Hello Steve - there has been some discussion about this before. One obvious thing to do is switch over to a euro camshaft, if you have a US spec car. It adds about 10-15 HP by most accounts and is not (readily?) available in the US, but can be found readily in Europe, for less than $500. You may also need new cam bearings, depending on your current style. Check the vendor database: SLS, Niemoller and Van Dijk come to mind and there are others. The other simple modifications that people have been positive about in terms of adding performance, are a K&N airfilter and electronic ignition.
Here's several comprehensive lists of modifications from my own archives:
"I have tried to incorporate every performance enhancement that I am aware of:
Valve Clearances
New Cam
New Timing Chain
Rebuilt Distributor with Pertronix unit
No resistance in wires
Ceramic Coating inside exhaust manifold and exhaust system.
New Injectors
Rebuilt Fuel Injection pump
New Fuel delivery system
It runs great, but I always want more. Any other thoughts?
Yeah, early header pipes. Matching all the ports in the head. Hotter coil. Synthetic oil ETC.
Here is the tried-and-true list of performance options used by the hotrod community. They are all meant to increase the horsepower-to-weight ratio or reduce horsepower eating drag.
Reduce Driveline Friction:
Synthetics in engine, transmission, rear-end & wheel bearing.
Adjust bearings on the loose side.
Better Air Flow through the air pump (engine):
K&N Filter (direct attachment cone is the best)
Add an air scoop for some positive pressure at speed and utilizing cool (denser)outside air and not warm engine compartment air.
Modify the exhaust after the two header pipes come together to three incches with a non baffled muffler, i.e straight through.
Modify head with larger valves
New cam grind for the most desired RPM/speed
Better timing:
Electronic ignition for more precise timing
Advance ignition to 1 degree less than ping
Reduce rolling resitance:
Higher air pressure in tires
Purchase tires with the lowest rolling resistance
Less air drag:
Good wax job
No radio antenna
No right hand side mirror
Drive only with the hardtop on
Keep the windows rolled up
Lower the car
Lessen the weight:
Empty every non essential out of the car (carpet, radio, passenger seat, AC, trailer hitch, etc.)
Go on a diet
Part of this is extreme. The idea is to get one into the mind set of less weight, less resistance, and putting air through the 2.3 engine. In my racing days these principles plus true intake and exhaust headers allow me to get a 1966 1300 cc VW to run 100 mph plus a little.
You probably could turbo charge your car and reap great benefits. If you keep the turbo small enough and the boost low enough you should be able to have the best of all worlds. Having though of this myself(Having not even driven my own car yet but having read the 0 to 60 time of 11 seconds) a couple of the major hurdles would be manifolding the exaust gasses to the turbo and enrichening the fuel mixture to accout for greater air density. You might be able to solve the latter easily enough just by connecting a tube from the intake to the atmosphere port of the injection pump (it would have to have a check valve to the atmosphere so the port would see only boost and not vacuum) but you would probably be much better off adding a later fuel injection system which would be far more adaptable.
I did a lot of study on this subject while building my vintage race 230SL. First I was lucky to find a 2.8 engine out of a 300SEL 2.8 with the Euro "09" cam in it. I had the head ports matched and polished. New valve job with good quality three angle valve seats ground. I also had the intake and exhaust manifolds extrude honed to clean them up. I had the engine cleaned up by installing new pistons and had everything balanced to 1/2 gram tolerances. This helped in acceleration out of the turns. I had the injection pump rebuilt and recalibrated for racing by Hans at H&R. I used him because he has had experience building racing mechanical fuel injection pumps for Porsches. Then I installed new injectors. Has recommended the early style injectors found on 230SL and early 250SE and SL's. He thinks they flow better. Lastly I did install an abbreviated intake system using a large K&N filter. I actually removed the entire canister and attached the K&N to the intake manifold. The exhaust system was modified by using one large 3 inch pipe into a very small straight through muffler. I have since replaced this with a Borla stainless steel which seems to flow very well. I used the Crane emitter and detector style point replacement system and it has worked flawlessly. With the Euro cam and a 3.92 rear end ratio, I can rev to 7,000 RPM in first and second gears. After all of this, I think the engine barely makes an honest 200HP. I believe they were a bit overrated when new like all engines of the period. I had an engine builder evaluate this engine on a computer program and he believed it would require a much hotter cam, larger intake valves and thinner exhaust valve stems, a compression ratio of 11.5 to one to get 250HP. He though the intake manifold throttle size could be made larger and possibly get up to almost 100HP per liter. I figured this would cost an additional $4-5K. This would cost too much money and destroy the reliability of the engine which is very good at this time, so I opted for reliability and placed most emphasis on handling, braking and driving schools."
Cees Klumper in Amsterdam
'69 white 280 SL automatic
