M272 intake port dimensions and decarbonisation of intake valves.

[Conor]

A looong shot.. but here we are.

My M272 CGI engine is a bit different to the regular variant, in the sense that it is direct injected.. so no fuel passing the intake valves to keep them clean. And the recirculated blow-by etc means plenty of coke/carbon/gunge in the valves.. And at 208k miles, I suspect there will be quite a bit.

Also given my symptoms. Engine pinking when under load at low RPM, sometimes if the engine is warm, it will hesitate to start and require a few extra turns to get it going.

So.. I am going to walnut blast the intake valves. For this I need an adapter that sits over the intake port. This adapter will allow me to insert a nozzle for the blaster and also will accept the hose of a vacuum cleaner to suck out the walnut husks.

Has anybody done this? Supposedly some marques require this. A bunch of BMW/Mini (N54 Engine) lads have been doing it a while and some MKV Golf GTI owners too.

A quick overview of the process can be found here.

Here is a 3D model of the BMW N54 adapter. - I am wondering if I can take that model and adapt it so suit the M272 intake ports, if I can find the dimensions.

So.. does anybody know the dimensions of the port? Or I wonder are they fairly standard. If I made a slightly oversized version of the above model with no holes would I be able to shave it down to fit and drill the wholes for screws in the correct place?

Thanks a lot.

Here is a screen grab of what the ports look like on the M272 - at least the non CGI version. Once the inlet manifold and all the bits are removed, "it should be fine"

I plan on doing this the same time as the valve stems seals as the remove of the above should help with that job too.



Image below of adapter. You can see the hole where the blaster goes in.. then the manifold thing is what the vacuum hose is attached to.



An interesting picture that shows some before and after pics.

 

[Uncle Benz]

Have you carried out a compression test, wet and dry? I think that would be my first step

 

[Conor]

Have you carried out a compression test, wet and dry? I think that would be my first step

No I don't have the tools for that.

What is the purpose of them and what are you checking for? Obviously compression but are you trying to see if the piston rings are shot ?

I will investigate. Thanks.

 

[LostKiwi]

You run a compression test. If a cylinder is low put one squirt of oil into the cylinder and remeasure. If it's significantly higher rings are worn. If not valves are leaking.

 

[Conor]

You run a compression test. If a cylinder is low put one squirt of oil into the cylinder and remeasure. If it's significantly higher rings are worn. If not valves are leaking.

Ok - Makes sense - So the logic is that the oil will provide some interim sealing of the piston/cylinder wall.

When you say valves are leaking - does that just mean it could be anywhere or specifically valve seating or guide/seals etc?

Thank you

 

[Uncle Benz]

As LK says, a dry test of all cylinders will give you an initial comparison of whether they are all the same, or some are low. If you find some low one/ones you can then start to home in on the problem. A few cc’s of oil squirted into the cylinder will help create a temporary seal on the piston rings. If the compression pressure rises to match the others your rings are worn. If it doesn’t you have valve seat sealing problems, or possibly a head gasket issue. If two adjacent cylinders are identically low, and oil doesn’t help you likely have a head gasket blown between cylinders. The next test is cylinder leakage. Different equipment, more words. I’m tired now…

 

[Conor]

As LK says, a dry test of all cylinders will give you an initial comparison of whether they are all the same, or some are low. If you find some low one/ones you can then start to home in on the problem. A few cc’s of oil squirted into the cylinder will help create a temporary seal on the piston rings. If the compression pressure rises to match the others your rings are worn. If it doesn’t you have valve seat sealing problems, or possibly a head gasket issue. If two adjacent cylinders are identically low, and oil doesn’t help you likely have a head gasket blown between cylinders. The next test is cylinder leakage. Different equipment, more words. I’m tired now…

Ok thank you.. plenty to research there first anyway

 

[rifiki]

Look on ebay for a compression tester, around 15-25£

 

[LostKiwi]

DHA Cylinder Compression Tester Kit For Petrol Engine Compression Gauge Pressure Test Kit For Car Motorcycle Automotive 0-300PSI : Amazon.co.uk: Automotive

Buy DHA Cylinder Compression Tester Kit For Petrol Engine Compression Gauge Pressure Test Kit For Car Motorcycle Automotive 0-300PSI at Amazon UK. Free delivery on eligible orders.

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If you're working alone the type that screw into the spark plug hole are best.
That kit has everything you're likely to need.

The adaptor only needs to be screwed into the head finger tight.

 

[Conor]

DHA Cylinder Compression Tester Kit For Petrol Engine Compression Gauge Pressure Test Kit For Car Motorcycle Automotive 0-300PSI : Amazon.co.uk: Automotive

Buy DHA Cylinder Compression Tester Kit For Petrol Engine Compression Gauge Pressure Test Kit For Car Motorcycle Automotive 0-300PSI at Amazon UK. Free delivery on eligible orders.

www.amazon.co.uk

If you're working alone the type that screw into the spark plug hole are best.
That kit has everything you're likely to need.

The adaptor only needs to be screwed into the head finger tight.

I don't know if you seen the pics of the M272 CGI engine before but cylinders 4 & 6 are near impossible to get to.

I should be able to test the other 4 and get an idea. It's 2&3 which are problematic..i'm now nervous because they adjacent lol.

Would a headgasket issue cause the symptoms as above. I mean when I floor it, could the smoke be coolant and not oil? Would coolant get into the cylinder?

 

[Uncle Benz]

It was when you said pinking that my hackles came up about headgasket. See them blown between cylinders a lot on BMW S54 engines. Always pink under load

 

[Conor]

It was when you said pinking that my hackles came up about headgasket. See them blown between cylinders a lot on BMW S54 engines. Always pink under load

Arrrgh. Well spotted so. I was under the impression the pinking was due to the carbon getting red hot..

Are you saying that when the head gasket is blown then you can also get pinking?