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Old 10-14-2003, 12:43 PM
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Join Date: Sep 2003
Posts: 222
Best friend just gave me a '86 420sel for free

My friend just gave me a 86 402sel in very good condition. It did have a loose chain that was making a rattling noise. My mechanic is fixing it. The car has 120k. While in there fixing the chain, he noticed that the passenger cam shaft had some wear in several of the lobe. He recommended to replace that and replace the cam towers. He showed me the wear on the lobes. Looks like some of them are not rounded smooth, but nearing flat. The cam towers have some groove in them that one can feel. Can a machine shop regrind the cam and polish out the cam tower? What would happen if these are not repair? Poor performance? Burnt valves?

Also, he recommended to install new rockers and lifters. Other things were recommended, ie, new front seal, new injectors, replace all the seals in the intake system. This turning out to be a very expensive job. Other things to fix is a A/C hose that is leaking. Odd and ends are new upper and lower ball joints. New brake pads/?rotors in the rear.

I will have him fix the necessary things like the chain and the chain ramp. Does the cam/cam tower need to be replaced as I described? It sounds like he is trying to renew the engine to its original condition. Also, does the brand of the cam make a difference. He said that he try to use OEM parts, not aftermarket. There is quite a difference in OEM and aftermarket cams in terms of cost. Are the OEMs, ie, Lemforder better?

I want to know what you guys think. I don't want to end up getting taken on this project. Anybody have any experience with these kinds of repairs? Hesaid he wants to do it right the first time instead of skimping on the repairs and have to do it again later.

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Old 10-14-2003, 01:56 PM
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Join Date: Nov 2001
Location: North Central Kentucky
Posts: 1,061
Do the chain and guides and drive the car. Could be he's just very particular about the condition of the car. Could be he's trying to get the labor charges way up over $1000. can you imagine why?
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Old 10-14-2003, 02:48 PM
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Join Date: Sep 2003
Posts: 222

I understand that he has financial incentive to do this. My question is do the cams cause any trouble if they are worn and at what point is it necessitate a complete new cam and cam tower.

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Old 10-14-2003, 02:49 PM
Join Date: Mar 2000
Location: Gainesville FL
Posts: 6,844
If there is any noticable wear on the cam then it is shot. The cam is surface hardened and once any material is removed that surface is gone. Once gone they wear incredibly quick.

The wear is both on the cam and rocker arm and will put a lot of metal into the oil. I have seen scores of cars sold with a new rocker on a bad cam and they can go 10k miles before they are rapping again. The only reason to ignore it would be to dump the car.

I would say any change of shape or lip at edge of wear would be reason to condemn. Slight surface roughness might be lived with but the rockers must be evaluated as they are what wear out first.
Steve Brotherton
Continental Imports
Gainesville FL
Bosch Master, ASE Master, L1
33 years MB technician
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Old 10-14-2003, 03:15 PM
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Join Date: Sep 2003
Posts: 222
cams and rockers

Thanks for the reply. The mechanic is also changing the rockers and lifters on the other driver's side camshaft. There is some wear on the cam, surface roughness only. He states he can live with it!! He states that the cam towers are aluminum; that's why they wear out . I forgot what he said about the cam. My goal is to have this car running as long as possible without any major damage to the engine, ie, lots of money to fix.

The other question is OEM versus aftermarket cams? Which brand is good and reliable?


P.S. I posted the ad on my 78 450sl that had a jump timing chain causing the driver's side valve damage. That car had 234K and the cams on both side are still in excellent shape. Are earlier cars SL better made than later SEL?
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Old 10-14-2003, 03:48 PM
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Join Date: May 2000
Location: Soperton, Ga. USA
Posts: 11,235
That is my kinda friend that would give someone a car but I have to wonder - it does not sound like they did regular oil changes to have those components already worn out at that low a mileage. You have to wonder what kinda condition the bottom end is in .
good luck
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Old 10-14-2003, 04:51 PM
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Join Date: Sep 2003
Posts: 222

My friend is a outstanding guy. I ask the same mechanic who service this car regularly. He was only aware of the loose chain and odd/ends on the car, not the worn camshaft. He speculates that it is because it was driven in very short trips around town. My friend does not drive it on long trips with this car.

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Old 10-14-2003, 05:00 PM
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Join Date: Sep 2003
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You have private mail.

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