Engine Work Part 3: Going 13B EFI

If you’ve been following this build at all, you’ll know that over the last several months we were working on getting this RX3 powered by a 12A bridge ported engine. After several dead donor engines and housings, we had to go with ‘plan C’ (plan A was stock port 12A, plan B was bridged 12A). Plan ‘C’ was to go with the “big block” swap and drop a 13B into this classic.

There are SEVERAL things you have to overcome when doing a 13B swap on the older RX-# cars and there are even more hurdles when you add EFI to the mix. Many of them kept us from having the 13B EFI swap as ‘plan A’ to begin with. The hurdles of dropping a 13B in are:

  1. Cost
  2. Mounting
  3. Driveline
  4. Exhaust
  5. Cooling

Hurdles of adding EFI to the equation:

  1. Cost again
  2. ECU/Harness
  3. Redoing fuel system
  4. Ignition

Luckily you can shortcut a ton of these issues by simply going with an early 13B 6-port from an ’84 or ’85 GSL-SE RX-7. Why does it shortcut the process? Well for starters, the 13B in the ’84-’85 RX7s utilizes the same front cover engine mounting configuration and oil pan/sump configuration as that of the earlier 12A & 13B carb’d cars (minus RX-2s, the oil pan on a GSL-SE engine will not clear the subframe on these cars). Secondly, the GSL-SE ignition system is the same as the 12A setup our car already had. Driveline issues are handled as the flywheel/clutch combination will mate directly up to the ’74 REPU transmission in our car. So that long list above gets shorter pretty quick if you use the right donor setup.

The reason we avoided the swap as the first plan was because at the time we assumed it would blow us way out of the budget. The opposite is actually what we’ve now learned is true and once that realization hit us, it was game on. The 13B 6 port EFI swap is actually going to cost us $0.00 for the engine as opposed to the $250 we’d factored in for the 12A Bridgeport as we’re no longer including the previous donor cars purchased for this project in the build as no parts from them are being utilized. Instead, we acquired a FREE, COMPLETE 1984 RX7 GSL-SE four YEARS ago before this project began and decided to us it instead. Why free? Well, there is no title for starters and it seems as though the car may have been a bit of a soar subject for it’s previous owner. The seller literally gave us the car just to get it out of his sight.

The car was banged up on the driver’s side and did not run at the time. The previous owner was informed the engine may have been rebuilt, but couldn’t produce paperwork to support that statement. We didn’t care. Got the car home, found a dead fuel pump being the culprit of it not running, replaced the pump, drove it into the woods and shut the door. At the time, we were just going to keep it around for parts for other projects. A GRM $2013 build wasn’t even on our minds back then.

The day came when we realized that we hadn’t pillaged all the parts from the GSL-SE that would make it viable for our swap into the RX3. Actually, all we’d really taken from the car were interior bits. Looking at the car for the first time in years, we quickly determined it wasn’t going anywhere near the garage. Four flat tires, busted clutch line and no brakes meant this engine pull was going to happen in the woods.

We wanted to get the engine running again before pulling it. At this point in the GRM project build, we don’t have time for another rebuild and if this engine is cooked, we weren’t going to waste more time on it. We rigged up a temporary fuel system, two jumper boxes and hit the key. It almost immediately started up and ran (once we realized we reversed the fuel return/feed lines).

We let the engine run for a bit, brought it to normal operating temps and checked for any leaks, burps, smoke, etc. NOTHING. This engine was in GREAT shape. Took a lunch break long enough to allow the engine to cool off a bit to run a compression test. Compression came back to even 82-88PSI on both front and rear all three faces. About normal for these engines. Considering the engine has been sitting, we expected lower numbers initially.

We grabbed the tractor and got on with it. An hour later the engine was sitting in the back of the truck to transport back to my home garage where the RX3 project is being assembled.


I know this was pretty lengthy and wordy, here are some videos we made while getting the engine tested and pulled from the donor car:

And some photos for your enjoyment:

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