Another area of an RX-7 that needs to be upgraded for an LSX engine is the fuel system. Even though the stock fuel pump is capable of flowing well enough for a stock engine, the pressure of the fuel needs to be regulated before it enters the fuel rails. I found a helpful post on NoRotors that explains how to remote mount a Corvette fuel filter in the rear of the car. This filter regulates the pressure at 58 psi (what stock engine requires). By placing the filter near the fuel pump, it frees up room in the engine bay and remains hidden in a relatively easy to access location.
Note: We performed this installation before we reinstalled the rear subframe in the previous update.
Nearly all of the parts required were purchased through Summit Racing, the newest sponsor for the project. The hose and clamps were purchased at a local auto parts store.
LSX RX-7 Fuel System Part Numbers
Qty 1 – Dorman 800-080 – Sold in packs of 2
Qty 2 – Dorman 800-085 – Sold in packs of 2
Qty 1 – Dorman 800-155
Qty 1 – Wix 33737 (Corvette fuel filter)
8 feet of high pressure fuel injection hose
Qty 6 – fuel injection line clamps
M8X1.25 bolt – 12-15mm long (standard bolt used throughout most import cars)
Special Tools Required
High quality tubing bender
The first step was to bend the steel tube. We started by using a cheap tubing bender from the auto parts store that was advertised as capable of bending steel tubing. It wasn’t. I ended up having to ask a friend with a nicer one bend it for me. The only measurement that was critical was the end exiting the fuel filter had to be less than 2.5 inches from the stopping point on the tube. This allowed it to bend before contacting the chassis. The rest of the bends were approximated.
Next, 1 of the 5/16 and 1 of the 3/8 quick disconnects were attached to the ends of the fuel filter. The barbed ends of the quick disconnect fittings were attached to 24″ sections of the tubing. There was an existing threaded hole on the chassis that was used to mount the fuel filter using the M8X1.25 bolt. Instead of drilling another hole like the post suggested, we just made sure to sand down the paint in the mounting location so that the filter bracket made contact with bare metal.
We then installed the pieces of tubing to the feed and return lines going to the top of the stock fuel pump. A short section of 10″ tubing was used to attach to the bent steel tube to the factory hard line running to the engine bay. On the engine bay side, we used approximately 36″ of tubing and the extra 3/8 quick disconnect to attach to the LS1 fuel rail.
Ideally, I would have preferred to use AN fittings and braided hose for the entire system, but these stock GM replacements should work for the time being. I plan on upgrading the fuel system when I move on to Stage 2 of the build (head/cam swap). At this point, the fuel system is complete and the engine is nearly ready to start! This type of fuel filter setup would probably work well on just about any import car that is being swapped with an LSX engine.
More in-depth instructions for this modification can be found here.
[Source: NoRotors.com]
Previous posts about Project V8 RX-7:
Update 11 – Rear Subframe Modification and Bushing Install
Update 10 – S4 Turbo II Parts Car
Update 9 – L33 Modifications and Preliminary Install
Update 8 – Ronin Speedworks LSX Mount Kit
Update 7 – Improved Racing Oil Pan Baffle Install
Update 6 – Parts Engine Teardown
Update 5 – 5.3L Engine Purchase
Update 4 – The New Shop
Update 3 – Drivetrain Choices
Update 2 – Interior and Wiring
Update 1 – Engine Bay Preparation
Introduction to the Project