New debate, Sleeved block options

[rich]

I thought I'd toss this around the collective and see if I could get some feed back.

Our engines are slowly wearing out. Many of us have a few dead cores laying around that have been rendered non-op for an number of reasons. Eventually recycling will be the only option.

We have Nikasil which requires boring, application, and honing to size. Pistons are required as the stock iron coated pistons won't work with Nikasil. (so were told) The cost is approx $ 1000-1500+ Then the cost of pistons.

Herr-Kuhn has an iron sleeved block. Cost to duplicate this process? Then new pistons. Then how well does it work and for how long? This could be a lower cost option if it works.

There is also a Alusil sleeve. Anyone ever had this done? How does it work? The up side is the ability to retain the stock pistons.

The there is the ability to bore the blocks from 4.5 to 4.7 and 4.7 to 5.0 If you do this you still need to locate pistons.

Then there has been a couple of piston coating tried to mimic or replace the iron coating of our stock pistons. What worked? What didn't?

Anyone have real world experience they want to share? Myths, Legends? Out right lies?

[Danglerb]

There are projects in the works using sleeved motors for high performance, but right now I think its a WAY too risky option. What seems to have a working balance is the long life of the factory block, vs the frequency of totalling wrecks, so demand is not exceeding supply. The simple measure of that is the cost of a used block, 4.5 and 4.7 are easily found less than $500, 85/86 a $1000 or less, GTS seems about $5000 or less, with S4 and GT in the middle, and those aren't just bare blocks, but short blocks and even long blocks (includes heads).

Once a steady market exists above some price point, maybe $3k to $5k, somebody will start casting new blocks. I'm kind of surprised it isn't already happening, but could be the racing guys are restricted to Porsche only blocks.

[rich]

Oh ya, I forgot the cut out liners. This seems way out there as a repair method.

[Danglerb]

It wasn't a direction I was considering for myself, so I haven't followed that closely, but my impression is that there are serious questions about the strength of the block at the base of the cylinders.

[Herr-Kuhn]

The best and least intrusive option is Nikasil. I see no reason the ferrostan stock pistons won't work on Nikasil...it also holds oil for better lubrication. As long as the sulfur level in the fuel is low you should not have any issue.

"I Love Goooooold, Da smell, da test, da texture"...From the 2004 nikasil rebuild of the infamous "Goldmember"...

[rhjames]

Let's see.....

cut the cylinders out, machine the block for Mr. Todd's liners, cut the top of the deck off to install a full deck ala Mr. Gee's, machine the new top deck (counterbore the liner holes), insert Mr. Todd's liners, fill the bottom of the water jackets with concrete (up to within 3 inches of the deck ala Mr. Gee's).


Result:

a block that uses replaceable liners for the life of the owner, with massive cubic inches (at least 427 ci) and bullet proof lower and upper cylinder areas. No need for fancy nikasil coatings.

Mmm.....just like our diesel truck engines, only smaller. Wear out the rings and cylinders,? Just pop out the liners, put a new set of rings of rings on the pistons, and get back after it for the next 500,000 miles.....


I just hate to think of the cost------


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[rhjames]

Danglerb may be onto something----cost versus availability of used blocks, but casting new blocks?

Doubtful.....again, let's look at the demand for such? It took nearly 30 years for Chrysler performance to re-introduce (new castings) street HEMI blocks, and only after the price of HEMI powered cars went thru the roof......

When's the last time you saw the price of a 928 top $100,000??? Until then, blocks might get modified, but new castings??? Nope.


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[Herr-Kuhn]

I see the sleeving resulting in a block that:

Runs higher piston to wall clearances (i.e. 0.005" or more)
Has the potential to fail prematurely (i.e. dropped cylinder, etc.)
Has diminished cooling capacity due to reduced cooling jacket area (if you cut it all away and go big bore and cement it in)
Costly

There are many stories of sleeved 928 blocks going south fast. The "Gee" block you refer to lasted 5,000 miles and went south...I suspect it was not machined properly, but it still was a miserable situation for him after spending the time and money to build it up...he since replaced it with a Nikasil plated block and has had no issues that I know of. I think the sleeved block I have was done right since it is 20+ years old now and is still in-tact, but it's still a sub-par method compared to Nikasil plating the bores.

The Nikasil process is used on the Carrera GT and has been used on 911s for decades. Virtually all motorcycle engines run nikasil...as do formula 1, Nascar and many other forms of motorsports. I've built 3 such blocks and have had no issues. I agree a cast iron block is a good long lasting block, but for low thermal expansion delta, long life and the best possible hear transfer it is hard to beat the alusil or nikasil over aluminum block.

