Date registered: Apr 2004
Location: Edmonton, Alberta & San Tan Valley, Arizona
Mentioned: 0 Post(s)
Quoted: 0 Post(s)
RE: 1973 450 SEL Fuel Economy
I have the same car except newer - 1978 with CIS MFI, but my 1972 280SE 4.5 has the same engine.
Remember that the engine combined with the hefty curb weight earns this car on average 19.9L/100 km (11.8 mpg) fuel economy, so for starts, you are not that far off of the factory specs.
I don't think the exhaust manifold bolt missing would attribute to it that much. Be careful drilling into the head. Hate to hear a horror story come out of that.
Read up on how to adjust the D-Jetronic - and I know it is possible because my 4.5 has the same system. Remember that new ECU's are very expensive so start with cheaper avenues. If you need help with this I can post some instructions from my Bosch FI book. Also take a look at your injectors, they are not hard to remove and inspect - perhaps they are worn out. Still pricey to replace but not as much as an ECU.
Maybe start looking at things like gaving the tires inflated to specs and trying to accelerate a little slower. Avoid using the kickdown. I know how fun these cars can be if you want to give them a little juice but it will cost you later.
Something I just learned as well. Be careful what spark plugs you place into these engies. They demand high temperature plugs.
Try other standard things like FI cleaners - Lucas makes some good stuff. Maybe a new air filter...the usual.
Good luck and let me know!