all the stock pistons are anywhere from .032 to .050 thousands in the hole. i have seen one side of the block .015 thousand difference but never all over the place like this.
I'm sure you are Joe, but you are checking them over the pin Centerline, yes??? If it makes you feel any better. Before I take ANY stock "Nail" apart one of the things I check BEFORE dis-assembly is to check how far the pistons are in the hole. I come up with the same as you. NOBODY EVER checks this stuff. DETAILS DETAILS DETAILS Tom T.
If it's been overheated to the point that it was near seizing, the rings will butt and start trying to rip the piston tops off. The ring groove itself might open up .010". The rods themselves might have .005" variance, in addition to the deck being tilted a bit.
or bent? I could see one rod being bent due to hydrolock, but can several rods be bent? I had a Jeep I-6 that had the pin bores a little out of parallel. That made one side of the piston a few thou higher than the other. I took them back to the machine shop and they showed me how they passed on the go/no-go gauge.
I like to take the block down to bare block and have the deck height measured out and then squared off perpendicular to the crank...
2 I have here now seem to be @ 10.00 from factory, but I can't say for sure as I haven't always measured that before cutting. I don't always plan a deck height until all of the other components are actually in hand and have dimensions after inspecting...kind of like grinding your crank last to establish clearance.
All the "Nail" 401's I have measured are between 10.011 & 10.022. Joe, if the block is square since EVERY set of my custom pistons will take the deck into consideration. Along with all the other specs. I will ask for. NO NEED TO DECK THE BLOCK FOR THE PROPER QUENCH/SQUISH. Each build usually requires a diff. pin/compression height. It will end up being within a couple thou. And, just to let everyone know ALL the "Nails" I have done they ALL measure diff. from one side to the other over the pin. Why???? I couldn't tell you other then maybe???? factory tolerances???? Tom T.
must be the cast pistons are different heights. am going to deck the block anyways so i will have some wiggly room for the piston deck height. i will be calling you soon about getting some pistons.
Have never done this before so I measured mine at the edges of the piston over the pin centerline with a straightedge on the (clean) deck. My depth micrometer would not fit in that area due to the dome. Anyhow, I came up with .036 the most shallow and .052 the deepest with the rest in the low .040's. Stock 401, original pistons. Steve
My best guess would be varients in the the stk pistons, and differant rod lengths. I has a 455 the was line honed. Squared decked to be same on both sides, je forge pistons, stk rods and I had 2 rods .007 long and 2 .005 short. With the other 4 being plus or minus .0005 to .001. So that would be a .012 from the longest to shortest. Had to all be in the rods since I would like to assume the pin height and compression distance would be the same on a new set of je pistons
Many used rods have a wide tolerance or are out of square. Bent rods or rebuilt a few times are short. Bent could be very short, like .060". You might not see that with a deep skirt piston around it, or still in the engine.
