Crank, any need to rub the oil stains off the journals. (kind of a line where the oil exits the crank jounal.) otherwise, they are shiney polished looking.

CT wants to take cheezecloth or 600grit sand paper to them. I said WAIT, until i talk to you guys! i thought those journals were supposed to have a 10 micron finish or something so shiney, any sand paper would ruin it!!!!!!!!

I say, just stick the crank back in after a washing with soap and water.

how about the pistons? those are stock 82 euro pistons . they have a coating that i would think you wouldnt want to remove too !

Now, the final finding on the old block was that the piston compression rings were found to have a 1.6mm ring gap!!!!!!!!!!!!!!!!!! spec is supposed to be .2 to .4 mm and on the 3rd bottom ring, its .4 to 1.5mm. Im thinking if that top ring has that much of a gap (3x spec) that the corners of the ring could gouge into the cylinderwall. sure seems like thats what happened when it seized. one piston and ring set were totally destroyed and broken, while the other were just siezed and the piston totally gauled up. looks like it started at the ring gap. also, the rings were terribly brittle. wonder if that is part of the reason.

anyway, the new engine top ring gap is in the .6mm range which is still larger than spec, but it could have been a re ring job on that engine too.

Mk

 

I think that using anything less than 1000 grit on the journals would be a mistake. If it's just a stain/discoloration, try some aggressive solvents before abrasives.

Regarding the rings... IMHO, removing a piston from a bore calls for re-ringing to spec. Assuming that it was assembled to spec in the first place, 3x gap implies the rings are badly worn. Are you tired of tearing this thing down yet? My take is, rings are the last place you want to think about cutting corners.

 

Isn't this the engine that had the 'XXX' dose of ether? If so, that was the cause of the rings demise; however, you are correct on spotting ring gap for the new engine.
On the previous assembly, were there just new stock rings on stock pistons? If so, that does not explain the large end gap. If the rings were well worn/used, Dave has the answer.

 

My drag racing buddy polishes cranks with fine scotch brite. It has worked for me.

 

Thanks guys. Now, what about pistons ?? i hear of all this "coating" stuff. is that only when you have JEs made up for a stroker? or is there a coating on the stock pistons we should be careful of. want to know how aggressive we can get on the cleaning of the pistons.

as far as the original replacement euro block, we only took it apart, and i only cleaned the pistons. didnt check ring gap as we didnt want to disturb the rings. advice was to re-use rings, now i understand why that is a BAD IDEA!!!!!!! the ring gap was 1.6 mm and should have been .2 to .4mm.
cylinderwalls were only honed up top near the welding, and only silicon paste'd to clean them up everywhere else. the pistons on the original euro were used again, and were 1 size oversized. (97.465mm) the rings are definitely larger than the new ones we are using, but maybe they were just not large enough! New rings on the newer euro short block make the ring gap right at .25mm or so. what a difference. can wait for scots sake, to get this thing together!!!

mk

 

The pistons have an iron plating on them. Don't clean them with anything stronger than a towel.

There's no need to remove staining or discoloration from the crank or pistons. If it's a build-up that's different. I'd use some solvent and a rag first.

The crank should get a professional polish, magnaflux and a straightening, if needed.

You should check the ring gap _before_ assembling the engine. They're not all identical and you can do some matching of bigger rings to bigger hols. Stick them about 1" down the cylinder and make sure they're flat across the bore.

After a few million cycles the bores get a bit bigger and it's hard to meet that gap spec. Use one ring to check each piston and rank them for size. Then stick all the rings into one hole and rank them for gap. Match the orders and you've matched the gaps as well as possible.

You can't get rings for bores that are 0.2mm over. That's get you a 0.6 larger diameter and blow the gap spec. Boring the cylinders is $$ and the new pistons are $$$.

 

I thought our pistons were Nikasil coated? OR is the bore Nikasil lined? Can't recall if it is or not. Don't sand or burnish the crank journal, just keep it ultra clean and have a polish job if needed. Egge machine can duplicate any piston. Still pricey, but it can be done. They will make any ring land yo want and supply modern, or original type rings. They made rings for my 1937 Cord, and my 1963 supercharged Studebaker(forged).

Doc

 

Doc,

You're correct. I should have said you can't get them off-the-shelf.

 

KS pistons are lightly chromed. Mahle were FeSn coated, but are not using a Ferroprint coating that is a little different.

No Nikasil coatings in the 928 originally.

Thanks,

Garrity

 

so how hard can you clean the pistons? just warm water and oil like at the shop? scotch brite pad too coarse? the skirts have a shiney area where they have worn the coating off , but its kind of normal from what ive seen. getting the carbon off the sides of the pistons is what we are trying to do, and i dont want to damage any more of the coating.

thanks,

Mk

 

Mark wrote:
>>so how hard can you clean the pistons?

No abrasives. I used permatex spray on gasket remover to remove carbon and that brown tar-like build up with pretty good luck. These were Mahle 968 pistons. I'd do a test spot first on the '82's to make sure it doesn't affect that coating. Spray it on, let it sit for a minute, wipe off with warm soapy waterand a soft rag.

 

Look at the thread entitled: "Preparing an Engine for Assembly"

There is a lot of info I put their for your use.

Remember to brush out those crank oil passageways before assembly!

 

so a towel and some solvent or warm soap and some hard rubbing?

the pistons are spotted, like a stain, but feel smooth. there is a shiney area above the skirts where the coating is (has) been removed by wear. Looks kind of normal, but what do you think about that?

we put in the crank and the new main bearings and seals yesterday with the assembly lube. looks like it is coming together finally. we will clean up those pistons and re-ring them after checking ring gaps and put them in.

Mk

 

Be carefull with solvents around your aluminum parts. Caustics can ruin aluminum. I also wouldn't think that soap and water would be the best to use for the crank (steel) due to possible oxidation. I guess if you imediately dried and oiled it afterwards it would be OK.