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Old 02-17-2021, 08:58 PM
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Join Date: Nov 2014
Location: Las Vegas & N. Cal
Posts: 342
Mercedes 250S Cam Towers Swap Head to Head

So I am working with a 1968 Mercedes 250S that I bought with a Blown Head Gasket it seems that the best way forward is to Change out the Head.The Head is Warped on top and Bottom as well as cracked bottom side quite badly
It is cost prohibitive as to repair the head is more then a New one on Ebay
As well A head like that may not stand up long term .The Engine Block is fine.

So the issues : I have found a Good used Head with the same part number But with no Cam and " Cam Towers "Are they the Cam Towers "Swappable ? " Head to Head ?
( My Cam looks perfect in all respects )
Can ? I just use my Old Cam Towers from the original Head I removed (they show no damage ?) *Or are all Cam Towers Line bored to each Head they came with ?. I was thinking to simply place my Cam Towers on the replacement head and Tighten them up with Rocker Arms removed
*to make sure the Cam rotates smoothly with no binding
Tentative Plan was to try the Cam on the head with the 4 smaller Nuts holding the Cam Towers down but still off the car and rotate the Cam as I tighten them up checking for binding.
Shimming Cam Towers :
If I resurface the Head must I shim the Cam Towers to insure the Timing Chain well be tight ? Just how much does the Chain Tightener take up possibly not requiring such Shimming ? Example I remove say 15 Thousands from the Head surface.
If the Cam Towere are not Swappable Can I simply have them Line Bored on the head *

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Old 02-17-2021, 10:18 PM
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Join Date: Feb 2011
Location: Modesto CA
Posts: 4,077
Answers

1) Cam towers are swapable as a set.
2) @.015 of the head, no shimming req'd.

Suggestions

To check the cam/towers, either, a-Insure (with straight edge) that the replacement head is un-warped, and then use it as a base for checking off the block, or, b-Bolt the head to the block w/o head gasket, and then install the cam/towers.

Question

What would suggest that the head will require resurfacing? If it is slightly warped (.015 longitudinally), and the surface is essentially free of pitting & corrosion, that deflection will be pulled out when the head is installed. If the block surface of the head is not flat, and it is cut, then the top surface must also be cut parallel to the block surface.
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Old 02-18-2021, 01:12 PM
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Join Date: Nov 2014
Location: Las Vegas & N. Cal
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Hello Frank *Thanks for the help
I have not Yet Bought a Head ( looking for a good used head )
I have located a Possible Head but it has no Cam or Cam Towers with it as such. I was thinking could I use mine ? As per your post it looks like I can
( My Cam towers look perfect as well as the Camshaft as well )
The Used head seller (ebay in N.M.) checked the Bottom of the Head and said its straight @ my request he failed to check the Top edge of the head as I requested darn it .

I don't know if The Head well needs resurfacing just speculating it might and thought of possible Cam Towers shimming .
The Removed & Cracked Head : I brought it to the Machine shop but at the Machine Shop they wanted a huge amount $800 / $900 to do the work and by description I felt a poor job would be done . I asked about straightening the head and their Procedure for such and they said for that amount ( I measured 12 Thousands ) they would just resurface the head . As the Top of the head is also warped
I felt the top of the head perhaps should be Straightened first so the Cam would be aligned
Upon Removal of the Bad Head I noted with all rocker arms removed the Can spins free with both ends tightened down with the Nuts & flat washers on Cam towers ( Not the head bolts ) however when I began tightening the center 2 Cam Tower Nuts the Cam bound up right away > I am talking the bad cracked / warped head I removed . As well I noted upon disassembly about half the head bolts
where Very Loose like finger tight . All 4 of the center Cylinders had little compression only the end cylinders had good compression
I checked all these things before Tear down : This Loose Head Bolt's discovery leads me to think this is the whole possable cause of the problum .This would cause water to leak out / Head to get Hot / warp / Crack Ect .It got so hot the Temp Guage Needle Broke off
The entire Motor was rebuilt about 20,000 miles ago I was told , I think they did NOT Re Torque the Head down . I fact I read you should re torque the head right away after just running it a bit then again after some miles are on it .
In any event a Replacement head if straight would be the best option I think .
I like your Mention to Bolt the head down to the bare Block to check the Cam
is free spinning and aligned a great idea .I have Not Bought a Head yet still looking for one and is no rush in spite of liking the idea to get the Car running , I bought it dead but it looks not bad and not rusty at all & Wood is good .
I watched a intersting Video about straightening Aluminum Heads https://www.youtube.com/watch?v=A3cRq-4nmt8
and I wish I knew the Procedure for exactly How they staighten a Head in a heated oven at 500 degrees for some what ? 5 hours then cooling it down humm that Must be an art ? 2 Photos of removed Head ( should have taken 1 of the Big Crack )
Humm I see a Video how they Remove warpage with Heat https://www.youtube.com/watch?v=1z4vA8ZhLPc&t=171s Bolt it down
On the One I removed just like this Video the bottom is Warped U shaped upward in the Middle However the way the cam becomes
tight when Tigthtened in the Center 2 Towers the cam Binds up indicating a reverse U shape of the bottom side ? I expect that may mean you should " straighten " the Top side First then Perhaps the Resurface the bottom perhaps ? .Frank says the 2 sides must be Parallel I am not sure why ? perhaps so the Timeing Gear ( and Chain ) is at a Perfect 90 degrees to the Motor Block .

*Mercedes 250S Cam Towers Swap Head to Head-dsc00305-1-.jpg

Mercedes 250S Cam Towers Swap Head to Head-dsc00308.jpg


Last edited by aluminum; 02-18-2021 at 06:01 PM.
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