3500 stuff and a Q

[Superdave]

I'm re-assembling my 3500 today and still debating on which pistons to put back in, the ones that originally came with the engine (1400 miles, very clean but have a dent from the exhaust valve) or the set i picked up off a member here..

Here is a pic of the dent:



and a pic of the heat mark that's on some of the rods, this mark is only on the ones from my engine, the ones i bought in B/S/T are fine but have 29,000 more miles and need a good cleaning..




Also, the P/N on all 12 rods i have is 12568558 which dosen't show up in the GM listings.. just 12568557 which is listed as the 3500 LX9 rod from '04-07.. kinda strange.

[ForcedFirebird]

I would clean up the new-to-you pistons to make a decision.

Has anybody found out why the 3500's seem to be so dirty after low miles? the pistons I have from a 23k mile engine look just as bad.


I wouldn't trust those heat marks. Heating metal and letting it cool at an unmonitored rate causes it to be either hard and brittle (prone to cracking) or sometime malleable (prone to warping) - both undesireable in a high HP engine.

As they sit, I would vote for the B/S/T pistons and rods.

[Superdave]

i got the B/S/T ones cleaned up, 2 look like they were dropped or something.

1 of them has a mark below the oil ring that bound up the oil ring and made it really hard to get out, also has some small nicks in the side, the other has some scars at the top. I think both are fixable...

[ForcedFirebird]

Yep, looks like a drop. Doesn't look like it will hurt anything, just a little sandpaper should do it.

Lots of gunk still in the oil ring there. I like Formula88 and a soft wire brush (preferably aluminum) to clean pistons. It dies a nice job. What did you use?

[Superdave]

lol, wire wheel on my dye grinder...

i'll clean them up more before they go back in the engine, i'm also planning on using the rings from my old pistons since they are basically new.. lol

[ForcedFirebird]

I've re-used rings. In fact the 3.4 got the same rings even though they had over 100k on them, still looked brand new after cleaning.

[IsaacHayes]

Yeah I'd use the best of what you have to make a good set. Save the rest for spares.

Not sure about that heat discoloration. That's crazy.

[Superdave]

soaked the "new" ones in degreaser and got them all cleaned up nice.. of course they're all dark grey now

Found 2 others with slight dings in the tops so i guess this gives me an excuse to have them shaved .020"

[Joseph Upson]

I would clean up the new-to-you pistons to make a decision.

Has anybody found out why the 3500's seem to be so dirty after low miles? the pistons I have from a 23k mile engine look just as bad.


I wouldn't trust those heat marks. Heating metal and letting it cool at an unmonitored rate causes it to be either hard and brittle (prone to cracking) or sometime malleable (prone to warping) - both undesireable in a high HP engine.

As they sit, I would vote for the B/S/T pistons and rods.

I've been concerned about heat marked areas also but I suspect it's not a problem given how often I've seen it, including on rods from a machine shop after new pistons were installed and most resently on the steel crank in my 07 3900. I should have taken a picture of it. I don't have the distinctive bluing on either of the other two steel cranks I have so maybe the cutting blade was getting dull, the hot area is hard to miss on the crank though so I imagine if it was that critical they would have pulled it.

[Joseph Upson]

What's the reason for the rebuild Dave? The under carriage of those pistons make them appear very strong.