kdml Posted November 23, 2015 Share Posted November 23, 2015 I was looking at replacement hard fuel lines for my '65. I see listings for both 3/8 and 5/16 lines. What is the original size for the hard line running from the tank to the fuel pump? When I slide a wrench over the outside diameter of my line it appears to be 3/8, but I haven't pulled the hose to see if it gets smaller where it slides on. The fuel pump inlet appears to be 5/16, but that wouldn't make sense if the hard line is 3/8 ThanksDoug Link to comment Share on other sites More sharing options...
RivNut Posted November 23, 2015 Share Posted November 23, 2015 It does not get smaller. Actually there's a "bump" in the line you have to slide the hose over. If you're replacing fuel hoses, why aren't you replacing lines? They can corrode and cause problems just like old hoses. Link to comment Share on other sites More sharing options...
kdml Posted November 23, 2015 Author Share Posted November 23, 2015 Thanks Ed So if I am following you, the hard line is 3/8. Seems strange that the hard line would be 3/8 and the fuel pump inlet would be 5/16, as they share the same hose. The reason for my questioning is that I am running an Edelbrock carb with a 3/8 inlet and I was considering of stepping up the line coming out of the fuel pump to 3/8. I was also researching replacing the lines/hoses between the pump and tank to 3/8. When I inspected them it appeared they already were. Since the main hard line is already 3/8 and in very good shape, I would not need to replace it. BTW, the service manual indicates the hose the the main hard line should not slide over the bump, but be tight up against it - at least that is how I was reading it (see attached). What you describe makes more sense to me as going over the bump would prevent the hose from sliding off, which is the way I have it installed Scan.pdf Link to comment Share on other sites More sharing options...
RivNut Posted November 23, 2015 Share Posted November 23, 2015 When I removed mine, I can't remember if it was over or up to the bump. I just bought staight fuel line from my local jobber and ran it from an inline electric pump to the new line to the fuel pump so it will have no bump in it. It's real bitch to get the hard line over the axle, so I left that section in place and just ran new hose to the sending unit. The up and over line looked to be in much better shape than the section that ran parallel to the frame. The real bugger is getting the new hose through the clamp that's inside the front spring pocket. I was able to loosen the clamp enough so that I could pull the new hose through the clamp once it had been secured to the old hose. I cut the head off a bolt and screwed the two together. I then went back and was able to re-tighten the clamp in the spring pocket. It takes a long skinny extension and a wiggle joint socket to reach that clamp if the brakes drums, etc. are still on the car. Good luck. At the same time, I ran a new return line back to the tank. Link to comment Share on other sites More sharing options...
arnulfo de l.a. Posted November 24, 2015 Share Posted November 24, 2015 When I removed mine, I can't remember if it was over or up to the bump. I just bought staight fuel line from my local jobber and ran it from an inline electric pump to the new line to the fuel pump so it will have no bump in it. It's real bitch to get the hard line over the axle, so I left that section in place and just ran new hose to the sending unit. The up and over line looked to be in much better shape than the section that ran parallel to the frame. The real bugger is getting the new hose through the clamp that's inside the front spring pocket. I was able to loosen the clamp enough so that I could pull the new hose through the clamp once it had been secured to the old hose. I cut the head off a bolt and screwed the two together. I then went back and was able to re-tighten the clamp in the spring pocket. It takes a long skinny extension and a wiggle joint socket to reach that clamp if the brakes drums, etc. are still on the car. Good luck. At the same time, I ran a new return line back to the tank.So if I am understanding this correctly , you have 2 fuel pumps connected in series, one electric, one mechanical ? What is the purpose of having 2 ? Does the electric run all the time ? Link to comment Share on other sites More sharing options...
RivNut Posted November 24, 2015 Share Posted November 24, 2015 No more than I drive the car and with the high evaporation rate of today's gas, the electric pump is used to get gas to the mechanical pump and fill the bowl in the carburetor so everything is primed. Link to comment Share on other sites More sharing options...
Rufcar Posted November 24, 2015 Share Posted November 24, 2015 Ed that was installed on my 65 gs when I got it but it didn't work. I found for me the only way was to turn the key to on do 5 light pumps and the car started right up.any other way took 10 15 cranks while pumping all the time. I removed the elect pump system. But I see it works fine for you. Link to comment Share on other sites More sharing options...
