dgjks6

Ouch. That hits home. I think that is why I am so fascinated by this thread. Few more thoughts. I know I said I am not an engine builder, well I kind of lied. But I only rebuild real engines. Singe cylinder Kohler's for my Wheel Horses. All iron. Aluminum? Nikisil coating? Liners? More than one cylinder? Nope. Not me.

My problem is you have three bigger pistons on one side. Even if it's a little they have to make more power. And not sure if center of gravity of a piston matters but it has to be different. And things like clearances (which Kohler publishes and from what I have read Porsche does not) are a problem. I have learned that they make a difference. The single cylinder cast iron beasts will run with about any clearance. But the difference between running, running well, and running for years is huge.

I really would like you to keep the car and drive it. And after 20K miles come back and say I did this to the engine with these specs and the engine is perfect.

But I get it. Guys buys car for 5K non running, puts 5K into it to get it running across an auction block, sells it for 12-15K and makes a little money. New buyer drives car a while and engine blows and he gets on line and finds out this is what these engines sometimes (not often, but sometimes) do and either sells it as a non runner or fixes it right.

And we never know.

DTMiller

But shouldn't we be thanking him Jake? He's developed a new fix.

DeWolf

Well this is a good option for not wanting to spend $$$ on a rebuild just because of one bore.

http://www.hartech.org/porsche_996_9...er_liners.html

Imo000

Cool stuff!

Flat6 Innovations

No, this isn't a new fix. Anyone with low enough standards could have done this years ago.

So, why even bore the block at all? Just find a block half from another engine and bolt it on, it doesn't even have to be the same displacement!

My experience is that IF one bore does this, the rest are right behind it. Repairing just one bore makes zero sense to me, unless you want to be doing this all again in the future and in the mean time the engine isn't going to run optimally.

Maxtegroom, please post a screen shot of the rough running index of this engine. I want to see it.

Ahsai

Lets do some ballpark math here. 0.030" increase (assume he meant diameter) on a 96mm piston is 1.6% increase of the swept volume. The chamber volume may have changed due to different piston crown shape. If it stays the same, the c.r. will drop. If the new piston is modified to keep the stock c.r., all bank 2 cylinder will be 1.6% more power. If the c.r. drops, this 1.6% maybe offset by the c.r. drop.

Many variables in play here but is 1.6% power difference significant in any case? I would guess that can be easily absorbed by the DMFW?

JD ARTHUR

I think it will run fine with no seat of the pants difference. I think its a mickey mouse fix to a tired engine, there will be more problems. These cars require good maintenance and money to fix things properly if they are to stay as they were when new. Fixes like this lead to the car eventually becoming a track car and then after a crash or some other mishap it becomes a parts car. Until then someone who needs a bargain will buy it and drive it. Most people like that will not have the money to maintain it and wont spend unless there is no other choice. After all is said and done I think who ever owns it can do whatever he wants without any of our opinions mattering anyway. I've been in the trucking business for 48 years and have seen every mickey mouse repair that could ever be thought of. Its amazing how many actually work against all the odds.

Flat6 Innovations

If having specs this loose didn't matter, the bore sizes of engines could be +/- .75mm (.030) and no one would care. Thats not the case.

Yes it matters, everything matters. This is a precision machine.

Imo000

I think its statistically insignificant. Yes it's not optimal (aka perfect) but it won't matter that much. How many engines run "fine" and yet have scored cylinders? The only signs are the piston slap and the smoke. To a perfectionist this, and many other things, are not a solution. As much as I like to cheap out, I would have went with the another used case half with used pistons route.

Ahsai

Will using a half casing from another engine create other problems? What if they don't line up perfectly e.g., rms, ims casing holes. I think the casing halves are machined together from the factory and not to be mix and match with other casings?

DeWolf

Anyone?

Flat6 Innovations

There are no coatings!!!!! Lokasil is not a conventional coating. Nikisil is also not a coating, it's a plating!!

Also, if the work would have been comprehensive the whole engine would have been torn down and all 6 cylinders bores the same diameter and treated the same way, using the same Pistons.

If this would have been done the 3 new Pistons would not have needed 28 gram heavier wrist pins. All 6 pistons would have matched and you would not have all the issues we've gone over here.

But that was too hard and cost too much, it was easier to just half way do the job. I see engines half way built like this all the time. It was much better before people were working with these engines. Today we see engines molested every week, a few years ago they were all virgins.

No, using block halves from two different engines is not advisable and has its share of issues. That said, it's a hell of a lot better to take those risks and experience that compromise rather than putting in mismatched Pistons. I am astonished that a few of you can even remotely understand how anything good could come from this practice.
Would you buy a car knowing it had mismatched Pistons? What if you bought one unknowingly?

Somebody will be buying one unknowingly soon and I hope like hell they are members of this forum!

Noz1974

The cases are line bored in the factory, the case halves are together when the various holes holes split along the centre line are machined, I would imagine if you got a bad match from another casing half you might get oil leaks as the main seals would not seat properly??

Flat6 Innovations

No, not with this engine. There are no align bored main tunnels with the M96 as it has a separate crankshaft carrier.

JD ARTHUR

It was a cheap way to half *** fix the engine. In the long run or short run it will end up costing more than if it was done right. I hope the buyer understands about the half *** fix before he lays out his money, at least if he is aware all is fair. If I bought a car without knowing anything about 3 cylinders having different bores and heavier wrist pins to make up for lighter pistons etc there would be problems when I found out if I could still find the seller.