The 1975 914-6 Conversion I bought just over a year ago has....had 993 heater boxes with Cats. The heat worked great, no complaints there.

Decided since I'm running essentially a stock HP 2.7 with CIS, put original 914-6 heater boxes back on.

These clearly required some modification to work on a 914 including having the passenger side flanges clocked differently. It took some time to wiggle a wrench or socket to remove the nuts on that side.

Here we go, some pictures!

Installed still, shows how the tubes and flapper install:

Closer shot showing the modification. Looks like they used exhaust pipe from a local parts store:

Other side, note how the holes don't line up with the flanges. This made it very challenging to remove. Two of the nuts were almost impossible to get to even with special tools:

Shot with the Cats.

Will say if you have a 1975 914, live in CA and want a Six, this worked for the guy. It sounded great, nice and quiet and very classic six sound.

I converted a set of those for a 914-6 hot rod, verified they fit, but sadly never ran them.

Cool to see someone else had the same idea and that they actually work.

They are really well made and flow excellent so it think its a great choice for a 6 conversion with a larger engine.

Been told the tubes are 1 5/8" which is good, but not equal length.

Dunno what I'm going to do with them. I'm migrating back to stock 914-6 boxes.

Will say the heat worked really well, flowed very nice. The guys welds aren't the cleanest, but the system worked well.

The prior owner did this on a 3.2 I purchased. I’m not a fan and they were removed.

The guy certainly gets an A for effort, but agree with you, going back to stock 914-6 boxes. My 2.7 with CIS is only 175hp and essentially stock. 1 1/2" pipes should be fine.

With cats, they weigh only a bit more than stock 914'6 HE's. He also fabbed up a bracket to use straps to hang the muffler. I'm not using any of that, just reverting back to all 914-6 stuff.

The 993 heat exchanger is a pretty good design and more ideal for a turbo application. Had them on my turbo. Great heat but man that setup is a bit rough. I still like them though. Not equal length and thats the big problem.