wiseco forged piston: how snug should the pin feel?

[haywire4130]

just tore down a recently built motor (about 1k on it) that had a head gasket failure... was wondering how snug the rod should feel moving back and forth? wiseco forged pistons and the pins are press fit on the stock rods. i would have thought when placing the piston on the bench upside down, the rod would just flop over under it's own weight, but they are snug enough to stay upright. sorry if this sounds like a ridiculous question, but i'm used to building motorcycle/snowmobile/watercraft engines that all use needle bearings on the wrist pin lol

 

[3.8L V-8 eater]

I had this same problem and it was because the flat tappet cam wiped out. All the debris froze up the wrist pin to the rod..I would say it should not be that way!!!

 

[LOT]

flop over

They should flop over, as you say--need to open the pin bore .0005.

 

[TurboBuRick]

Good time to have them converted to full float.

 

[haywire4130]

so hypothetically, i could take them to a competent machinist and they could ream a half-thousandth out of the wrist pin bores? how do they do a full-float, hone the small end of the rod? i'm assuming the same pins i have would still work, and i would need to get locks too. is full float the way to go? it would make future disassembly easier

 

[Mike Licht]

Rods need to be bushed and grooves need to be cut in the pistons for locks if they are not there already. If starting with useds stock rods it can be cheaper to buy new rods than do all the work to the old stockers
Mike

 

[haywire4130]

theyre definately not frozen, just a little tighter than i'd think they should be.

 

[haywire4130]

the pistons are already grooved for locks, there just arent any in them. i think i might just have the bores fitted nicer and stay press fit, i don't want to get into changing rods/balancing etc... the whole thing will snowball into buying a forged crank/rods etc. before i know it! hahaha

 

[Jerryl]

......... i don't want to get into changing rods/balancing etc... the whole thing will snowball into buying a forged crank/rods etc. before i know it! hahaha

GREAT self advice and observation! LOL!!

 

[S10xGN]

They should flop over, as you say--need to open the pin bore .0005.

theyre definately not frozen, just a little tighter than i'd think they should be.

4 of my 6 were like this on my recent rebuild, my machinist honed the pin bores just enough to loosen them up....

 

[haywire4130]

4 of my 6 were like this on my recent rebuild, my machinist honed the pin bores just enough to loosen them up....

awesome, thats what i wanted to hear hahaha, mind if i ask what he charged you?

 

[S10xGN]

Not sure, the price wasn't broken down that far. When I went to pick up my stuff, he charged me $376 for a hot tank, crank turn (rods & mains), new cam bearings (installed), new main & rod bearings, new rings, rod "big-end" roundness check (+ hone), and piston pin fit up. I wasn't going to ask for a breakdown. :biggrin:

 

[haywire4130]

hahaha i wouldn't either, that sounds like a bargain! i just hope i can find a decent local guy that will at least put them back on facing the right way... good machinists are a dying breed! maybe "grumpy" will chime in, his town is right up the street, maybe he would share his guy?