Reviving Dead Cobra

[C5GTO]

The engine transplant and new EFI/ECU conversion is complete. I took the Cobra out for an hour and half drive this morning and all seems to be working well, now for the details.

I did end up going with the Holley Terminator X multiport EFI system.





With the oval air cleaner in place, I had a friend take a quick look at the engine and he said, “So you did end up going with a carburetor.” I had him look again and his reply was, “Nice job in disguising the EFI.”



It’s basically a 1000 cfm 4 barrel throttle body on a single plane high rise intake with fuel injectors in the intake runners. The other bits include a Holley dual sync distributor, MSD AL6 box/coil, Terminator X ECU and engine wiring harness. Running the wiring harness through the firewall and grafting it into the other wiring took some work but the provided instructions were good and it was fairly straight forward.

The intake manifold is fairly tall so I did a couple of things to make it all fit under the Cobra hood. First, I milled about 3/8” off the intake top and re-angled the flange so the air cleaner top would run parallel with the hood scoop. The air cleaner base plate that came from Holley is raised about 5/8” above the top of the throttle body to provide clearance for the throttle cable/linkage. I made a new base plate from .090 aluminum with no rise in it and trimmed some off the throttle body linkage to clear the now lower air cleaner. With these modifications, the oval air cleaner with a 2 ½” tall filter sits very nicely inside the hood scoop.

I bought the EFI system from Prestige Motorsports and they loaded a base tune into the ECU that included all the particulars about the cam, timing, fuel injectors, etc. so I didn’t have to run through the typical wizards for EFI configuration. I made up a new set of fuel hoses using PTFE hose and set the fuel pressure to 43.5 lbs with the regulator. I did have to set the base ignition timing and install plug wires in the proper firing order after installing the new distributor.

After purging the air from the fuel rails, the engine fired right up. The nice LED display included with the Terminator X shows readouts for A/F ratio, rpm, coolant temp, and whether the ECU is in closed loop and if in learning mode. All things that are very helpful during initial engine startup. The A/F started at about 12.5, once the coolant temp reached 160F, the ECU went into learning mode and started optimizing itself. Soon the A/F was about 13.5 and has stayed in the high 13s/low 14s since.

After putting a few hundred miles on the new engine/EFI, I’ve got to say that I’m very happy with the Prestige Motorsports and Holley products. The engine starts right up, runs and sounds great. I’ve had zero issues so far and it’s been a great build experience.

As to other components changed out as part of the Cobra revival. There’s no comparison between the Tremec TKX transmission and the prior Richmond Gear 4+1 transmission. The TKX is easy to shift and the gear ratios are spot on. The engine turns at 2,300 rpm at 70 mph now. The new Wilwood front calipers have improved the braking performance. I can’t really comment on the new posi differential because I’m not stressing the engine yet and it’s hard to gauge a posi without giving it some real juice.

I didn’t know how much I missed driving the Cobra until getting it back on the road again!