What would the compresion ratio on my 87 300 e euro be after shaving 17 mil of the head, and would there be a difference in performance?
Also,should I expect for my engine to run a little hotter than usual?
Thanks
Ticobenz

17mil as in 17mm??

3/4" would tend to bump up the compression ratio . . . and valves and piston heads . . .

Thats 17 one thousands of an inch

Ticobenz,

>What would the compresion ratio on my 87 300 e euro be after shaving 17 mil of the head, and would there be a difference in performance?

17/1000" are somewhat at 0.43mm - that's not a problem at all if it's done once and for the first time. Mercedes allows to machine max. 1mm off the head.

Do you intend to change your comression ratio to get more performance or are you just machining the head for a new gasket?

>Also,should I expect for my engine to run a little hotter than usual?

No. The engine should behave like before, water temp just a bit over 80°C under normal conditions.

bis denn,
Christian

1989 300TE

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Hello Chris,

You seem very knowledgable in the technical aspects of our cars. I have a 300CE with the M103 engine. It' has been burning oil and I intend to do a valve job in a month or two. At the same time I wish to extract some additional power out of the engine. Car has about 160,000 km now.

What's the maximum I can shave off the cylinder head? You mentioned Mercedes allows a maximum of 1mm. Can we do more than that? I'm also planning on a mild port and polish.

While I'm seeking your technical expertise, My auto transmission was overhauled 12,000km ago. It seems to exhibit slow upshifting when on full throttle i.e. the transition from 2 to 3 is slow when on full throttle acceleration. Any tweaks to improve this and make the tranny shift faster?

I'm sure there are other members who can contribute on this as well.

TIA!

BlackBeauty,

>You seem very knowledgable in the technical aspects of our cars.

Thank you so much - but I failed
Mercedes permits to machine a maximum of 0.5mm off the head (not 1.0mm as I wrote before). Please check with job no. 01-4180 from the workshop manual or cd.

>What's the maximum I can shave off the cylinder head? You mentioned Mercedes allows a maximum of 1mm. Can we do more than that? I'm also planning on a mild port and polish.

Sorry, I can't help you with numbers and Mercedes only gives numbers for repair or overhaul, not for performance improvements.

But you can check the free height below the valves - just before you take off the head - as follows:
Make a ball of some flexible material e.g. wax (I don't know the right words in English, sorry, it's Karosseriedichtmasse or Knetwachs in German) and insert the ball through the spark plug hole. It should be placed in the middle of the piston. Turn the engine once (or twice) without running it! and take off the head. Now you can measure the free height below the valves, add 1mm for safety and start your grinding machine

The maximum also depends on the fuel you are using and the ignition. I suppose, you will not want to buy racing fuel or methanol for your daily drive.

Years ago my brother tuned a Fiat 500 (it had a displacement of 0.5liters and 18hp) by grinding about 2mm from the alluminium head (by hand!). That little engine ran like hell but died at a torn off valve some day

>the transition from 2 to 3 is slow when on full throttle acceleration. Any tweaks to improve this and make the tranny shift faster?

Standard answer: check the fluid level in the trans.
For further questions: did you ask the workshop that did the overhaul for support? 12000km after an overhole, the transmission should be like new...

>I'm sure there are other members who can contribute on this as well.

I hope so!

bis denn,
Christian

1989 300TE

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Chris, thanks for the tip.

Blackbeauty,

The best method would be to reduce the piston to head clearance to 0.040". This will increase compression and increase turbulance in the combustion chamber allowing better burnig of the fuel and also decreasing the chance of detonation.

The easiest way to do this is to use a thinner head gasket.

You also need to check the valve to piston clearance when it's done to make sure the valves have enough room.

When porting the intake ports make sure not to open them up. All you want to do is remove areas in the ports that cause turbulance to the airflow.

Don't polish the port walls. This creates a larger boundary layer of still air on the port wall and can cuase the fuel to drop out of suspension.

Jeff

Thanks Jeff!

Ok so does this mean that port and polishing the head on the M103 does not help performance? That's interesting to know... usually port and polish is a pretty universal performance procedure.

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-Kevin

Where do you find a thinner m103 head gasket?
What about camshaft lift or duration?

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Andrew
300e 294,000mi
380sel 185,998mi
380se 309,980mi

And when you check piston to valve clearance make sure there is enough additional clearance for rod stretch.