30-09-2019, 01:43 PM
Hi All, over the decades i have had corner failure, full horizontal block failure and rear of crankcase failure and have spent some time on the current engine trying to solve the problem. Here are my observations and views: The best way to cause this type of failure, is to include all of these factors and i tend to believe that failure usually happens when more than one factor is in play.
1, Pistons making contact with the head.
2, Pistons making contact with the head gasket.
3, bottom face of block not perfectly flat.
4, Top of crankcase not perfectly flat.
5, Valves making contact with the head.
6, Bore size, the bigger the bore the weaker the block.
7, Coilbound valve springs at max lift.
8 High horse power output.
9, Movement in the block to crankcase joint, the front and rear nuts tend to loosen, allowing movement, causing displacement of the paper gasket (and leaks) leading to effectively 3 & 4 above......
10, That movement, if tolerated will cause a hammering effect which can't be good.
11, Cam profile and finally:
12, valve spring rate.
Of these i think 11 & 12 are the least significant factors. All the above seems obvious but i'll bet few of us routinely consider all of them! My own hot engine never has an easy mile, has always had single standard valve springs and has an 1 1/2" Phoenix crank which still whips a bit though much less that a standard crank.
Some favour late blocks, saying that they are stronger.....
My block is attached with additional external studs at the back and hollow "bolts" through the drain holes in the tappet chest, these make assembly bl***y awkward....
W
1, Pistons making contact with the head.
2, Pistons making contact with the head gasket.
3, bottom face of block not perfectly flat.
4, Top of crankcase not perfectly flat.
5, Valves making contact with the head.
6, Bore size, the bigger the bore the weaker the block.
7, Coilbound valve springs at max lift.
8 High horse power output.
9, Movement in the block to crankcase joint, the front and rear nuts tend to loosen, allowing movement, causing displacement of the paper gasket (and leaks) leading to effectively 3 & 4 above......
10, That movement, if tolerated will cause a hammering effect which can't be good.
11, Cam profile and finally:
12, valve spring rate.
Of these i think 11 & 12 are the least significant factors. All the above seems obvious but i'll bet few of us routinely consider all of them! My own hot engine never has an easy mile, has always had single standard valve springs and has an 1 1/2" Phoenix crank which still whips a bit though much less that a standard crank.
Some favour late blocks, saying that they are stronger.....
My block is attached with additional external studs at the back and hollow "bolts" through the drain holes in the tappet chest, these make assembly bl***y awkward....
W