GMKF

Thats just the answer I wanted. Some day in the future...

Carl Fausett

To help customers understand what options are available, and how it affects the price, I have a page on our website where you can "build" your engine on paper and total it up. It's not perfect, but it's pretty good.
It is here: https://928motorsports.com/parts/long_block.cfm

As to what is the max bore size: we found that at 4.25" bore (producing a 7.0L motor with a stroker crank) we had to completely remove the 928 cylinders and install a wet-wall cylinder sleeve.
Pics of this are available here: https://928motorsports.com/parts/wet_sleeves.php

I've seen a pic, posed by ptuomov (I think) that shows where, if you go larger than that, the cylinders will be exposed out the front of the block casting.

Strosek Ultra

The pictures are from Todd Tremel. I was faced with the same problem when boring out the block for 114mm OD sleeves.
Åke

Carl Fausett

There you go. Those are the pictures I was thinking about. Thanks!

Carl Fausett

I forgot to add, another consideration that I don't see mentioned is that the maximum fire-ring I can get a gasket maker to make for the 928 is 106.5mm
That sets a limit on bore size, too.

Strosek Ultra

Well, I make my own solid copper head gaskets and machine a groove for a stainless steel O-ring at the top of the sleeve flange. Can be made in any size desired.
With 114mm OD sleeves it would be possible to go to 110mm bore (7242cc). I know of a guy in Germany running 110mm pistons. Think Mike Simard had a 109mm bore but a little shorter stroke than the usual 95.25mm (3.750").
Åke

Carl Fausett

I appreciate your answer.

The difference between your answer and mine is: I am referring to the largest gaskets I can have made (my MLS head gasket for the 6.54L and 7.0L motors are made for me at Cometic); and your answers represent the largest gasket you can make yourself.
Good job - no doubt. Its just that most customers don't have your equipment or skill.

Again - just thought I should bring this topic up so others would know if they go wild they may have difficulty fining head gaskets for their project. It's something to consider.

GregBBRD

Carl:

Since you are obviously building engines that have had a large percentage of the web structure machined away, you must have a really good grasp of the reliability.

It's well known that Porsche was not able to remove material from the block structure in the 944 GTR program without the blocks cracking in the main bearing area....and 928 engines are virtually identical in this area.

How many hours/miles has your lonest lastimg 7.0 engine gone?

Strosek Ultra

I just like to add that the making of solid copper head gaskets is a hell of a time consuming job. The bores can be machined in the mill but everything else is handmade using a die grinder, files and emery cloth. The outer edges are roughly cut in the band saw but the finishing job can only be done with the die grinder.
Åke

Strosek Ultra

Rumors say a 7.0 engine built by Todd Tremel experienced a cracked block depending on knocking and too high CR. I like to know more about that, maybe Hacker can chime in.
Åke

Carl Fausett

I do not really know, Greg. The engine is in Sweden and I never asked my customer that.
My job was to make the 7.0L short block only. I did not assemble the complete motor as my customer wanted to do it himself.

When it did not produce the power numbers that were expected, we helped him to discover why. Turns out, he
installed a stock 5.0L intake manifold, stock heads with stock valves and stock cams upon the 7.0L short block.
I told him he was choking off the big motor, and that's why it was under-performing.

The short block has now changed hands, and the new owner and I are chatting.
He wrote me this today:
I think this is going to be interesting!

Carl Fausett

I would like to correct my earlier answer on head gasket sizes.

Cometic, who makes our head gaskets, can go as large as 4.250” or 107.95mm on special order.

They made the gaskets for our 7.0L motor before.

Previously I had stated incorrectly that they would only go to 106.5mm

GregBBRD

Amazingly enough, I admire your "boldness" in doing these oversize wet liner steel sleeved engines, much less marketing them.

I've looked at the possibility of doing this a couple of times and just can't get past the failures that Porsche experienced in the prototype GTR engines, with the blocks cracking in the main bearing area, when the structure for the cylinders was machined away. (As I'm sure you are aware, Porsche continued, through the 944 and 968 program, to dramatically strengthen this area, as the power output (and rpms) increased in these engines.)

I actually had a block at one of the Southern California sleeve makers (who make sleeves for the 944 engines, so this seemed like a perfect place to go.) After over a year (literally) of the block sitting at their machinist, waiting for him to machine a cylinder away, so they could design a proper sleeve, they finally decided that it would not work, as the 928 block has significantly less material in the area where the cylinders need to sit than even the 944 engines have. Their "engineers" felt that there would not be enough material left to properly support the cylinders and that the block would crack very quickly. Additionally, they felt that the lower flange on the new cylinder was going to have to be so low on the new cylinder that stability of the cylinder was going to be an issue. (Why it took over a year to get to this conclusion was way beyond my paygrade.)

I'll be interested in seeing how long your engines actually "live" and although extremely dubious, I hope your experiment works!

In the meantime, I'll keep working on a billet block.....to get away from the extremely brittle Alusil material and make the web area of the block stronger.

Carl Fausett

I have three thoughts:

1) I would encourage you to take a closer look at the pics I have posted about our removal of the cylinder walls in order to install the 4.250" wet walls. The webbing between the cylinders was not completely removed, as shown in the pics at the bottom of this page: https://928motorsports.com/parts/wet_sleeves.php Point being that only that part of the cylinder walls that were unsupported already was removed.

2) Additional strength between the cylinders can be added after the cylinders are in with the addition of a solid block filler, like this one that I use: http://www.hardblok.com/how-to-order/

3) On our dry-lined motors motors, that are only just a little smaller at 6.54L, we do have many miles and many years on many of them. My first ones were built in 2010 and they are still going. Customers have me build about two a year on average. More some years, less others. None have reported cracked blocks, including my own that has been raced at 900 BHP and 960 BHP for 5 years now. We have been waiting to crack a block at 900 HP, figuring it would be a "given" at some point in time, but just haven't had one let go as yet. I also believe that the addition of the steel girdle on the lower end (part of the crank scraper we install) is adding some additional strength to the casting in critical areas. Picture below is of our Stroker Crank Scraper of the kind that is installed in these big motors. You can see how the main bearing journals would be hard-pressed to move axially from bay-to-bay while strapped together like this. So, maybe this has something to do with why we have not cracked any blocks in those "944" areas as yet.

Catorce

Greg - Billet block?

I am not sure how hard you have looked at this, but when I started making my 964 cases, I was quote 18K each in billet. This was from Dart, who makes all kinds of billet blocks. There are a ton of Chevy / Ford billet blocks out there, but they cost BANK and frankly there doesn't seem to be the demand for 928 blocks. Ideally, you would make a casting, but that is also cost prohibitive. To give you an idea, the tooling for my 964 cases costs about 250K but allows me to produce a finished case for 5K. Clearly there are more buyers at 5K than at 18K.

Mine are made from A356 heat treated to T6 specs and are way stronger than the original in the testing we did (about 20%).

A 928 block casting would not be hard to make - it would be easier in many respects than a 911 case, but the demand is not there.