WHY HD BLOCK ?
I'm finally getting around to going back to this reply to JDBlairs earlier note questioning the need for the HEAVY block. I have just written my rambling thoughts. This is not a lecture, just good natured banter.
What I really want to add to the thread is this: Do we really need these heavy, (133 lb.) blocks for reasonable (5-600 HP) levels
Jon actually asks quite a good question. Some of the answer is when the initial design of the block occured, and how the modifications for higher output were accomplished.
Most current turbo engines (including Buick) were designed 10 years after the pinto block that has had no major design changes since originally drawn in 1968/69. I dont know the exace date, but remember seeing the prototypes running around in 1970. I believe the Buick block is special for the turbocharged application. The real question though is why did I add so much mass to the bulkheads and cylinder head deck and cylinder walls. Why siamese bores?
Before answering the question, I will agree somewhat with Jon, in that a stock block properly prepared might live at a drag strip making more than 400 HP. I'm not sure of 600+. But I will limit that agreement to Drag Racing, where durations are very limited. On the negative side, that engine will be limited to very short rods and a maximum of 2.7L. And that with pretty thin bore walls. Hell, Tom Reiders original engine is still running with more than 80 passes in the 11's. Standard deck block. This is the first "Heavy Duty" engine I built. Any form of racing that provides sustained power where block distortion leads to the failure needs increased structure. We can accomplish this in two ways. The prehistoric way that I did, to add mass where you think or know how to improve integrety, or the modern methods by analytical methods. I had no resources available to me and had to resort to the old ways of doing business. Now I approached this like a technician, not an engineer, and limited resources in the plant. What we do know though is the block distorts in several ways.
Bore distortion due to cylinder pressures.
Bore distortion due to cylinder head and main bearing cap clamp loads.
Cyl deck distortion
Main bearing cap walk or main bulkhead movement. Torsional distortion. Deforming in a trapazoidal shape.
After underestanding how Lee White, at Roush Racing accomplished the job, (another story soon). I knew that the SVO boys would not accept the cost. I estimate the cost of a Roush block at about 10,000 $ US.
We must remember that SVO wanted a block that could go to 3 litres and that meant a tall deck, as well as capability of longer rods. AND they really wanted a 4.00" bore. That wasn't part of the requirements, but it was really something that they wanted. It is possible to do 4.00" with gas filled "O" rings with my block, but not many did. The current 100mm configuration still gives me 6mm of bore wall thickness. Plenty to not have deflection, particularly at the top where the head deck was also thicker. It also works with the FelPro 1035 gasket. The larger bore tends to unshroud the intake valve and enhance air flow.
What I was most concerned with is main bearing caps and the fact that we were limited to 2 bolt mains, and were limited to 12 mm or 1/2" main fasteners. My personal engines use billet main bearing caps rather than cast Iron and I have not had a problem with movement. I do use arp fasteners only once on the bottom end and have tested so we know exactly what clamp load comes with what torque. Not TTY, but close.
The torsional deflection cannot be eliminated with conventional methods. Analytical methods now tell us where to put ribs or fillets and what section thickness should be, and we really have a good correlation to real world. The modern ingine is designed that way..
Keep in mind, that SVO wanted a cheap, strong, reliable block to make 3 litres of N/A power. It gave me to selfishly design my own block that could take up to 1000 hp (with the excpetion of main cap clamping). We have something close to that. (the Roush engines were reported to make that number if totally unrestricted.)
The SVO block has run thru its life with NO reported failures. That is the objective A $700 Heavy duty block that will make obscene HP, and NOT fail. I don't want to take a chance with a standard block on my motors and Jon doesn't either. We cannot afford to do it twice.
OTOH the SVO block is not a street part. If you run a car on the street and sometimes drag race, and if you make somewhere around 400 HP, you do not need the heavy duty block with the extra 26 pounds of iron. We made a hand full of parts for a hand full of people.
