Planning the EFI system
First step was to plan the system out. What parts would be needed, and what system was the best choice?
I already knew I wanted a top-fed system (pic 1) rather than the front fed systems (pic 2).
Top-fed
Front-fed
With a top-fed system I could hook up a cold air induction via a L-88 hood. The front fed system would place the aircleaner just behind the radiator, where the air is the hottest.
I realized I would need a L-88 hood. All the pre-made systems use a high rise single plane intake that would not fit under the stock BB hood. There was the possibility to have my Torker II converted to EFI and maybe, maybe make it fit under the stock hood. I decided against this for a couple of reasons. First was no cold air. More importantly though, is that the Torker II is just not a good intake. Even Edelbrock told me so when I called and asked them. According to edelbrock I'm loosing 20-30 hp and 40 ft-lbs of torque in the intake alone compared to a Performer RPM. Looking at the EFI manifolds made me drool. A Victor JR style single plane a full inch taller than the performer RPM. Hello top end power! The EFI manifolds are a full 3" taller than a Torker II. That increased plenum spells major power gain. And with Port EFI you don't get the low-speed driveability problems tall single plane intakes have with carbs.
The choice fell on the Holley Commander 950 system. I ordered it with 30 lbs injector that support 450-550 hp. Prices have come down since the last time I looked at EFI. The complete Holley system was $2100 after the 10% summit discount.
I also ordered a L-88 hood and fresh air chamber from Ecklers.
The Holley system gives the option of also controlling the timing advance if a computer controlled distributor is used. I ordered a 7-pin Accell distributor for 81-86 GM cars for $170.
I decided to install the system in 3 stages:
Stage 1: L-88 hood open, without the fresh air chamber. Use my old drop-base aircleaner. This will let me get the car running without worrying about the cold air.
Stage 2: After the EFI is dialled in and runs well, I will bond in the fresh air chamber, and installa L-88 aircleaner base and make the cold air functional.
Stage 3: Paint the hood.
I also identified several installation issues:
Controller mounting: The Holley Commander 950 controller is very small at 4.5x5.5x2 inches. I will mount it behind the passenger side dash pad.
Fuel return line: The stock 1/4" return line is insufficient for EFI. However, the vapor purge line is 5/16" inner diameter and will work. It is also convienently ;ocated on the drivers side frame rail (the return comes off the drivers side fuel rail).
O2 sensor mounting: Mounting the O2 sensor in the header collector can create problems at low speed/idle. The exhaust temp goes down to 300-400F and the sensor will read lean even though the mixture is correct. The controller will richen it and the engine will idle rich. One solution is to go open loop at low rpm, but this does not appeal to me. Another solution is to mount the sensor in a primary tube. This will let the system stay in closed loop at low rpm. Drawback is that the sensor only measures one cylinder. Due to distribution issues, that cylinder could be richer or leaner than the other cylinders. Even with the potential distribution issues, I think this is what I will do. My cam is very EFI friendly (relatively short duration at 224/232 dgr and a wide 114 dgr lobe separation). The short overlap should make the location in the primary tube work well.
Fuel pump: The Holley comes with either a in-tank or in-line pump. Unforunately, the in-tank pump does not fit inside a corvette tank. If I want the in-tank pump I will have to change out the tank. I decided to try the in-line first. If the noise is too loud I will look at an in-tank system at a future date. I will use lots of rubber mounts and I'm considering building a dynamat lines box for it. We'll see how quiet I can make it.