LS1 Conversion, A Retrospective Build Thread Options

[andys]

Here's the start of a retrospective build thread of my LS1 conversion. It took a few years to get it done mostly due to not wanting to be a slave to the project, and work on it for the enjoyment; and of course when family obligations allowed......teen daughter and high maintenance wife (IMG:style_emoticons/default/biggrin.gif)

What I started with was a local orignal owner '75 2.0 with 139K miles. The original owner "drove the heck out of it" until something died in the electrical system and he parked it in the garage for 14 years, as evidenced by the renewal tags. Only body damage was when he submarined the rear of a Mustang and creased the hood and flattened the left signal light pod. Otherwise, it was a good condition rust free (SoCal) car.

Brief specs are: '01 LS1 Z28 motor, Audi 01E 6 speed tranaxle, 911 front suspension, custom made rear trailing arms, Koni shocks, 993 wheels, and AC.

Below, are photos of what I started with, and what I ended-up with. I'll do my best to re-trace the build process, so if you have any questions along the way, please ask.

BTW, how does one place text between photos in the same post?

Andys

[andys]

Thought I'd go through the fuel system next. The LS1 EFI system requires 58 psi. The PCM runs the fuel pump for 3 seconds when the key is on. The fuel pump resumes running once the PCM senses the crank rotating. So the basic fuel system has an external electric fuel pump which feeds a bypass style fuel pressure regulator with one line running to the motor, and the other returning to the fuel tank.

In order to adapt -6AN fittings to the stock 914 fuel tank, I tapped the exisiting inlet and outlet bungs to 3/8NPT....I got this tip from 914WORLD; Thanks! I installed some -6AN X 3/8NPT fittings. What I did on the outlet fitting, was to silver braze a tube and screen (sock) to mimic the 914 in tank screen (actually a VW part) to strain out any big particles. I used Summit Twist Tite push on hose and fittings that's good for 250psi. The feed hose goes through an Earl's 100 micron course filter before entering the Walbro 255 electric fuel pump. One of the two sure death's of this type of pump is particulate contamination, so an additional $50 for the pre-filter is worth it. The high pressure side of the pump feeds into a Vette filter/regulator to bring the pressure down to 58psi. It has a bypass which is plumbed back to the the orignal 914 return line bung. The regulated pressure feed hose goes to a thru-tunnel steel tube, but more on that in a minute. The Vette filter/regulator uses GM type push-on connections; one 3/8' male inlet, one 5/16" male return, and one 3/8" female out. To couple the two male fittings to -6AN, Russell makes adapter fittings, but here's a work of caution: The early style uses a plastic retaining clip that reportedly fails on occasion, according to experiences on the LS1 boards where some fires resulted. Russell subsequently offered a re-designed adapter that employs a positive locking system (644120, 3/8" x -6AN, and 644110, 5/16" x -6AN). The adapters shown in my photo, are the early stlye which I replaced as soon as I read the failure accounts. For the regulated side with the 3/8" female connector, I bought from NAPA a steel adapter tube that had the appropriate swaged male ends, cut one end off, and installed a 45 degree flare nut and flared the othe end. I then made a 180 degree bend to better route the hose under the tank and to the through tunnel steel tube. I purposely made the hoses long enough to allow me to pull the fuel tank up high enough to service anything underneath it without having to romove the hose fittings.

Now to the steel through tunnel line. Since I knew I wanted a steel line with fittings capable of sealing 58psi fuel pressure safely, I decided on a 60" pre-made 3/8" steel brake line with 45 degree flared ends. Here's why I went this route: NAPA offers brass 45 degree flare 3/8" x -6AN push-on high pressure hose adapters in both male and female. This kept things really simple without the need for all kinds of fittings cobbled together. The brake line was bent to shape by trial and error untill it had the shape I was looking for. It passes through the stock 914 rubber fuel line grommet at the front. I did have to slit the grommet to get the line in it, then I plugged the return line hole and pushed the grommet into place. The brake line at the engine bay makes a 90 degree bend towards the passenger side. Here, I added a flare line coupling and used a second pre-made brake line formed to run a path up, then turn towards the passenger side under the engine shelf, all hung from Adel clamps. This line stops just above the engine shelf where another NAPA flare to -6AN hose fitting is used. With another Summit hose, it runs to the LS1 fuel rail through a heat reflective tube. The fitting on the fuel rail in also a GM push-on, so another Russell adapter fitting was used there.

That was long winded for sure, but hope it helps detail what the photos don't show.