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Post by dhofman on Jun 28, 2007 11:17:01 GMT -5
Hello All!
It has been a while since I have been able to participate anything Mustang related. I hope everyone is doing well!
My car is being taken apart and I have a number of different things I am starting to work on with it (new exhaust system, new fuel delivery system, paint the underside of the car, chassis strengthening, etc.).
This post is specifically aimed at the fuel system. I am looking to replace my current Carter Mechanical Fuel pump on my 67 Mustang with an Edlebrock Electrical fuel pump but have many questions. Right now the factory fuel sending unit is installed in the factory gas tank. I am thinking I would like to replace this with something larger so this is not a bottleneck point.
With the fuel pump itself, I have been looking at the Edlebrock pumps, but how do I know which one to get due to supposed output (550HP) of my engine (the 120 GPH or the 160GPH)? Also, then do I need a regulator? Which style? Something that returns extra fuel back to the tank? What is the recommended way to go? The regualtor controls volume and pressure to the carbs. How am I supposed to know what to set it at?
When using an electrical fuel pump, I know I want to place it as close to the gas can as possible (ie. rear of car). However should the fuel filter come before or after the pump? Should the regulator come soom after the pump, or should it be as close to the carbs as possible?
I am trying to make sure I build the best, foolproff system possible so I do not loose any HP because my car is starved for fuel, but I want the car to run right as well. Anyone have suggestions or help they could offer?
Thanks
Dirk
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Post by nosub4cid66 on Jun 28, 2007 15:05:56 GMT -5
If your gonna' build a good fuel system I would put a sump in your gas tank when putting on an after market electric fuel pump. As far as how big you should go with the fuel pump you didn't say how big your mechanical fuel pump is right now, is it 80 GPH? and when do you start starving for fuel? Above 5,500 RPM? Also to help you determine how much more fuel you need whats the power band of your cam, what size are your carbs, do you have an auto trans, whats the stall speed, etc. If the bigger pump is only $20 more go with the bigger that way you don't have the same problem again and lose money on another new pump. The fuel filter goes between the pump and carbs because the after market electric fuel pumps, well, pump, they are not very good at sucking the gas out of the tank, gravity does that (thats why a sump is a good idea also), and having the filter before the pump would put added resriction on the fuel getting where you need it. I would also put a pressure regulator on as well, mechanical fuel pumps and carbs like the pressure lower around 10-20psi and electric fuel pumps can make 120-140psi! So get an adjustable regulator, start small and adjust it as needed. hope I didn't confuse you more and good luck
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Post by dhofman on Jun 28, 2007 23:06:07 GMT -5
Since I did not put the car together and I have only a rather crude spec sheet that came with it, I will try to provide what I can. Plus I am a novice trying to learn. Reading articles can only get me so much. It is a 390 block with a .060. overbore (Ron Mack in Grand Haven built it). The cam is a Sig-Erson hydraulic cam (.551 Lift/.296 Ex./228 In) I am still trying to figure out what that means! It has a dual holley intake with two Braswell 390 Holley comp prepped carbs. The Fuel pump is a Carter 427 high performance mechanical fuel pump (I cannot find any numbers on it so I cannot tell you the flowrate.) The transmission is a 4 speed wide ratio top loader and I could not tell you the stall speed. I find the car is starved at higher RPM's in 3rd and mainly 4th gear. After looking at the fuel system before I started thinking about replacing it, it has the stock line, the carter fuel pump, and then everything near the carbs seems to be a little beefed up. You recommended a regulator, where in the system is that typically placed? After the fuel filter? Are they typically hooked right up to the a fuel log?
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Post by nosub4cid66 on Jun 29, 2007 9:42:43 GMT -5
Wow your cam has a lot of exhaust duration. A good cam (that is still streetable) will have lift of .490-.560 and duration in the 220's-230's...those numbers tell us how far the valves open and for how long and with your numbers with a dual plane intake after 5500rpm, your basically just making noise, if you have a single plane intake with long runners like a victor/victor jr you can rev to 6500 rpm. Carter make fuel pumps that are oem replacement to full race so who knows where yours falls unless it has a part number to reference a 427 hi po could fit all 352-428's and who knows how old it is and how well its still working. Since you have a manual trans for get about stall speed, that applies to the torque converter on autos. I would start by replacing your stock 5/16" 40 year old fuel line with a larger 3/8" replacement, get a edlebrock mechanical fuel pump that is rated at 130gph @ 13-14psi, and an adjustable regulator, mounted between the pump and carbs where you can get to it, you are correct, mounted on the fuel rail would be best. This would be an easy setup you could do in several hours and wont be as complex or expensive as an electric fuel pump. Since mechanical fuel pumps also suck the gas out of the tank you can put a good filter before the pump and another small one between the pump and carbs. I believe this would solve your problems because I know people who have used a similar set up on cars with power adders running over 500hp. If you do decide to eventually go with an electric fuel pump you already have the larger fuel line, regulator and filter all you'll have to add is a sump on your tank, connect to your fuel lines, wire up the pump (make sure you put in an inertia switch). good luck
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Post by dhofman on Jun 29, 2007 10:00:18 GMT -5
nosub4cid66,
Thanks for all the information! The main reason I wanted to go to a electric fuel pump was someone told me a mechanical one robs HP. Is this true? Or in the grand scheme of things does this not really matter?
With a mechanical fuel pump should I still use a regulator like us suggested? Right now the current mechanical pump does not have one as far as I know. Is there any brand regulator you recommend?
With regards to the cam. Is there a different cam I could put it that would make the car more street-able but I would not loose any of my quarter mile times or HP? If I am simply making noise at 5500RPM, could I not change it out to utilize the higher RPMs and improve performance?
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Post by nosub4cid66 on Jun 30, 2007 9:05:23 GMT -5
yeah a mechanical fuel pump does take HP to run because of the friction it creates, but stock fuel pump you can operate by hand so how much HP does it steal, so little you would have to put the engine on a dyno to find out, a higher flowing higher psi pump will take more power to operate, maybe 2-5HP so are you gonna notice that when make gobbs of HP? You lose much more HP to your mechanical water pump or power steering. I'd say if you were gonna race the car for profit and every tenth or hundreth of a second counted then it would be worth the investment... I would still use a regulator because they are cheap and if you starve of fuel at 6-7 psi that a street pump makes and a race pump might make too much pressure at 13-14 psi, you can start at 8psi and dial in more if you find you need it I get most my stuff from Summit (summitracing.com) As far as making more HP at higher rpm can be very tricky, and expensive...have you had the car on a chassis dyno? There is a place in k-zoo I heard they give you a couple passes for something like $120. Then you can see how much HP you make at what rpm and trouble shoot some problems like fuel starvation and weak spark, you could spend that much money on a cam or an intake and end up buying the wrong one. you said before that you were losing power in your higher gears and you have a wide ratio manual trans, maybe you have plenty oh high rpm HP at the sacrifice of it at lower rpms? A day at the dyno might shed some light on that issue as well.
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