M28/22 Engine work thread
 

So over the last couple days I have taken this Euro S engine from this complete engine to the short block. This car was originally a Saudi Arabia car and so was the low compression version. As I have taken it apart, I was expecting to see pistons with some sort of dish to lower the compression, but as the pictures show, they are just flat tops with good sized valve relief cuts. I haven't measured yet, but they seem low in the cylinder (the two that are near TDC) could it be that they just used the same piston configuration and altered the pin height of the piston?
I don't have the tool to remove the flywheel fasteners so don't have it on an engine stand yet. I have just removed the stuff from the top and front of the engine, the water pump was done in the last 3-4 years and looked very clean as did that part of the block. I will be interested to hear your observations.https://cimg1.ibsrv.net/gimg/rennlis...f751e451ee.jpg

#7 near TDC
https://cimg9.ibsrv.net/gimg/rennlis...b6c9c83ec5.jpg

#4 near TDC
https://cimg6.ibsrv.net/gimg/rennlis...0cfb71b899.jpg
https://cimg1.ibsrv.net/gimg/rennlis...56bf95eaa6.jpg
https://cimg8.ibsrv.net/gimg/rennlis...8f100eefef.jpg
https://cimg8.ibsrv.net/gimg/rennlis...4cc108c3d5.jpg

I have wondered about how they reduced the compression. I also have a low compression 86 S2.
PET certainly calls for a different set of pistons under Option M151 - engine with different parts relevant to M28.21/22.

I would think the easiest was wold be to machine the wrist pin hole a little higher
wow dirty motor where do the Saudis get their gas

the **** comes out of the ground and goes straight into the tank.

https://cimg8.ibsrv.net/gimg/rennlis...628f35d026.jpg

So a little more dismantling done, the bottom end looks brown, but otherwise quite clean.
https://cimg0.ibsrv.net/gimg/rennlis...1eb0bbbdfd.jpg

The oil pan on the other hand... This was after sitting upside down all night.
https://cimg2.ibsrv.net/gimg/rennlis...98c44de132.jpg

Is this piece of plastic siliconed on the oil pan supposed to be there?
https://cimg3.ibsrv.net/gimg/rennlis...fb87579172.jpg

How do I get these end pieces off the cams? they look like they should just slide off, but I have pulled fairly hard by hand and tapped with a rubber mallet. I was afraid I would break something if I got more vigorous.

^^ Those cam bearings (what Porsche calls them) do pull off of the cam towers. If hey are being stubborn you can use a hub puller to remove them.

Just do it slowly and carefully as to not damage anything. Especially those cams.

You have to remove the key in the cam, before pulling the house. It is only the friction of the o-rings that holds them after the 3 bolts are removed.

Yes, the plastic part on the underside of the oil pan shall be there. Electrical insulation.
Åke
https://i.ebayimg.com/images/g/37QAA...D8l/s-l300.jpg

Got the engine pulled down the rest of the way. Considering having the crank offset ground to 3.200" to Honda 1.889 journal to take advantage of really good, cheap Clevite bearings, and then sleeve to 4.125 to take advantage of cheap (by Porsche standards) LS7 pistons and 6.200" rods. Calculates out well with a 18-20cc dish in the pistons to 10.1-1 compression ratio and 5.6 liters. The bigger engine should move the power band down in the RPM range a little and make the cams not quite so "peaky". It would be nice to have a little something below 2500 rpm for around town driving, when you need to chug. I will have to cc the heads, but if this truly is a 310hp engine, it was very un happy.https://cimg9.ibsrv.net/gimg/rennlis...10dde00f12.jpg

All the bearings looked real good, front and rear main bearings looked good on the crank side, but looked like they had been "talking" to the block a little.
https://cimg8.ibsrv.net/gimg/rennlis...3d93ee0dd8.jpg

Cylinders looked nice except where #2 rod had gotten away from me and nicked the bore...

Being a M28/22 , if you look at the Porsche workshop manual ( section 13 page 24b ) it shows the difference between the M28 /21/22 high compression pistons 10.4:1 which is what you have ,and the M28 /21/22 with the lower compression pistons 9.3:1 which have a very noticeable / large concave dish in the middle of the piston/s which naturally lowers the compression to the lower 9.3:1 ( you do not have this )

In Australia we received both versions over two years , for the 1984 year model 928s only the M28 /21/22 with the high compression ( no concave dish ) flat top pistons with valve cut outs only , then in the 1985 year model 928s M28 /21/22 we received the lower compression pistons with the large concave dish and the valve cut outs

Regards
Bruce Buchanan

Thank you Bruce! I see that now.

"Washing dishes", my favorite thing.
https://cimg6.ibsrv.net/gimg/rennlis...92302c75d4.jpg

After working on the block and seeing how well the outside cleaned up, the girdle looks shabby and obviously needs more work.
https://cimg1.ibsrv.net/gimg/rennlis...23f2a5f168.jpg

The girdle spent a week in odorless mineral spirits while being worked on with a plastic bristle brush every night.
https://cimg9.ibsrv.net/gimg/rennlis...e353124879.jpg

Outside of the block is cleaning up nicely, the inside is still stained with whatever was in the motor oil.

I wouldn't worry about the light staining. But if you want to get rid of it quickly you can soda blast it, then rinse it in water.

It did wonders for the pistons in my 81.