Very interesting....certainly the least intrusive way to support the top deck. I suppose you could use the head gasket to get the coolant passage way correct.

What keeps the epoxy from slipping down on the block? I suppose you have the natural draft angle of the block so if it tries to slide down then you end up with it getting tighter and it doesn't have to seal on the head gasket as the natural aluminum structure of the block did that in the first place.

Really it looks quite unique.

Your correct, I(others) use the headgasket to template the coolant passages and then route them out.

The material is very tenacious and bonds to the inner walls of the coolant passages and onto the cylinders provided proper cleaning and surface prep is completed. Most grind the inner area with sand rolls on a dremel tool but I think this creates risers in the material(weak). I mask and cap off the cylinder bores and blast the bond area with an aggressive soda media(8-20grit), then clean/prep with tier 300 cleaner. Less chance of a stress riser and cracking. Do this after the block has been thouroughly cleaned and degreased though.

I'm looking into the Zytel HTN for future blocks due to it much greater stability, and the fact the the material was designed to do this exact procedure. The cost is far more as the Zytel is not sold in small volume as of right now(that I'm aware of anyway).

Certain blocks, like the EG33, have cylinder that are siamesed (touching) and can actually get away with bonded wedge plates between the cylinders and outer case for a simple semi-closed deck to keep the cylinders from migrating under high horsepower and blowing head gaskets on the center cylinders (what currently happens on the EG33 above 1bar boost). The 928 blocks don't have the siamesed bores and a simple way to wedge the bores doesn't really exist. Thus it would "need" the fully casted closed deck.

Again though, have you guys had any major issues with the 928 block bores migrating under boost? The 928 motors seems to be pretty stout sofar :) I saw your dyno charts with your biturbo setup, very impressive numbers!


-Regards

Honestly, I think the stock block is good to over 700 HP. Others have claimed the towers flex and balloon on boost and that this causes head gasket failure. I have never blown a head gasket on a boosted 928 engine, but I'd better knock on wood, right? It would seem to me that the modulus of the material is low, but that if it did creep it would quickly crack...there is little ductility on that cast 390alloy. I'm just not a fan of inserting steel into an all aluminum block...I'm intrigued by this process, as it would have to provide some extra support upstairs on the towers. I could have my block nikasil plated and then do this process and have it locally decked off I suppose. I always try to be the least intruisive as possible. That material would likely never last the acid etch bath for the Nikasil process so it would have to be post-Nikasil. Still though I think there is at least another 150 HP to go on this block before I hit the brick wall.

Thanks for the feedback on the twin turbo. I think is is a nice addition to the shark's engine bay. The question is how much more should I do to it? It is already insane on the streets, but I know with lower CR I could pump about 5 or so more psig into it. In this cooler weather the top side of 2nd is very loose.

Detonation and air in the oil seem to be the two biggest issues on well maintained engines. Breaking a block is certainly serious heartache, but until we see it happening, why fix it?

OTOH we don't have much data on long term use of sleeves in 928 blocks, without maybe expensive engineering and modeling that is something that will just have to play out and see how it goes.

Cracking of the block in the vee has been seen and well documented. Porsche saw it during testing and it is mentioned in "Projekt 928". Engine builders have seen it and it has been discussed on Rennlist and pics have been posted. Greg Brown has seen it, Erik Munk has seen it. The reason it hasn't happened more is because there aren't a whole lotta' people pushing these engines hard. I would imagine that we will start seeing problems more and more as we get more people boosting their cars and trying to push them higher.
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It all depends on how long you use the "pushing it hard" button.

If you're thinking about doing this, I'd recommend going the Zytel route as the material is much more suitable for this exact application. I'm going to be looking into getting some smaller quantity of the material, rather than a 5gal pail of the stuff($$$$$$$). I'm actually going to be trying it out on my next EG33 block for my new kit car, as well as dowel pinning the heads to the center cylinder(as the cylinders are siamesed and have the necessary material to do so ). Both those should allow ~17-2.0bar with little worry of cylinder migration and blowing HG's all the time. Too thin to o-ring with long term durability in mind :(

I had contemplated Nikasil in the bores of this motor too :) Who's a reputable place to go to to have that done?

For Nikasil, I use millennium in Pilgrim, Wisconsin...three 928 blocks thus far without issues. I'm not sure my driveline could handle more than 1.2 bar before it scatters so I think the decking might be overkill for my use...but I'd still like to attempt it.

I used to help run a drag car in VA. We used hardblock to fill the water jackets to add strength. This could also work with the 928 block if you kept some water passages open. We used to insert tubing before pouring the hardblock to keep a passage open if it was necessary. Hardblock is similar to a ceramic grout. That was back in 1994 and is probably old technology by now. I like the idea of using a soluable base and pouring the "stiffener" on top of it. It sounds pretty trick to me. How thick would you need to pour this stuff in this application?

