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Old 12-14-2002, 03:27 PM
afmcorp's Avatar
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Join Date: Jan 2002
Location: NW Indiana LaPorte
Posts: 571
Question how far to go repairing the engine (126)

hello, i'm looking for some help rationalizing how much work to put into my 88 420sel.

i bought this car this time last year. soon after the motor started the awful lifter noise. so i left it to sit till i slowed down enough for some time to fiddle with it. what it ended up being is a rocker arm got lunched on the right side. just one. so i'm committed to repair this issue. i bought a new cam, rocker, ball stud and vlv cover gskt.

now here's the question. 1st the car really is cherry. excellent interior, everything works, runs super. and i got 6k in it now. now i need a car that can be a daily driver as well as looking good for guests when i call on them. now i was planning to just fix what was wrong. however i keep eyeing the chain assy mostly the plastic parts. i mean i am right there and it wouldn't cost me much except another 150 bucks to do a new chain and all the plastic goodies. i really need a nice car without the cost involved. i just ran my 98 merc grand marq into the ground value wise at 90k.

i figure i could ride another 100k on this mb 420sel and all it would cost is the 6500 i would have in it. so with all this information......

should i replace all the ball studs (i own the special vlv spring tool and the height check) and maybe the cam even though it is now looking just fine. i've read a few comments of this happening on the 126's due to poor oiling. so should i expect the non replaced parts to last another 100k miles. the oil pressure is super the car rides good with no bad tire wear noticable.

part of my indecision is the xtra 260 bucks but it will add quite a bit of time to the job.

if i fix the top end and the timing chain, can i expect to see 100k more from the bottom end i.e: block / pistons & crank.

it was a southern car so there is no visable rust but who knows about the little crevises and what is hidding.

any advice is welcomed.
tks much

this forum is probably the best source of info i have ever seen for depth of knowledge and on point of issues.

here is my other mb '72 350sl red w/black int
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how far to go repairing the engine (126)-350sl-d.jpg  
Thanks Much!

1972 350sl Red/Blk 117k
1988 420sel charcoal/Blk 140k
1987 420sel gold/tan 128k
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Old 12-14-2002, 11:31 PM
MikeTangas's Avatar
Senior Member
Join Date: Apr 2000
Location: So. Cal
Posts: 4,430
I'd say spend the bucks. I highly doubt you'd be able to wear out the bottom end, unless you absolutely neglect the engine. Bottom end is likely good for 400K+ miles.

Replace the drip tube connectors while you're in there, and make sure the drip tube passages are clear.
Mike Tangas
'73 280SEL 4.5 (9/72)- RIP
Only 8,173 units built from 5/71 thru 11/72

'02 CLK320 Cabriolet - wifey's mid-life crisis

2012 VW Jetta Sportwagon least its a diesel

Non illegitemae carborundum.
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Old 12-15-2002, 10:57 AM
Join Date: Mar 2000
Location: Gainesville FL
Posts: 6,844
I see no reason for wholesale replacement of the ball studs/lifters. The rocker arms are another story. MB says all rockers should be replaced with a new cam.

Rockers that have had one failure usually mean they are wearing through the surface hardening. Its a mess very soon afterward.

These motors are basically indestructable! They do not wear out. The only bottom end damage I have ever seen came from running without oil or water for amazing intervals.
Steve Brotherton
Continental Imports
Gainesville FL
Bosch Master, ASE Master, L1
33 years MB technician
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