W111 230s Low compression after engine rebuild.

[Hassan]

Hello all.
I've just gotten my 230s motor rebuilt,
1) Sleeved the Bore size to Standard.(pistons were all good)
2) New Piston rings.(trw germany old stock)
3) new exhaust Valves and Guides, seals.
4) got the head checked for Cracks and Straightness..
5) checked the Block Deck
6) new gasket.

First time around after doing it up we found some problems with the valves and seals so we opened it up again and did the head job.

Put it back together ( reused the new head gasket)

Now I am getting a reading of 100-108 psi reading on all six cylinders.( Wet and dry) which I know is low for this engine and won't help me set up the car for idle.
( Checked all tappet clearances )
 
I'm at my wits end as to where the compression is leaking or why it's not building enough!

I maybe looking at it with blinders on so any help to bounce off ideas would be greatly useful.

Spare part support isn't all that good in India so I can't be throwing parts at the engine as that would mean a lot of wasting of time to import.

Thanks a ton in advance.

[Mike Hughes]

Even though it is a new one, it's not a good practice to reuse a head gasket. I'm afraid you will need to get a new one.

[Cees Klumper]

Maybe double/triple check the engine timing, perhaps the cam is out of sync with the crankshaft just enough to not create interference issue, but still allowing the valves to open such that compression is not built up properly. Just a wild guess.

[Atazman]

Have you made sure your pressure gauge is accurate?

[kampala]

Perform a leak-down test.   This should reveal if the leak is the gasket, intake valves, exhaust valves, or rings. 

[Ozone]

A leak down will tell you a lot. Stating the obvious, but find the issue before throwing parts at it.
Were the head bolts replaced? Are the compression numbers at operating temp?   

[Hassan]

Ok so I’ve the engine to idle around 900rpm. Waiting on. Head gasket and a leak down tester  I’ve ordered online . Yes compression gauge is fine as I cross checked with another one I have.

Since I’ve been running it on the stand for the last week or so the compression has increased slightly by 5psi (now at 115 psi) across all cylinders and she has started to idle well ,vacuum gauge  needle stay steady at 13 inches of mercury (i know you need 14 min) .  Could it be that the new rings and valves are bedding in?

I had blocked the pipe  on the intake manifold in between the carburettors to tune the carbs they seem to be almost there my question Is  should I run the engine while it’s blocked or open ended.? Opening it increased the vacuum reading to 14-15 .

Regards

[Hassan]

Update:
 Still waiting for the gasket and Leakdown tester. Did. A quick compression test again today. All the values have dropped down to 95( first 3 cylinder)-100 psi.
Engine runs but not very well now

Would this be indicative of a head gasket failing or something else?

[Cees Klumper]

See my earlier reply, no 2, something to check and rule out (or not). It's probably something simple and I doubt it's the head gasket because then I would expect compression to be more uneven between the cylinders. Have you checked that the cylinder head bolts are torqued to specification?

[Benz Dr.]

A leak down will tell you a lot. Stating the obvious, but find the issue before throwing parts at it.
Were the head bolts replaced? Are the compression numbers at operating temp?

No need to replace head bolts on this type of engine unless they are damaged. I check compression figures on a cold engine as this is what you will have when starting after sitting over night.