S65 cylinder bore condition OK for rebuild?

[nocomment]

Hey all,

I am looking for some second opinions on the condition of these cylinder bores, if it looks good for pistons to go back in, and if not options for fixing it (sleeves? Machine shop?).

Car is a 2009 e92 M3 DCT with a ESS supercharger.

Some context below:

Photos are after an AN-30 and felt tip "hone".

Engine has been previously built before (CP pistons, arrow rods), but had a horrible oil burning problem through ring blow-by. Looking at the cross hatch at the top and bottom of the bores I suspect that whoever built the engine previously honed them incorrectly. I do not know how many miles are on the rebuild, car was purchased (for a deal) in this condition.

Bores are straight and measure 92mm within +/- 0.02mm measured via dial indicator bore gauge.

None of the visible lines catch my fingernail or can be felt otherwise.

The CP pistons also measured 91.89mm in diameter as opposed to oem 91.99. The Mahle replacements I have are 91.97mm, but they are the less ductile aluminum compared to the CP.

This is my first post on this forum so I appreciate any help and feel free to ask me any questions, thanks!

[spammysammich]

Check the #1 crank main journal as well as the bores. More than a few of us have found cracks there leading all the way up to the oil gallery on used “good” blocks.

There should be NO crosshatch in the bores of these engines. None.

[nocomment]

Oh wow, I didn't notice anything super obvious when I had the crank out but I'll take a closer look thanks

[Chrisyphus]

Originally Posted by spammysammich

Check the #1 crank main journal as well as the bores. More than a few of us have found cracks there leading all the way up to the oil gallery on used “good” blocks.

There should be NO crosshatch in the bores of these engines. None.

Is this block not sleeved?

[nocomment]

Originally Posted by Chrisyphus

Is this block not sleeved?

From what I can tell it isn't. Photo attached of what sleeves on an S65 typically look like. Unless some generic sleeves were installed or something. The build sheet I received from the original engine build showed alusil coated pistons were speced. My guess is that the machine shop that refreshed the block knew nothing about alusil and honed the bores incorrectly (hence the cross hatch patterns being visible) and that's what led to the oil burning. I have ordered a good used block and will build off of that since it was cheaper than getting this one sleeved.

[omgzirra_exe]

The CP piston diameter makes sense when you account for thermal expansion.

Did you measure the piston exactly as CP specifies, which is 0.500" up from the bottom of the skirt and 90° to the wrist pin? That's the measurement point used to determine piston-to-wall clearance.

Based on the wear pattern and condition of the bores, you'll likely want to have the cylinders properly honed to expose fresh silicon in the Alusil surface. If the bores are out of specification or cleanup requires additional material removal, you may end up needing to machine the block to 93.00 mm and move to an oversized piston set.

To address your photos, from what I've learned over the years through my own build and from knowledgeable people who specialize in these engines, a properly prepared Alusil bore should not resemble a freshly honed cylinder.

After the silicon exposure process, the bore typically has a semi-matte or satin appearance rather than a sharp, highly visible crosshatch. The critical factors are proper silicon exposure and surface preparation, which are best verified through profilometer readings rather than visual inspection alone.

personally in my opinion... I would just sleeve the block if you plan on keeping the supercharger.

[RocketyMan]

That block looks 100% sleeved. You can see the metal difference at top and bottom of bore. Also, that top looks way too clean indicating the top of the block was decked.

Who ever did the sleeving doesn't look like the VAC motorsport sleeves--which are flanged sleeves. These pictures show different. This block looks similar to say something like a GM LS aluminum block and the stock sleeving. Look here:


As for the condition of your bores, those bores look like the piston scuffed. Maybe the stock pistons were used. And this makes sense as clearances are different between the aluminum bore vs steel-sleeved. Stock pistons are 91.99mm nominal. You need more piston to wall clearance if using sleeved as the difference in bore of aluminum vs steeved. That's why on the VAC website they have you specify the pistons to be used by stock aluminum bore vs sleeved.

[RocketyMan]

OP. I guess I'm confused. What pistons did you use in this block? The CP pistons or the Mahle replacements?

[nocomment]

Originally Posted by RocketyMan

OP. I guess I'm confused. What pistons did you use in this block? The CP pistons or the Mahle replacements?

Hey Rocketyman, the original engine that I disassembled was already built by the previous owner using CP pistons. on the receipt he had it showed 92mm bore and alusil specified. I agree it kind of looks sleeved, it may also be discoloration from where the compression rings of the head gasket were sitting. I just find it odd that all the s65 sleeved engines I've seen run flanged sleeves, due to how close the bores are to each other that this one wouldn't run that. Unless there's some other design I am not aware of.

