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  #1  
Old 09-06-2007, 04:29 PM
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Join Date: Feb 2007
Location: Sacramento, CA
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Need opinions on rebuilding or replacing engine

Hello all

I have a decision to make that I would like some imput on. I have a '82 300SD with a bad engine. the car has 290k on the odometer but looks like it has been taken pretty good care of. I posted a thread about it back in April of this year, but the short story is this: After cruising down from Sacramento towards San Francisco the engine started loosing power and smoking like crazy on the San francisco Bay bridge. I had it towed back to Sacramneto and eventually did a compression test that turned up as follows: #1- 395, #2- 390, #3- 60, #4- 395, #5-325. This was after adjusting the valves and letting MMO sit in the cylinders for a couple of days. I did a leak down test with my air compressor on #3 and #5 and it sounded like the air was comming from the crankcase. I have an engine & tranny out of an '82 300d that has only 134k miles on them. My original plan was to put the 300d engine and tranny in the 300SD but am having second thoughts.

I have been wondering if it would not be better to try to fix the engine that is now in the 300SD. With the excellent compression in #s 1,2,4 and decent compression in #5 I am thinking the engine might have been rebuilt or be a replacement being as there is 290k on the car. If I pulled the head and found the bad compression in 3 is due to cracked rings maybe I could replace the rings and end up with a good engine in the car without pulling the engine, switching the transmission parts and engine mounts and putting the 300D engine in there.

One of the reasons I have been contemplating this is that I have seen several 300d's on craigslist, want ads etc. that looked like the body and interior were in excellent shape but went pretty cheap because the engine did not run or ran poorly(saw a '77 300D that went for $500 that had reportedly 151k and owner claimed was immaculate). If I could pick up one of those and install the 300D engine in it I could end up with a nice pristine 300d for a fraction of its worth. I have a daughter that will be needing a car in about 1-1/2 years and I like the idea of her having a car that was not too fast and has a high saftey factor. I have plenty of room to work on the cars.

Any way, what would you all do in my position?
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Sedecrem

82 300SD 290k(needs engine swap)
79 240D 354k with new heart transplant w/220k
82 240D w/auto tranny soon to be manual 4 speed
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  #2  
Old 09-06-2007, 04:47 PM
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Join Date: May 2002
Location: Blue Point, NY
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Quote:
Originally Posted by sedecrem View Post
I have been wondering if it would not be better to try to fix the engine that is now in the 300SD. With the excellent compression in #s 1,2,4 and decent compression in #5 I am thinking the engine might have been rebuilt or be a replacement being as there is 290k on the car. If I pulled the head and found the bad compression in 3 is due to cracked rings maybe I could replace the rings and end up with a good engine in the car without pulling the engine, switching the transmission parts and engine mounts and putting the 300D engine in there.
All conjecture at this point.

If you want to take a flier on the existing engine, you've got to pull the head and see what you have. You might have a bad valve..........simple fix. It might be a cracked ring.........more difficult fix.........or it might be a scored cylinder wall..........very difficult fix.

So, until the head comes off, it's difficult to provide a firm suggestion.
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Old 09-06-2007, 11:14 PM
t walgamuth's Avatar
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Join Date: Apr 2005
Location: Lafayette Indiana
Posts: 34,736
With air coming from the crankcase it must be in the cylinder/ piston....if he is correct about where the air is coming from.

It also could be a hole in the piston, although if that it would probably have zero compression not 60.

It is a long shot on fixing one hole but possible if the stars are aligned and you have been an excellent person.

If the cylinder wall is good you may get by on ringing that piston or even replacing it, but if the cylinder is scored or worn too much it will have to come apart and then you may as well do all five cylinders.

As Brian said, you will just have to tear off the head and see what you have.

Good luck.

Tom W
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[SIGPIC] Diesel loving autocrossing grandpa Architect. 08 Dodge 3/4 ton with Cummins & six speed; I have had about 35 benzes. I have a 39 Studebaker Coupe Express pickup in which I have had installed a 617 turbo and a five speed manual.[SIGPIC]

..I also have a 427 Cobra replica with an aluminum chassis.
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Old 09-06-2007, 11:22 PM
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Join Date: Mar 2006
Location: eastern shore,MD
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if ur intrested, im selling my sd... it has about 125k on new motor and about 225k on the tranny... send a pm if interested
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