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FWIW the 3.0L 944 cranks weigh practically the same as a 2.5L 944 crank of any valve count - 59 lbs.
Interestingly the 3.0L 968 crank was only 52lbs, some shrinkage done with the counterweights perhaps related to their dual-mass FW?
On the 100mm bore 944 blocks the max practical dry-sleeve is about 104-105mm bore. To fit the bore and the sleeve this means taking the 100mm barrel out to ~109mm hole.
IIRC the OD of a 100mm 944 barrel is ~114mm so you're getting VERY thin on parent alusil material. Believe 5.0L 928s are similar dimensions.
There were a number of 106mm bore ones done about 15 years ago...I only know of one that made it past 100,000 miles.
104mm (2.7 + 3.0L) blocks are another ballgame with the raised floor as mentioned, along with siamesed barrels.
The crankshaft, because of its length and cylinder head offset, turns out to be pretty heavy. And it is that mass that pounds on the block. Certainly, extremely light reciprocating components would reduce the required mass of the counterweights, but a crankshaft anywhere near 50 pounds is probably not possible, unless reliability is sacrificed. 55 pounds might be obtainable.
Mike Simard certainly recognized the "issue" with removing the stock cylinders and boring the block to accept the 109mm cylinders that he made. The amount of material that remains is frightening, from a pure structural point of view. We talked/debated this subject quite a bit. To partially compensate for the loss of this structure, he made a beautiful billet piece that acted as a stiffener for the main bearing cradle and improved on the studs that held the cradle to the block. I'm not sure this engine has been run enough to know if these pieces were enough to prevent the very brittle upper section of the crankcase from cracking. Time is the only way to find this out.
Hi Greg, I have seen the billet strengthening “girdle” that he made, do you know what material he made it from? Feedback on whether this helps will be an important step.
Its looks a good effort to strengthen what appears to be the critical failure point for a wet liner engine.
I believe you have shaved some weight off the crank over the years, What would be required to take it to 50lbs. - even lighter pistons/rods, smaller big ends,
I worked with Bob Norwood years ago on my 1st stroker engine. He indicated that all of the heat in our motors was generated at the top of the cylinders. the top 3 inches to be exact. I personally grouted the lower portion of the block, The reason was that the smaller water jacket and the ratio of the radiator along with the cooling capacity would keep the engine plenty cool. I ran that stroker engine in 110 degree Dallas stop and go traffic with no issues. We did this for structural reasons.
I think to really create a 7 liter 928 engine, someone would have to anty up and have a billet block made with the reinforcements and designed for wet liners, also addressing the oil drain back issue from the heads.
Here are a few pics of our wet-wall 7.0L build. Built in January 2013.
The engine runs well, and is very smooth. Good torque, as expected. But it is under-cammed and under-intaked. The owner put his stock cams and stock intake manifold back on it. So I have never really seen "what could be".
Remember that as the CID gets larger, the camshafts get relatively "smaller"
Knowing what I know now, I would like to try again. We have found new porting techniques for the heads, and new cam grinds for more air, and as you know, two new intake manifolds (boosted and NA) that can flow significantly more air. It would be fun to see what we could get with those mods.
Carl,
What was used to hold they cylinders in place? Were they notched in some way to keep them from rotating? Thanks for showing the block with the cylinders removed. That is really interesting to see. You could grout the block all the way up to the machined level to give the block more rigidity.
You can see the block in the oven in one of those pics, and we had to heat the aluminum quite a bit as a) that's a big chuck of aluminum, and b) we went for a tight press fit. Then we also used Loctite Sleeve retainer in the mating areas.
Cylinder rotation was not considered a big concern. When finished, the block was decked and we sent custom MLS head gaskets along with the engine to the customer. When the heads are clamped down over those MLS head gaskets, those cylinder walls are held quite securely.
Missing from the photos is a little material was removed from the outer walls in the Siamese areas to facilitate coolant flow around the outside of the cylinder walls. Not so much as to weaken the cylinder, of course. The outer cylinder walls do not actually touch each other, and we just widened the gap a little more.
Yes, you certainly could fill the block up to the bottom of the cylinder - but even better would be to fill the block up almost mid-way. All the heat is produced only in the flame area, of course, and that's about the upper third of the cylinder wall. Both Hard-Blok and Morosso make fillers for this.
However, we did not do that, and this engine has been in the field now for 5 years in the customers hands and I have no reports that there is any issue with it. Granted, with stock cams and intake manifold, he is under-stressing the engine.
Last edited by Carl Fausett; 02-08-2018 at 12:37 PM.
Carl, I have an S4 block much like the one you show here, with the steel (?) cylinders pressed into what remains of about half of the original Alusil cylinders. Mine is bored to 105.5mm, which, with a stroker crank, will end up about 6.7 liters. I now wonder if you made the one I have? Did you happen to make one at 105.5?
These pictures show Todd Tremel’s work on the 6.1 he built. No girdle on this one but it did have a design of liner that a flat surface on the outside which sat against the neighbouring liner. I was not sure if this was due to the size or whether this was designed to add rigidity to the liners. Lovely looking work
Jerry, I have not made any engine with those specs - dry cylinder liners and a 105.5 bore. When we make a wet-wall motor, I end up with a finished bore of 4.25" or 107.95 mm bore.
Would you consider using a girdle strengthening plate in future builds like the one Mike made?
Of course I would, if I saw the need for it. Mikes girdle looks great, and no doubt it is machined perfectly. The only question I have is whether it is needed or not. I have run my supercharged 6.5L motor for 5 racing seasons now including Bonneville, We make 900 to 960 HP depending on the tune. I have inspected the bearings numbers of times and not yet seen any evidence of block movement. We also have not had a cracked or damaged block. So, I just don't see the need. Now, we are attempting to go up still higher in HP, and maybe I will find it necessary then, but so far, we don't.
Consider Todd Tremel's turbo motor at 1000 HP, which also has no girdle.
...mopar 383/440 block has exactly the same bore spacing as 928...
can get them new, and in aluminum still..need to adapt the head bolt pattern somehow...
02-06-2018, 10:29 PM
