johnb

Hi All

I have been sure for some time that the process of preparing our blocks for new rings was NOT rocket science or expensive.

The forum entry below is long winded BUT well worth reading and is very detailed. Gets interesting from about page 8 onwards.

http://forums.pelicanparts.com/showt...t=137346&pp=20

The long and the short is that you can easily prepare alusil bores for new rings, so long as they are not mechanically damaged. (Scoured, galled, cracked or pitted)

Conclusion:

Buy some AN30 from Sunnen (50% Silicon powder suspended in oil) this is the product recommended for the final lapping of the alusil bores.

Buy a cheap and cheerful three legged bore honing tool, wrap some rag around its legs, put some AN30 in the bores and polish away!

What this does is to remove some aluminium from the bore to expose some more of the silicon particles for the rings to run on, the 'setback' aliminium provides the space for the oil to go to provide lubrication when the engine is running. (all on microscopic level)

Anyway, check it out.

john

mark kibort

makes sense! Now, who wants to step up and give it a shot!

mk

johnb

Hi Mark

Just about to!

john

John Struthers

AND.....? Do it yet?
Still wondering about the hone legs (I assume you just cover them stones and all).
What's the chance of metal/stone break-thru -thru the rag- even at low rpm's?
I agree the boring and honing of the 928/944 cylinder blocks could not have been so
futueristic that it wasn't feasable (economic or otherwise) to do by a engine shop.
Anxiously waiting....
What's Mark doing with his engines I wonder... Proprietary?...Jim, what's the skinny ?

UKKid35

John has done the work and has his engine running, I'm sure he'll report in detail when he gets a chance.

johnb

The story so far:

Couldn't obtain any of the AN30 so;
After doing a fair bit of research on Alusil (Block material) I decided to gently polish the bores with an aluminium polish to remove a very very small amount of ali and expose some more of the silicon. This is very similar to the final polish the bores get in production, except they used a silicon based abrasive polish (Sunnen AN30). Ali polish is usually ali oxide based.


I wasn't able to buy a three legged hone locally either, so I made do with what I had to hand.

I took a soft cotton rotary mop that just fitted down the bores, coated it with the ali polish and gave each bore a quick couple of up and down whizzes with an electric drill. Made quite a difference, and I made bl**dy sure I removed all traces of the polish! The mop turned black as the polish removed some of the ali (microscopic level here)

Looking at the sort of surface finishes shown in pictures of 'sunnened' blocks I managed to obtain the same sort of visual apperence. The bores felt very smooth, and when coated with engine oil they seemed to almost 'suck it up' some how.

The engine turned over easily by hand with the plugs out, but fantastic compression with the plugs in.

The engine is now back in my car and running beautifully, seems more responsive, and oil pressure is up on hot idle (3.5Bar). Early days but I am trying to put miles on as quickly as I can.

Oil is still clean, although I have been advised that the new rings can throw quite a bit of rubbish into the oil. Running on 15w-40 semi synthetic, been advised to change to a 20w-50 as this can help with better bearing protection?

I will keep posting as my engine either:

1. Settles down for he long haul.
or
2. Destroys itself due to my unauthordox preperation!

John

Warren928

John,
That is good news, I haven't heard of anyone like a do-it-yourselfer taking on this challenge. I hope it works out great for you. The fact that its doing good right now for the first days is encouraging news too.
I have some aluminum polish here made in Germany, comes in a 1 quart can. I think its called Tec, or some other 3 letter name. I will have to go look for it.

So for instance, a person needs to bore his motor .030" over, could he feasably take it to a shop, do that and then use this honing process? Or would it be bore, hone and then polish? Maybe its too early to know.
But one of our 928 experts might know how it works...

Rick Carter

Why is oil pressure affected?

johnb

Rick

I have completely rebuilt my engine, new bearing shells alround, less space for oil leakage; therefore slightly higher oil pressure at idle.

john

docmirror

Ruh-roh. Everything I've ever heard, don't use syn oil during break-in. There is a period of time when the engine is supposed to 'make metal' while the rings bed to the walls of the cylinders. If you use syn during this time, the oil control rings never seat, and oil consuption will always be higher than normal.

This is very critical in aircraft(chrome rings on steel, air cooled) but the theory is the same for Iron on Al bores. I thought the 928 had Nikasil coated bores? I must be confusing it with the Mondial, hmmmmm.

SwayBar

You can tell right away by looking at the oil whether it's going to self-destruct or not. If you pull the dipstick and look at the oil on it, and notice a small black drop at the very bottom (..the black-stuff is very fine like talcum powder), it's more than likely aluminum scuffing off of the pistons and the engine is doomed. On the other hand, if the oil's color is uniform throughout, then more than likely you're good-to-go!


As Doc mentioned, running a synthetic during break-in can be problematic as the cylinder's cross-hatch glazes over due to the synthetic being too slippery and not allowing the rings to cut into the cross-hatch. But then again, maybe Alusil bores are different as there is no cross-hatch on the cylinders.

Man, great job getting this done so quickly!

And here's to a perfectly running engine:

drnick

john, like everyone else im keen to see how the engine goes with the alluminium polish you used! i also wonder if its not best to use regular dyno oil during break in. how are you breaking in the engine by the way? i opted to basicaly cain mine after warming it up

bkingdon

I have read that Corvettes and Camaros are factory filled with synthetic oil. Not aluminum bores I agree but still trying to seat iron rings. Must be a reason for the added expense.

Brian.

SwayBar

As soon as the engines are built, they are filled with organic oil and ran on a dyno to check the engine and to break it in; once done, the organic oil is drained and then filled up with Mobil 1. The bottom line, the engine is already broke-in by the factory, and the reason for the factory-filled synthetic oil.

DK

I had my 5.0l hybrid bores 'freshened' by a local machine shop. They did some research with Sunnen and determined that it was the same product and process as used for the chebie vega blocks. They had everything - I think I paid less than $200...