wrist pin education

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I too would suspect the re-size operation. Correct me if I'm wrong but doesn't the pin float slightly in the rod and is pressed into the piston? That way the rod can swing on the pin as the crank turns. If the pin was loose in the piston then it would pound with every stroke and maybe even move enough to contact the cylinder wall. That is the only explanation I can see for the intact pistons where the pins are sticking out the side.
 
inspection of parts for was done before assembly was done by myself and a couple of my career mechanic friends. pin inspection was eyeballed and not taken apart to measure clearance. piston to valve clearance was good to go. was never a problem with dish pistons and not a real wild cam. engine was sent to scrap. when you gather all your parts up and have the machine shop do their thing and take your stuff home and assemble it yourself your on your own around here. like i said earlier this was about a five year process where i would buy parts when i could (eagle crank,resized gm rods,crower cam,summit pistons (kb),new valve train,summit intake, edl,carb). myself and my lifetime car friends have been doing this for 50 years and nobody can believe what happened here. this was my retirement project. crank,bearings,and rings looked perfect. this left a bad taste in my mouth, won't use this machine shop again. assembly was done about 2 years after work was done when i retired.

hindsight is always 20/20. i'm lucky to have some career mechanic friends around here and engine assembly was never a problem. but yes,warranty is always very good.

the person who pressed in the pins ought to have noticed that the pressure to install the pins was less than it should have been. The interference fit was not within specs and the machine shop is responsible for that. It was clearly not the fault of yourself who assembled the engine. Your friend should step up and make it right. I have friends who come to my office for legal representation and if they expect to pay less than my normal fees due to our friendship I remind them it goes both ways so being a good friend they should offer to pay twice my normal hourly rate.
 
Greetings Denny & all; Sorry for your MESS, the phase Brown Soft Smelly Stuff Happens comes to mind. I would agree the the pin Press fit was - is incorrect. That's the pin diameter vs the small end rod bore. If memory serves it should be .0007 to .001 PRESS? The pin should float in the piston bore. For home builders I would suggest full floating pins with pin locks of course. Then the clearance would be preset from the piston manufacture as most pistons come with pins. Then the shop would drill & chamfer a oil hole in the top of the rod, then finish the bore (small end) to .0007 to .001 clearance, assembly disassembly is very easy then. Quality rods right out of the box will have this work done & only requires checking - inspection. Never take any thing for granted from any shop as us humans tend to screw up from time to time. In the past I've paid the shop to but the bearings in & torque the main caps then use the dial bore gage to measure the bores & record them on paper. Same with the rods, bearings in caps torqued, measure. Then of course measure the crank. The cheap way to do this is called plastic gage! Piston skirts, # the pistons & insert, no rings use feeler gage! Rod side clearance at mock up assembly, feeler gage. And of course piston to head-valve clearance with lifters adjusted, use clay & let it harden. Save it for future reference as you may want to change cams. Oh don't forget crank end play. These steps will most likely result in an engine that will live. Sorry we couldn't help you before the mess. Good Luck, Ole' Bob.
 
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Total mess - obviously there was improper clearance for the pins to move - Thought you had new rods but who ever re-sized them is at fault. Were the piston bosses cracked?? Might be another problem and the reason for the piston hitting the head and blowing apart(cast pistons). Is there any contact with any of the other pistons?? Is there any witness marks of valves hitting the pistons?? Seems like something else going on besides the pins.
bosses were cracked on the outside boss on the three shown. other 5 good. none of the other KB pistons hit the head. clearance was good when assembled. no witness marks. some of the other rods have most of the small pad removed. some of the markings on the rods are 4245,4246, and a 4247. probably gram markings? still stumped on the rod with the pin still on and the piston gone. lets hear from some of you auto machinist out there that run a machine shop. i'm sure you have seen this before if you have been doing this for a while. this is my first small block in about 35 years,always had bbc. some of my friends say the only way that can happen is too loose pins, which backed out. this happened last spring and i'm just starting to get over it.
 
If the pins were installed as they should be with heating the rod end and some cool the pin there would be no pressure just side them in. Against the grain but I press mine.
he had the proper tools to install the pins. looked like a setup that heated things up and then pushed in.
 
Pins in the freezer works well also. But measure first.
i think that was the problem. not accurate measurement. i ran my bb for years with pressed pins,no problem. probably 10 times more pressed pins out there than floating.
 
I too would suspect the re-size operation. Correct me if I'm wrong but doesn't the pin float slightly in the rod and is pressed into the piston? That way the rod can swing on the pin as the crank turns. If the pin was loose in the piston then it would pound with every stroke and maybe even move enough to contact the cylinder wall. That is the only explanation I can see for the intact pistons where the pins are sticking out the side.
looks like the pin is pressed into the rod small end tight. engine blew at an idle in about 2 seconds. locked up with water coming out the side of the block. happened to be working on this by myself at the time. gives you a real funny feeling in your belly area.
 
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