If it is sleeved, and he was running alusil pistons, that would also explain why the rings never properly set. I also agree with the piston to wall clearance not being the issue after seeing that the material the CP pistons are made out of is the more ductile aluminum that expands more.

[nocomment]

Originally Posted by omgzirra_exe

The CP piston diameter makes sense when you account for thermal expansion.

Did you measure the piston exactly as CP specifies, which is 0.500" up from the bottom of the skirt and 90° to the wrist pin? That's the measurement point used to determine piston-to-wall clearance.

Based on the wear pattern and condition of the bores, you'll likely want to have the cylinders properly honed to expose fresh silicon in the Alusil surface. If the bores are out of specification or cleanup requires additional material removal, you may end up needing to machine the block to 93.00 mm and move to an oversized piston set.

To address your photos, from what I've learned over the years through my own build and from knowledgeable people who specialize in these engines, a properly prepared Alusil bore should not resemble a freshly honed cylinder.

After the silicon exposure process, the bore typically has a semi-matte or satin appearance rather than a sharp, highly visible crosshatch. The critical factors are proper silicon exposure and surface preparation, which are best verified through profilometer readings rather than visual inspection alone.

personally in my opinion... I would just sleeve the block if you plan on keeping the supercharger.

Thanks for the input, after what people are saying and what I have seen, I agree that in order to fix this block sleeving or boring it out would be required.

[Chrisyphus]

Toss a magnet in that thing and let’s put the theory crafting to rest lol.

You don’t necessarily need a flanged sleeve, and an flangeless sleeve is going to be cheaper. It’s just going to have worse thermal expansion characteristics.

The difference in color is VERY out of character for any S65 I’ve ever seen.

If that’s the case, as mentioned above, and a ring set designed for alusil was used, there’s your failure mode. Good to know.

Re:sleeved vs. reconditioned- hard disagree that sleeving is the only option. We have multiple 700whp+ supercharged S62s running without sleeves, and they’ve all lived long happy lives. They have the same bore spacing as the S65 and they’re 94mm cylinders BEFORE we bore and recondition them (.008” IIRC). It’s a non-issue unless you’re trying to get into horsepower numbers far above the average SC S65.

It is, however, the only safe option if you choose to work with a shop that doesn’t specialize in AluSil reconditioning.


Now, having covered all of that, if you want an economical solution to getting this car back on the road that takes all of the guesswork out of the equation, we offer a short block package for $10,000. It’s a fully forged rotating assembly including our custom manufactured forged and fully machined rods, MAHLE power pack pistons in either 12.3:1 or 10.2:1 compression ratio. Fully machined, blueprinted, and built in-house by us. This short block, properly maintained (good oil change interval and standard warm-up considerations), should outlive your original motor. MAHLE’s 4032 pistons are as long lived as the OEM pistons, and with our improved bearing clearances all around, the full packages is better than OE, not just in performance, but also in reliability.

We’re also working with MAHLE to have them produce custom pistons for us in the same alloy that the S58’s OEM pistons are made from. Not an inexpensive endeavor, but worthwhile as M142 offers nearly the same strength as 2618, while having a CTE more similar to a cast piston than even 4032. But that’s going to take some time to come to fruition.


My final point…. Brother you’re in Raleigh. When I first started working at Partee Racing, I moved to Chapel Hill and commuted up to Danville every day.. drop by and check us out some time if you’re at all interested. We are open to the public and have dozens of people come by every month who will almost certainly never be customers, but we still show them around all the same, because that’s not the point.. hanging out with other enthusiasts is.

[charliev68]

Your block definitely looks sleeved! Notice the difference of the 2 metals on yours vs original.

[nocomment]

Originally Posted by charliev68

Your block definitely looks sleeved! Notice the difference of the 2 metals.

I agree after looking at it more. Just very odd they installed generic sleeves (unless there's a brand im unaware of that looks like that) and then ran the wrong pistons with it. But then again it was burning about 4 quarts of oil every 50-100 miles so clearly they did something wrong lol

[spammysammich]

Originally Posted by Chrisyphus

Is this block not sleeved?

I missed that detail. My bad.

[nocomment]

Originally Posted by Chrisyphus

Toss a magnet in that thing and let’s put the theory crafting to rest lol.

You don’t necessarily need a flanged sleeve, and an flangeless sleeve is going to be cheaper. It’s just going to have worse thermal expansion characteristics.

The difference in color is VERY out of character for any S65 I’ve ever seen.

