4.5 Cam-valve lash adjustment - Mercedes-Benz Forum

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post #1 of 17 (permalink) Old 01-30-2009, 04:32 PM Thread Starter
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4.5 Cam-valve lash adjustment

I've got a few other post's up about my '75 4.5 that runs a bit weak.
But the funnies thing about this motor has to be the valve lash adjustment's I made.
When I set the lash to specs, the engine is weak but runs "ok". Then I opened the lash up to 3 or 4 times the spec and it runs great! and very strong! Of coarse it's unbearably noisy with valve train noise and I won't drive it like that. But my question is this. Dose this indicate something wring with my valve train? Like worn cams or rockers? Maybe there is a trick to this adjustment that you guys may know of? How about timing chain? I feels tight from what I can feel with the valve covers off.
Any advice?
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post #2 of 17 (permalink) Old 01-31-2009, 10:18 AM
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I think it might indicate that your doing something wrong
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post #3 of 17 (permalink) Old 01-31-2009, 11:38 AM Thread Starter
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I think it might indicate that your doing something wrong
Bill
I'm open to suggestions. I followed the adjustment procedures in the book. But the engine just doesn't run great that way. Maybe timing chain?
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post #4 of 17 (permalink) Old 01-31-2009, 01:49 PM
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Well I recently posted a set of directions on the exact same subject, I think the thread was or started as what's in here referring to a camshaft but anyway I posted it so do a search. The only thing I may not have said is that the camshaft lobe needs to be exactly opposite the cam follower. Also I didn't say how to determine the correct location for each lobe. Intake lines up with intake port on manifold and exhaust to the exhaust port. take a compression test with the valves the way they are adjusted and note the answers for posting..... somethings rotten in Denmark.. as they say.
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post #5 of 17 (permalink) Old 01-31-2009, 06:16 PM
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Was the engine cold before you adjusted the lash? Were your feeler gauges full of crud or warped?

http://i30.photobucket.com/albums/c328/nutz4benz/W123/6C3A9CA5-EDFF-4834-8125-34B70B20A676_zpsiyesrawz.jpg
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post #6 of 17 (permalink) Old 01-31-2009, 06:41 PM
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Actually the best situation is to drive it in and remove the rocker boxes at the end of day, adjust the valves in the morning. As for gauges I use 12 inch long Feeler strips cutting the ends off as they wear. Your ability to determine as to wear in the feeler by feel isn't really very good. Using a dial indicator with a bridge is how I used to do engines for racing. They wern't a standard construction engine though as they hit 9200 at the end of a straight entering a turn.
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post #7 of 17 (permalink) Old 01-31-2009, 10:02 PM Thread Starter
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Was the engine cold before you adjusted the lash? Were your feeler gauges full of crud or warped?
Nope. new gauges. There are specs for hot and cold adjustments. I did both.
Book says... Cold, intake.10mm exhaust.20mm and Hot, intake.15mm exhaust.25mm.
No problem getting them adjusted right. It just runs better if I make it more like .5 and .8mm
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post #8 of 17 (permalink) Old 01-31-2009, 11:09 PM
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In doing that your retarding the cam timing basically. Did you do a compression test and if so what were the readings. I once had an engine brought to me after another shop did a valve job. It was an early one like yours. It would try to start but it wouldn't run. After a big bunch of going in circles I did a leakage test. The comp test was OK. it didn't pass a leakage test and it was through the valves. I pulled the heads and it turned out the machine shop has reversed the angles of the grind so the interference was at the bottom of the seat. Hence when it lit it lifted the valves and negated most compression. A regrind and it ran perfectly, I earner my 2 bucks on that one. So do the next set of tests.
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post #9 of 17 (permalink) Old 02-01-2009, 11:09 PM Thread Starter
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In doing that your retarding the cam timing basically. Did you do a compression test and if so what were the readings. I once had an engine brought to me after another shop did a valve job. It was an early one like yours. It would try to start but it wouldn't run. After a big bunch of going in circles I did a leakage test. The comp test was OK. it didn't pass a leakage test and it was through the valves. I pulled the heads and it turned out the machine shop has reversed the angles of the grind so the interference was at the bottom of the seat. Hence when it lit it lifted the valves and negated most compression. A regrind and it ran perfectly, I earner my 2 bucks on that one. So do the next set of tests.
Bill
I've got about 120Lb on each cylender exept #8, which is 90. I put some oil in the cylender and it bumped up to 105 or so. So I know it's the rings at fault there. I don't have the tools for a leakdown test. But I know the history of the car and the heads have never been removed.
How do I check the timing of the camshafts? I suspect that above all else.
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post #10 of 17 (permalink) Old 02-02-2009, 07:36 AM
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20 is light by a significant amount. Its even but light. It may be your gauge but it warrants inspection. These are the fun ones, I loved to take something that troubled others and resolve it. The cam timing is easy to check, TDC on the crank wheel.....compresion stroke and not 180 out obviously. Mark at tdc valve covers both removes you will inspect the front cam bearing at both sides. There is a thrust washer that is notched and located by woodruff key at each camshaft, it also has a relief that will align with an embossed indicator at each front cam bearing. The washer's notch will be in line or trailing behind the pointer by most half the width of the notch. If this is not in order then the chain is stretched or something else has happened. To check the chain and gear condition you will grasp the chain at the center of the gear on top and lift. It may lift 1 mm. If the chain raises much more it is indicating chain stretch and or gear wear that needs resolution. The actual camshaft timing is adjusted with offset woodruff keys. This procedure or the replacement should be performed by an experienced mechanic as a mistake could have catastrophic results.
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