Mechanical fuel pump pressure regulation? Self regulating?
Thread Starter
Le Mans Master
Joined: Oct 2002
Posts: 7,098
Likes: 378
From: Las Vegas - Just stop perpetuating myths please.
Mechanical fuel pump pressure regulation? Self regulating?
Does anyone using a mechanical fuel pump and not using a fuel regulator monitor there fuel pressure?
In process of building new fuel hard line from pump to Qjet. I have a calibrated Holley regulator but having secound thoughts. Aren't the mechanical fuel pumps advertised as self regulating. Mine is a Carter street model advertised as 6psi continuous (fine for Qjet). I'll be using a small recirc line to tank with a tiny orifice for continous flow.
I just want to run hard steel 3/8" line from pump to my humungous Fram fuel filter to Qjet with recirc at filter. Why install regulator if pump is self regulating? That filter is heavy enough by itself and a regulator would only add restriction reducing full fuel flow. What ain't installed ain't gonna break.
I used an electric fuel pump on my GTO and found out right away I needed a regulator. But now I'm thinking I should give the mechanical pump a chance to prove itself.
Lets hear it. cardo0
In process of building new fuel hard line from pump to Qjet. I have a calibrated Holley regulator but having secound thoughts. Aren't the mechanical fuel pumps advertised as self regulating. Mine is a Carter street model advertised as 6psi continuous (fine for Qjet). I'll be using a small recirc line to tank with a tiny orifice for continous flow.
I just want to run hard steel 3/8" line from pump to my humungous Fram fuel filter to Qjet with recirc at filter. Why install regulator if pump is self regulating? That filter is heavy enough by itself and a regulator would only add restriction reducing full fuel flow. What ain't installed ain't gonna break.
I used an electric fuel pump on my GTO and found out right away I needed a regulator. But now I'm thinking I should give the mechanical pump a chance to prove itself.
Lets hear it. cardo0
Le Mans Master
Joined: Oct 2000
Posts: 8,897
Likes: 1,357
From: Santa Ana CA
Re: Mechanical fuel pump pressure regulation? Self regulating? (cardo0)
I use a Carter high volume fuel pump and a 600 cfm dp Holley with just hard line and a filter between the two. My fuel pressure gauge, after the filter, maintains a steady 6# of pressure even when I blip the engine. (Of course I can't actually see it under load.)
BTW, I changed to the Carter because I had a lean stumble at the big end of the 1/4. When I put the gauge on the line, I found the stock pump was only delivering about 3# of pressure. The Carter took away the stumble and the fairly mild 331 ci (327/350 hp hydraulic cam) makes 293 hp at the wheels on the chassis dyno. Based on that number, I don't think fuel is now the limiting factor.
BTW, I changed to the Carter because I had a lean stumble at the big end of the 1/4. When I put the gauge on the line, I found the stock pump was only delivering about 3# of pressure. The Carter took away the stumble and the fairly mild 331 ci (327/350 hp hydraulic cam) makes 293 hp at the wheels on the chassis dyno. Based on that number, I don't think fuel is now the limiting factor.
Melting Slicks
Joined: Jun 2002
Posts: 2,844
Likes: 99
From: Orrtanna Pa.
Re: Mechanical fuel pump pressure regulation? Self regulating? (toddalin)
Somewhere between 6-7 lbs is what I see out of my Edelbrock mechanical street pump. Supposedly 110 gph which from what I'm told is twice the stock pump rating.
Melting Slicks
Joined: Dec 2000
Posts: 2,041
Likes: 0
From: Wichita, KS
Re: Mechanical fuel pump pressure regulation? Self regulating? (cardo0)
I'm using a stock GM fuel pump on my 406. It has a return line to send excess fuel back to the tank. My pressure stays steady at 6 psi except at the drag strip where it drops to 4 psi on the top end.
Any filter that is doing a good job of filtering junk will have some pressure drop from the inlet side to the outlet side of the filter. I would expect that you will get a 1 psi drop across the filter.
Any filter that is doing a good job of filtering junk will have some pressure drop from the inlet side to the outlet side of the filter. I would expect that you will get a 1 psi drop across the filter.
Race Director
Joined: Nov 2002
Posts: 12,142
Likes: 54
From: Taylor Michigan
Re: Mechanical fuel pump pressure regulation? Self regulating? (cardo0)
Stock 3/8 two line pumps will work with just about any combination of small block or big block well tuned normally asperated engines and no regulator. Electric pumps sometimes require a nightmare of lines and fittings as they push rather than pull and require near or in the the tank installations to work properly. Once that is solved, then try and find a place for a regulator. Keep it simple and stock! None of the high HP engines such as the 427 L88`s or 454 LS7`s ever required an electric pump or regulator at well over 500 HP.
Thread Starter
Le Mans Master
Joined: Oct 2002
Posts: 7,098
Likes: 378
From: Las Vegas - Just stop perpetuating myths please.
Okay thanks everyone. This was all helpful information and I plan to use the Carter pump without regulator.I just installed a brass bushing in my Qjet inlet. Drilled, taped for 1/4" NPT, cemented it in with JB Weld. Man do I have an ugly carburetor now. Shame a recent lars rebuild too. Used super extra care (oiled rags for plugs, then vacuumed and swabbed with alcohol) to prevent drill and tap chips from entering carb innards. But now I can use a 1/8" brass tee to connect both a 1/4" recirc line and a electric press sensor/sender (for my Holley electric press gauge). Yes even ugly'r. Don't want to post a picture of this unless it really works great. At least I can monitor my fuel press while driving with this set-up.
Anyone ever drill a 0.040" hole in brass? I broke one of those tiny drills already and still no orifice hole.
I didn't like the 180* bends in the stock flex lines so off came the fuel pump again for repositioning those inlet & outlet fittings on new Carter pump. Now to rebend tube to carb with hard line and with only Fram filter between. Just a little worried about the wieght of that big filter hanging between tubes. Or maybe I'm just too lazy to bend up a new steel support bracket for it (right now).
Thread Starter
Le Mans Master
Joined: Oct 2002
Posts: 7,098
Likes: 378
From: Las Vegas - Just stop perpetuating myths please.
Maybe 4 ounces of fuel. The stress from the added weight of fuel when compared to the tensile strength of 3/8" steel tubing isn't even worth arguing.I already mentioned I wanted a bracket. When I put one on is for me to judge.
Your guessing Steve. You guessed I would lose 1 psi through the filter. And your guessing I'll bust the fuel line before I fab & install a bracket. If you installed all those mods on your car yourself then you would know how long it takes to do things right. If you didn't have such a nice car I'd tell you where to install your guesses.
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