I know that modern multi-port EFI systems operate at higher fuel pressures than the old carbureted engines, and that they require specific lines and fittings to handle the additional pressure, as well as a return line to the tank. A couple of questions since I've never custom plumbed an EFI system before. 1. How much pressure does a typical GM multi-port system operate under? 2. Is the return line to the tank under equal pressure, or is it much lower, like on power steering? 3. What are the proper fasteners/fittings/materials for fabricating the rubber portion of these systems? (from tank to lines, and from lines to fuel rails.) Running hard steel lines to the front and rear of the car is no big issue, just wondering what you use for the small rubber connections to the tank and fuel rails. (Not a traditional system, but trust me...it will be well hidden under a mountain of rusty vintage metal for your viewing pleasure...you'll never even know it's there!! )
well hack i'll try but i'm working with a fading memorey fuel pressure for an efi is 18 to 22 pounds. the return line is under less pressure. the factory uses hard line all the way up and some high pressure rubber conectors on the return. there is high pressure rubber line you can buy. you should be able to buy what you need from the after market there are all kinds of efi companys now.
1. A typical TBI set-up only uses 25-30 PSI, but a multi port uses anywhere from 25 to 65 PSI, depending on the manufacturer and system. 2. The return is really not under pressure, though it 'can' be. It merely returns unused fuel back to the tank. The fuel regulator isolates the pressure in the supply line, bypassing any excess. 3. Each manufacturer uses different type connectors for it's injection lines. They usually consist of a plastic housing, with an O-ring or 2 and a clip to keep the 2 lines together. Makes it tough to plumb in an aftermarket system, though suppliers like Godman make adapters from popular EFI fitting to AN (aircraft) fittings.There is a special EFI hose you need to use to hold up to the higher pressures of EFI. You can buy it in the usual sizes (1/4, 5/16, 3/8") in regular parts stores, but be sure it's EFI hose, it's printed on it! Recommended for attaching rubber EFI hose to a steel fitting (be sure it's barbed, or has a ridge to prevent it backing off) is using special hose clamps, that have a 'rolled edge' to prevent the clamp's edge from digging into the hose and creating a weak spot. Some manufacturers use EFI rubber hose, and clamps instead of special fittings, like BMW. I like to use 86 BMW 325 fuel filters on my cars, as they are rated for high pressure, but have a barb fitting inlet and outlet (5/16"), and filter down to like 6 microns. Regular carb filters only filter 50 to 100 micron sized particles out. So you can use rubber hose, and clamps on your system, or use factory connectors, or a combination of factory and AN/JIC aircraft fittings, with the proper adapters. If using rubber EFI hose, use as little as possible, plumb as much as possible with hard line!
oops, figured that would happen. sorry, should have kept my mouth shut. thanks for the info chopolds, i'm thinking efi also.
Go to slantsix.org and check the articles section... a guy did a 2X1bbl fuel injection setup, with tb's from a fiero. Real slick Jay
I think if you get fuel injection hose from a parts store (if they give you the right one) I think it is rated at 125 PSI. I might have just made that up, though.
Rocket J2, you hang around .org to? They have a lot of talented people over there but alot of attitude/ignorance aswell. -Jesse
Yeah, pretty much just lurk. I had a 79 Duster (volare) with a Super Six, and my 74 Duster had a 225. I love slants, but don't have one at the moment I know what you mean about certain attitudes (my alias there is sixgunner, I have about 6 posts and have been a member there longer than here!) Jay
I put TBI in my 41, The TBI line pressure is 8-15 psi, the return line, doesnt get alot of pressure, I used transmission cooler line, it holds 100 psi and it is a HELL of alot cheaper than actual fuel injection line.. Also get the fuel injection hose clamps also...If you need'em I have all the earls part numbers to from the metric o-ring fuel fittings to -6AN....IF you got any questions or need any pics let me know...When I worked at the parts store the gates book recommended tranny line for high pressure fuel line replacement..its like 1.29 a ft. compared to 4.79 a ft. Matt
The new chevy multi port is 45-60 psi. i think its 97 to 03 gas engines. I have had alot of fuel problems on my gas engined trucks with the newer injectors with fuel pumps not keeping pressure up. mostly on the 98 99 trucks. Have you thought about building your fuel lines out of aircraft fuel line??? Too much rubber line and they are not going to let you play on the drag strip if you want to. I think the rule is you have to have under 8" of rubber line or something like that. Is that right drag boys????
Hay-Hack- I know the perfect Injected motor for your ride- [I am looking for one myself] an olds 350 with multiport factory injection- and it was produced pre computer- in 1977 and was installed in the Cadillac seville-dont know what was used as a controller- but it had to be simpler than what is out today-they ran really nice though- I had one and cant find one now.
Yeah and it ran hard.....was real clean and uncluttered too!I never thought about it when I had it but afterwards I was sorry I sold it- only made that deal 2-3 years I believe.......
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