Looks like one of the "freeze plugs" ,which are actualy sheet metal plates bolted on, is weeping. I'm not sure if its the gasket yet but I plan on taking the intake off to be able to reach it better.

Any thing else I should look at while I'm at it? If they are cheap I might replace them all but I'm thinking gaskets at the least.

Michael

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Usta haves '69 250/8, '76 280C, 1971 250C 114.023, 1976 450SEL 116.033
Current have, 1983 300SD 126.120

Intake manny is easy removal.... be glad its not the exhaust pipes that can be a nut-cracker snapping dowels in the process of removal. Marinate the threads overnight anyhow, just to be safe.

Am wondering if *polishing* insides of solft alloy intake manifold to mirror finish instead of original rough surface would help air flow, improving performance....... Sort of part way measure to porting and polishing cylinder heads - which is far too radical for close tolerance, heat sensitive alloy heads that have been known to blow headgaskets under overheat.

What does the room think of polishing intake manifold *inside* surfaces at machine shop?? Honestly, i cant see how it could hurt.

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Last edited by 300SDog; 07-06-2004 at 05:06 PM.

As for polishing the intake there is a process called extrude hone which is very expensive (I've heard of $500.00 manifolds) but widely used in racing.

http://www.extrudehone.com/

The PO did the butterfly valve just months before I got the car. But I will remember to marinate the threads.

I may port match the manifolds if I can keep the metal out of the engine.

Port matching uses the gasket as a guide to ensure that there is a smooth transition from head to gasket to manifold. Not really opening it up but removing any steps or bumps.


Thanks for the input,
Michael

__________________
Usta haves '69 250/8, '76 280C, 1971 250C 114.023, 1976 450SEL 116.033
Current have, 1983 300SD 126.120

Flexible steel brush on electric drill is what I was thinkin for polishing the manifold. Or even sandpaper on fingertips or flexible plastic prod wrapped with sandpaper could reach alot of the surface too. Alloy has gotta be soft as butter, so it should be easy to work.

Well, I never did get around to any port grinding/polishing/cleaning but I did get the freeze plugs fixed.

On three of the small ones, the hole in the block casting isn't round like the plug. This forms a pocket that traps gunk and rust.

Folks might want to take a good look at their plugs. Any sign of paint bubbling is not good, every one that had bubbles had holes after wire brushing.

I just brazed mine up and sprayed them with LPS cold galvanizing compound.

Michael

__________________
Usta haves '69 250/8, '76 280C, 1971 250C 114.023, 1976 450SEL 116.033
Current have, 1983 300SD 126.120

a little roughness helps keep the fuel in suspension as it goes thru the intake. it will flow more polished, in a fuel injected engine its ok to do because the fuel is mixed later than with a carb