::actually your information is wrong. Pin clearance from a floating pin bore in a forged piston is tighter from the factory than it is from a press pin style from Nissan.
:Eh, maybe it depends on the piston, but the pin fit is looser on Wiseco pistons, not tighter. I can push them in with my fingers, whereas with the stock pistons the pins are an interference fitmeasure a pin bore on a wiseco out of the box. They are within .0002-.0005 in oil clearance...way too tight for a performance application. Feel free to contact any aftermarket piston manufacture, they will all tell you that if you want to keep the pistons working properly you need to hone the pin bores. Just because you can push them in with your finger doesn't mean too much. Thats like AMS saying "its close enough"...I don't buy it.
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: That is why you must hone the pin bores. I hone my to a specified clearance depending on the use of the engine. I've pulled many engines apart and the evidence of wear is significantly lower than if you don't hone the piston pin bore.
:You pulled many of your built engines apart again? For what reason? none of my own...they are all still running and running very well i might add. I'm referring to other engines that were built at my previous employer. Customers would run a season or bring the engine in for a freshen after 3 events and the evidence of doing the extra machining pays off tremendously. :I'm not necessarily disagreeing, but it seems odd that a performance piston absolutely requires additional machining to work properly in a performance application. The piston installation instructions go into great detail about cylinder finish, ring gaps, ring positioning, bore clearance, etc, but I don't recall seeing anything about modifying the pin bores for clearance. Not with Wiseco pistons anyways. Any machine shop you ever walk in does pin bore honing for rods and pistons. If you are going for an aftermarket build it is very important to not leave any area untouched..with you think so or not. No matter if the piston expands..the pin expands too so the clearance as is from the piston manufacture never keeps true...so you add clearance to ensure the survival of the part(s). This is the difference between machinists/engine builders and others honestly. Many feel "eh" and machinists/engine builders look at so many other things in detail. Its these attributes that I do to the engines that ultimate allow the engines to run smoother and better.
:Your engines run better and smoother? How do you quantify that statement? Do you have before/after dynos? Just curious.
Well dynos only going to tell you power potential..a dyno doesn't tell you how smooth the engine runs. I have quite a few engines around the country now that have better than average compression in the 175-180psi category and all the customers come back to me with info on how things are running. What I do works and is being proven as we speak.
::The movement of the pin is the critcal variable. Its not just the pin bore in the rod that you should be focusing on. Just like piston rings and lifters...they all rotate/spin.
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:Piston rings rotate? Then why do piston installation instructions typically say to precisely place the compression rings so that their gaps are 180 degrees from one another? absolutely..rings and lifters rotate/spin...however you want to label it. Please dont' tell me you think that rings/lifters don't spin/rotate in the bores. If that were true score marks on teh cylinders would only be in one area and lifters would only have one wear mark on the tops of them. Lifters show a star pattern with wear marks from spinning/rotating in the bores. The literature on assembly is very important and the reason why they tell you to 180 the rings is for blow by issues...its very hard to allow rings to dynamically move around the ring land if they are both slotted at the same orientation...the gases will escape too quickly and wouldn't allow for ring seal. The pin is no different, when you go to assembly and the pin does NOT spin inside the pin bore of the piston once assembled to the rod you will absolutely have premature wear issues down the road.
:I've never seen galling on the stock pistons I've diassembled. Perhaps that is because the pin bore clearance increases with temperature. I haven't had a reason yet to disassemble any forged pistons on engines I've assembled, but I'll take a look at mine when I pull my motor to install manifolds and refresh the bearings. I'll let you know. exactly because the stock pistons are press pin. Means that the pin is pressed into the pin bore and only the rod rotates/ricprocates around the pin. Thus the rod pin bushing is designed for a floating pin. If you are interested I can come by and give you a hand if you'd like. Just let me know. It is very vital that you leave NO area of two parts that are in a dynamic environment untouched. Everything must be made more effecient at all times.
:I wouldn't say it is vital, as many engines run fine without anti friction coatings, modified clearances, etc. But, to each their own. with the way customers are wanting to make power it is absolutely important to go the extra mile on key elements.
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