Vintage Cars: what should one check before buyin, timing chain replacement, pressure gage

Question
QUESTION: I'm considering buying 1979 450 sl, test drove it and runs great.It accelerates quickly no smoke the gas pedal seems fairly hard/stiff to push down on(is this normal).Cruised well at 70 or 80. Cool day but temp seemed normal around 180, oil pressure gage was pegged at 45 the entire time(made me wonder if gauge was working) The upshift was very firm/noticeable at times.Would i be wise to have it put on a diagnostic machine, unsure how much feed back the computer on thse give. Unfortunately not much in the way of maintainece history avaible. how hard/expensive is it to get things like cam chain/belt(s) and tensioner checked or changed. I'm a pretty good mechanic but no experience with this type motor, can most of the maintainence be done by myself ?

ANSWER: Dan
If you are handy with tools, these are pretty straight forward, you will some manuals but they are available
The engine is a good one but you will have to learn about the KJet bosch injection system.
The temp sounds good as does the oil pressure, you should be pegged at normal driving, lower when at idle or out of gear. Firm shifts are also normal , these cars use flex discs in place of differential joints and they have a firm feel. Gas pedal firmness is also OK
How many miles?  Without a service history you need to have it checked out by a MB mechanic, for $100 or so , may be the best money you can spend.   a properly mainteained 450 will go forever, the non maintained will have you running to the bank!
If you have done timing chains before this engine is similar, but it is a big job, pros charge nearly 3000 for a timing chain replacement
look for rust, pull the carpets and look in the trunk
AC is a big issue on these car.  Check for heat and cool , if they do not work the servo is bad, that part alone is 500$
Let me know what else you find as you look at it and let me know how I can help.  What is the seller asking, remember there are lots of them out there!, esecially with gas prices so high.  Expect 12-14mpg
Godo Luck Dan
Happy Motoring
Ron

---------- FOLLOW-UP ----------

QUESTION: Thanks for the information, it has 160,000 on it that is why I'm concerned about some of the higher mileage maintence items. They want 4,500 for it and it only has the soft top.The paint is still great looking and all the chrome and badges are there and in good shape.The heater works great. The interior shows normal wear for a car this old and many miles.I'm confident I could perform almost all the maintainence.I guess my main concern would be something unseen like timing chain breaking and destroying the motor.Whats the recommended mileage to change one ?
Thanks for your time I would definitely buy a service manual if I decide to purchase.
Thanks again,
Dan

Answer
Well if the maintenance has been done, you can expect a chain to  go 200K or more. These have double row timing chains ( the earlier 380's did not) and usually give some warning.  At start up they clack and clang if loose or worn.  Take a stethescope and put it on the valve cover - you should here a whirl and no metal on metal noises.
The V8 in these cars are pretty bomb proof, The  1979-1980 450SLs, are solid performers, 180HP and handle well.  The HP was decreased in 74 Iin line with emisions standards.  MY 72 has 230 HP.  $4500 is ballpark for this car but  without the hard top, I would offer less (although you could pick one up for 500-600$).  .
Original paint?, no rust? Hows the soft top?
Also check under the hood, a well maintained V8 of this era should have good looking rubber hoses and connections.  They should not be original at that mileage.  Why no service history?  remember this was a car that cost upwards of 30K in 79, most folks took care of them and kept records.  I am always leary of one with no records!
The climate control is the Achilles heel of these cars, so really check it out.  Also remember , despite what you are told, that these are really not much of a collector car, so the money you put into it, you may or may not be able to get back.  On the other hand if you pick it up for 3500-4K , you would not be able to get that much of a car on a car lot, nor would it be as much fun.
let me know how else I can help
Happy Motoring
Ron