow enough at lower speeds? I dunno but a thought that maybe you should look into before trying it. Just thinking out loud trying to be helpful.

Rod.Yes, I thought of that too my friend. But then I thought that just as the fuel pump output is limited by lower RPM's, so is the fuel demand of the engine limited by RPM's. For example, a 632 cubic inch displacement will only move half the CFM of air at 3,000 RPM's that it will at 6,000 RPM's. So the slower the pump is operated, the less fuel it supplies to the engine, yes. But at the same time, the slower the engine turns, the less fuel it requires.

The point being, that unlike electric fuel pumps, mechanical fuel pumps keep pace with the engine speed since they're operated by the engine speed ( assuming they're properly matched to the engine that is). Electric fuel pumps have only two speeds....On and off. And their volume is only varied by the pressure they come up against (more pressure, less volume). Mechanical fuel pumps on the other hand vary in volume output by the engine speed that drives them rather than by pressure.



But I won't take lightly what you've stated. For the first hour that I have this engine running, I'll be watching that digital readout of the wide band A/F ratio monitor device I have, very closely from the second that I first fire up this monster. And if during those first few seconds of low RPM operation I see the digital readout indicate anything higher than a 13.5 reading for any longer than one full second or so, then I'll shut it right down, and re-jet the carb. In that case, once I have significantly bigger jets in the carb (bigger by 3 to 5 #'s) I'll start her up again, and if I still get the same readings, or worse, then that would be a clear indication that this fuel pump cannot handle the task at hand, and I'll have to shut it right down, and fit this thing with an electric pump.

If this fuel pump isn't up to the task, then I believe that it's inadequacy will be reflected in the A/F ratio pretty early on. Certainly within the first few seconds if there's a shortage of fuel in the lower RPM's. And if the shortage is in only in the mid, or higher RPM's, then I would think it will be reflected within the first 10 minutes of operation. Remember, cold engines require a richer mixture to run properly, and the monstrous Holley Dominator carburetor that there is on this engine doesn't have any choke plate either. So in this case, that might even serve as an added built-in fail-safe (to a certain extent).

I've worked on carbureted engines that weren't getting enough fuel at idle due to fuel pump damage, and usually the symptoms that occur at very low RPM's (such as at an idle) are an inability for the engine to hold a normal idle, stalling out, and backfiring through the carburetor because of a lean condition. I've never heard pinging at 900 or 1,000 RPM's because of a lean condition like you would get with the engine under load at a higher RPM.

Consider this.....have you ever had a fuel pump bite the dust while the engine was running? If so, then what happened? According to the people who I've talked to that had that happen, the engine in question just cut out. it didn't detonate or ping. By the same token, I had a 73 Vette a few years back, and one day the fuel filter was severely clogged. Until I figured out what it was, I tried to drive it several times that way, and it would run intermittently for me. I got angry and frustrated with it one time during that week, and I did a 6,000 RPM burnout through first gear in hopes to blowout some obstruction from somewhere (:o ), and it ran great for about 5 or 6 seconds during the burnout, and then it just cut out all together and stalled. that happened to me several times, and I didn't notice any pinging, nor was there any engine damage. It just stalled abrublty and wouldn't start for 10 minutes.

However, all of this may be moot because of the fact that I still need to ask the engine builder if this engine has a camshaft that has a lobe that's been ground for a mechanical fuel pump to be driven off of. I telephoned the camshaft company yesterday to ask them that, but even though I gave them the camshaft part # as well as the grind # which is clearly stated on the cam card that came with this engine, they were not able to answer that question for me. They said that while most of their cams are ground with a lobe for that, the engine builder could've specified to have that left out. :rolleyes:

So until I call the engine building company (World products) the only way for me to know would be to remove the fuel pump block-off plate, stick a fuel pump pushrod in there, and hold one end of it while someone else turns the engine over by hand with a socket on the damper bolt (and try to avoid getting my fingure crushed :eek: ). Sorry for this long post. I guess I can get pretty caught-up in this Hi-perf engine stuff at times. BTW, below is a pic of that wideband A/F ratio monitor that I just bought......and here's the link to where I found it also.... http://www.ngk.com/afx/

[looking97233]

Sounds like you have thought this out pretty well then.

I just thought of one other thing, Holley used to have a tech. line you could call. You tell them the speffics of the motor, they plug the numbers into their computer and can give you a good jet size to start your tuning at. I don't know if they still do this or not.


Okay just got this from their website...

Holley Performance Products provides award-winning technical support via phone Monday through Friday, 7AM to 5PM CST @ 270 781-9741.

As I said they used to have some software for their computers where they could enter your engine + carb. specs. then tell you what size jets to use.

Hope this helps.
Rod.

[BillyGman]

Sounds like you have thought this out pretty well then.

I just thought of one other thing, Holley used to have a tech. line you could call. You tell them the speffics of the motor, they plug the numbers into their computer and can give you a good jet size to start your tuning at. I don't know if they still do this or not.


Okay just got this from their website...

Holley Performance Products provides award-winning technical support via phone Monday through Friday, 7AM to 5PM CST @ 270 781-9741.

As I said they used to have some software for their computers where they could enter your engine + carb. specs. then tell you what size jets to use.

Hope this helps.
Rod.That sounds like a pretty good service., so I'll save that number. This engine was already broken in and dynoed. Allegedly the company who built it has already tuned the carb (atleast as far as getting the jetting pretty close). So I expect it to be in the neighborhood of where I'll need it to be. They also told me that the header primary tube size that they use on the dyno for this engine is 2 1/8" which just happens to be the same size I'm going with. but I may call Holley anyway just out of curiousity. it can't hurt, right? They also have a mechanical fuel pump that flows 170 GPH that is set for an 8 PSI maximum which wouldn't require a fuel pressure regulator. The tricky part about the possibility of me going with that pump is that it uses a -10an size inlet and a -8an size outlet. The outlet size is no problem, but I'm not sure how I'd be able to plumb the whopping -10an inlet since I'm using a stock fuel tank that merely uses a 3/8" fuel line.

