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Author Topic:   Mechanical pumps
FASTLAP
Member
posted July 31, 2004 05:55 AM
A few of my buddys are running mechanical alky pumps over 7,000 w/ no problems as long as you regulate it properly. One runs with no return line w/o problems.



FASTLAP
Member
posted August 01, 2004 05:22 AM
I'd be lying if i told ya, I will have to check on that for ya. Maybe one of these alky guys could help you a little better.



NJantz
Member
posted August 02, 2004 06:09 AM
I run the high volume mechanical pumps and have had no fuel related problems of any kind.

I run methanol, turn 7400 - 7600 RPMs regularly, and run a diaphram type regulator mounted on the rear of my fuel log with a return line. I use the Edelbrock Victor series pump available from Speedway (PN 325-1711) for $80 and the Adjustable Pressure Relief Valve also from Speedway (PN 910-11579) for $60. Use a good top end lube to keep the system in good shape.

I have talked to several guys and have gotten no real good reason to upgrade to a belt driven pump. If anyone has any substantive reasons please share them with us all!! And please be specific!

Kromulous
Member
posted August 03, 2004 07:58 AM
What kind of lube do you run?

Dum question but you run some lube in the alky, to keep the fuel system from drying i out i guess (diaghrams etc)?




WesternAuto17
Member
posted August 03, 2004 08:04 AM
I curious, what is fire slotting?


droper23
Member
posted August 03, 2004 08:48 AM
I run a mechanical fuel pump at about 6800-6900 rpms and have had no problem. I do not run a regulator or fuel return line. I bought I pump that puts out 9-11 lbs of fuel. Runs good. No leaning or rich fuel mixture. This has seemed to me to be the easiest and cheapest way.


2nd2none
Member
posted August 03, 2004 08:49 AM
I've ran both a BG 15 psi pump and a CV 15 psi pump without a problem turning over 8000 rpm. I liked the CV pump better but is a little more pricey.


Look at every NASCAR engine out there, they are required to run a mech. pump and they are turning their motors close to 10,000 rpms.


dirtbuster
Member
posted August 03, 2004 09:07 AM
Nascar boys also use gas not alky.

On alky i think you will have less headaches now or in the future with a belt drive pump over a mechanical. Whenever i hear of people having problems with fuel delivery on alky you almost always hear mechanical pump along with it. Thats just been my experience anyway. Plus the mech pump pulses fuel delivery while a belt drive pump is a steady flow, There is no high and low pressure spike everytime the diaphragm cycles.


rickbraley
Member
posted August 03, 2004 09:35 AM
I use the Red Line alcohol fuel lube you can get from Speedway (PN 607-10008, $6.95). It helps keep that white, flakey stuff from building up everywhere the fuel goes. Has worked great for me so far.

You definitely need a regulator if you are running any kind of HV pump; you have to keep the fuel pressure below whatever your carb manufacturer recommends to keep from blowing fuel past the float mechanism. I run a Holley 4150HP and Holley states it should be less than 8 PSI. I run my pressure at 6 PSI and have never had a problem.

The comment about the pulsating supply the mechanical pumps put out is interesting. However, since all the pump does is keep the bowls filled I don't personally see how this really matters.

There are a lot of guys running the belt drive pumps so there surely has to be a better reason?? Is there any significant difference in the amount of power required to run either? Between the extra cost, the need for a belt that can break or come off, etc I still need to be convinced of their necessity! Show me the light...

dirtbuster
Member
posted August 03, 2004 10:09 AM
What i meant by the pulsing is that every time the mech pump delivers fuel the pressure spikes then resides as it draws in more fuel then repeats. Ea time the pressure spikes the needle and seat see this and are constantly cycling open and closed ea time. The belt drive is constant flow and the needle can react much smoother not so erratic. Maybe it doesnt matter but that is how i was looking at it.

Also for cost i know the belt drive is higher initial cost but take our KSE tandem pump. We ran that pump for 5 years and it was used for 6 before that with nothing more than a seal kit every couple years. I cant help but think a mech pump would require more maintenance/replacement than that and cost more in the end. Not to mention that you have a combined power steering, fuel pump in one unit that is nearly bulletproof. I dont know about weight but i cant help but think it is close if not lighter than a stand alone power steering pump. As for power to run it i am not sure either. We have never had a belt break or come off and never even worry about it. We have since switched to gas and is still think belt drive is the way to go.


NJantz
Member
posted August 03, 2004 10:20 AM
Hey dirtbuster, your point is well made. I guess it is possible that the needle and seat could wear more with the mechanical pump; or at least it is put under more stress in this configuration.
I really tried to justify buying the KSE tandem setup when I put my system together but by the time I bought the pump and the mounting hardware, etc it was going to be a very expensive piece of equipment!! I will certainly spend the money if I need to but I still can't justify the expense based on what I know to this point in time. My mechanical pump is now on its second season and I have not done a thing to it. I don't know how long I can expect it to work but they also have a rebuild kit for it for somewhere around $40. At this price I can afford to rebuild it every year and still stay way below the cost of the KSE!
I guess the point I am trying to make is that you don't have to spend the big bucks to have a reliable and capable fuel system.


Kromulous
Member
posted August 03, 2004 05:20 PM
Rick Braley, what kinda fuel log are you running, and size of fuel line.

I'm setting up an alky set up for our new engine so i want to get it right from the get go, if you would share the info.

Our current fuel log is about 1" dia and 12" long. I read somewhere that the size of the fuel log can affect the carb, not sure thou.

rickbraley
Member
posted August 09, 2004 01:44 PM
Kromulous, sorry it took me so long to respond!!

My fuel log is just under 12" long and ~1 1/4" dia. I use #10 line from the tank to the pump and #8 from the pump to the log. I also use #8 on the return line. My filter is the mounted back by the tank; I run a stainless element and I got the filter from Speedway.

I would expect the one you defined to work fine.

tcmod
Member
posted August 17, 2004 10:05 PM
A belt driven pump delivers more fuel the faster you turn it. Mechanical pumps reach a point where they start to loose efficiency or top off. With alcohol and a big track you need lots of flow so you don't run low on fuel at end of straights, mechanical pumps work fine on shorter tracks and smaller cubes, in short- more cid, rpm, and wot, = more need for belt drive.


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