I was looking at going with some braided Nylon fuel line from my tank to my pump because I have to have a 1/2 line to feed the engine, but someone told me that it would go bad within 6 months and start leaking and I would have to replace it all again. I thought this was a problem of the past from everything I have read. Can anyone that has used this recently tell me if this is true? Thanks!
Just curious. Why do you need a 1/2" line to feed your engine? 600HP, 600CID? I only have a 535HP and it runs just fine with a 3/8". I'm not trying to be offensive, just asking. I put the braided line on my 68 Norton Cammando from the tank to the carb, it worked perfectly for 30 years untill I rebuild. It sat outside in the sun most of it's life. Didn't have ethanol then though.
I am using it because that is what my builder said I would need and also the the makers of the fuel pump I am buying from Robbmc also are telling me that I need a 1/2 line. I have been told that it would also run just fine if I wasnt going to be putting my foot into the accelerator pedal, but at the higher RPMs that is where it would be needed to keep the 800 cfm carb full of fuel. Thanks for the info about your lines, but are or were your lines the steel braided?
No, the line was nylon braid. Interesting. I have the original fuel line from the tank to the pump on my 68. I also have 464 cid, have run the thing to 7,000 rpm and have not run out of fuel in the 800 cfm carb. I had a problem with fuel starvation when the engine was still 428 cid. I put a fuel pressure gauge in and I was losing pressure at about 6000 rpm while going up a long incline. I replaced the fuel pump and have not had a problem since. (Thank you to the folks who suggested the gauge) Is the robbmc pump mechanical or electric ? Do you have a return line or just the feed line? I'm a fan of bigger, if I replaced my line it would be larger, can't hurt.
No, the line was nylon braid. Interesting. I have the original fuel line from the tank to the pump on my 68. I also have 464 cid, have run the thing to 7,000 rpm and have not run out of fuel in the 800 cfm carb. I had a problem with fuel starvation when the engine was still 428 cid. I put a fuel pressure gauge in and I was losing pressure at about 6000 rpm while going up a long incline. I replaced the fuel pump and have not had a problem since. (Thank you to the folks who suggested the gauge) Is the robbmc pump mechanical or electric ? Do you have a return line or just the feed line? I'm a fan of bigger, if I replaced my line it would be larger, can't hurt.
Robbmc pumps are mechanical, and they make two for the Pontiac, one that pumps up to 550 HP and the other to 1000 HP. They actually state to use a 1/2 / -8AN line for anything over 450 HP. I am not sure what my top HP will be right now, but it will for sure be over 500HP so that why I want to make sure I go with something big enough to handle what I throw at it and not have to go back and redo the system. Is your carb a duel feed carb? I know the one I have is biut not sure if that will have anything to do with it or not.
What pump do you run? I had fuel starvation issues with my mechanical so I went to a Holley red elect and the problem seemed to go away but it still went lean on the top end so I think it was better but still there. I have a system in place now that I think will work but as yet still have not tried it out to see.
I have a Holley mechanical on mine. a few years ago I had starvation problems. I put in a fuel pressure gauge, the pressure was dropping at high rpm. I put in the new pump and the starvation went away. I since thought I was running lean at high rpm so I installed an air/fuel ratio meter, it's actually on the rich side right up to 7000 rpm. I also installed a AN 6 braided steel line from the pump to the carb but have to original fuel line from the tank. My carb has only one inlet. Bob, maybe you need larger jets on the secondaries if you're running a bit lean. I changed mine out four times to lean it out as I was too rich after the rebuild. I got it close and stopped, I thought with 10.5:1 compression a little rich wouldn't hurt. Ordy, Aeroquip makes hose for socketless slip on fittings for fuel and oil, I think it's fairly inexpensive. If I ever change out my lines I would use that or another brand of slip on fittings and hose for the line from the pickup to the carb and the steel braided for the pressure side from the pump to the carb.
800 qjet, so no jet in the secondaries. I figure it's the bowl running dry because the stock mechanical pump can't fill it as fast as its being used. I've got an oversized needle and seat so if the pump is up to the task it should be good to go. I now have an elect pump installed by the tank set to kick in when the secondaries begin to open. I have not been able to try the system out yet to see if it is the fix I've been looking for. If the problem is still there then I'm going to swap in a Holley carb and see what that does for it.
Robert, Right, no jets just the metering orifice plates, what about trying richer secondary metering rods, AX orCC? Although the CC may be too rich at lower rpm levels. If you feed your mechanical with an electric are you going to put in a fuel pressure regulator?
An engine typically uses about 0.5 pounds of fuel per horsepower at wide open throttle. One US gallon of gasoline weighs about 6 pounds. A 500 HP engine will need 250 p/h, 250/6=41.67g/h. A mechanical pump delivering 80-100 g/h at 5-6 psi should feed most of our engines well, even with 20% loss due to friction, etc.