If that’s the case, as mentioned above, and a ring set designed for alusil was used, there’s your failure mode. Good to know.

Re:sleeved vs. reconditioned- hard disagree that sleeving is the only option. We have multiple 700whp+ supercharged S62s running without sleeves, and they’ve all lived long happy lives. They have the same bore spacing as the S65 and they’re 94mm cylinders BEFORE we bore and recondition them (.008” IIRC). It’s a non-issue unless you’re trying to get into horsepower numbers far above the average SC S65.

It is, however, the only safe option if you choose to work with a shop that doesn’t specialize in AluSil reconditioning.


Now, having covered all of that, if you want an economical solution to getting this car back on the road that takes all of the guesswork out of the equation, we offer a short block package for $10,000. It’s a fully forged rotating assembly including our custom manufactured forged and fully machined rods, MAHLE power pack pistons in either 12.3:1 or 10.2:1 compression ratio. Fully machined, blueprinted, and built in-house by us. This short block, properly maintained (good oil change interval and standard warm-up considerations), should outlive your original motor. MAHLE’s 4032 pistons are as long lived as the OEM pistons, and with our improved bearing clearances all around, the full packages is better than OE, not just in performance, but also in reliability.

We’re also working with MAHLE to have them produce custom pistons for us in the same alloy that the S58’s OEM pistons are made from. Not an inexpensive endeavor, but worthwhile as M142 offers nearly the same strength as 2618, while having a CTE more similar to a cast piston than even 4032. But that’s going to take some time to come to fruition.


My final point…. Brother you’re in Raleigh. When I first started working at Partee Racing, I moved to Chapel Hill and commuted up to Danville every day.. drop by and check us out some time if you’re at all interested. We are open to the public and have dozens of people come by every month who will almost certainly never be customers, but we still show them around all the same, because that’s not the point.. hanging out with other enthusiasts is.

Thanks for the info, what's the name of your shop? May have to swing by sometime. Currently don't have the budget to buy a fully built short block, have any good blocks you're willing to sell? Also would you like to buy mine as a core to rebuild? Gonna make a table out of it or something otherwise lol

[nocomment]

Originally Posted by spammysammich

Check the #1 crank main journal as well as the bores. More than a few of us have found cracks there leading all the way up to the oil gallery on used “good” blocks.

There should be NO crosshatch in the bores of these engines. None.

Well, you might have jinxed me, the "good" used block had the exact damage you described when it arrived, so I am still in search of a block before I shell out for machining and etc lol

[spammysammich]

Sorry man, I really hate that failure mode. I’ve been wanting to buy a block to rebuild as a long term learning project and this kind of block is all over eBay lately. Some of the pics even unknowingly show the crack but describe the bores as good or salvageable

[Chrisyphus]

We buy ~5-6 S65 cores per month. Of the cores we’ve bought, 50% have had a spun front main bearing failure, and have this exact damage, or have the main bore damaged but not quite cracked like this. Either way, with the exception of VERY expensive machining services (like what those guys over seas do, can’t remember their name), the entire block and matching bed plate are trash. Because of this, every month we get $1000s back from the recycling shop for the low low cost of $10000s. STONKS.

[nocomment]

Originally Posted by Chrisyphus

We buy ~5-6 S65 cores per month. Of the cores we’ve bought, 50% have had a spun front main bearing failure, and have this exact damage, or have the main bore damaged but not quite cracked like this. Either way, with the exception of VERY expensive machining services (like what those guys over seas do, can’t remember their name), the entire block and matching bed plate are trash. Because of this, every month we get $1000s back from the recycling shop for the low low cost of $10000s. STONKS.

Gotta spend money to make money

[former 240 s14]

Originally Posted by nocomment

Well, you might have jinxed me, the "good" used block had the exact damage you described when it arrived, so I am still in search of a block before I shell out for machining and etc lol

Welcome to the club friend, sorry to hear you are dealing with this.

I am currently finishing up a build myself from a front main bearing failure at Road America last October. We tried finding a used block and ran into the same issues you are experiencing.

The number of bad blocks out there are becoming quite the problem, even engines that are technically still running are getting close to terminal.

I ended up building a sleeved short block with forged pistons but Partee was absolutely in consideration as well. I also would of considered going LS if I knew how much I was going to be in for at the beginning of the process.

You need to really come to grips with what you want to do with this car before making a plan moving forward. i.e. is this going to be a street car or a track car? There are specific things you need to plan your build around if you are picking to do heavy or even occasional track use. If you decide to do a budget friendly fix it's just a band aid and you will be bound for more pain, trust me.

Good luck and keep us posted!

Rubin