I have a 1975 450 sl with 150,000 miles on it. The top end of the engine is brand new and the compression is 160 lbs +/- 10. The problem is I have loose valve guides. If I have a valve job done on the engine, will the increased compression make me start burning oil or worse, could I blow a ring? Thanks for any feedback!

"The top end of the engine is brand new"

Elaborate on what has already been done. With a 8.0/1 compression ratio and 160lb of compression it seems to be healthy. Maybe you need valve seals ?

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Happy Benzing
Darryl, Hill
2005 SL55 AMG Kleemanized
1984 500 SEC
1967 W113 California Coupe
[SIGPIC]
https://picasaweb.google.com/lh/myphotos

The camshafts, cam towers, cam oilers, rocker arms, lifters and valve seals are new. The engine is so loud it sounds like a disel! If I didn't know better, I would think it was a bad lifter noise. My mechanic thought replacing the cams and lifters would get rid of the noise. Since it didn't and he also replaced the valve seals, he says it must be the valve guides that are loose. The head has not been pulled and he has expressed concern about blowing a ring and/or excess oil burn if we do a valve job. It doesn't make sense to me since the engine is already holding good compression, why would a valve job increase the compression enough to start burning oil? Also, does the engine block have to be machined before the head is put back on?

Have a Mercedes speacilist check it out. Quite a few things don't make sense. Second opinions even if they confirm the diagnosis are worth it for peace of mind.

__________________
Happy Benzing
Darryl, Hill
2005 SL55 AMG Kleemanized
1984 500 SEC
1967 W113 California Coupe
[SIGPIC]
https://picasaweb.google.com/lh/myphotos

Second that. If you are holding 160 psi, I don't see why you would do the valves. But you ought to get to the bottom of the noises.

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Chuck Taylor
Falls Church VA
'66 200, '66 230SL, '96 SL500. Sold: '81 380SL, '86 300E, '72 250C, '95 C220, 3 '84 280SL's '90 420SEL, '72 280SE, '73 280C, '78 280SE, '70 280SL, '77 450SL, '85 380SL, '87 560SL, '85 380SL, '72 350SL, '96 S500 Coupe

Princess, since you are here in Texas you should plan on coming to the Texas Fall Shindig which will be held at McKinney Falls State Park in Austin in Nov... check the sticky in the Diesel forum for details.... Greg

Improper valve clearances will make the engine louder. I set them on two high mielage engines recently and the result was a quieter engine. Seems like they get tight over time.

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MB 72 250 M130.923 114.011 170k The Beauty

Well, I took it to an MB certified mechanic and he said the timing chain was bad. We replaced the chain, tensioner and guides, adjusted the lifters some more and double checked the new parts (cam, rocker arms, lifters) to make sure the correct ones were installed. Runs much better, not as loud but still much noisier than it should! He is doing further diagnostic work as we speak. Thanks for all the input!

Wow, with all that work, it should run like new and sound like it too!

Is there any oil in the engine?

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Ed
1981 300CD (Benzina)
1968 250 S (Gina) 266,000 miles!
1983 Alfa Romeo GTV6 (Guido)
1976 Jaguar XJS-saved a V-12 from the chevy curse, what a great engine!
1988 Cadillac Eldorado (better car than you might think!)
1988 Yamaha Venture (better than a Wing!)
1977 Suzuki GS750B
1976 Yamaha XS 650 (sold)
1991 Suzuki GSX1100G (Shafty Gixser)
1981 Yamaha VX920RH (Euro "Virago")
Solex Moped
1975 Dodge P/U camper


"Time spent in the company of a cat, a beer, and this forum, is not time wasted!"

Also, it doesn't seem right that the valve guides would be worn that bad at this mileage. Hmmmm.

__________________
Ed
1981 300CD (Benzina)
1968 250 S (Gina) 266,000 miles!
1983 Alfa Romeo GTV6 (Guido)
1976 Jaguar XJS-saved a V-12 from the chevy curse, what a great engine!
1988 Cadillac Eldorado (better car than you might think!)
1988 Yamaha Venture (better than a Wing!)
1977 Suzuki GS750B
1976 Yamaha XS 650 (sold)
1991 Suzuki GSX1100G (Shafty Gixser)
1981 Yamaha VX920RH (Euro "Virago")
Solex Moped
1975 Dodge P/U camper


"Time spent in the company of a cat, a beer, and this forum, is not time wasted!"

EUREKA!!! I think we found the problem and believe it or not, I diagnosed it! We are pretty sure that the camshaft that was installed was either bad or was the wrong camshaft. I was checking prices on replacing the cam on the other side and the part guy I talked to told me that there were five different camshafts that went onto my engine. He said that the engine and VIN numbers were not enough to know which cam I needed, he needed the number directly off the old cam shaft. Once I discovered this information, I told the mechanic to check the new cam and sure enough he said that the lobes did not hit at the right time, there was too much clearence! The new cam goes will be in on Monday and should be ready to go on Tuesday. Wish me luck!

Princess,
I hope the new cams do the trick, but I would never replace a part by going by the # off the old part. Since you are having so much trouble with cams who is to say the existing cam is the correct one. You could be installing a new wrong unit. There are two ways to determine the correct cams for your car. You go by engine serial # stamped on the back of the bank or you look it up in TDM (Mercedes Benz technical data manual). Your certified MB mechanic will know exactly what that is. If your parts supplier can't work from the engine # he or she is working with limited data. Also I would not recommend rebuilt cams as they tend to be noisy; go for new.

I served my apprenticeship when the 4.5 liter engines first came out. Traditionally you change valve seals at 125k, you grind valves at 200k to 250k, and put in new pistons somewhere after after 400k. The M117 engine was a tough engine with the only drawback being the weight which meant poor fuel mileage. While it is in the shop you may want them to check the left lower control arm for cracks. There was a design problem, and I believe MB will still replace the entire subframe under warrantee. If you have trouble determining what cams you need, give me year model(not production date),Calif. or Federal, and engine #, and I'll look it up for you.

Good luck,
Peter

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Auto Zentral Ltd.

I pulled it out of the shop and decided to do some research and find the right mechanic. Something I should have done in the first place. I should be able to hear it run tomorrow at the new garage. After having it sit for 3 months, I had it towed in and they are putting on new plugs and wires (again). Once it is running again they will be able to DIAGNOSE it better. One thing that they did determine is that I need a new wiring harness (ouch!). The last mechanic welded the ends to the various engine parts when the ceramic ends broke apart instead of repairing it correctly. They also informed me that there was gas in the oil which means it was running too rich which could have fouled the plugs and that may have been the problem the whole time. Oh well, live and learn. At least my baby will be home soon! I will keep you posted.