Deck height and deck clearance?

[eastin82]

my concern hear is after pricing dif machine work it would be cheaper to take my crank, rods, pistons one place and block and head another.im wanting to achieve a deck clearance of .0005. would i be safe telling them i need .045 taken from the block or should i get crank pistons finished and take them with block? i guess what im aasking is there any change in deck height, clearance or an allowed variance from stock?

[Exos]

I had the same question when I started. There are too much variables to "theoretically" deck the block. The machinist will need your crank, bearings, rods and pistons.

[eastin82]

thats kinda what i figured thanks for the input.

[5-90]

"Deck height" - vertical distance between centreline of crankshaft and ground block deck surface.

"Deck clearance" - vertical distance between the piston static deck line (irrespective of any "domes" or "dishes") and the ground deck surface of the block. A positive value meas the piston static deck line is /below/ the block deck at TDC ("depressed piston") and a negative value means the piston static deck line is /above/ the block deck at TDC ("proud piston.")

Neither should be mistaken for "quench clearance," which is the vertical distance between the piston static deck line and the ground cylinder head surface at TDC - which is usually the deck clearance plus the /compressed/ thickness of the head gasket.

If you're going to set these values with any sort of accuracy, it is necessary that the machine shop have as many parts as possible, and that they know /exactly/ which cylinder head gasket you're using (save them some trouble and look up the /compressed/ thickness of the head gasket and provide that. They may look it up themselves to verify it, but that's a good thing.)

No machinist worth the money you pay him will bore out cylinders without pistons and rings, and no good machinist will try to set deck clearance without parts in hand to verify results.

It will also simplify things greatly if you have all of your machine work done by the same shop, believe me...

[Exos]

I don't understand why they would need the head gasket, nor the rings? If you know your head gasket thickness, and you decide how much you need to deck, they don't need it, I would think. And why would the rings be needed to bore cylinders? They should only need the pistons or am I missing something?

[IH 392]

They DON'T need the gasket, just measure recession deck it to "0", ANY of the available composition head gaskets would be good with "0" deck clearance.
TELL them what kind of rings (Molly, Chrome or plain cast iron) you are going to use so they can put the correct finish in the cylinders.

[eastin82]

lots more good info! im still going to take crank to a different place but ill wait to get it back and take it and rods, pistons, rod and main bearings and block and a detailed list of what i brought and expect to achieve. I think head will go elsewhere also.

[Muad'Dib]

When taking things like this to a machine shop should new bearings be given to them to install and use for getting the proper deck height? If so, im assuming this doesnt ruin the bearings.

[RAPTORFAN85]

When taking things like this to a machine shop should new bearings be given to them to install and use for getting the proper deck height? If so, im assuming this doesnt ruin the bearings.

Definitely need the bearings for checking deck height. No, it won't ruin the bearings, they will be fine.

[SilverXJ]

x2. They don't actually have it assembled during machining. They assemble it, measure deck clearance, determine how much needs to be cut, then disassemble it and cut it.