As long as the line bores are good what's the difference if the block is a few thousandths out of square anyway? I've always wondered this.o No:
If the cylinders aren't perpendicular to the crankshaft centerline on both planes, the pistons could be sliding back and forth on the pins. or the thrust of the pistons on the cylinders could be more or less depending on which way they are out. The small differences betweeen a crummy, good, and great running engine can sometimes not be explained by the parts. I often wonder if the secret isn't in the randomness of these machining problems in a factory block (or the lack therof in a nicely done block).
When small block chevys are machined at the factory they cut the pan rails first this is whats sets up the rest of the machineing.Now out in the real world we regerster every thing of the main housing bores.Most machines out there set up this way for decking.BHJ makes a plate that goes on a round bar that is machined to 90 deg so when you use an indicator on this plate to get it straight it sets the deck 90 deg to the mains.We measure from the deck to the bar to get our deck height say if we want 9.00 as most small block chevys get cut to.This is how a block gets squared i have not seen one so far out that you could not square up.Now if i were building a nascar engine i would have blue prints from GM and would square the blocks like they do pan rails first,bell housing end, timing cover end,then the decks,the aline bore, the cam bore for roller cam bearings,bronze bushings for the lifters and finally the cylinder bores.The blocks are first magna-fluxed and sonic checked for core shift.A winston cup block when fully macined is any were from $7,000.00 to $10,000.00 they cost about $45,000.00 to $55,000.00 to build and rent them out for $60,000.00 mike
I thought Buicks were expensive to build. This is 3rd hand info, but I was told that the entire machining operation on a Winston-Cup style engine is indexed off of one bolt-hole in the corner of the block. The entire block is then CNC's according to the blue-print dimensions in relation to that hole. Pretty amazing stuff compared to the old boring machine that sat on the deck surface with a 1.5" bar running through the mains to "help" indexing.
What they are reffering to is if you look at the bottom of a small block chevy there is a 1/2 round dowel hole that is what they use to index off of. mike
Generally, all machining should be indexed off of either a datum point or edge...It's the blueprints that have dimensions indexed from all over the place that have you scratching your head wondering where the so-called "engineer" got his degree...
