Below are three tables from a NOS 351 Cleveland XE block. The first table contains data from digitizing the block cylinders on our CNC machine. This block has had no machining since it left the factory about 40 years ago. The first column shows the blueprint location or where the cylinders are supposed to be in the X andY planes. The X plane is length wise of the block parallel to the crank centerline. The Y plane is cross wise of the block or perpendicular to the crank centerline. Any locational difference in the Y plane will effect the rod/stoke ratio and how the piston transfers load thru the connecting rod to the crank. Piston dwell at TDC is greatly effected by the Y plane location, not so how much dwell but if the dwell is biased before or after TDC. Any difference in the X plane can cause the valve to be shrouded more or less by the bore.

	Bluprint Location			Probed Location			Difference in Location
	Right Bank 1st Cylinder			Right Bank 1st Cylinder			Right Bank 1st Cylinder
X	2.19			2.1798			-0.0102
Y	0			-0.0058			-0.0058
Bore	4			3.9934			-0.0066
	Right Bank 2nd Cylinder			Right Bank 2nd Cylinder
X	6.57			6.5607			-0.0093
Y	0			-0.0052			-0.0052
Bore	4			3.9925			-0.0075
	Right Bank 3rd Cylinder			Right Bank 3rd Cylinder
X	10.95			10.9417			-0.0083
Y	0			-0.004			-0.004
Bore	4			3.9932			-0.0068
	Right Bank 4th Cylinder			Right Bank 4th Cylinder
X	15.33			15.3239			-0.0061
Y	0			-0.0029			-0.0029
Bore	4			3.9933			-0.0067
	Left Bank 1st Cylinder			Left Bank 1st Cylinder
X	3.03			3.0249			-0.0051
Y	0			-0.008			-0.008
Bore	4			3.9931			-0.0069
	Left Bank 2nd Cylinder			Left Bank 2nd Cylinder
X	7.41			7.4064			-0.0036
Y	0			-0.0071			-0.0071
Bore	4			3.993			-0.007
	Left Bank 3rd Cylinder			Left Bank 3rd Cylinder
X	11.79			11.7868			-0.0032
Y	0			-0.0062			-0.0062
Bore	4			3.9936			-0.0064
	Left Bank 4th Cylinder			Left Bank 4th Cylinder
X	16.17			16.1685			-0.0015
Y	0			-0.0053			-0.0053
Bore	4			3.9914			-0.0086
	End Of Report			End Of Report

The second table contains data from digitizing the lifter bores from the same block. The X and Y planes have the same orientation to the crank centerline. differences in Y location greatly effect cam degree or valve timing and differences in X location cause the lifter to contact the cam in a different location than designed. This is especially critical in flat tappet engines as the tappet location is important on how the lifter spins in the lifter bore.

Lifter Angle		45
Cam Centerline		5.0441			Probed	Probed		Difference	Difference
Lifter	X position	Y position			X Position	Yposition		X position	Y position
1 intake	1.37	-3.56671			1.3795	-3.538		-0.0095	-0.02871
1 exhaust	3.1	-3.56671			3.1057	-3.5381		-0.0057	-0.02861
2 intake	5.75	-3.56671			5.7572	-3.5326		-0.0072	-0.03411
2 exhaust	7.48	-3.56671			7.4894	-3.5325		-0.0094	-0.03421
3 intake	10.13	-3.56671			10.1402	-3.5324		-0.0102	-0.03431
3 exhaust	11.86	-3.56671			11.8676	-3.5339		-0.0076	-0.03281
4 intake	14.51	-3.56671			14.5193	-3.5325		-0.0093	-0.03421
4 exhaust	16.24	-3.56671			16.2474	-3.532		-0.0074	-0.03471
5 intake	2.12	3.566715			2.1093	3.5488		0.0107	0.017915
5 exhaust	3.85	3.566715			3.8413	3.5513		0.0087	0.015415
6 intake	6.5	3.566715			6.4949	3.5538		0.0051	0.012915
6 exhaust	8.23	3.566715			8.2235	3.5561		0.0065	0.010615
7 intake	10.88	3.566715			10.8736	3.5578		0.0064	0.008915
7 exhaust	12.61	3.566715			12.6024	3.5634		0.0076	0.003315
8 intake	15.26	3.566715			15.2553	3.561		0.0047	0.005715
8 exhaust	16.99	3.566715			16.9822	3.562		0.0078	0.004715

The third table contains the data from digitizing the blocks deck height. Differences in deck height cause differences in compression ratio and heads not sitting square on the block. Twist in the decks cause twists in the heads which cause valve seats to become distorted in roundness and being unconcentric to the valve stems. Differences in height also cause intakes to not seal correclty.

9.2060  = Deck Height
 
  Right Bank
 
   9.1994    -0.0066 = Front Inner
   9.2009    -0.0051 = Front Outer
   9.2037    -0.0023 = Rear Inner
   9.2023    -0.0037 = Rear Outer
 
  Left Bank
 
   9.2057    -0.0003 = Front Inner
   9.2035    -0.0025 = Front Outer
   9.2068     0.0008 = Rear Inner
   9.2054    -0.0006 = Rear Outer
 

     It can be seen from the three tables that  the blocks cylinders bores, lifters bores and deck surfaces are not machined perfectly from the factory. Since this was a special race block from the factory this block should have better machining than regular passenger car or production blocks. It can also bee seen that traditional automotive machining does not correct any of these difficiencies because traditional machining centers from the existing bores and levels from existing surfaces. CNC machining of the block  is a way to find and correct the difficiencies of a block to turn it into a fully blueprinted block, capaable of making the power the rest of the components can deliver. It has been theorized that these misplaced components in blocks cause the differences in engine performance seen from supposed identical engines. The components may be the same but the differences in goemetry cause the power differences.