OK I am restorodding a 69 cutlass convertible, car originally had a 350 , my question is I have purchased a new stainless fuel line, my car did not have the vent line, and I just bought the stock replacement size tube,' 1, should I add the vent line? As I am putting a mild 455 in it do I need to increase the size of the line? If so does anyone make a prebent larger tube in stainless? I plan on using the stock style fuel pump. Thx in advance

 

u don't really need a vent line for a mild build. i would say 500HP+ would benefit from a vent line. for a 455ci, i would go with a 3/8" for sure (i have 3/8" on a 330ci). also, if you increase hard line size, make sure your sending unit matches. if your car came with 5/16" hard line, it probably has a 5/16" sending unit. you definately want those to match. it's good idea to replace the sending unit anyway if it hasn't been done recently.

 

Depending on what your definition of "mild" is I would make sure the line you bought is 3/8" and then get a 1/2" RobbMC pickup for the tank.

I am using the 1/2" RobbMC and then I step down to the stock 3/8" steel line, then at the front I use -6 from the steel to the regulator and then -6 from the regulator to the carb.

For a stock fuel pump, you can use 3/8" rubber from the steel line to the pump and then again to the carb. I will say this, if "mild" is my definition (500 HP) then the stock pump isn't going to be sufficient. I ran 12.73 with a stock pump in February...switched over to an electric and went 12.11 on a hot night in May.

 

I think I got the 3/8 in stainless will check my mild build is probably an honest 400 ponies so not close to the 500 maybe it is a mold not mild :-) I am replacing the tank sending etc so now is the time lol thx for replies

 

Along this same topic, I have a '67 442 w a 400 ci. Stock is 5/16 supply and 1/4 return. Should I increase to a 3/8 supply? I have already purchased the 5/16. I will only be out $60, but I do want it right.

 

Jeff I hear you, I checked mine on line and stock is 3/8ths I hope that is good enough, I do not want to mickey mouse with this later as it looks difficult to change again once the body is back on the frame. this was why I was asking about the vapor return line, I could chalk it up to a might as well, and get the correct tank/sender, and pump now, then to try and add these later. That said I have never had a fuel issue with the 350, but then again I was not traveling in the 400 hp circles before either.

 

I guess I am mistaken but I thought most all cars came wth 5/16 line back then.

 

i was under the impression that 8cyl were equipped with 3/8" hard line, 6cyl were equipped with the 5/16" hard line.

i just bought a bunch of goodies for my fuel system because i am having a fuel volume delivery problem. i'm pretty sure my 8 year old pump is the problem. also, i am planning on doing a bigger cam & some major head work this winter, so i want the fuel system to be ready to deliver plenty of fuel, here's what i'm going with:

-550HP RobbMC mechanical pump http://www.robbmcperformance.com/products/olds550.html

-3/8" stainless sending unit http://www.ebay.com/itm/120694500239...84.m1497.l2649

-3/8" hard line (already on the car)

-Holley fuel pressure regulator (# 12-840, for carbs 4.5-9psi, non return style)
http://www.ebay.com/itm/221037572369...84.m1497.l2649

-6 AN stainless braided lines and fittings under the hood

 

the RobbMC pump can have a return port for an extra $15 i believe, and it doesn't hurt to get a sending unit with a return option and not use it for the time being. at least this way it would be equipped to have a return installed if it became a problem. even if you didn't get the return option on the pump, i'm pretty sure you could just add a regulator with return option and run the return line from the regulator to the tank, not completely sure on that though. the sending unit i got is return ready, but i do not plan on installing a return line unless absolutely needed. for m application, i'm being told i shouldn't "need" a return line, however.

 

I like the look of that, I may just order the return line its 95 bucks I think, in stainless I have 3/8 on the car and I will be getting a new pump and sending unit and tank anyway I have a Holley high performance pump on there now but it is chrome looking for a sticker look

 

yea, i have a chrome Holley on mine now too and it's shitting the bed on me. plus it doesn't look chrome anymore, LOL

i've heard nothing but good things about the RobbMC products. i was gonna do the 1/2" sending unit as well, but don't plan on having over 500HP anytime soon. i'll be happy to get to the 400-450HP range, so a 3/8" sending unit should be fine for me.

 

I added a bunch of might as wells to my 455 icon pistons ,eagle rods, sfi balancer and flywheel, mild port and polish, performer manifold heat cross over blocked with welded and machined plate center divider cut down , recalibrated q-jet 780 cfm, custom cam by sig erson via cutlassfi, garland sharps, petronix, had good valves put in the C heads, and I am just hoping for an honest 400 ponies I think I am there I have a 4 speed and dead 3.08 gears in the posi, should be fun and hopefully get me in the low 14 s

 

I am the 2nd owner of both of my Supreme's and they both have 3/8" factory feed line and 5/16" return / vent line. Both are factory 350 cars, the convertible being a 2bbl lol!

 

OK, I stand corrected.......thanks.

 

Well, inlinetube.com confused the heck out if me. I had thought that we misplaced the fuel lines after frame off. Inlinetube.com states that all GM 1967 and older were 5/16" stock supply line? After I received my order, I thought something was wrong. After talking with Fusick.com and service manuals, I found that in 1966 the big blocks had 3/8" stock lines. I went back to the garage were my dad and I tore the car down and found the lines out back. They were actually a little larger than 3/8". My cheapo calipers read 0.41". Anyway I called inlinetube and this guy named Truck basically said duh and if I had phoned in my order, they would have caught it. WHATEVER!!!!

 

The size of the fuel line would be 3/8" inside diameter or 0.375" so if you measured with a caliper the outside diameter would be right at about 0.41". So I guess now you can be sure you got the right tube and don't have to worry about sending back the "5/16" lol!

Glad you found out

 

Well, that is what I thought. I asked inlinetube that and they told me that all tubes are measured OD. So, yes I have to exchange for the 3/8 OD.

 

Wait, if you measured the outside diameter to be 0.41" then that has to be a 3/8" line. If it was 7/16" it would measure 0.4375" and why would they sell a 7/16" tube for your car anyway? It never came from the factory like that...

I would keep the line you got, even if it's a little too big that isn't necessarily a bad thing.

 

The old tubing I found out back measured 0.41. The new tubing is 5/16, so I do have to send it back

 

Well that sucks...

 

Gotta love those kind of improvements! Years ago I went from 12.36 to 11.75 by adding a 1 inch carb spacer and ET Streets over no spacer and recapped cheater tires. It happened about two weeks apart and boy was I happy!