Datsun Roadster: 2020 Challenge Build

Fladiver64 (Forum Supporter) said:

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.

That's a great question, and I spent this morning working on my answer.

Unfortunately the motorcycle pumps exit from the bottom of the tank. That makes this much harder than it should be (or maybe I only say that because I am used to cars, that normally mount pumps from the top).

My first thought was to just hook up the pump, cut a pump-shaped recess in the foam inside the tank, and drop the pump in. Unfortunately, the pump won't fit inside the existing hole.

another option is to take the pump apart, then. Unfortunately, I need this fitting for the pump output, inside the tank (the pump assembly output is female).

If I take the pump apart more, I've got a male fitting, which is easier to confidently deal with. But then I lose the nicely integrated pressure regulator and filter assembly.

so what do I do?

1. Cut a hole in the bottom of the tank, and bolt this assembled fuel pump to the bottom. Cross fingers and hope it doesn't leak. I would need to make a nitrile gasket probably, and maybe a reinforcing plate to go inside the tank.

2. Take pump apart, mount pump inside tank with some way to connect to pump output. This could be ditching the filter and doing a manual T to the regulator, or it could be finding a way to cut up the fuel pump base. Assembly inside the tank (or worse, dis-assembly) could be difficult.

3. Build a small swirl pot external to the tank for the pump to go in. I'm thinking a short tube with a flange and a cap. Gravity drain from aluminum tank to pot, pump mounts in pot. For some reason, it feels like this will be easier to make not leak than option 1.

169 hours.

I could vote for cutting a hole in the bottom and mounting the pump as intended.  If it sealed in the M/C it should work here too, right?  Factory gasket?

Bolt holes might be the big question-mark.

We used a similar pump on an FSAE car, I believe we welded studs into the bottom of the tank and used the factory o-ring to seal it.  It was located in a sump made out of large diameter aluminum tubing with a plate welded on the end, which is actually visible poking out under the car in this photo from the tilt table at the Michigan 2012 competition:

I'm putting the fuel tank aside for a few days as I wait for supplies to come in the mail.

Today I did a quick job, mounting the bottom of the oil cooler.

Started by bending and cutting the stock bracket.

Then I trimmed the end and welded on a nut (mostly because I really hate building things that need to have two wrenches to tighten or loosen).

There happened to already be a hole in the front engine crossbar in the appropriate location, so I went with it. Better to be lucky than good I guess!

Here you can see my plan for the top mounts.

Yes, this area will be "not optimal" for airflow. Even on a bike however, this is behind the front wheel so not perfect there either. If necessary, I'll build a little diverter that scoops air from under the car and points it up toward the cooler.

170 hours.

In reply to Robbie (Forum Supporter) :

I think the heat coming off of the headers will actual heat the oil.  The headers can reach 1,200 degrees. At a minimum I would install a heat shield.  Great excuse for some cool gold tape too :)

What about cutting off the weird fitting and brazing on a usable one?

Box4VIR said:

In reply to Robbie (Forum Supporter) :

I think the heat coming off of the headers will actual heat the oil.  The headers can reach 1,200 degrees. At a minimum I would install a heat shield.  Great excuse for some cool gold tape too :)

Yeah, it would definitely seem so. But this is the stock location on the bike. This pic of a similar bike with fairings removed shows the stock setup. The lines don't give much choice in the matter either, as they are hard the whole way except for a couple inches of braided line. The stock setup is interesting, for sure.

A heat shield is a good idea except I don't see how to make one that doesn't kill 100% of the poor airflow that this cooler might receive. For now, I'm going to trust that Suzuki engineers knew something I don't, and I'm going to send it as is. However, if I find it isn't working, I can always make adjustments.

Started on the upper oil cooler mount today. I need to stop trying to bend brackets. It never works out for me. Just cut the dang thing and weld it since that is what I'm going to end up doing anyway...

The bends ended up about 1/4 inch wider than I wanted them. So I'll be straightening the bracket and probably cutting and welding. 171 hours.

Some unbendy, some cutty, some drilly, some tappy:

I would probably wire up a fan and make a simple duct to blow on that.  Yes the headers in the bike would tend to heat that cooler with radiant heat but generally whenever the bike motor is working hard it would have airflow at a minimum keeping convective heat from comming of the header forward to the cooler.  In your arangement with the seat in front of the cooler you likely will get stagnant conditions around that cooler that will tend to heat the cooler.  

Ok our FSAE cars it was amazing how hot the back of the seat could get for that reason.  You will spend a lot of time with this idling at slow speeds (unless you push It to the line all the time)  It won't take much just using a heater fan from a parts car with a simple box duct to blow air through the cooler.  Also probably a good idea to wrap the header.  That will help keep heat out of the wedge behind the seat.  It's harder on the rest of the exhaust as heat isn't disapated but I'm guessing your system would be able to handle it.  

Good thoughts on heat. I'm actually planning for the firewall behind the seat to be shaped such that it helps with airflow in from around the sides of the seat. And I do have some spare fans in budget already that could help.

This morning I removed some rust and made some speed holes. This guy is done for now. Speed holes are totally not worth it to me right now. They take forever and don't make the part much lighter. And then there are tons more sharp edges to deal with. And getting the holes to line up exactly is difficult with my junk drill press.

172 hours.

