so how do you measure this, does the crank shaft with a rod and piston need be installed. This may sound funny but wouldnt a true zero deck mean you have to shave everything , down to and maby a bit off the piston.? I know that may be wrong . Is it really just near zero deck.?
You can measure it with piston and rod/crank in. But there is a blueprint that measures deck height(almost always is wrong dam gm machinist) then add rod length and compression height of piston.
http://www.v8buick.com/showthread.php?181425-Your-new-Diamond-pistons See post #4. Using the 6.8" eagle rod, and custom Diamond piston requires a lot less decking.
Still requires a lot of milling to get to 0 deck. I quote from the post I linked for you, "I would be remiss not to mention the TA Sportsman rod here.. That's really a great quality rod, no doubt, I have used many, many sets. It's certainly the easy rod for a "drop in" replacement, for you guys having machine work done at maybe a less than "savvy" machine shop. I will get to that later. But being a drop in replacement, it has to work with available Buick pistons, in both the pin diameter and compression distance, so we are now back to the massive decking issues."
thanks Larry , now that i read that , i answered my question. In order to get Zero deck i have to shave the block and then match it with the intake side of the head. Im sure that goes for any head when you shave the block. If I dont zero deck how close does it get to zero as it is. ?
The piston can be in the hole as much as .050 or more if you don't mill it to 0 deck. Milling that much off an already light weight block isn't the best thing, or cheap for that matter. Using the longer rod and custom piston requires LESS milling, a good and money saving thing. All that is in the linked post.:grin:
I have seen stock 8 to 1 pistons (1.805comp height) be .090 in hole. Hyperutectic and racetec/Scott brown pistons have a compression height of 1.855 . then figure the block was machined poorly at factory .my deck was .023/.028 too tall from blueprint. That puts you about .025 below deck. Pretty close . .040 off deck with a .043 thick felpro and your pretty good.
too late for the longer rod. I have the TA sportsman, and TA spher dish pistons, but that longer rod in the post you linked must only be longer by a few thousandths, Or is it different with pin placement. a THIcker bearing might make up some more distance. So does turning the crank make you even farther, ? Dang my brain just caught up to my typing , a thicker bearing will be canceled out by turning the crank, . ......
Stock BBB rod is 6.602. The Eagle rod used in the 470 is 6.800. The Diamond piston uses the .990 pin diameter, and the pistons are designed for a 10.550 deck height. Again, all of this was in that post #4 of the linked thread.
So you have piston and rods now you have your machining done with the set parameters of the dimensions of the parts on hand. "Zero" decking the block is to improve quench, if you don't understand what that means you should do some research on that subject. To "zero" deck you take 1/2 the stroke + your piston compression distance dimension + your rod length dimension added all together to equal your deck height. Aftermarket parts will have a tighter tolerances than most 40 plus year old factory parts as well as less expensive aftermarket parts, so a competent machine shop will be able to add all the part dimensions up and square deck machine the block's deck to that number. Will it be exact, probably not but it will be a whole lot closer to the factory tolerances, probably + or - .002" which is a very acceptable tolerance and not enough to even worry about. The parts you have will work just fine, don't over think it. If those are the parts you bought and plan on using they'll work well together with the proper machine work. Actually .005" in the hole with a .040" compressed head gasket thickness will give you a .045" quench which is still in the optimal quench zone with better safety margin for the piston not to hit the head if your engine has excessive rod stretch for some unforeseen incident. Just because the factory didn't machine the deck to the blue print dimension and left it slightly taller doesn't mean you shouldn't take the deck down to the optimal quench zone when building a performance engine. You wrote that you are using a spherical dish piston, I'm not sure if zero decking the block is that critical with that piston design(no quench pad on piston). You might want to research that before you commit to the machine work or a zero deck gives you the compression you're looking for.GL Derek
Ahhhhh hmmmmmm thanks Overkill, that helped get my thinking in order. Its all about maximizing every aspect of an engine build. Zero deck is another piece to the puzzle, unless its grossly under truing the deck may be all that is really needed for my purposes and combination.
Another way to reduce the excess quench distance is to offset-grind the crankshaft. The limit here is the availability of undersized bearings. If the smallest bearings you can get are .040 under, you'd only be able to raise the piston about .015 in the bore, (and that's only if you start with a standard crank in reasonably good condition. Welding the crank's rod journals before grinding would allow you to gain considerably more stroke, and close that quench distance more. It's all about where you'd want to spend the money, but machining the crank gains you some cubes in addition to tightening up the quench. It'll reduce the clearance between bottom of piston, and crank counterweight. Could lead to a conflict there if full-skirt pistons are used.
Don't think for a minute that there was a machinist working on one block to mill the tops. They used a broaching machine to do a continuous flow of blocks in a production line. From "Buick City": "I ran a broach in the head department from 1996-2004. I heard that the broach was made by the Cincinatti Broach company in the 1950s. According to what I heard the broach was made to machine v-8 heads and when Buick bought the V-6 tooling back from in the 1970s they were retrofitted. The broach uses a long series of carbide cutters to shave off metal. This process is quicker that milling but cruder. We used to have a .004 limit on flatness variation. The broach could run one hundred and fifty parts in a good hour. Chris Balog" Link: http://buickcity.blogspot.com/2008/03/inside-factory-36_09.html
I know you are all discussing the use of steel rods and zero-decking,but just a reminder,you do NOT want to zero-deck a block for an aluminum rod application. You need room for it to expand. Generally,I just take enough off to make it square and flat. It’s not oncommon to take more off one side than the other.
To correctly deck and index the block, the mains need to be line honed, then the cam tunnel corrected, finally, the fixture that the machine locates from uses the crank and the cam centerline as reference. The accuracy of the deck index accuracy depends on those two datum lines. Deck height will be accurate to all 4 corners in any case, when the truing fixture is used. The way to properly measure is from the deck to the fixture, sweeping across the width. There is a special mic for that. Measuring observed deck heights using components and cranks that are not all exacting in length/stroke is not going to give a true square height to the mains. You can measure from the saddle to the decks as a close method for rough checking squareness. Here’s a quick video, and how the deck accuracy affects cylinder index as well, when boring. https://www.facebook.com/video.php?v=329512201217946
