Datsun Roadster: 2020 Challenge Build

If it's fuel injected, do you have to mount the tank up high? Any way you could mount it down low, maybe behind the rear axle? 

In reply to Mezzanine :

I could, but that means a longer fuel line, and also splicing in a long section of wire harness to the pump. Neither is a huge issue, but neither is really ideal either.

Here are the decision tree issues running through my head. Maybe it will help to write them down.

Stock bike tank - pros:

1. stock location, stock fuel line, stock wiring harness (this is pretty huge)
2. Front mount is really easy to build
3. Stock venting/charcoal canister/purge valve/etc
4. Stock location means it won't interfere with other stock things, like cooling systems or exhaust

Stock bike tank - cons:

1. It's a bit heavier, and the shape and size mean putting it anywhere other than the stock location is a bit goofy.
2. Rear mount will have to be long pieces of metal. This means in order to be stiff and strong they will be heavier.
3. The one I have has a bit of surface rust inside. Probably fixable, but also probably annoying.
4. The cap is keyed. I don't have the key. I will need to figure that out.

Aluminum tank - pros:

1. Smaller and lighter
2. Inside is clean
3. Mounts easily to a big flat surface
4. I'd save probably $15-20 in budget net (I spent $23 on the motorcycle tank, but I'll need some supplies to mount the pump in the aluminum tank and reconnect lines and wires).

Aluminum tank - cons:

1. I'd need to fab the pump into the tank
2. I'd need to extend fuel line and wiring (and possibly create issues for myself in so doing).
3. I don't really have a big flat surface to mount to

While the great fuel tank debate rages on, I figured I'd get to work mounting some other critical accessories. As it turns out, this was a good idea as it may drive the fuel tank debate.

Here are a couple radiator options. Honda vfr above (came with the f440), and gsxr1000 below.  The gsxr one is aluminum I assume, and is way lighter, as well as being larger. I will probably use the hoses from the f440 though!

Bike powered cars make me so happy. Now turbo it! 

After a few hours today, I'm at about 160. Today I built a frame to support my gas tank and radiator.

Started with some tape aided design.

Next I cleaned all the metal off, and tacked it together.

Make the noise!

Sometimes I feel like I'm getting pretty good at this welding thing.

Then I go and to something like this.

Oh well, that's what they make a grinder for.

Here is is all ground down and ready to go. I'm currently thinking this whole thing will bolt on, I'll weld tabs to the roll bar and this will bolt to those tabs. I could weld it in and still get the motor in and out, but that would necessitate difficult maneuvering of a heavy object.

It just dawned on me, you'll have a center steer Datsun, and the tank up high. It might look a bit like a headrest fairing. May I suggest a tonneau, maybe of metal, because you'll have to climb over the thing to get in?

It is surprisingly hard to find a picture of what I'm talking about. Those two get the point across.

Fiberglass would work too! I really like that idea joel.

In reply to Robbie (Forum Supporter) :

Glad im not the only one that welds like that. I have just about the same thing, just when I think Im getting better at this, I burn a hole in something or generally make it look bad. That is why Kurt does most of the welding you can see,

Started on the tabs this morning.

Re: metal tonneau, I love it! Maybe I'll have some sheet metal skills before this is over.

In reply to Robbie (Forum Supporter) :

I made this pictured aluminum on a steel tube frame tonneau cover for a Sprite a few years ago. Framed with 3/8 "Bundyflex" steel tubing with 20 gauge X1" flanges brazed on. .040 3003 then wrapped on with pliers. A slight compound curve gently tapped in with my palm on a soft bench. This technique would work for you. Very light weight. Note that there is over a year between first and last photo! I can work pretty slowly sometimes.

In reply to TurnerX19 :

Wow that looks amazing! Great work. What does bundyflex mean? Is it just a brand name or is it some type of different alloy?

In other news, I'm at about 162 hours. Some drilling, some tapping, some grinding, some cleaning, some adjusting, and I'm darn close to ready to burn my tabs onto the frame! I think I still need to clean up the frame areas first to get to the freshest metal possible.

In reply to Robbie (Forum Supporter) :

Bundyflex is/was a brand name. It is the standard steel tubing sold at your FLAPS for plumbing a vehicle.