Yea Hardblock is pretty trick stuff too although I don't know how well it actually would bond to the block in a 1/2-3/4" thick suspended layer :( I know guys do exactly what you said....surround the cylinders with copper tubes for coolant flow and fill the gaps with hardblock. Works very well in drag applications where short engine runs occur. Not sure how well hardblock would work on a daily driver with heat transfer from the cylinders over long runs/trips :confused:.

I usually pour(spread) a 1/2-3/4" thick layer for the deck. Seems to hold up well. I wouldn't go too much more than that because you cover up cylinder area near the head that needs to be cooled fairly well. The Zytel you could run thinner, another reason to go with that vs the epoxy.

in reading Sterling Gee's writeup of his first stroker build, he stated that Porsche had found that the heat area of the liner was in the top three inches, therefore you could concrete everything below.

however, he then goes on to say that the coolant drain holes were blocked by the shop that did his engine work, possibly contributing to its early demise......

Mr. Gee is really on to some high end (read: very expensive) engine building, but it will be an interesting engineering exercise if he gets it to stay together this time.

I still believe, however, that if you are really trying to push these engines to the "edge" of power production, steel liner/full deck is the way to go (o-ringed on each end of the liner similar to a diesel). you could concrete the bottom and then Zytel the top for a deck (?) or maybe Zytel both ends......

you wouldn't get the benefits of close tolerances with Nikasil coating, but you could run almost any piston/ring combo and really huge cubic inches with big boost numbers.

again, it's an interesting discussion, but this is getting into big bucks for serious long term high boost applications. the average 928 owner wouldn't even consider this stuff unless he just had a hankerin' to build a 997 killer with a bank account to match.;)

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I'm wondering when people will finally come the the realization that proper tuning plays the largest role in engine life of a boosted motor? All this talk of blown head gaskets and cracked blocks, etc. are likely a result of one of several conditions (or a combo of the four):

A. Too much ignition advance
B. Too little fuel (i.e. quantity)
C. Too much boost
D. Too little fuel octane

Often people assume they don't need to do anything with "A". BIG mistake. Anybody who has put boost on top of any 928 motor and done nothing to address ignition advance is asking for trouble. Your knock sensor will only pull so much timing...after that you're done. They get a system that works well, then get addicted to the boost and then turn the screws up but often times these guys don't follow the standard protocol for adding boost to the engine, they get ambitious and then break something. Then suddenly the excuses start rolling out. I often wondered if the comments about how much easier it is to add a supercharger to the 928 as compared to a turbocharger takes into consideration the time people spend pulling the motor to fix what they broke after the initial install? Isn't that the true installed cost? Of course, either system works if you tune it properly and don't go crazy with it. Additionally, there is the "bad kharma" effect that has its way of isolating certain "loud-mouth" individuals. This has been proven positive many times in "the field". At least two loud mouths have suffered the wrath of the bad kharma effect. But what do I know? Afterall I'm just a dumb monkey :D

My point is this: When properly tuned a stock 928 block works very well. No forged piston, heavily o-ringed head, or steel sleeve will stop parts from scattering under sustained detonation. It's all about the tune. And of course if you act decently towards others you are typically offered some form of high level protection from the infamous "bad kharma" effect.

Of course if chasing dispalcement is your game then the stock block does have it's limits. But consider the stock block can go to 6.5 liters and then you could add one bar+ (turbocharged of course :)) and be making close to, if not over 1000 HP. Now, where does one use that sort of power anyway? SmileWavy

well.... I know of several places I'd like to use 1000 hp;)

unfortunately, John....my ride doesn't have knock sensors or computer controlled ignition or fuel maps, etc......you get the idea.

I don't advocate boosting until the the blows to eternity, but just having fun with the discussion about where you can go IF you had unlimited resources (money) to play with.

Remember, I am just starting on my journey of head work, cam grind work, then displacement work, and then pressurization work....

It's sort of like starting from the inside and working outwards......

(It's still a fun discussion.....!)

--rhj

:D I second that .

John, congratulations on your project. It appears you are getting it sorted out in a very clean fashion. I think you are correct that with a good tune up 700hp is on tap. Can either transmission handle much above that?

I doubt more than 700 ft-lbs could be held. 800 HP...maybe if the engine turned 8 grand to make it and the torque was lower, perhaps.

This AM I applied 1/4 throttle and the car was smoking the 10" meats in 1st. I really need to get it back onto the dyno, last time the temps were way up there and I had limited airflow over the coolers. It really feels like another 30-50 HP in these temps. Reeves Callaway once told me the difference between a cold and hot day on a turbo V8 could be as much as 100 HP!

I think generating the 700 hp might be easier than dealing with it once you do.

Got any pics of that Monster?

There are some good photos on here...I will see if I can bump the thread back up and re-name it.