Can't get rev's past 4500 rpm

[ryanpe56]

I have a '71 280SL automatic which sat in a barn for 16yrs. I have resurrected it to the point that it has become an enjoyable driver. However, it has one persistent issue and that is it will not rev past 4500 RPM in any gear. It gets to 4500 and starts to plateau - it still is "running" but just not pulling anymore. If you up shift, it pulls hard up to 4500 and repeats itself again. Here are the major repairs done to the car relative to fuel and ignition: 1)valve adjustment 2)rebuilt electric fuel pump and it flows 1.3L in 15 sec 3)new fuel tank and lines(all flushed before & after install) 4) rebuilt Bosch pump by H&R 5)Pertronix ignition(module, coil, wires) 6)linkage tour adjustment(one time) 7)rebuilt injectors and tested with rebuilt pump by H&R 8)new plugs w/original heat range
9)100% of all fluid carrying hoses replaced 10) 100% of fluid carring tubes, manifolds, valves, pumps, radiator, heater core, & components thoroughly cleaned or rebuilt if needed 11)all filters replaced 12)initial timing set to spec.
I have not tried to rev it freewheeling(not under load) so don't know if it will go past 4500 but I suspect it may. The cold start works perfectly. Warm start is immediate.Idle @ 850. It never backfires or stumbles up to 4500. Pulls hard and can get rubber shifting into 2nd. Runs unbelievably well.   I am at 7200 ft elevation, running 91 octane, 125psi of compression - within 3%  across all cyl's. It smokes at start-up but clears up quickly. Car is original mechanically and has in excess of 145,000 miles. I have read almost every thread on this great forum but have not found a solution yet. I am thanking everyone in advance with any help or ideas on this issue. Thx, Pat.

[roymil]

If you haven't already, you should review the "linkage tour" posted at top of this section.   It's a very detailed step-by-step explanation of every adjustment and measurement of the linkage between the FIP and the venturi.  It could be that your pedal to linkage, or FIP, or venturi is not allowing full throttle, or they are not closely synchronized to maintain proper mixture at higher throttle settings.  Following the procedure solved several throttle problems for me.  Several can attest that even worn bushings in the linkage can allow enough slop in the linkage to impact performance.

[ryanpe56]

Thanks for the comment. I went through various posts and the linkage tour and have adjusted everything to spec. I'm not saying its perfect as some of the bushings have some wear but in general the rod linkage is 233mm, the intake throttle butterfly is set using the MercedesSource(Ken) video, the throttle butterfly is wide open at full throttle, the pedal stop is properly adjusted. I plan on seeing if I can get 4500 out of it in my driveway today. The trans kick down switch is defective but I am not worried about that at this point...or should I be?

[rwmastel]

The trans kick down switch is defective but I am not worried about that at this point...or should I be?

I wouldn't worry about it regarding this issue.

[ja17]

Ignition Coil?

[stickandrudderman]

Three things to check:
Fuel pressure
FUEL DELIVERY RATE
Ignition timing at 3500rpm as well as idle.

These are the basic fundamentals that must be right before you start further down the diagnostic path.

If they are correct then you have to wonder whether the problem is fuel or spark related.
As Joe has stated, it could be a coil and is an easy test by swapping out with another if you have one.
However, before doing that I would do the split linkage test at 4000 rpm. Try adding fuel via the pump push rod at 4000 rpm and see if there's an increase in RPM. If there is then you know you've got a fuel delivery issue.