'67 running out of steam at the top end

[redlineAMG]

Hello everyone, I'm new here and I've got a problem I need some advice on. It's a 1967 250SE and it ran bad when I got it but it would do 80 on the highway. Since then I've set the timing, point gap and dwell, adjusted the valve clearance, fixed a vacuum leak etc. and it idles really well and is responsive at moderate throttle input but if driven at all aggressively (more than 40% throttle) it will stumble, not misfire like, more like loss of fuel it seems. So the issue is at somewhat higher rpm's and is directly related to throttle input, meaning you can kinda drive around it around town but it will now only do 60 on the freeway and it's right on the verge of the symptom but if there is a slight uphill grade the bog comes into play and I'm holding up the slow lane. I will soon be changing the fuel filter (tomorrow) and I will measure the pressure output from the electric pump. By the way what is that spec I'm looking for, anybody know? May I have missed something on the tasks I performed previously? I'm a professional mechanic but this is my first classic Mercedes. Thanx in advance everybody!

[ja17]

Hello RedlineAMG,

Sounds like fuel starvation.  Change the main  filter first.  If it is full of rust or dirt, you will need to remove the electric fuel pump intake fitting. It has a filter screen built into it. The main drain in the fuel tank is next on the list. It also has fuel screen built into it. Do not by-pass any of these steps. When the tank drain/screen is out, examine the inside of the fuel tank. You can remove the fuel sender in the trunk and view the inside condition of the tank. If the tank is full of crud, it must be cleaned.

If the fuel system is clean, most  the linkage on the engine may be incorrect and you may not be  getting full throttle.

Welcome to the forum and keep us up to date!

[redlineAMG]

Thanks ja17, that's the plan. I hope it's just some simple blockage.  I cringe at the thought if injection pump issues. 

[Benz Dr.]

I've seen timing do the same/similar thing. Are you sure you are getting full advance? It should be about 36 degrees BTDC @ 3,000 RPM or above for optimum performance.

[redlineAMG]

Thank you as well Benz dr. , I will check for full advance tomorrow as well, good point. Hopefully tomorrow will be an eventful day in my cars high speed drivability.  Really appreciate the input guys, thanks.