twayne24365
Well-Known Member
How do you measure block deck height. Center of main journal to deck, also what tool do you use?
Deck height
- Thread starter twayne24365
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A machine shop.
PeniroN
Member
I've never done this, but to get pretty close I think you would use a 9"-10" OD micrometer with a ball and cup for the anvil that would go against the bearing seat. Take the measurement, subtract the ball diameter then add the radius of the bearing seat. The cost of the tools for this would probably be pretty close to the cost of having a shop take the measurement.
Assuming you are working with a bare block.
Assuming you are working with a bare block.
twayne24365
Well-Known Member
what do you think a shop would charge?
They'll charge nothing if you let them deck the block to spec and square it up. I can almost assure you it's out of spec. They always are. That usually runs around 150 give or take. It's money WELL spent.
See, the problem is this. Not many people have the equipment to measure deck heights correctly. It's not just about the height. It's about the decks being parallel to the deck surface, being even on both sides and being square corner to corner. I have never yet seen one single Chrysler engine meet ONE of those requirements from the factory. That's why I recommended a machine shop.
EDIT: I meant to say the decks should be parallel to the CRANK, not to the deck. Damn.
EDIT: I meant to say the decks should be parallel to the CRANK, not to the deck. Damn.
PeniroN
Member
I've thought about this a little for when I start looking at components for building my engine. My approach would be to take the height measurements front and back on both decks. Then take a precision straight edge and feeler gauges to see how out of flat the deck is. Then I would determine the amount that would need to come off to get both decks equal and square and probably add a few thousandths. Then I'd start looking at pistons and other components to get the desired compression ratio, quench, etc... The engine would be going to the machine shop, but I'd still like to take the measurements myself so I'd have an idea of components that would work. Then I could verify my measurements with the machine shop and possibly make component adjustments. I've never been involved in an engine build but this process has been in the back of my mind since I purchased my car. I also have access to the various tools described. If you know anybody that works at a machine shop (not necessarily automotive) they may have these instruments. In the end the engine building shops are going to be able to give you the most accurate measurements.
twayne24365
Well-Known Member
Yea, i lnow machine shop would be best but id rather learn to do it myself, i realize its probably gonna need decked but i still like to know.. Is there a name for the tool?
Woods74
Broke Senior
Hang out in the back while they do it and watch. They will probably do it for free, they enjoy to measuring stuff.
It requires having a mandrel to put into the crank bore to get a reference off of. It would be much cheaper to pay a shop to do it.
femtnmax
Well-Known Member
I make sure the crank rod journals have been equal stroked and indexed. then with the crank/main brgs in the block I install the same piston/rod combo at all four corner cylinders. Install piston w/o rings or some like to have the oil ring installed to add a little drag to the piston so it wont slide up/down too easily as you find tdc. Using magnetic dial indicator I find exact tdc of piston in each cylinder, then measure the distance piston is down the bore from deck surface. Like Rusty said the four measurements probably wont be the same. then have shop machine the block decks so they are parallel with crank centerline. after machine work I mockup the crank/piston again to verify all four corners have the same measurement...or at least real close.
twayne24365
Well-Known Member
Gotcha, guess thats just something you gotta have the machine shop do
CPMotorworks
Well-Known Member
Its not just a simple crank CL to deck- you also have to correct the crank/cam CL to deck angles- 45 from Crank/Cam CL and 90 to each other, along with parallel to the mains. It requires a special fixture or a CNC with indexer, not just a surfacing machine. You need a point of reference other than the OEM decks that are far from accurate. You need to line hone the mains first to really do it right.
Going off the 4 corners only tells part of the story and is still a matter of tolerance stack.
Going off the 4 corners only tells part of the story and is still a matter of tolerance stack.
moper
Well-Known Member
Its not just a simple crank CL to deck- you also have to correct the crank/cam CL to deck angles- 45 from Crank/Cam CL and 90 to each other, along with parallel to the mains. It requires a special fixture or a CNC with indexer, not just a surfacing machine. You need a point of reference other than the OEM decks that are far from accurate. You need to line hone the mains first to really do it right.
Going off the 4 corners only tells part of the story and is still a matter of tolerance stack.
x2.
This is functionally close enough for most engines, depending on intended usage. If all four measurements are close I would not worry about it. My "68" 383 block was .012 difference from one side to the other. My "64" 273 was within .002. I had a machine shop deck the 383 while I did not deck the 273.
twayne24365
Well-Known Member
Ok, thanks guys.... To the machine shop it will go
Its not just a simple crank CL to deck- you also have to correct the crank/cam CL to deck angles- 45 from Crank/Cam CL and 90 to each other, along with parallel to the mains. It requires a special fixture or a CNC with indexer, not just a surfacing machine. You need a point of reference other than the OEM decks that are far from accurate. You need to line hone the mains first to really do it right.
Going off the 4 corners only tells part of the story and is still a matter of tolerance stack.
Is that the BHJ Block-Tru you're using there?
Ted
We get all that, but "I" was trying to keep it simple for the sake of conversation.
Its not just a simple crank CL to deck- you also have to correct the crank/cam CL to deck angles- 45 from Crank/Cam CL and 90 to each other, along with parallel to the mains. It requires a special fixture or a CNC with indexer, not just a surfacing machine. You need a point of reference other than the OEM decks that are far from accurate. You need to line hone the mains first to really do it right.
Going off the 4 corners only tells part of the story and is still a matter of tolerance stack.
CPMotorworks
Well-Known Member
Its similar, I built this one the way I wanted it to work. Any block I do gets done with it.
Rob, don't take everything as a personal contest. You gave good advice about having a machine shop do the actual measuring, other than the "they" will work for free. I do enough of that already..
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