question about wrist pins

[Matt McClung]

I have just pulled the engine on my 86 gn and dissasembled. I just wanted to freshen up the heads, replace all gaskets and clean up the block. I have to say that everything looks great in the engine, no blowby, the cylinders look superb, cam and lifters are showing no signs of wear, but I noticed after I removed the main and rod caps to inspect the bearings that two of the six wristpins are tight, the other four move like they should. Should I replace all pistons and pins or worry about the two? Or could I press the two out and clean them up and reinstall? This engine was rebuilt about 10,000 miles ago and bored out to .040.

Thanks

 

[charlief1]

this has been an ongoing discusion. The interference fit between the pin and piston is a little tight. You can hone the pistons slighty or soak the pistons in solvent to free them up some.

 

[Matt McClung]

Thank you Charlief1, I did consider pressing the two pins out and use a brake cylinder hone with the spring pressure low and very slowly clean up the piston. I already did free them up a bit with PB Blast, but they still are not as free as I would like.

 

[charlief1]

Go to wally world and pick up some of their cheap carb cleaner. A case is 8 cans and you will use most of it. Spray it on the wrist pins to desolve the crap that builds up in them and then try the pb blaster.

 

[turbodave231]

NO!!!!! Don't use a brake hone!!!!! You'll make paperweights out of your pistons.

Take the pistons and rods to a competent machinist!!! They can probably be pressed apart and pin fit (honed) if they are not already galled. The person who assembled your engine most likely overlooked pin fitting because they were "new" pistons..........wrong answer.

Even new pistons and pins need to be checked. They are often too tight out of the box and cause just the problem you described.

 

[bison]

Have a machinist hone the pin bores and polish the pins. No brake hone! Correct any tuning issues that are putting excess heat in the tops of the pistons.

 

[Matt McClung]

thanks guys, I already have sent in the pistons and rods to the machine shop
along with the crank. As far as any tuning issues, they have already been corrected. I originally took the engine out so I can see what has been done in the past and clean it up, but as I took it apart I found these other problems. I purchased the GN 3 years ago after I lossed my 84 GN, and for the first time I found out things about the engine, such as it is punch out
.040 over. Now that I know exactly what I have, I'll be much happier knowing it is done right after I put it back together.

 

[Chuck Leeper]

While U R at it, check the ring grooves, to make sure they haven't been hammered shut. If the wrist pin bores are hammered, it's likely the ring lands may also be????

 

[Alky V6]

Make sure the pins are checked for straightness before anything else.