Block- 1975 Buick 455 I got these numbers off the internet... are they correct? deck height= 10.57" rod length= 6.607" stroke=3.9" Wiseco Dished Pistons: Compression height 1.98 deck height- (1/2 stroke)- rod length- compression height= piston to deck clearance 10.57-1.95-6.607-1.98= .033 in the hole Sound right?
Maybe in a perfect world. I think the deck height of the blocks varies so much there is no "constant" height. The only way to measure it accuratly would be mock up your block.
Is there an external reference point on the block to measure deck height from? I'm asking because I've inherited a 455 with no engine codes on the deck surface, and wonder if it's been decked, and if so, how much. Can you measure without tearing it all down?
Is the motor still together? If it is you will half to take the heads off, to check deck on both sides. Run the piston up, a dial guage is a good thing here, when the piston is at the top of it's stroke, measure from the top of the piston to the deck. I hope this helps . There are better engine builders on board than I.
Of course you can do that when you have a piston in the bore. But what do you do when you want to find out how much to deck a block for your new overbore pistons to get a certain amount of compression?
Mock-up assy. This the only way I know of toget it right and to be sure of it. I'm sure there are some machinist on this board who may know of another way, but this is what 95% of racers do.
I have a calculator, but one of the things you need to know is how far down in the hole the pistons are. I was trying to calculate what that would be. I'm a little surprised that the deck height could vary all that much (other than being cut when rebuilt). If the factory had such a variance on deck height, the compression from motor to motor could be very different.
