Block decking question

[Anonymous]

If you took a block into a machine shop to have it decked, how much would you tell them to remove? Is it a situation where they measure and let you decide how much to remove? Or what?

Thinking of my next build. Won't probably happen this year but I still need to plan for it. Having the information available ahead of time seems helpful.

 

[Anonymous]

I was told the best way is to actually assemble the crank, rod and piston to determine to the deck height.

 

[gtm1086]

With the piston at TDC you will need to measure the distance the piston sits below the top of the block. That is the amount you will have to have machined off. or Decked

 

[Anonymous]

With the piston at TDC you will need to measure the distance the piston sits below the top of the block. That is the amount you will have to have machined off. or Decked

Thats what I did....assembled the new rod & piston installed it in the cylinder and measured it.....In my case, it needed to be shaved .020

Later,

Doug

 

[Anonymous]

Okay, now that I've gotten that straight, is it possible to have a negative squish band? If so, advantages/disadvantages?

Again, just trying to gather information for my archieves.

 

[addo]

It needs to be done after the rods are closed and honed. Check each for length against the others. They can vary some.

I had a 302 with one 289 rod. Its piston came above the deck almost the entire gasket thickness. This was a "Repco" brand rebuild. I understand you're supposed to allow 15 thou for rod stretch in a worked eight; maybe a little less in a slower revving six.

 

[80Stang]

Seems like it variates a little. I installed in my D8 block no1 and no6 pistons/rods and crank, used a straight ruler on the block and measured the distance with a feeler gauge; got 0.030 and 0.032, so I decided to mill the block 0.030 down. At the time of the short block build up we checked the deck height and it indeed was between 0 to 0.002. Measure it yourself and you'll be sure of the numbers.

 

[CZLN6]

Howdy All:

New replacement oversize pistons will frequently be down on pin height .005" too. Manufactures do this to counterbalance CR creep with overboring. That's another reason why it is best to do all machining, combined with the new and reconditioned parts before measuring. It is also possible for the crankshaft centerline to be out of square with the block surface. This should be checked and corrected if need be on a rebuild. .002" is not a critical variance.

Adios, David