I just re-measured my fuel supply line it's 3/8" but the specs show stock lines are 5/16". I wonder if they put larger lines on 400ci cars than 6 cyl and 326 cars?
Ordy, sorry to have gotten side tracked on your post. Did the makers of your Robbmc pump suggest you change out your gas tank fuel pick-up to a half inch as well?
Yeah, sorry about the high jack on the post. Some of is sort of related. We went through this last year I think, about how they measure hose by ID and steel line by OD. So a steel line that measures 3/8OD is actually 5/16" ID. Where as a 3/8" hose is actually 3/8" ID.
I will just say that on paper maybe the pump should keep up but that's not what I found to be the case. My 400 only runs about 360HP(320at the wheels) and the car would nose dive at the 1000 ft mark with the mechanical pump and it didn't with the electric, no other changes at all. Apparently it was still going lean with the electric but didn't actually run out of fuel entirely before the 1/4mile. I installed a return line from the fuel pump to the tank and am counting on that to work as my pressure regulator. The elect will supply fuel up to the mech and then, hopefully, the mech pump will be able to keep up with useage. If that doesn't work I may run the return line all the way up to a pressure regulator by the carb and block off the return port on the pump. I heard from plenty of guys that said the stock fuel line was big enough to support 550-600 HP as long as the pump was up to it. No real need to go to a larger supply line.
I'm guessing that RobMc would suggest you buy their pump with the 1/2" pickup. I'm not sure it will accommodate a return line.
Hey, no worries about going on about fuel systems, it is all good info to look at. Bluebird, they did not suggest I go to it because I had already told them I was planning on using their half inch in tank pick up.
Yeah, sorry about the high jack on the post. Some of is sort of related. We went through this last year I think, about how they measure hose by ID and steel line by OD. So a steel line that measures 3/8OD is actually 5/16" ID. Where as a 3/8" hose is actually 3/8" ID.
I will just say that on paper maybe the pump should keep up but that's not what I found to be the case. My 400 only runs about 360HP(320at the wheels) and the car would nose dive at the 1000 ft mark with the mechanical pump and it didn't with the electric, no other changes at all. Apparently it was still going lean with the electric but didn't actually run out of fuel entirely before the 1/4mile. I installed a return line from the fuel pump to the tank and am counting on that to work as my pressure regulator. The elect will supply fuel up to the mech and then, hopefully, the mech pump will be able to keep up with useage. If that doesn't work I may run the return line all the way up to a pressure regulator by the carb and block off the return port on the pump. I heard from plenty of guys that said the stock fuel line was big enough to support 550-600 HP as long as the pump was up to it. No real need to go to a larger supply line.
I'm guessing that RobMc would suggest you buy their pump with the 1/2" pickup. I'm not sure it will accommodate a return line.
They (Robbmc) told me to use a rubber hose to adapt the two ends together for the return line.
Ordy, I checked out their stuff, are you putting an inline filter somewhere between the pick up and the pump? I like the looks of the pickup with the large intake pipe. I may follow your lead and install the pickup and half inch line on mine, just cause.
Robert, could your problem be a plugged pickup sock?
Ordy, I checked out their stuff, are you putting an inline filter somewhere between the pick up and the pump? I like the looks of the pickup with the large intake pipe. I may follow your lead and install the pickup and half inch line on mine, just cause.
Robert, could your problem be a plugged pickup sock?
Yes, I am looking at putting an inline filter also.
A good in line filter is a good idea. I have just one of those regular canister type that I need to replace with a good one. One of those things on my to do list.
No, sock's not plugged.had it out last year when I did the return line. All was clean. Couldn't find a sender unit that suited me so I installed my own return pipe into my existing unit.
I have one of those in mine just before the carb, A large volume high flow filter between the tank and pump would be a good idea especially if going with the robbmc pickup with no pre filter AKA "sock". Don't want any lumps getting into the engine driven fuel pump, or electirc for that matter.
I had problems running a stock fuel line 3/8 running low of volume on the top end. I tried a Holley mechanical pump, several in fact and had constant valve failures. I went with a block off plate and a Jolley blue electric, then a red electric and could never get them to deliver reliable pressure. I had an oil guage sensor that made ground at 4psi, and set up a light to come on if it made ground. It really helped teach me how I was running out of fuel volume at the top end. I replaced the fuel line with 1/2" and it fixed that problem. Unfortunately I used this aluminum fuel line that would wear through and leak.
I wonder if one could add one of the gas tanks set up with a electric pump in the tank and regulate the pressure near the carb and still be able to use the stock fuel line?? Has anyone tried that?
FWIW I was having problems with the gasoline vaporizing this weekend since the temperature has been getting above 90 degrees here. Apparently today's gasoline has a lower boiling point and I'm sure my under hood Temps were at least 160 degrees. While driving home from the track and getting stuck at traffic lights I was totally loosing fuel pressure till I was moving again. Everything was working just fine a month ago when Temps were around 70. I will have to try some alcohol free gasoline and do some insulating of the fuel lines.