You have to remember that a pressed in steel sleeve is very different than a sleeve that is cast into place. Cast in sleeves are a good thing because they are sure to not slip out. When one machines and presses in the sleeve then the fit becomes very critical...I've seen some with cracked cylinder towers as a result and others where the sleeve slips downward into the crankshaft area.

Nikasil offers:

Ability to run low piston to wall gaps (0.0025" with a 2618 forged piston...less if you run no boost)
Maximum heat transfer
Oil retention on the cylinder walls
Extremely hard and wear resistant (can only be cut with diamond hones)
Lower cost compared to sleeving (about 40% less)

Its only negative is that it is not tolerant of high sulfur fuels.

I don't follow the logic of completely removing the entire cylinder tower and then relying on the base web of the block to support new cylinders. There is no imtimacy of the block material to the bore and you are reyling on a small amount of bearing area of aluminum to hold the new tower. Additionally the cooling jacket area is greatly diminished...I can't see how it will cool as well as the factory setup (more fuel burned while reducing the cooling water jacket size) Time will tell how well this methods works.

[rhjames]

John,

if you look at Mr. Todd's liner design, you will see that it has an o-ring at the bottom, and the top deck of the liner is very wide, doing two things: preventing rotation on it's axis because of the flat side of the top liner deck, and side to side movement because of the wide flat surface of the top liner deck.

if there is one flaw in the 928 block design, it's that there is no top deck on the block.

the cylinder liners are not supported in any way, other than butting up to the head gasket and cylinder head, therefore they are subject to splitting just like Rich's motor did. Had there been a top deck, his motor may have sustained some cylinder wall damage, but the liner probably would not have split-requiring removal of the entire liner. There are cylinder side loads in any engine, but the 928 engine has very little support on the top side of the cylinder to support these issues......

I proposed the "put in a top deck-then counterbore it to accept an o-ringed liner" for several reasons:

you never wear out the block per se, you just change out the liners and piston rings.

you can run much bigger cylinder volumes (bigger piston diameters and bigger crankshaft stroke).

you may be able run less exotic pistons.

no need to worry with sending your block out to be nikasil plated, no matter it's benefits.

you probably would not experience liner splitting, the most prevelent block damage I have seen with this design.

As for heat transfer properties, this is beyond my meager education, as I am not an engineer. However, the removable liner example does work in other applications such as the diesel engine theater....

it's just a thought for someone who's got the time and the bucks to make it happen?

[rhjames]

I didn't quite follow the piston to wall clearances (nikasil---.0025) you spoke of.....

The FWM's recommend a clearance of .025, which seems very, very loose.

I never ran anything bigger than .015 in my race motors, and they rattled like heck with that much clearance......especially with forged pistons. the Factory's numbers seem far away from the numbers you were quoting for nikasil(?)

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[Danglerb]

There is a 4.5 block in FL that apparently can't be given away, scheduled to go to recycle on the 20th.

Available options seem to have everybody satisfied enough not to want to spend much more for anything better.

[rhjames]

and you are surprised by this, or just disappointed?

sure, there are a bunch of these cars (and motors) that are just collecting dust with weeds growing up around them, but even the early 911 cars don't ring much money to warrant their survival.....

On a recent trip to Georgia, I found an early US spec just sitting in the weeds on the side of the interstate, right at the end of the of ramp. It's Guard's Red, has black interior, and the usual options. Sticks out like a sore thumb, so to speak.

Problem with it? Broke motor--- timing belt broke, owner just let it sit.

Is is worth going after, maybe for a $200 parts car, but again----it's an early 928, and you know what the demand is for those......little, if any.

[Herr-Kuhn]

I run 0.0025" diametral on the Nikasil plated 390 block and this is with a 2618 forged piston. Really tight engines run like 0.001". If you were running steel you need much greater clearance. More clearance means more wear on startup. 0.015" is a huge amount. That would rattle all over the place.

I've run 12 or more psi on these open deck designs without issue. No doubt a closed deck block is stronger but I'm not sure you really need it for a mildly built car.

I would think the 928's block could support 700 HP, maybe a tad bit more in a pinch. Remember, heat transfer is very important to performance as well as strength.

[Herr-Kuhn]

Here's a shot of the Bastard's 4.5 liter with a 2618 JE piston set installed...these are shots from 2003 whilst I was cutting my turbocharger teeth.

