Is there a chart available that has piston deck clearances for the 455? If I recall the 76 blocks had more than the 1970. But what are the ranges for each year? Thanks!
No such chart exists AFAIK. I think the 75-76 pistons could be down in the hole as much as .090? Most others ended up .040-.050 I think. Not sure on any of this. You need to measure to be sure. That is just the way it is.
this is a measurement that is different on every engine. I'm sure there is a blue print spec out there but most engines are no where near it out of the box. in my experience with buicks the pistons are always very deep in the hole. I believe their philosophy was to err on the side of caution and have a higher deck height. the only way you will know for sure is to measure it. everyone I've taken apart has been at least .060 deep. the worst was a 76 that was .110 down! 76s have a different pin height so they are usually deeper, but that is still nuts.
Early motors will be .035 to .045, Later ones can be up to .100+ below the deck. The "blueprint" spec is .010. JW
Related Chevy story: Chevy was having problems with Camaro engines not meeting the horsepower goals and/or emissions compliance. Might have been a lawsuit involved. Chevy engineers go to the manufacturing plant, measure a hundred engines. Discover that the compression ratio is way down from what they expected. Blocks have excess quench distance (Piston in the hole too far, and they're all in the hole the same amount.) Plant manager deflects,says they're within spec for manufacturing tolerance. (Manufacturing tolerance is really wide, allows for huge engine-to-engine deck height variation.) Engineers say "they're all the same". They prove that the plant has the capacity to cut the manufacturing variation allowance to half or a third of what it is, and still meet it easily. Plant manager was deliberately cutting the decks to the high side of the tolerance range, ALLOWING LESS STOCK REMOVAL SAVED TIME AND ALSO SAVES ON TOOL SHARPENING/REPLACEMENT. Plant manager was getting pay bonuses for cutting costs--but he was sabotaging engine power 'n' emissions. Chevy engineers cut the spec for variation, made the plant manager put the decks where they should have been all along. Engines met the goals set for 'em.
Awesome story I can relate to. Not having worked with whatever they used but have seen how machinery, tooling and inserts have changed over the years machining castings from raw as well as having the task of finding those limits is a constant process learning curve. Depth of cut and feed rate with a beefy part has long been much less of a problem than the rotational speed of the tool wearing down the corners of the inserts, but there are facilities still making parts on those little Haas mills you see on the Discovery channel carving fancy wheels struggling with machine and fixture rigidity, lol.
