What would cause piston-to-deck height to be negative? I.e. the edge of the piston goes slightly higher than the top of the block.

Besides the fact that I can see the piston go past the top (a small amount), there is evidence of this by worn points on the edge of the piston (which correspond to areas on the head, etc.).

 

Maybe because the block has been decked too much. Usually you deck a block according to the rod/piston combination that you're gonna run. You shave off the deck just enough so that the depth height from each cyl is no more than about .002"->.003". When you change to a different configuration all those values are gonna change.

One cheap fix is to get a thick head gasket. Or you can push the piston pin slightly higher

 

Assuming that the depth height was ~0 before assembly...and it is now negative, after assembly (1 year later)...then would could account for this difference (on a fully built motor).

As for pushing the piston pin higher...how is this done? Are new pistons, etc. needed?

 

So the piston to deck height was for sure at zero on the final assembly? What pistons are you using? If you are using the stock rods and you have been reving the engine absurdly high the rods could have possibly stretched?

 

I would assume you'll need new custom pistons. I'd stick with a thicker headgasket. How much is the pistons sticking out exactly?

I'm assuming you're rebuilding the motor? Are you reusing the same rods/pistons/crank?

 

I am currently running custom JE pistons with Saenz connecting rods. I am in the process of installing a different set of iron sleeves, and noticed the head-piston contact during disassembly. The pistons can't be coming out that much, because there is only ~5 small contact points for all 4 cylinders.

Yes the same rods/pistons & crank will be used, and the motor is not reved over ~8200rpm.

 

I built a motor for a customer a few months ago that had .008 pop out. It was on a b16a and with the shape of the combustion chamber it was alright and is still boosting fine with no problems. If you could get over the contact (shorter piston or what ever) i would run it. Pop out will actually help in making power by pushing the mixture towards the spark.

 

Would u run into any problems by simply removing/opening up a little of the combustion chamber where the contact was occuring?

 

two things can do that..

one is connecting rods do stretch, maybe you were reving past the recommended limit which allowed them to stretch just enoug to hit the head (bad) you can rework the head a bit, but i'd be curious to see if the rods will stretch some more....

imagine a bungee jumper jumping and kinda have a rop that gives a bit more just before he's about to stop abd go back up he smacks the ground and then moves back up.. sure that guy will have a headacke or pains but now imagine that everytime.. won't you think he's gonna get tired of that after a while and give up, now replace example this with your piston

even better your head bolts

 

Would it be okay to remove the material from the problem areas shown above (if the block was simply decked too much and there is no rod stretch)?

 

personally id take an alumum stone (NOT CuTTER), and re shape the areas of the head where collision occured, then would take come catridge rolls and some 120grill(WET) with a low speed grinder and finish the combustion chamber, but not before matching each cylinder's CC volume. because if one chamber is bigger than the other it affects your CR and how the motor reacts. always best to match as close as possible all combustion chambers for a properly balanced motor..

 

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so how much did your pistons stick out of the block?[