I have about 11,000 miles on this engine since the rebuild and it still runs extremely well...I'll never sell this car.

[Danglerb]

Maybe the Rolling Stones said it best,

"You can't always get what you want
But if you try sometimes well you just might find
You get what you need"

Good options for everybody I think are out there, its more a question of what X or Y costs relative to some other way of doing it.

[rhjames]

As I am constantly learning new stuff about these engines, I am amazed at the things that don't apply to alloy engines, but do apply to iron blocks.

I've said it before, I'm no engineer.

The .015 clearance is great for a drag race motor......revs really fast, but sucks for street driving. For street motors, I always tightened up to .005 piston to wall. Less than that seems really tight, but I have no history with alloy blocks other than dealing with the 928 stuff of late.....

If you didn't want to go as far as installing a top deck (for added strength), I suppose putting concrete in the bottom third would help. At least you might not have to worry so much about side loading or shifting of the bottom end of the cylinder....

Oh well, back to my 5.0L hybrid build!!!!

[Herr-Kuhn]

It would be ideal if these had a top deck on them...problem is if you put one in that usually means welding. Opens up a lot of opportunity for issues. I often wondered if there would be a way to just bridge into the towers for support without welding an entire deck into place.

[rhjames]

just from what I've seen welding alloy, it's finicky stuff once it's been welded on.....

in my opinion (which doesn't matter much sometimes), I believe once you start down the road of building support for the top of the cylinders, you may as well put in a complete top deck.

And if I was going that far, I'd build it similar to Mr. Todd's steel sleeve design, but with the new top deck counterbored like a diesel and the liners o-ringed on each end. In this example, you would not need as wide of a top cylinder surface as Todd's, because the deck would be holding the upper cylinder flange in place with the counterbore.

It would be an interesting engineering excersize, but probably way beyond a cost effective way to go for block repair/longetivity.....

[BoxxerSix]

Originally Posted by Herr-Kuhn

It would be ideal if these had a top deck on them...problem is if you put one in that usually means welding. Opens up a lot of opportunity for issues. I often wondered if there would be a way to just bridge into the towers for support without welding an entire deck into place.

I suppose I'll put my input here on this. There have been a few guys I know, myself one of them, that have built a handfull of open deck motors where the top deck is closed with a composite material. Some people like to use Belzona. I prefere the titanium metal epoxy made by Devcon. I've used this process on a few of my turbocharged subaru SVX engine(EG33 3.3L boxer six motor)

The basic idea is to fill the block coolant passages around the cylinders with either salt or compressed baking soda, to a height below the deck sufficient for a top deck(ie .5" for instance). The product is mixed well(no air bubbles!!) and pressed evenly into the remaining space up above the deck line and allowed to fully cure. Block(or case halves) are then hot jet washed to remove the salt/baking soda. Block is then decked to remove material above deck line, and then coolant port passages milled according to the head gasket layout and head passages. Before filling the salt, the block should be fully cleaned and the inner walls where the epoxy material is to bond should be blasted with an aggressive soda material to promote adhesion.

Devcon titanium epoxy pdf tech file http://www.devcon.com/techinfo/124.pdf

Here are some pictures of this done to an EG33 open deck block(not my own)

Case filled with salt:
http://i123.photobucket.com/albums/o285/Boxxersix/salt.jpg

Epoxy applied
http://i123.photobucket.com/albums/o285/Boxxersix/epoxy.jpg

Block decked
http://i123.photobucket.com/albums/o285/Boxxersix/decked.jpg

Coolant passages routed
http://i123.photobucket.com/albums/o285/Boxxersix/routed.jpg

The two customer motors I've done this too are still running strong, both turbocharged well into the 1.7bar range and one with near 25K hard miles on it sofar. Still ticking.

I talked with the Devcon engineers for awhile on this subject and they felt the material was more than adequate for this application due to it's compatibility with aluminum, thermal expansion rate, and coroosion resistance to glycol mixtures. Plus stable up to a minimum of 350F.

Personally though, as stated before, I doubt the 928 block really needs this unless you crossing some serious HP territory


dupont actually now has another product specifically designed for this(was made for Nissan) called Zytel HTN, which nissan specifically used first for a composite internal block guard on their open deck VQ series motors.

Both composites are readily available via dealers, yet do cost some coin(devcon about $400 for a 3lb tub enough for 1 average motor)

Just some experience I thought I'd share on this topic...

Regards

[rhjames]

pretty trick stuff......