What I might be able to do is since I had planned on going with a returnless set-up, and blocking off the return line going back to the tank, I was thinking about using a "Y" block in the reverse direction that they're usually used for. they have ones that have a -10an line going in and two -6AN coming out. So I can turn it around and use both of the 3/8" fuel lines to go into it (if I can find plumbing adapters that convert 3/8" to -6AN) and then have a -10AN going out to the fuel pump. But I need to find the plumbing adapter fittings for that. I've been looking on the Summit Racing website for what I need. if I can do that, then I can run that 170 GPH rated mechanical fuel pump, and I'm positive that will be plenty of fuel for this beast.

[looking97233]

damn Billy, don't you ever sleep?

[Marauderjack]

Water....8.3# per gallon

Gasoline.....~6.0# per gallon.....This will vary slightly depending on specific gravity of the blend.....;)

Marauderjack:D

[BillyGman]

Thanks Jack......

[BillyGman]

damn Billy, don't you ever sleep?NOPE :D........I work nights.......

[Warpath]

Typically, at wide open throttle, full power, an engine requires 0.5 lbs. of fuel
per horsepower every hour. A gallon of gasoline weighs approximately 6 lbs.
Therefore an engine rated at 350 horsepower will require about 175 pounds
(29 gallons) of fuel every hour.


That seems oversimplified and I wonder what assumptions were made. If I remember correctly, we calculated required fuel in my internal combustion classes. I think you need to take into account volumetric efficiency (VE), displacement, A/F, and probably other things I'm not thinking of at the moment. I tried calculating it from memory and got about 1/3 what Holly did. So, I'll have to dig out my old textbooks (and dust them off) and see if my calculation is correct.

(I didn't read every post since I'm short on time - Forgive me if I'm repeating).

[looking97233]

well that explains it then. I have been off work due to an injury so my hours are kinda skewed.

[BillyGman]

That seems oversimplified and I wonder what assumptions were made. If I remember correctly, we calculated required fuel in my internal combustion classes. I think you need to take into account volumetric efficiency (VE), displacement, A/F, and probably other things I'm not thinking of at the moment. I tried calculating it from memory and got about 1/3 what Holly did. So, I'll have to dig out my old textbooks (and dust them off) and see if my calculation is correct.

(I didn't read every post since I'm short on time - Forgive me if I'm repeating).No, you're not repeating anything, and i really do appreciate your input. I find this topic quite intriguing. If you look at my lengthy post,(the first one :D ) you'll see a link that I gave to a website that offers an online calculator where you can punch in the numbers for any engine, and it asks what the volumetric efficiency percentage is. I typed in 90% volumetric efficiency for my 632 C.I. engine ( which a street engine never has) and I still only came up with 70 GPH required at WOT. I believe that calculator also takes into account the A/F ratio.

[BillyGman]

well that explains it then. I have been off work due to an injury so my hours are kinda skewed.WOW...I hope it's not too serious (your injury I mean).

[BillyGman]

Okay, I checked with World Products, and they said that all their engines come with camshafts that can use mechanical fuel pumps. So I'm going to run a Holly mechanical pump part # 12-454-20 which is rated at 170 GPH with an 8 PSI max. which should be plenty for any gasoline engine. And it requires a -10AN fuel line going into it and a -8AN going out. I purchased a new factory stock tank, which is only available with a sending unit that has a 3/8" diameter fuel line, so here's what I'm going to do. I'm going to alter the fuel tank sending unit to fit a -10AN line into it just like the pics in the link below......


http://www.novas.net/forums/showthread.php?t=327

[looking97233]

naw just tripped comming off a ladder on a piece of scrap lumber a framer left laying around, It has been a month so, it is just about healed.
Rod.

[Warpath]

No, you're not repeating anything, and i really do appreciate your input. I find this topic quite intriguing. If you look at my lengthy post,(the first one :D ) you'll see a link that I gave to a website that offers an online calculator where you can punch in the numbers for any engine, and it asks what the volumetric efficiency percentage is. I typed in 90% volumetric efficiency for my 632 C.I. engine ( which a street engine never has) and I still only came up with 70 GPH required at WOT. I believe that calculator also takes into account the A/F ratio.

Yep - I skimmed too quickly and missed the link. I flaked and forgot to check my text books when I got home. The calculations in that link look thorough and look to have what I was thinking about and more. If I remember today, I'll look for the text books. But, I don't think I'll find anthing anymore than what's in the link.

[BillyGman]

Ya know, I thought that I had this thing figured out, and that I'd be able to keep this fuel delivery system on this car real simple and easy. But in light of what I've just been told, that might not be possible.......

One guy who has a N/A 454 Chevelle did just fine with a 172 GPH mechanical fuel pump, and didn't see any ET reductions by adding an electric fuel pump either, and another guy who has a N/A Merlin 540 engine in his Chevelle tried running a 172 GPH mechanical pump, and his car fell flat on it's face at around 600 feet down the track, and that was with a 1/2" diameter fuel line feeding the pump and a sump welded onto the bottom of his fuel tank. So he then went to a 280 GPH Barry Grant electric pump and a fuel cell, and his ET's imediately dropped.

That's tough for me to ignore, since it's based on their track experiences with their cars. So even though I didn't want to put a fuel cell in the trunk, nor have to plumb and mount an electric fuel pump, it looks like that would be the best thing for me to do if I don't want to be setting this up a second time later on. :rolleyes: This isn't going to be cheap. It sounds like I'll be working some O/T for the next two months. :o