1982 piston issue
 

Hello Gents (and ladies of course)

During my dismantling of a standard 1982 928S engine, I hit on a rather disturbing discovery. 6 out of 8 pistons show cracks in the land between first and second compression ring. One piston was in such a bad condition, that a piece of the piston actually came of!!!

The cylinders them self show absolutely no wear, scratches or any other indication that something was wrong. The engine ran fine prior to dismantling.

So what started out as a "clean, inspect and repair as necessary, has now turned into a somewhat larger project. A few questions. Is this a common problem? What is probably a more interesting question - what to do now. I am tempted to have the block bored to accept 97 mm pistons, but am unsure if i can get away with this without modifying a bunch of other stuff.
Another question. The engine in question is a US 928S with a LH jetronic injection system. I am lucky enough to also own a 928 Euro - albeit a CIS system. As far as I can tell, the Euro motor has a somewhat higher compression, and I am tempted to strip and use the parts I need from the euro engine. Has this been done before? What are the implications?


Any thoughts on the matter?

Thanks allot
K.c.

put the whole euro engine into the driver. The pistons have tolerance codes on them so the first step is finding the right code for your cylinders, boring isnt an option unless you have lots of money then its a better idea to supercharge

Yeah - kind of my thought also - but the change from LH to CIS - ´has anybody done this yet? And if so, is it a major issue?

K.c.

If your talking about using just your engine (euro s) and ditching the efi and using your cis, I did it and it works fine. I actually had an 81 Euro Block that was seized and put an 82 US Block (non S) in mine.

Did you have any electronic gremlins that gave you grief during the transition from LH to CIS? My main concern is harness redesign etc.

Mine was originally CIS, so no electronic conversions at all. If your going to do a EFI to CIS Swap, I would not. Seems like way too much trouble

Some how the car ran lean and broke the ring lands.

You need to find out why that happened and fix that first. Check the injectors . Have them flow tested. Then check the fuel pump. And the vacuum lines as well . Then the distributor.

Would a lean mixture really have the ability to ruin the pistons? Does that suck or what...

OK - on with the work. I see a few options.:

1. Buying replacement original pistons. Expensive and potentially impossible.

2. Buying other pistons (different spec) and having the engine block prepared to accept them. Cost and ramifications unknown at this stage.

3. Swapping engines and going with my Euro CIS engine instead of the US LH engine. Form and fit should be good enough, and the performance should actually be better:) But the conversion from LH to CIS might pose (read - will absolutely) be an electronic nightmare. Price low - complexity high

4. Using my Euro engine block, including pistons, rods, heads etc, BUT fitting EFI systems. This would negate my EFI rewiring concerns, but has this been done? The higher compression of the euro engine should improve performance, but will the EFI have to be reprogrammed (which would really be a pain in the ...)

5. Scrapping the entire project and use the engine blocks as coffe tables :) A solution my wife would love as the never ending money pit would be no more. This solution is not really to my liking.

Gents - HELP

Thanks
K.c.

Use your euro engine and use your LH system with it . I have done this with mine. If your car is a us 82 then it is ljet. I would find a set of lhjet runners and TB That is for a lh jetronic and put it on your euro egine and put it in and just hook everything up and go.

I have the runners, a new wirering harness and everything else for the EFI, so it shouldent be to hard to retrofit the euro engine with the AFC EFI. Any detonation issues with this combo? I mean - higher compression ratio and en EFI mapped for a different ratio?

Thanks - and I guess coffetables are out ! :)

K.c.

It will just plug right in . You don't need a new wiring harness. The timing you will need to address a little. But i would send the injectors out and have the check and cleaned and flow matched. And put on all new fuel line on the injectors. and new vacuum line as well. And check the distributor.

Are you still going to use the AFM?

well, I kind of think I will. The rest of the car´s wirering is set up for the AFM, so hooking it up shouldent be an issue. I already have the new harness made - the old one was rotten to the core. The AFM, throttle body, vacume manifolds and all have already been through a clean up and adjustment, so I would hate to ditch them. At the same time, the AFM should provide better fuel distribution then the CIS. My issue was more a concern towards the somewhat higher compression ratio in the euro engine then in the US engine. Any thoughts?

The system itself - spider, etc should hook right up to the heads.

Thanks again all

K.c.

US motor is likely Ljet, not LH (all were 32v motors USA), so what I would use is the Euro S block and heads, find a set of Euro S LH intakes, and reuse the flap style afm etc from the Ljet, maybe upgrading to newer rail style injectors.

You will want to do some tuning, but an adjustable fuel pressure regulator might be sufficient.

more later, but I had 5 min free waiting at Heathrow, home in 12 hrs. ;)

Hey Danglerb,

I think i got the main points of your mail. Two questions though - why the euro runners? The geometry of the euro CIS runners is identical to the AFC runners - although the AFC runners have different location for the injectors?

Second question. Rail style injectors? point me in the right direction please :)

Heatrow is one of the more enjoyable airports - so have a pint on me.

K.c.

CIS and L or LH injectors have different fittings on the runners, CIS screw in I think, and the electronic use orings etc. You might be able to drill out the CIS fitting and put in some kind of adapter, but if you look around the LH intakes aren't that costly and issues with the throttle body and U may be easier to resolve.

Ljet injectors are OLD, and have that nasty barbed hose fitting. With a bit of work the fuel rail from a newer model 928 can be made to work with a correct fuel rate injector for your car (Bosch is used in many cars, so a set from breaker yard or even new for a different cheaper car works well).

I had two litres and a BLT, flight left at 9 am. ;) Too early for the free breakfast at our hotel, and I was just getting used to beans on toast with an egg and kippers.

A set of used pistons that should work with your old US block might be fairly cheap, check the tops of the ones you have for a tolerance group, 0, 1, or 2 I think. A little work, and you or someone else would have a spare block.

A BLT in London.....should go for the fish and chips next time. They are horrible - but when in London do like a Londoner :)

As for the runners. I actually have a set of both, so the shift from CIS to AFC should - from a runner standpoint - be simple. I got your point as for the injectors, and agree that the old style flimsy injectors connections (AFC) are prone to early failures and leaks.

I think I will stick with my euro block, euro heads, switch to AFC from the US engine (this will also give me less of a electronic headache then the harness switch would have caused me).

The only thing - in my opinion - that could be an issue, is timing. The Euro engine run a 10:1 compression ratio compared to the 9:1 US ratio. The last thing I want to do is to detonate the working eight pistons....Comments? Idears?

And now I have a spare block and spare heads.....I think that will be my next project....a little turbo project in the woorking that the wife knows nothing about.. yet.

K.C

Joy !!! The other engine is almost stripped - and so far, no flaws. Two out of the eight pistons are out - and no cracks detected. I am a happy camper. And the blocks are even both tolerance group 1, so I do have a spare.

I will keep you posted. Its an ongoing project - so I think other questions will pop up.

But so far so good.

K.c.

Just to be sure we are on the same page, post a few numbers, the motor ID stamped into the plate at the top front of block, and the casting numbers on the heads and one of each type intake tubes, plus some pictures. The more numbers and picts the better.

California tomatoes can be amazingly good, and in Orange county where I live many local farmers sell them fresh in stands or in a few special smaller shops. OTOH UK bacon I find most tasty, with a flavor and texture I prefer to US bacon, which is a completely different cut of pork.

I love sandwiches, and except for it driving my wife nuts, I'd be happy to eat sandwiches of various varieties all day/week long.