wrist pin education

[denny]

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.

thanks for the reply Bob. we used plastic gauge and the feeler gauge method and clay for valve clearance and mic's on everything and things looked good at the time. this was a 388ci sbc and a bunch of time was spent on the crank throws for crank and cam clearance. i think this crate motor thats in the malibu will take me to the finish line (i'm 72 now). this remove the motor and trans a few times in about 2 months working by myself kind of knocked the crap out of me for a while, but i'll get the fire back since i started this stuff in the late 50's and was very lucky to have gone through the muscle car days and miss them very much.

 

[denny]

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.

thats what i thought. those pins would have gone in very easy. didn't want to storm up to the shop right away because i know myself and things might get very ugly. we assembled the engine about a coupe years after everything was ready so i know what he might say. i'll see him sometime and i have one of those pistons in the trunk of the car then we'll see.

 

[64nailhead]

For the 2nd time I'll say - I feel your pain. Sounds like you've moved on and that's probably best.

Your description of how the pistons were installed on the rods describes ALL of the issue IMO. That system will work fine, but he needed to measure the amount of interference and, obviously, that wasn't done.

I have to admit though, I once made a pretty big tuning mistake that broke several pistons. I was so ticked that I couldn't overnite parts fast enough - VISA was my friend that day lol. Sounds like you might have experienced a similar feeling.

 

[vanrah]

Hi Denny & all; I too just finished my 72nd lap around the sun. Due for a pit stop, fresh fluids & body work will be required for a few more laps. And if my pit crew is as old as us, this pit stop could take a while! Post up a couple of pictures of your ride. Take care Ole' Bob.

 

[pontiacgp]

Hi Denny & all; I too just finished my 72nd lap around the sun. Due for a pit stop, fresh fluids & body work will be required for a few more laps. And if my pit crew is as old as us, this pit stop could take a while! Post up a couple of pictures of your ride. Take care Ole' Bob.

Thanks, you guys are making feel young again...... ouch, that dancing at my age hurts the back.....🙁

 

[denny]

For the 2nd time I'll say - I feel your pain. Sounds like you've moved on and that's probably best.

Your description of how the pistons were installed on the rods describes ALL of the issue IMO. That system will work fine, but he needed to measure the amount of interference and, obviously, that wasn't done.

I have to admit though, I once made a pretty big tuning mistake that broke several pistons. I was so ticked that I couldn't overnite parts fast enough - VISA was my friend that day lol. Sounds like you might have experienced a similar feeling.

thanks for the reply nailhead. exact experience. the 375hp crate engine in the malibu has helped very much. Visa was also my best friend that week lol

 

[denny]

Hi Denny & all; I too just finished my 72nd lap around the sun. Due for a pit stop, fresh fluids & body work will be required for a few more laps. And if my pit crew is as old as us, this pit stop could take a while! Post up a couple of pictures of your ride. Take care Ole' Bob.

thanks for the reply vanrah. got a pit stop for next month but i'm very lucky with my health. should get that right front tire checked out anyway. i'll have to get one of my grandkids over here to get this photo stuff taken care of. message said too large to download. you know how our generation is about new stuff lol.

 

[denny]

Thanks, you guys are making feel young again...... ouch, that dancing at my age hurts the back.....🙁

lol

 

[denny]

Hi Denny & all; I too just finished my 72nd lap around the sun. Due for a pit stop, fresh fluids & body work will be required for a few more laps. And if my pit crew is as old as us, this pit stop could take a while! Post up a couple of pictures of your ride. Take care Ole' Bob.

 

[lilbowtie]

You guys are making me feel young - be 70 in a couple of months