Need some help on block issue.

[Jas89TTA]

I was cleaning the block deck and the top of the pistons today and noticed that when the piston is fully up it's not even with the block on both sides. On one side (front) it's evenly flat with the block other side (back) it's a little down in the bore still I checked the block with a flat metal ruler for flatness and it looked fine. I'll try to get a straight edge to check it the correct way but it's like this on all 6 cylinders. Is this normal or something bad I would have thought the piston would be even with the block on both sides. The heads checked out OK at Champion they were not warped, but I'm now concerned that the block could be warped or the rods bent. Thanks, Jason

[TexasT]

This could be many things from production tolerances to damaged parts.

Judging by your post you are in the middle of an overhaul of some sort. Is this due to some type of failure? Was the block decked when it was machined? Are these production pieces that you are putting back together? What about the crank? Was it machined? Were the rods resized? The pistons compression height might be uneven. It could be a combination of all or additional factors.

How about some additional background on what you are doing there.
Thanks

[Jas89TTA]

Thanks for the reply. I blew a headgasket last week so I'm just replaceing the headgaskets. It's a stock block, stock crank, stock rods, with .030" TWR pistons. I don't think the block was deck on the last rebuild but it was line hone and bored .030 over the crank was polished and the rods were resized and installed ARP rod and main bolts and ARP head studs all done less than 3,000 miles ago. THanks, Jason

[TexasT]

So at this point you could have an "unsquare" block. The line bore 'could' have been performed where the crank is not parrallel with the deck. Some measuring is in order. The rods could have been machined incorrectly and yeilded different lengths measure htem too. Also the compression height on the pistons might very and these should be measured too. All of these things could stack up causing the condition you describe.

Do some disassembly and measuring an post back.

[Kendall Frederick]

Are you sure you're not just describing the piston rocking on the pin a bit? When the motor's apart and cold, the pistons will rock a few thousands side to side on the axis of the pin. This is especially true for forged pistons, which should have more clearance since they expand more.

[buickv6]

I'm with Kendall....mine pistons do the same.

[Jas89TTA]

The pistons are forged. They don't seem to move from side to side When I turn the motor over by hand and the piston comes up to the top you, can see that the back side is futher down than the front side. I just wanted to know if this was normal and not to worry about it. I'll try and get some pics of it and post if it turns out you can tell in the pics. Now what I'm calling the front and back of the piston is if your standing on the side and looking at all three cylinders, the front is towards the frt cover and the back is towards the rear of the block. I was able to move the piston aliltte up and down, pushing up towards the lifter valley and down towards the pan. Thanks, Jason

[SHADOWII]

or depth gage to check the front and back dimensions. It will reveal whether or not the deck is out.

[puddinpower]

Originally Posted by Jas89TTA

I was cleaning the block deck and the top of the pistons today and noticed that when the piston is fully up it's not even with the block on both sides. On one side (front) it's evenly flat with the block other side (back) it's a little down in the bore still I checked the block with a flat metal ruler for flatness and it looked fine. I'll try to get a straight edge to check it the correct way but it's like this on all 6 cylinders. Is this normal or something bad I would have thought the piston would be even with the block on both sides. The heads checked out OK at Champion they were not warped, but I'm now concerned that the block could be warped or the rods bent. Thanks, Jason

Is it possible that the rods are turned wrong when they were installed??I have never done that so i can't say from experence,but If the piston was on the rod on the wrong side, (Kinda hard to explain by typing ) You know most all pistons have the Arrow that tells you and the machine shop which way the piston is supposed to face when installed.If it wasn't could this be a factor??? I am just as courious as Jason is.

Puddin