Thread: Decking the block: How much material?

I haven't decked a block yet, but we have a few that are going to need some material shaved since there is detonation around the mating surface on the exhaust side of the cylinder walls.

Anyone have any experience with regards to HOW MUCH material can be removed? This is assuming a stock Avenir/Bluebird block.

My only concern is that with shaving the block, you have increased the CR, and I worry about piston clearance issues.

Thanks in advance.

YouTube - Nissan SR20-DET Block Resurfacing

thats a good little video shwing the process and they give you a little bit of insight into decking the block. personally i think the bock decking process are going to be partial o the block in quesn being decked, how much material removed is going to depend on the quality of the existing block deck as to weather or not a little more or less material is going to be removed. i also fel its going tobe partial to the machine shop also in question decking the block as to how much material they feel is safe to remov to where it doesnt effect the compression ratio/clearence isues/timing issues..i think that is going to be partial to each machine shop, again its really going to depend on the deck existing surace as to how much material needs to be removed to obtain a flat even smooth surface.

Buy a thicker hg based on how much you take off.

That was a lot of run on stuff, bluebird...

I know what the process is, this isn't my first build. Please re-read my specific question...


Jeff, I need to know how to calculate, I guess is what I'm thinking. I guess I'll need to do more research.

Yeah, you'd need some sort of large tool measuring to the tenths or hundredths of mm.

I would take the first reference from the FSM.

FSM gives minimum block height, so I would measure the current height - the calc of what needs to be milled, if calculated new height will be less than FSM limits by too much, I would not use that block any more.

I think my straight-edge will suffice.



Ah, good idea. I hadn't even thought about looking in the FSM. Thanks.

when i worked in auto parts and we sent them off to the machine shop they would take any more that 0.025 in. of course that was for stock applications

You need to cc the combustion chamber to get the most accurate CR

remember to advance timing by 2.5* on cams for every .050" cut.