'71 Prep: Phase Two

[Jordan]

So after getting the car together and taking it to a couple events. I found a few flaws with some of my initial designs or things I felt I could have done better.

Primarily, fuel delivery was continuing to be an issue. I was having trouble tuning the car due to inconsitant fuel pressure as well as it sucking up too much air and the pump losing prime in long sweeping corners.

Long story short, Luke discovered (through having to hole saw through another tank) that I was not using the correct pickup, which is very well baffled even in the very early tanks.

As added protection for long periods of G-forces, a simple surge tank to would be put into play as well as an external pump to feed the surge tank.

My first design, before I knew about the pickup, was to use an in-tank pump to feed the surge tank. Being hesitant to drain a full tank, clean out metal shavings and worry about re-sealing all the extra stuff I'd be putting into the tank I opted for keeping everything external.

Also, in an effort to get the car a little more comfortable for longer journeys, the noisy fuel pump will be located into the trunk, enclosed in a box with the rest of components. Also a rear bulkhead would be made to block off the trunk area further.


Here is the progress so far.

Here is the tank Luke made for me (mounts vertically). Basically fuel is fed into the side port and will fill the tank. Any excess will get returned back to the tank along with any air sucked up through the pickup. The bottom port will feed the main pump assuring a constant supply of fuel. A bracket was made to be used with hose clamps so the orientation could be changed.

Here is the box I've been working on. I had to notch out the stock cross member in the trunk to get the best use of space. The ports for the tank return, fuel pickup and lines to the carbs will poke out of the box with some grommets in order to keep it sealed up. Just need to get it welded up and mount the components.

The external fuel pump that will keep the surge tank full. It's 30gph around 4-6PSI, which is nice since if either of the pumps die, the other should be able to take over and get me home if I close up the return.

After STPR Luke , Jason, Jared and I worked on the rear bulkhead. I brought a 24" x 48" .063 Aluminum sheet down and we proceeded to get rid of all the right angles , flat surfaces and scratched up the polished finish. We ended up with this.

I still need to get some fasteners and mount it up, but it fits great.

[Geoff]

Fancy rear bulkhead! Most sedan 99 rear bulkheads I've seen were made out of the metal plate that came off the back of the stock rear seats (or in my case, a piece of aluminum laid over the metal rear seat plate and hammered until it took the shape of the dimples in the stock rear seat plate ). Yours is much more elegant!

[DrewP]

I'd been worried about the pickup in the tank in my '73, can you elaborate about what you learned about what's in the tank? When I got it the accumulator leaked so I just ran it without one for a while - engine cut out badly when turning left with less than ~1/3rd tank of fuel.

I'm considering welding a collar on the top of it to mount a later C900 in-tank assembly with a Walbro pump and keeping the whole thing under the trunk floor.

[Jordan]

The pickup tube extends down from the upper most side port next to the filler diagonally to a low spot on the tank. If you look at the tank from underneath , there is a small rectangular area that sits down a half inch or so from the rest of the tank. Apparently, both sides of the tank are baffled as well as having some sort of directing plates to handle fore-aft sloshing and move fuel into this area. Luke found this out by hole-sawing a 3 or 4 inch hole in order to clean out a softball sized tarball from a '74 tank.

I was using what I thought was the pickup tube, which was the straw that extended down into the middle of the tank through the fuel-level sender cover plate .. that was most likely a return of some sort. I had just capped the actual pickup tube thinking IT was the return. I tested this by draining at least 8 gallons out of the tank, hooked a vacuum pump up to the port and it pulled gas up easily.

Basically my set up will be Tank -> Filter -> Pump 1 -> Swirl Tank -> Pump 2 -> Carb. Any overflow from the surge tank and air will get pushed back to the tank.

If you are doing EFI where it is far more critical to keep the fuel pressure up while I just have to keep the bowls full @ ~3 psi. I would definitely do a swirl tank if I were you. Add another inlet to the swirl tank for the return line from the rail. Use a low-pressure hi-flow pump into the tank and whatever EFI pump you were going to use after that, feeding the rail.

[DrewP]

Good to know. I probably had my pump plumbed wrong then, I took all the lines off without marking everything the first time and had a bear of a time figuring out what went where on that crazy 3-port Bosch roller pump.

[Jordan]

Some progress. I should have everything back together today and be able to test out the system.

Box all welded up (Thanks Bob)..next came mounting it and all of the components and drilling the input/output holes.

Several hours later...

I just need to re run the pickup line from the tank and should be able to fire it up and check for leaks... all in all I'm happy with the way it turned out. I may add some foam or dynamat-ish stuff to absorb some of the sound and vibration. It's a very tight setup but still serviceable if need be.

[Luke]

Looks pretty spiffy.

[Jordan]

Got it all set up today, and drove it around. I think part of the reason the original setup was so loud was because it was getting fuel starved... or had to just pull a lot...now it is really quiet...Those facet pumps however are REALLY FUCKING LOUD... like a tiny knome trying to get out of the car with a hammer... or really bad valve chatter...but when they get full of fuel its not too bad. It's not droning like the other set up was.

I think with the bulkhead in place and maybe some sound absorption inside the box I can definitely live with it. I drove the car around most of the day. Does fine the way it's setup now.. just runs pretty rich according to the wideband. I might throw a simple regulator just to take another variable out of the mix. People say Webers are very sensitive to fuel pressure and right now those pumps run a tad high.

Fuel pressure was stable and I felt confident I wasn't going to have any issues. Next up is going to be my shocks. I realized today they are WAAAY under dampened for the springs.. I'll probably call up Bilstein and have some cores rebuilt to their recommendations. It would probably cost me the close to the same as those new "rally" valved ones.. but I;m interested to hear what they recommend.

[squaab99t]

I've talked to Bilstien before and they said about $75 per shock revalve/rebuild.

[Jordan]

Did you have a pair setup by them? If so what were the specs and what did you use them for.

For what I've heard is they ask you the weight of the car, type of driving you'll be doing and the spring rate and they give you some recommended rates.

The ones in there now are just the stock '76 EMS shocks so I'm sure I could use an update.

[Jordan]

So I called up Bilstein and they just said to fill out the rebuild sheet with the some info about the vehicle and they would figure it out then....hopefully if I get it out today or Monday I can get them back before Okemo.

[Jordan]

snapped a pic of the finished box. "Rally" Bob Legere is into Opels and TIG'd the plates up for me, hence the sticker

Fuel pressure regulator is on order. I just noticed today when everything is full .. it runs really rich and the fuel pressure gauge needle is jumping back and forth very quickly between 3 and 7. I think there has to be some feedback (or feed-through) of pressure pulses through the pumps . The float needles get over-powered and the bowls overfill. It's definitely been a learning experience

[DrewP]

When my new 'rally' Bilsteins showed up for the 99 I just stuck them on the floor and leaned on them, and they are significantly stiffer than the C900 HD's that I had right next to them to compare them to, haven't driven on them yet of course, but they seem REALLY stiff.


Fuel box looks really good, more stuff of yours for me to copy I guess.

[Jordan]

Fuel box looks really good, more stuff of yours for me to copy I guess.

If i had more vertical room or had a shorter 90º fitting on the surge return I would have had a side exit for that so it wouldn't have to be removed to take off the top. Still really easy to disassemble if I have to, just not ideal. I also would probably used a rotary pump instead of the facet...still might. You can't see it in the photo but the I've isolated it on vibration-damping mounts with pin studs.

[Jordan]

Got the bulkhead installed the other day.

Put some weather stripping around the edge for added seal and fit. Also I welded in two locating studs at the top to aid in panel alignment.