Heavy Duty Blocks

From: "Rick Byrnes"
Subject: Re: Tall Block Long and rambling

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.