| Re: Split Block ????
Pat,
Virtually all of the blocks that have been suggested, including the FMS blocks, are siamese bore blocks. I have never heard a word about overheating peculiar to the siamese race blocks. Although, I asked the exact same question when I first began to research them.
To the best of my knowledge the blocks begin to crack in the webbing walls of the mains. 4 bolt main blocks, almost by definition, have thicker webbing than standard 2 bolt main blocks, but as you have no doubt noticed, there is variation in the thickness between the different race blocks. Also, the 4 bolt main caps hold the crank tighter and prevent any distortion from even starting in a side to side direction which is to say a spreading of the webs(presumably how the whole failure mode gets started given that the blocks crack length wise: 90º to the spread.) They do the job that main girdles try to emulate on 2 bolt blocks. I have never seen a post mortem report on one of these to the high engineering standards of our friends on CSI :-), so I am, admittedly, speculating somewhat at this point.
Regards,
Lynn |