SVO BLOCK HISTORY
Many four cylinder owners are not intimate with the heavy duty
cylinder block produced by SVO in the early 90's. I was privileged
to be asked by SVO in 1989 do make design changes and coordinate
the manufacture of this engine at the Taubate Brasil engine plant,
near Sao Paulo. Brasil. This block is known as the tall deck block
because it is 16mm taller than production. It is immediately identifiable
by a noticeably larger land above the water pump opening on the
front face of the block. Many changes were made for increased
strength and capability of larger bores. The story begins in 1988
when I was assigned as a liaison engineer with Taubate Engine
Plant, Chihuahua Mx, as well as Lima engine plant. This was a
first attempt to listen to the plants relative to design issues
and new designs for future years. I had been pretty successful
in listening to the plant and made a lot of friends in all three
places, but particularly liked Taubate. With the blessing of SVO,
I had asked the foundry to make some rubbed core heavy wall castings
and ship to SVO. These were to be my High horsepower units. When
they arrived in Dearborn, Hank Dertian and Mel Wallace, immediately
loved the parts. Concurrently the sanctioning body of Off Road
racing, changed the rules that would allow modification to 3.00
Litres of displacement. SVO asked me what additional changes would
be required to reliably get to that displacement. I arrived at
an increase in deck height and an increase in bore wall thickness
that would allow a 100 mm bore and really large stroke with longer
rods. Needless to say, SVO decided to do it, and over the next
year we made changes to produce this Heavy Duty block for racing.
A six part prototype run was initially made in December of 89,
and after approval by SVO, a production of 223 parts continued.
The production of these blocks presented quite a problem in casting
as well as machining.
CASTING: we added 25 pounds of cast iron to the 2.3 Block. this produced a lot of excess gas as the metal was being poured and as it solidified. We had a problem with gas bubbles in some locations. Generally this is a common occurrence and in casting, the foundry people experiment with vents and flues to get these gasses out of the mold before the metal freezes. It is a long experimental process and when you are making only 200 parts (thats what SVO wanted for a lifetime supply) you cannot go thru that process. We instead did a 100% sort, after machining, and processed only good pieces. It took more than 1000 castings to get 200 good blocks. The blocks were of the same alloy as production parts.
MACHINING: Because the blocks were more than 16mm taller than the production block in a finished state, they would not fit thru any of the transfer mechanisms of Taubate engine plant. SVO was not prepared to pay for individual machining of these parts (Very Expensive CNC) so the plant decided to modify the production line in sections during down time. I do not remember how many actual machining stations there are, but we would, on a weekend, have a maintenance crew, change the height of all the cutters, clamps and measurement devices of about twenty stations. We would run parts thru those stations and remove from the line. When complete one maintenance crew would restore that part of the line, while a second crew would finish modifications of the next section. We would leap frog like this for all of Saturday and Sunday, but begin to restore on Sunday afternoon so production could resume early Monday. This machining actually took 3 weekends to accomplish and went off without a hitch.....until the last...... All of the prototype blocks were painted a different color than production parts to easily identify them BUT, someone put several of the blocks into production on Monday and it caused a big problem. One of the last operations is Bore and Hone of the blocks. These blocks were being rough bored, but no finish machine work since race engine builders want their own dimensions etc etc. The rough bore machine is a huge 4 spindle machine that brings the boring bar down to within about 1 mm of the deck very very quickly. When this occurred with the SVO block the tools crashed into the block. It broke two drive quills and hurt other parts that I actually never saw. I was advised to make myself scarce, as the plant manager was on the war path. I was an easy target being the only North American on site. We got thru those issues and Sr Ferron and I remained friends. Because of the gas bubble issues, I required a sonic bore measurement check in specific locations that we agreed would find faulty parts where the bubbles were not yet visible. I ended up with a map of each bore of each block that also made us be able to predict wall thickness. With a 3.821 bore on my turbo block, I have 6mm (.236") of wall thickness. Any blocks that slipped thru this inspection process, SVO would replace. (?)
The result of this project was 223 parts shipped to the US, that all sold initially for under $1000. Unfortunately they are now all gone. Esslinger Engineering purchased a large quantity when SVO wanted to dump them, and those have been all sold. I found and purchased one part last fall that I believe is the last virgin part in existence. This became my new Naturally Aspirated engine for this year. In a quirk of fate, and some poetic justice, this is the very first block we produced.
SPECIFICATIONS that differ from production 2.3: (as I remember
Deck height increased 16 mm
Deck thickness increased to more than .700" for increased stiffness
Bore wall thickness increased.
Siamesed bores for increased stiffness.
Increased thickness of main bearing bulkheads, including front and rear.
Slight modifications of oil drainback holes.
Cylinder head bolt bosses extended another 16 mm down bore. The results are a block that is so stiff that when the head is bolted on and the main caps are torqued, the bore wall distorts only .0004" (.010 mm). That is not much. With only 2 bolt steel main bearing caps my turbo engine has produced 650 to 660 HP (600 at the rear wheels) without failure. (knock on wood).