3.0L motor with scored cylinder walls - salvageable or not?

[Dimi 944]

I picked up a '91 S2 with chain tensioner pad failure. The car had the failure 8-9 moths ago. The previous owner had no idea how to fix it or take it apart to check the damage so he was undoing every bolt he sees in the engine bay (what a mess).
The head looks in good shape but the cams, tensioner, chain and valve cover are missing (thrown away by the previous owner).

Unfortunately, the car was not well maintained but it was running before the failure and it appears that everything else is working on it. It has good options that is why I decided to get it.

At the beginning I thought I can replace the head and make this motor run but that was not case. After I took the head off I found that cylinder walls #2 and #4 are scored. What is left of the head looks in good shape, no bent valves have been found yet.

Not sure what to do at that point. Is this block salvageable or should I part the engine bay and prep it for LS1 swap? Every input is appreciated.

Thanks!

[J1NX3D]

how long has it been like that? how many cylinders? 4 scored and 10yrs ago?

j/k

hope you find what you need

[Dimi 944]

The chain tensioner failed 8-9 months ago. The car has 200K on the odometer. I have no idea when the cylinders #2 and #4 were scored.

[924RACR]

Yes, I'd say that's salvageable. That's pretty minor; a few years ago I helped my S2 buddy Erik rebuild his engine. One of the pistons is now sitting in my dining room as a trophy; they were also not reusable. He had to send the block out to a 928 shop out west IIRC for proper boring and honing, and got a new set of beautiful pistons from Diamond - much less expensive than JE's. Naturally, they have the pattern now; I think he did a few neat things like have the rings set up to use Total Seal or some other readily-available ring, less expensive than stock.

Obviously it's now back together and very happy, and being tracked again (also has a near-race suspension, with double-adjustable coilovers all 'round). But the rebuild was very stock.

I'll point him at this thread, he can spell out all the details for ya.

I'd also point out that you'll want to fully tear down the head and inspect the springs; even without cam tensioner failure, we found 3 of the original springs snapped! One chunk had even made its way to the oil pan. Mind you, the car was in fact running when he bought it - though as you might imagine the top end was a bit flat! LOL

[Cocacolakidd]

If it is minor scoring on the cylinder walls the block is salvageable. Try the fingernail test - if the scoring is minor enough so as not to catch a fingernail on the cylinder wall then the block can be honed to be re-built. Otherwise repairs get pretty expensive quickly.

If minor scoring then hone the block with AN-30 Silicon/ceramic paste, and put it back together again. Otherwise the block will need to be bored by a shop that knows, and has the equipment for the Alusil Cylinder Bores (diamond boring) - this is expensive and so are over size pistons. So by the time you do the boring, replace pistons, and get the S2-16valve head rebuilt the LS motor install is a cheaper way to go.

[eohrnberger]

This is very similar to my bores when I did my engine rebuild. I've uploaded 2 pics of the worst ones.




Some people will recommend that you steel sleeve the bores, but I didn't like that. Other said that you needed to re-finish the bores, but who knows of a machine shop that can do this particular type of work (you have to remember that this is hyperutektic aluminum/silicon mixture, 29% silicone, and it's the silicone that you need to polish and the aluminum that needs to be under cut below the silicon finish).

My solution was to strip down the block and ship it to US Chrome in Wisconsin for Nikasil plating and honing to the new pistons. I had Diamond Racing fabricate for me

Shopping around for replacement pistons I found out it was most cost effective to have Diamond Racing fabricate forged replacements rather than buying Porsche 911 ones or J&E Racing ones. You do have to make sure that they use materials on the piston that will match the hardness of the Nikasil bores. The guys at Diamond typically fab drag racing pistons so they are well versed in creating really stout ones. I held back from altering the piston dimensions as I wanted replacement parts, but they had all kinds of ideas of things they could do. I did go with teflon skirt finishing and oil pockets.

So the order of execution would be this:

1. Pull out rotating assembly
2. Send best piston to Diamond Racing for fabrication of replacements
3. Ship block and piston set to US Chrome for plating and honing
4. Weight matching rotating assemblies
5. Reassemble and break in

While it was all apart, I had Crankshaft Craftsmen in Hamtramick balance the crank. It was close, but not perfect, as well as do the rotating assembly weight matching.

I have to admit that I got lucky in the rotating assembly weight matching. 3 are dead even, and one is .1 gram light. The engine runs very smoothly, as you can well imagine, and thing pulls like a raped ape once the revs hit around 3.5K, all the way up to red line when the valve lifters start floating.

Swap in an LS1? Well, I think you can get all the work on the existing engine done for less than a complete LS1 swap, which if I recall is around $5K or a bit more. I suppose it depends if you are a purist or not, but hey, it's your car.

Me? I'm glad that I did it the way that I did it.
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[Cocacolakidd]

++1^ Well said - the main thing is to understand the beast you are working with.

I would still hope that the bores will pass the fingernail test. So then the rebuild process is in the hundreds of dollars spent, and not the thousands spent. In passing the fingernail test one can do the honing of the block themselves, thus saving many dollars.

There again if the block does not pass the fingernail test then there are other options to get the car back on the road again - A,B, and C above.

Also option "D" is to find a known good low mileage used motor and replace it that way - savings in labor and money in most cases.

[eohrnberger]

If you are looking for a 3.0L short block, I noticed one at Munk's motors, and I was told that they had another one in storage in the back. If that's the option you are looking for, i'd call them and se if they are available for sale.

[JoshB]

Those don't look like bad scores at all. I would put the car back together and drive it - should be fine!

[mistertate]

+3 it looks great