XframeFX Posted September 2, 2020 Share Posted September 2, 2020 Hello, I'm bringing this back up because I'm stumped. All I want to do is replace all rubber fuel line hoses on my '63. The return line appears to be 1/4" but the main tubing along the rocker panel and fuel sending unit is .35". In-between 3/8 & 5/16"! So, which is it? The manual says nothing. In my early days, I remember big GM V8s were 3'8". The inline fuel filter I want to replace as well but they spec out at 5/16" for the Riv. and my old filter has no markings. As mentioned above, its a PITA to replace the fuel line, so I certainly want to be correct with the installation. 3/8" hose fits loose on the steel tubing. Thanks - John B. Link to comment Share on other sites More sharing options...
telriv Posted September 2, 2020 Share Posted September 2, 2020 The wrong fitting is on the fuel pump. It should be 3/8ths. Buy the good fuel injection hose as it will not break down as easily as regular fuel line hose. You only want to do this job once. The return is 1/4" front to rear. So in ending the supply line & hose is 3/8ths. from the tank to the pump. Then originally was 5/16ths. from the pump to the carb. You could change out the top of your original carb. to use the original air cleaner & front mounted inlet as opposed to the Edelbrock with a 3/8ths. rear side inlet. Link to comment Share on other sites More sharing options...
XframeFX Posted September 2, 2020 Share Posted September 2, 2020 OMG, Thank-You Tom! You're a walking encyclopedia! So it is indeed 5/16" between the fuel pump and carb. I will keep it that way with a future upgrade to 3/8" although I don't think an inline 3/8" fuel filter exists that has the 1/4" return port. Further to this, I too wanted to upgrade from the standard SAE J30R7 Fuel Line Hose. So, Continental Made-in-USA Fuel Injection Hose has worked in the past? Will work with regular gear clamps? Running out to buy the hose now before the stores close! Many Thanks! John B. Link to comment Share on other sites More sharing options...
telriv Posted September 2, 2020 Share Posted September 2, 2020 John, I use the full circle clamps on most everything I can. NOT the worm type clamps. The full circle clamps have a bolt & nut & are available from NAPA & other auto parts stores. Tom T. Link to comment Share on other sites More sharing options...
XframeFX Posted September 3, 2020 Share Posted September 3, 2020 (edited) I did use those clamps, the jobber referred to them as FI Hose Clamps. So use those regardless of which hose, the conventional 30R7 or the FI Hose 30R9? I used the latter for all hoses, 3/8, 5/16 and the return 1/4", about 7X the price! Intimidating with markings in the bulk dispensing box saying 'FUEL INJECTION ONLY" Also the 3/8" FI Hose fit a tad less snug that the conventional hose in the chassis tubing and sending unit. I'm perplexed why those diameters are just .355" when I discovered last that there's no mistaking 3/8 on the fuel pump inlet. It's larger than 3/8" at .39" past the barb to be exact! John B. Edited September 3, 2020 by XframeFX (see edit history) Link to comment Share on other sites More sharing options...
telriv Posted September 3, 2020 Share Posted September 3, 2020 Welcome to the world of metrics. Everything is a "tad" tight or a "tad" loose. The 3/8ths. fuel filter with the 1/4" return I believe is available from Cars or other Buick venders. I think you will be hard pressed to find a fuel pump with the 3/8ths. outlet UNLESS you have the old style fuel pump that's rebuildable with the screws that hold it together. Then the outlet takes another 3/8ths. brass fitting. Another note. Look inside the new 3/8ths. fitting to look at the sizing & you will see it will more than likely be smaller than 5/16ths. More China stuff. I usually drill them to the 3/8ths. size on both ends. Be careful as the drill will dig into the soft brass fitting. Go slowly & take your time. It's checking ALL the little things that can make the diff. between running a full 1/4 mile at WOT WITHOUT fuel starvation at the top end. Not a good thing as the engine is now running lean & can melt a piston or cause unknown detonation. Another engine damaging thing most times at WOT you mostly won't even hear. Believe me when I tell you this. It's ALL the little things that can add up no one EVER thought about in the past. Just my observations over the years. Tom T. 1 Link to comment Share on other sites More sharing options...
