"Is it possible to run a 1.7 16 valve boxer engine with carbs? Or is it better to stick to the standard fuel injection with ecu thing? Would it be reliable with carbs and run well as a road car?"
Conversion to carbs has been done in many cases. Higher torque, and horsepower can be achieved compared
to the standard (not chipped) Bosch ML4.1 ECU.
"Imagine an engine bay totally set up for an 1.7 8 valve. Fuel pipes, wiring, plumbing etc all in the right place. What would I need to consider adding, extending, shortening, re-positioning, changing etc if I bolted a 16 valve in it's place running carbs (if I can) and running fuel injection (standard)?"
First let's look the differences between the injection systems:
- Fuel pipes: no difference
- Fuel vapor recovery system: it's a little bit different. First you have to know what injection system fitted
to your current engine. Bosch LE3 Jetronic (before apr '92) or Bosch Motronic MP3.1 (after apr '92), because
adapting the vapour recovery for 16V is simplier to the Motronic MP3.1 system.
- Electrical connections: the whole ECU cable harness must be replaced (when keeping the 16v ECU), but you
can use the same lambda sensor without changing any of the wires if you have LE3 Jetronic injection, the
Motronic MP3.1 system uses 4wired lambda sensor, therefore the signal connector is different.
- Accelerator cable is different.
- Exhaust manifold is different.
- Starter motor is stronger on 16V (1,1 kW with planetary gear reduction) compared to the standard 1.7 engine
(0,8 kW direct drive)
- Starter motor mounting requires a spacer between the rear crankcase cover and the starter motor. This spacer
is present on engines with Motronic MP3.1, but missing on engines with LE3 Jetronic, because the flywheel is
- Air flow meter is different (too).
When using carbs reduced fuel pressure must be applied.
The pressure can be reduced with a variable fuel pressure regulator. The other way is a bit harder:
mechanical fuel pump. It requires the replacement of the original engine rear cover on the 16V engine.
You need to install a mechanical distributor which capable the RPM and load dependent ingnition advance
correction (or equivalent distributorless ignition system...). The original 1.7 IE distributor can't be used.
"My car has limited room for the engine and the 8 valve just fits. Is the 16 valve any different in depth? i.e. back flywheel casting to front plastic belt covers? Is it any different in height?"
The depth is somewhat differs, but the 16V engine fits in the place of 8V. Prepare some difficulties when
replacing the spark plugs.
"This could be tricky - Does a 16 valve engine run hotter than an 8 valve?"
Yes. Bigger horsepower generates more heat, but the 8V and 16V engines fitted with the same radiator and
cooling fan originally.
Maybe I forgot something, but I hope this is somewhat helpful.