Need advice on installing new fuel line

[RDJ]

My newly built 408 small block (67 Barracuda) has had problems at 4500to 5000 rpms. The engine gets off the line and runs great until I hit right around that rpm range. Frankly, that should be in its power range. (Eddie 800, Hughes 3237 cam). It seems to be cutting out from lack of gas. Tried bigger jets, different setup springs, changed the Carter fuel pump to a Holley high performance fuel pump.

So, thinking the old 5/16 line may be varnished or gunked up, I am putting in a new 3/8 line from the new tank to the fuel pump. It is a pre-bent line from Inline Tubes.

It looks pretty tight around the rear shock, gas tank, exhaust.

1) Will I be able to get it in there without removing a bunch of stuff? If I didn't have to put the line through a hole in the cross member, it might be easier, but I think that will have to come first.

2) Will the 5/16 sender be OK, or is a 3/8 sender necessary?

3) If I use the 3/8 sender, it has a vent, and sealing it with a vacuum cap it seems that the vacuum cap would rot pretty fast. What should be used to seal it?

Any advice on problems or solutions that others have had before I start would be a great staring point.

Thanks!

 

[RDJ]

After looking at it more closely, it seems that maybe if I drop the gas tank, I could send the whole line straight through?

 

[pettybludart]

Are you sure this is your problem?I ran 70 passes last summer with my 410 sb in my 66 Dart with 5/16 fuel line,never cut out once.What type of ignition box are you running?

It doesn,t hurt to change it out to 3/8 line and sender,but you might have other electrical problems.Also,has your dizzy been re-curved?

 

[RDJ]

Are you sure this is your problem?I ran 70 passes last summer with my 410 sb in my 66 Dart with 5/16 fuel line,never cut out once.What type of ignition box are you running?

It doesn't hurt to change it out to 3/8 line and sender,but you might have other electrical problems.Also,has your dizzy been re-curved?

Nope, not really sure that is the problem. And you are right, a 5/16 line should be fine. The current 5/16 line is over 40 years old, and it did sit for a while. Just want to make sure it is not the fuel line. It didn't cost a whole lot. Wish I would have changed it when the car was gutted.

However, I have the 3/8 line and it is going in. I have an FBO ignition system. Basically an upgraded version of the standard Mopar ignition system. The dizzy was recurved to run 16 initial and 32 total without the vacuum. I've run it with both the vacuum hooked up and without, runs about the same.

If this doesn't fix the problem, I've got an Accel 300+ CDI box sitting on a shelf which I may give a try. If that doesn't do it, I'm going to have to make some more posts for suggestions.

So, right now I'm looking for the easiest way to install the fuel line. However, I'm all ears for suggestions on my engine issues, and thanks for the reply.

 

[RustyRatRod]

Scott's dead right. The 5/16 line is big enough for what you have. BUT it's not a bad idea to upgrade. I guess you have a mechanical pump? That right there is the problem. It's easier for a pump to push the fuel up the hose against the car's inertia than to pull it. A properly chosen and mounted electric pump will solve your problem. If you do decide to upgrade to 3/8 line, it will be plum stupid if you continue to use the 5/16 sender. Only X amount of fuel will flow through that 5/16 hole and that ain't gonna change. Just cause it has 3/8 line in front of it means nothin cause it still has to flow through a 5/16 bottleneck. A stainless 3/8 sender ain't but 50 bucks. You can get pre bent 3/8 line for about 79 bucks. really a cheap upgrade. I'm even goin with 3/8 line on my slant six, just because. Of course...also as Scott pointed out, you need to make SURE your problem is fuel first. Last thing you wanna do is end up droppin money with no change. What "I" would do in your shoes if I determined it was a fuel problem would be this: Ditch the 5/16 line for 3/8.....just because. Add a GOOD quality (Holley Blue pump comes to mind) electric pump. Mount it as close to the tank as possible. Run an inline regulator with a GOOD quality filter AND include a fuel return line. This will keep cool fuel recirculating constantly through the carb. Will cut way down on hot fuel problems. Oh...and is this car driven on the street at all? If so, you WILL notice a big difference in fuel economy with the vacuum advance disconnected, and I garrantee you would see a difference on the time clock. If it's drag only, then ditch it.

 

[67Dart273]

it will be plum stupid if you continue to use the 5/16 sender. Only X amount of fuel will flow through that 5/16 hole and that ain't gonna change. .

Actually, while I agree that if you're going to the trouble, replacing the sender IS a good idea, the above ain't entirely true. Flow of air or liquids is a rather complicated deal, but FRICTION is a big part of the overall deal, and the fact is, that a short length of smaller tube in a long run of larger tube will not affect flow as much as if the entire run was the smaller size

include a fuel return line. This will keep cool fuel recirculating constantly through the carb. Will cut way down on hot fuel problems. .

This I absolutely agree with. I'm a big fan of vapor return systems. First one I eve saw was factory on my old 70 sixpack RR AND IT WORKED. (I tried removing it after installing an electric pump and instantly found that out)

 

[Mtrhed]

OK,
Here are some dumb questions. I've bought my first Mopar, a 68 Dart 2 dr post with a 440 in it. Sombody before stripped out the original fuel line and installed VERY scary 3/8" aluminum fuel line using adele clamps to mount it outside the frame rail. This line is even zip-tied to the front rear spring hanger for safety! The line runs behind the P-side front wheel and over the UCA before going to the mechanical pump. I'm guessing the idea was to try and get the line away from the TTI headers and exhaust but this is a death-by-fire waiting to happen.
Other then backing the car out of the garage where I bought it and onto a truck, I have not started or drivin this car. I don't plan to till this nightmare is fixed.
My question is where was the stock fuel line run in this car? Inside the P-side frame rail? I'll probaby buy a pre-bent 3/8 line as a start to an entire new fuel line system. I had hoped to mount a filter and pump on the P-side behind the rear wheel but if, god forbid, there was a leak it would drip right on the tailpipe and the car would be in flames. I'm leaning on mounting the pump and filter above the diff. Not the best place to mount them but it would be out of the way and inside the perimeter of the frame. Any photos of the stock set-up would be appreciated.