QuestionQUESTION: I have a 1985 380 SL what is the correct spark plug gap? I bought this car it has BOSCH ro 970 plugs but the gap looks huge, I can pass a quarter thru the gap easily but not a nickle. I don't care for points, condenser & the old tech. Can this ignition be switched to electronic? in fact I would like to put a more modern motor & transmission in this car. Is it possible & is there a combo you would recommend? I would like to keep performance as close to original as possible. The cruse, door locks, horn & cig lighter, flashers do not work. Any common problem associated with these besides the fuse box
Joe
ANSWER: It would appear that the vehicle has been poorly maintained. Plug gap should be
0.030" to 0.035". It comes with a very reliable electronic ignition. The engine
is an all aluminum SOHC with enough horsepower already. If it is sluggish on
take off from standstill then the stator is locked (in the transmission torque
converteer)--quite common. I would use NGK BPR5ES or Champion RN12YC plugs.
The door locks are vacuum operated and the usual culprit is either worn hoses
or the check valve found usually near the firewall in the engine compartment.
I believe that year still used the ceramic fuses--change them all and wire
brush the contacts and use WD-40 on the window switches.
All of this is from memory as I am not near my data library. So send another
query when you need more detail and will respond not so quickly.
One last thing. If the heads are removed for any reason you must have every
headbolt hole heli-coiled--unless you want the job done several more times.
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QUESTION: how are the cylinders numbered on the car. Where is number 1?
the firing order in the manual says : 1-5-4-8-6-3-7-2
How do I know what is where? Motor has a bad knock - I suspect a wire is out of place - Maybe?
Thank you for prior info...
ANSWER: The right bank (in USA passenger side) 1-2-3-4,
left bank 5-6-7-8
Pulling the plugs in order should give you the
bad cylinder. The original wires have a reistor
in the plastic spark plug boot--it fails readily.
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QUESTION: Thank you very much, you help is very appreciated. My wife actually thinks I have skills!!:) after a new cap / rotor / plugs it runs a little better & now I know that is not the problem. The plugs were worn down to a nub and the rotor had eaten up the contacts (its a wonder it ran at all). I am going to do the wires next. Can I use a universal set or do I need the Mercedes specific. The wires are all going to the right cylinders but I did notice where the wire connects to the plug contact some seem loose or just not as tight or solid as the others. It is still very ruff & sluggish. I don't start it any more than I have to. It is not ticking or clicking but is so ruff (shakes the car) it's like its out of time? If 1 or both of the timing belts broke or jumped will the car still run? (if I remember right its NO) It starts almost instantly but its very ruff. Many of the vacuum line splitters & joints are leaking & I am changing them. Is there a vacuum line that could cause this. The one to the distributor is good, I can feel a light suction on it. I blow on it & that one does not leak. Someone I talked with suggested the distributor shaft but it seems unlikely & I think there is more to check before I try to pull that. I fear this is a broken piston, valve or something similar. Your right about it being poorly maintained. It looks great with no rust & very good paint, the inside is not bad either, hard top, rag top & all. But mechanically I am going to have a lot of questions. If interested I will send you a pic. I paid $1200 for it knowing how it ran. It came with bran new Michelin tires, bran new (nice) battery & new starter. I think it's worth fixing. I've ordered the manual but its been a long time since I did this stuff. Its the little stuff that experience teaches that I am so ruff on or don't know about these cars. I understand how it all works & for the most part why. I do my own water pumps, batteries, brakes, starters, oil ETC... I am having fun, its coming back.
Thanks again
Joe
AnswerUse 8mm ignition wires from MSD or Belkin. That will eliminate the troublesome
reistor plug contacts on the factory ignition wires. Then get rid of every leaking vacuun
hose before thinking about expensive stuff. By the way, a compression gauge (even a cheap one
that treads into the spark plug hole is very good) and a vacuum gauge will help
greatly in troubleshooting the problem.
