BenzWorld Senior Member
Date registered: Jul 2006
Vehicle: European 1974 350SLC ,'78 300CD& '80 300CD sold , '81 240D SWMBO's Car '84 300CD & Euro
Location: Sunny So. Cal.
Mentioned: 0 Post(s)
Quoted: 19 Post(s)
First things first :
99 % of the flat spot problems I encounter all have incorrectly adjusted valves (usually too tight) followed by improper ignition timing or stuck advance flyweights in the dizzy ( I assume you know to remove the rotor and dribble in a few drops of engine oil monthly) followed by vacuum advanced can either not holding vacuum or not connected to the correct
" Ported vacuum " source (this means NO vacuum signal until the throttle goes off idle) .
Just tossing different carbies at it without taking the time to check and adjust everything else , is a waste of time & $ .
Pretty much every customer insists the valves are fine (they never are) and they've checked the timing when in fact they've at most checked the idle timing but never the advance range and tip in much less the amount of total timing advance when under load . (about 30 DBTDC , varies on each engine)
I don't want to give you bad advice so follow the basics and usually some minor little thing , once fixed , cures the problem .
I assume that when you have the engine off and remove the air cleaner & look down into the carby throat and work the throttle , you see a healthy squirt of fuel the instant the throttle linkage is actuated ? if not , there's your flat spot right there .
Old German cars & motos
vintage car mechanic