Step bit on each side of the hole real lightly with a hand drill is my go-to way of de-burring holes that small. 

Consider ceramic coating on the headers. In actual testing the heat radiated off the header 1" away is a huge drop from the surface temperature. When I coated the header on my Turner the hat radiated from the block was hotter than the header with my hand in between. We're talking 900+ degrees at the surface of the header and 190 degreees at the block.

I'm sad I made it this far and still no pictures of the body mocked up. :(

As far as cooler routing, your best option might be just cutting and splicing the pipes themselves. Find some tubing that slips over them and braze it all together. 

In reply to Crackers :

Close enough?

There's even a better one on pg 14. (That's over 100 hours of work ago, wow!)

Looks awesome, but will you be able to see out of it?

Lof8 - Andy said:

Looks awesome, but will you be able to see out of it?

Maybe through the grill & headlight openings?

Got a 2.5 inch hole saw, no turning back now.

Next I used the "grind a bolt to a point to make a transfer punch trick" that fladriver suggested much earlier.

I think it's going to work. The aluminum is actually much thicker than I thought, so that means I'm less worried of this not sealing well.

Next I drilled my holes. And then I tapped them, and installed some mounting screws from inside. I used red thread locker hoping that maybe that will help hold them in place, but also that maybe it will keep them "gas tight".

Finally, I had to file each of the holes in the fuel pump just a tad (since my drilling isn't perfect, apparently). Just waiting on my gasket now!

173 hours.

Pete Gossett (Forum Supporter) said:

Lof8 - Andy said:

Looks awesome, but will you be able to see out of it?

Maybe through the grill & headlight openings?

Huge easy view of the sky, guaranteed. 

You may be able to reach through and put a dab of some sort of fuel safe epoxy/JB weld/something on the back of those studs too.  I think you made the right call as long as you can keep fuel from leaking past the threads.

Actually, you know what?  If fuel does leak past the threads, spin the studs back out and do flanged head bolts from the inside with copper washers (or maybe something fancier with rubber) under them.

Ah E36 M3 I need more coffee, just reread and looks like they're already screws from the inside.  I still think flanged heads and sealing with washers is the way to go if that leaks.

In reply to ¯\_(ツ)_/¯ :

Yeah, they are flanged head cap screws. I really hope they don't leak - I'll also be making the gasket so that it goes around all the screw posts too, maybe that will help if gas manages to get past the red loctite.

Here's a question I have - I sanded the surface of the aluminum a bit to deburr the holes I was making. Then I thought that could make little scratches that gas could trickle through. Anyone know about how smooth a surface needs to be for a good positive seal with a rubber gasket? I can sand with finer paper if needed.

Onto today's work:

I tacked the gas tank support onto the rad support (first time I tried I didn't brace it with the wood and it was all kinds of crooked - the brace was really helpful).

next I unbolted it all from the car and final welded it. I also added some squares where the bolts will go in on the frame side, since these are going to be just threaded holes. The support is thicker than the frame, so I didn't feel like it would need thickeners, but we will see.

174 hours.

In reply to Robbie (Forum Supporter) :

Got a 2.5 inch hole saw, no turning back now.

I'm proud of ya!!! This was my favorite method; I think you'll be happy with it.

Rubber actually likes some some surface roughness to "bite" into. Too smooth will leak more. Of course, concentric circles are hard to achieve, but as long as the groves aren't "radial," rough it up.Make your sanding motions inside the bolts in a circular fashion, instead of running to the outside, and a coarser grit too.(yellow high-lite areas way too smooth) Whats the surface of the pump flange look like?

I would think the red loctite would be enough to seal the threads... I wouldn't want to gob anything on afterwards; too likely to fall off/apart and get in fuel system. If the locktite doesn't seal enough, use a fuel resistant RTV type on the threads instead. But trim any excess from around heads afterwards. I think copper washers under each head would be over-kill, but would def. do the job.

Again, I think the loctite will work fine. I haven't used it on gas tank studs, but unless someone has seen it themselves, I vote OK

In reply to 03Panther :

Thanks! Yeah the underside of the pump is actually pretty smooth, but it was made for an o-ring, not a flat gasket, so I don't know how that plays into this.

Today I added two more thickeners, drilled and tapped 4 holes, and installed the fuel tank.

best part is it all fits back on the car (no quite right however, more on that later), and yes, that is a STOCK fuel line from the cbr600 clipped onto the pump and rail. Booyah!

Ok, back to the fuel tank and radiator brace. I definitely warped it a little while welding on my new pieces. Dangit. It still bolts on, but now it takes serious futzing to get the holes to line up grrrrrr. I wonder if I bolt it in to all four and then hit it with a hammer a few times if that will shock it back into a better position. I wasn't even thinking about that possibilty, doh.

The rubber sheet came in the mail today and I couldn't wait to try it.

So I cut some circles.

I sharpened the end of that piece of nicopp line and used it as a punch to cut the bolt holes. Worked great, but was so soft I had to sharpen it like every hole.

Next I put it up on the tank and tightened down the pump in a star pattern. I cleaned out the tank again too. Then I added some gas and put it on a paper envelope to let it sit overnight and see if it leaks!

Also, I measured the low fuel sensor. It's about 4 inches down from the top in an 8 inch tall tank. So that means if the reserve light works correctly it will come on at about half a tank.

176 hours.