hacker-pschorr

They look just like the pistons in my US 81.

Big AL in VA

IAN,

It is a M28/22. It has twin distributors. A timing belt slaves one from the master distributor. Its supposed to be the 310HP engine.

Also, I just dropped the heads off at a machine shop to have them ported and polished. Scotch brite the ports so that fuel will suspend. A grind job on the valves with teflon guides. They will remove the bolt embedded in the head. Build it up with weld and then mill it down.

When these heads are done I will post pics of them. My quote for all of this...both heads 1020.00.
I'm happy with that.

Big AL from Virginia
84 928S Euro twin distributor monster

UKKid35

I really hope Jim's wrong, I think it has happened once or twice.

Big AL in VA

IAn,
I hope Jim is wrong too!
I visually checked over the area of the cylinder wall when #4 piston is at low point. I see no scratches on the wall. How would you check for such a thing?

Big AL from Virginia
84 928S Euro twin distributor monster

Jim bailey - 928 International

The only way to inspect the rod would be to remove that piston from the block. Bent rods have occurred when someone has hydrolocked an engine like drive fast into deep water a wave rolls up the front of the radiator and into the intake tubes. I also wonder how the rod bearing looks after such extreme pressures. The engine became a 250 hp stamping press pounding that bolt into the head and piston. I guess your downside is you spend $1,500 or so and it might be OK if not then you deal with it.

Imo000

Not a bad idea to have the heads done.

Do realize that milling heads will throw off the cam timing? The 16V cams can not be adjusted, unless the Porken adjustment kit is used. Also don’t forget to mark the heads, as per the manual, so if or when they come off again, it will let the owner know that the heads have been machines and that they can not be machined any more. I believe it’s an “X” stamped into the side, right around the middle of the heads.

Richard S

The pistons in the early 84 Euro S engines were left-over 83 Euro S pistons. I know from experience.

Rich

jpitman2

FWIW I once was trying to remove a head from an Alfa (also alloy block and head), which was very difficult to get a grip on the head, as well as being stuck to the gasket or studs. In the end we resorted to pouring boiling water into the block to try to get some differential expansion to break the corrosion. Worked in the end, but took several hours of water work.
jp 83 Euro S AT 50k

danglerb

My old 64 alfa had one of those, hides in the back screws that needed to be removed.

michael j wright

Al, I noticed that the water crossover is still in place. Next time remove that first it will help in the removale. In the mean time you might want to go ahead and remove it to help when you put things back.

mark kibort

there is a distinct difference in the piston cuts of an 84 euro and 82 euro. 82 euro pistons are the ones like the pictures here with the deep cuts, and flat piston faces. the euro 84 pistons are much more shallow cuts, maybe only .20" or so. this created the higher compression ratio of the later euro 2 valve engines. (because the heads are the same)

Thats an amazing imprint on the piston! it may have happened quick enough so the piston took most of the force (in the imprint) however, jim is right, that force would have been transfered to the rod and bearings. probably worse than a real bad detonation. im amazed how the screw got out of the hose clamp and into the runner. Did you notice you were missing a screw out of one of the clamps before assembly? real bummer! thats a ton of work. ive taken the cam towers off, and that was a real nightmare, plus cleaning the baked on gasket i had to scrap off over 8 hours.

so, do you think i twas worth it to do it in the car?? to get the engine out, all that work on the runners, cam towers is pretty easy. however, then you need to take the headers or exhaust manifolds off.

whats the concensus there?

Im thinking that removing the clutch, headers, and radiator, plus all the timing belt stuff, leaves only a power steering reservoir, and a few engine mount bolts from lifting the engine out and doing all this on a stand. we have to do this with scots car and im thinking about trying it in the car. however, while we had it out and the heads off, we are probably going to convert it to the 5 liter.

MK

Big AL in VA

For me, it was worth it to pull the head with engine in car. This might not work for others. I was on vacation this week and had no help. So I had the time to do it the hard way. I had a perfectly made socketed allen to get at the lower cheese head screws on the cam tower.

It was easier for me to undo the exhaust manifold studs. And not pull the manifold with the head. However. I can see why it would be much easier to install the exhaust manifold on the head first and then install.

The screw was a complete surprise. I must have goofed up a month ago when reassembling intake and plenum. I polished the runners and plenum and reinstalled. I am usually careful in such circumstances.

My only concern now is why I was losing fluid in the same location. The cylinder wall appears OK.Was the piston jacking up the head and pushinhing out coolant? I am really not sure. I would hate
to reassmeble heads and cam towers to find I had a cracked block.

Big AL from Virginia
84 928S Euro twin distributor monster

tv

Well we have a piston mystery, are they regular euro s pistons in an LH euro? As best I can recall looking into the cumbustion chamber on mine, i did not see such deep cuts.

You DO NOT have to remove factory exhaust manifolds off a euro engine before pulling that engine.

I do not remember where your leak was but the coolant bridge gaskets are often at fault.

Ian928

I think the combustion chamber would have been shiny if you had a leakage into the cylinder, yours is the opposite. So probably the leakage could have been external.

If it is true that your engine has 10:1 (more like 9,4:1) compression pistons instead of the 10,4:1 pistons in later S2 engines I would seriously consider milling the heads to up the compression to S2 numbers. Then you'll be sure the head is straight and the throttle response should be even better with the higher compression. The engine management on your engine is built to handle the higher compression so no worries about detonation. Of course, your engine will then become a interference engine...

According to my calculations, 0,1mm shaving of the head should raise compression by 1 points, so 0,4mm off the head would bring it up to S2 numbers. Please check my calculations before you do it! Mark Kibort knows the difference in volume between S and S2 pistons, that can easily be used to calculate how much the heads should be shaved.

Ian in Norway

mark kibort

we sure do!! Lets all find out how this is possible. those cuts are 82 euro pistons, are we sure this is a euro 84 928? if so, how is it possible that it could have the deep cut pistons? the 84s ive seen and used to mirror the piston cuts on my 85 pistons for the 5 liter conversion and they are very shallow valve cuts. the early years are 8cc volume while the 84 pistons are 2cc . combustion chamber is 48ccs on the euro head. it all works out to be about 10:1 on a 82 euro and near 11:1 on a 84 euro.

Hacker, US 81 pistons have a little cut dome on the face, dont they? maybe the 4.5pistons were flat top. the 4.7 us pistons have a little dish on them., but the combustion chamber is 53ccs.

now, the coolant leak. thats a real puzzle!!!



mk