Just saw this and a few min. ago, and had to look up bundyflex myself. 'Course being a Southern hillbilly, I've never heard of FLAPS, either!

They original owner of my hot rod 48COE made the fender well radius with brake line tubing as well. Looks great. Matches the 16" wheel radius better than leaving the F6 fender well opening.

And Robbie, Thats the same way I weld... more time grinding than welding... shamefull, but thats the best I've got. I try to tack things togather well enough to take to sombody that actually does good welds. If they weld over my stuff, without grinding it off to weld it right, I consider it well done!

163 hours, welded my tabs on. First I tacked and then unbolted the support to make sure it actually came apart and was reassemble-able.

It was (great news), so I went ahead and fully welded it in.

Some of the welds weren't even too bad - though I think I'm reaching the upper limit of my welder thickness wise.

Looks good!

I guess you made up your mind on the gas tank, then.

TVR Scott (Forum Supporter) said:

Looks good!

I guess you made up your mind on the gas tank, then.

For now I have! Hahaha. I didn't really discuss in this thread yet but the radiator forced my hand in the gas tank debate.

I don't want to run miles of coolant lines, but I want the radiator somewhere it will get good airflow. So that means the radiator is above the engine, where the stock gas tank would go.

Good news however is that if I need to unbolt this support frame and go a different direction it's pretty easy.

164 hours. I welded the insides of the tabs and ground them back down so the weld bead wouldn't interfere with the fit.

Next I started mocking up the radiator and fuel tank. I think I'm going for something about like this.

Nice! For some reason I was seeing the airbox as the factory fuel tank. I like the alu one better! :D

java230 said:

Nice! For some reason I was seeing the airbox as the factory fuel tank. I like the alu one better! :D

Same! I swore the black thing was the fuel tank.....

I've lost track of the scale here.  Is that roll bar much higher than the seat top?  Is the radiator basically going to be behind your helmet?  Above?

Coolant line rupture = boiling liquid shower?

I'm so glad I'm not the only one that was a bit confused! I even checked back a few pages looking for other pics of the gas tank.

edit: I like how compact that packaging looks.

Maybe I can clear some stuff up!

The gas tank is also black, and fits right over the top of the airbox. In fact, the foam on the airbox lid is so it doesn't rattle on the inside of the tank.

I was wrong before However, the stock tank is 5 gallons, not 3. So even though it efficiently covers the airbox, it's actually quite large.

Here it is on top of the airbox.

Next, I mentioned earlier the radiator forced my hand in picking a gas tank. Essentially the radiator is going right at the biggest point of where the stock gas tank would be. It is behind the driver's head, but back a couple feet. Also, all coolant lines will be behind the radiator. There will be a firewall between the engine and driver (up to the height of the harness bar), so it should be pretty safe from a coolant shower perspective.

In reply to Robbie (Forum Supporter) :

Ah, cool.  The less boiling-death-trap the better.

Would be cool to put that radiator below the body-work and then have a sweet NACA duct feeding it air.  You know, since you're almost finished and all.

About 4 hours today, but a lot was spent poking and thinking and sipping coffee. 

I built the radiator supports. First I marked and drilled holes.

I used the vise to squish this flanged nut into the just undersized hole.

Then I welded these in a bit later to make it permanent.

Next I bent and cut and welded in this diagonal support that bolts into one of the fan support holes. I also bolted on the expansion tank to check fit.

So radiator is mounted for now. It needs one more support on the other side, but I haven't decided how I want to do that one yet. I spent a lot of time looking at hose routing. The stock gsxr hose will fit from the thermostat to the radiator, but it's not exactly optimal bends-wise. I played around with a bunch of different moulded tubes and pipes from both Honda motors and the gsxr, and I'm confident I'll be able to plumb something really nice. It does sort of affect gas tank placement,so that's why I was working on it.

Finally, I drilled out the holes on these ears so that I could use these trick rubber isolators and large shouldered cap screws from the stock gsxr gas tank bracket. Next up, mounting gas tank!

In reply to Robbie (Forum Supporter) :

I have a very similar gas tank, what is you plan to mount a fuel pump? I am looking at mine and how to get an internal pump mounted. Just trying to steal ideas if you have come up with one.