RivNut Posted September 3, 2020 Share Posted September 3, 2020 .39 inches = 10mm 😁 Link to comment Share on other sites More sharing options...
XframeFX Posted September 3, 2020 Share Posted September 3, 2020 I re-visited the fuel pump fittings when the outlet fittings moved. 2 each 90 deg. elbows and 1 each 5/16" nipple for the hose. All 3 threads were 1/8-27 NPT. One elbow had an ID less than 7/32"! I drilled them out to 15/64. These are existing fittings on a replacement pump from the past. I wouldn't dare to drill them past 15/64! Perhaps there are pumps out there with an outlet port larger than 1/8-27 NPT? When I do the Timing Chain, I'll revisit this with an upgrade to 3/8" to the carburetor. My thoughts, John B. Link to comment Share on other sites More sharing options...
Turbinator Posted September 4, 2020 Share Posted September 4, 2020 The devil is in the details. Turbinator Link to comment Share on other sites More sharing options...
telriv Posted September 4, 2020 Share Posted September 4, 2020 John, 15/64th. is ONLY 1/64th. bigger than 7/32nd. 7/32" = 14/64". 5/16" = 20/64". This size or 1/64" larger is what I usually drill them out to. The fuel pump inlets & outlets are ALL 1/8"NPT. I don't believe there is enough room for a 1/4" NPT fitting, although to be honest I have never tried Link to comment Share on other sites More sharing options...
Riviera63 Posted September 4, 2020 Share Posted September 4, 2020 On 9/2/2020 at 5:16 PM, XframeFX said: OMG, Thank-You Tom! You're a walking encyclopedia! So it is indeed 5/16" between the fuel pump and carb. I will keep it that way with a future upgrade to 3/8" although I don't think an inline 3/8" fuel filter exists that has the 1/4" return port. Further to this, I too wanted to upgrade from the standard SAE J30R7 Fuel Line Hose. So, Continental Made-in-USA Fuel Injection Hose has worked in the past? Will work with regular gear clamps? Running out to buy the hose now before the stores close! Many Thanks! John B. John, As Tom said 5/16" from pump to the fuel filter and fuel filter to carb with a 1/4" return line. I don't know if you care about whether your fuel filter is AC or not. I believe all of the following AC filters are 5/16" in and out with 1/4" return: GF 67, GF 95, GF 96, GF 415, GF 418 and GF 423. I can personally vouch for the 96 and 423 for sure. When you do upgrade the AC GF 98 is 3/8" in and out with a return line which I am not sure of the size. That filter is for 65-67 Pontiac tri-power cars. There may be others. Bill 1 Link to comment Share on other sites More sharing options...
RivNut Posted September 5, 2020 Share Posted September 5, 2020 Wonder if the problem is not in the hose but in the size of the inlet/outlets on the newly made filters and pumps. Perhaps the overseas manufacturers can't size their metric tools to SAE sizes. Link to comment Share on other sites More sharing options...
telriv Posted September 5, 2020 Share Posted September 5, 2020 John, - Bill is correct as far as the A/C# goes. It's readily available from Ames Performance which their # is N132A. Tom T. Link to comment Share on other sites More sharing options...
XframeFX Posted September 5, 2020 Share Posted September 5, 2020 OK. AC Filter GF-98 for 3/8" Fuel Line Hose. Thanks Bill. Brass fittings have smaller IDs than steel tubing. It appears 1/8-27 brass fittings on the pump outlet port are spec'd at an ID of 7/32" (.219"). So, for my existing fuel pump 5/16" Fuel Line Hose it is. Thoughts: The pump outlet is 1/8-27 NPSF (straight thread - FUEL). The fittings are NPT (taper). The reason for not having restrictive 1/8-27 fittings on the pump inlet is because the line has negative pressure? Link to comment Share on other sites More sharing options...
XframeFX Posted September 5, 2020 Share Posted September 5, 2020 Speedwaymotors.com Link to comment Share on other sites More sharing options...
Recommended Posts
Create an account or sign in to comment
You need to be a member in order to leave a comment
Create an account
Sign up for a new account in our community. It's easy!
Register a new accountSign in
Already have an account? Sign in here.
Sign In Now