I have a question about ignition/fuel – Crankshaft/valve timing relationship? I have an 86 5-speed, project and just bought another 86 in automatic to drive, and both are fairly lethargic once you get them to 70 mph. I realize these were built during the 55 mph highway days, and probably set the parameters of the pre-88 engines. Both 86 engines have vacuum advance distributers, rather than ECU control. What modifications can I make that will wring out a little more top end without spending a fortune?

The 88 engine I am putting into the 86 5-speed has higher compression, and different tail gears in the rear end, that may help in top end power.

But what about offset woodruff keys in the cam gear, like used in the diesel to increase the RPM breathing range of the cam?

Maybe some type of modification to the Fuel distributer assembly governed by the its voltage input, or maybe installing a 300 series throttle body to increase cfm to compensate the engine displacement.

Or maybe modifying the vacuum advance linkage mechanism, to increase the engines top end.

With the split exhaust manifolds, a dual exhaust system should easily relieve any constipation.

The engines feel like they are being throttled back rather than running out of power – no wonder the bottom end of these engines never give problem if you can’t rev them.

No replacement for displacement - how about another liter? I prefer to have a gallon minimum. Failing that, I recommend a turbo like Max did on his W210 M104.
On your automatic, make sure the transmission control pressure cable is attached and adjusted correctly to give you good shift points. On my 85 190E that went a long way in compensating for its underaspiration.

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Prost!

My first race car (SCCA) was a 1986 190E 2.3 8V.

Biggest HP improvement was from higher compression. So the 1988 engine will help a little.
BUT even with all types of modifications the engine is a slug (160 HP), and that is due to the long intake runners & CIS-E injection system.

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