Just got another set of rods and pistons

Blown262 · Jul 31, 2015

So I found a killer deal for a set of rods and pistons on ebay and couldn't pass them up. They came in today and look mint, less a couple of nicks on the skirts of the pistons. The rods are absolutely mint. Now I noticed the pistons have what appears to be injector spray pattern carbon buildup on them. Is this normal? Is it bad? And what causes the pattern to build up on the piston like that? A lot of fuel, injection pressure, both?

Arisley · Jul 31, 2015

That is a normal fuel pattern from tunes. Bet they have been hot a few times. Measure the ring grooves really, really good, I bet the edges are hammered. Any nicks in the skirt, make sure you clean them up, nothing sticking up. If anything is sticking up, it will score a cylinder wall.

Blown262 · Aug 1, 2015

Arisley said:
That is a normal fuel pattern from tunes. Bet they have been hot a few times. Measure the ring grooves really, really good, I bet the edges are hammered. Any nicks in the skirt, make sure you clean them up, nothing sticking up. If anything is sticking up, it will score a cylinder wall.

OK will do. I'm sending to them to the machine shop to make sure the rods are straight and the journals are good and sized right. I'll have them check over the pistons as well and clean everything up. From what the guy was saying is they were purchased new and have less than 10k and it lost low side oil pressure. The bearings have some minor scoring so those are getting tossed. Do I need to worry about the bushings in the wrist pin journals?

ja_cain · Aug 1, 2015

Is the pattern outside the bowl due to higher than stock pw? Never payed attention to the combustion patterns on the top of these pistons.

Blown262 · Aug 1, 2015

ja_cain said:
Is the pattern outside the bowl due to higher than stock pw? Never payed attention to the combustion patterns on the top of these pistons.

That was my initial thought. Maybe These injectors were still firing a few degrees later than they should be?

ja_cain · Aug 1, 2015

Exactly. I'm no expert though. That's why bigger nozzles are important when increasing power. Also, de-liping the bowl is important as this can lead to cracking in high hp applications. The thin edge heats up faster than the rest of the piston thus causing cracking. May want to look into de-liping since you have them out.

Blown262 · Aug 1, 2015

ja_cain said:
Exactly. I'm no expert though. That's why bigger nozzles are important when increasing power. Also, de-liping the bowl is important as this can lead to cracking in high hp applications. The thin edge heats up faster than the rest of the piston thus causing cracking. May want to look into de-liping since you have them out.

I've never even thought of that but that makes a lot of sense. I'll relay the info and see what the machinist says. Thanks for the tip.

ja_cain · Aug 1, 2015

No problem.

TyCorr · Aug 1, 2015

Yea. You want to chamfer that edge or de-lip.

TyCorr · Aug 1, 2015

You are going to build a motor with used slugs and rods? Thats kinda wreckless imo

Blown262 · Aug 1, 2015

TyCorr said:
You are going to build a motor with used slugs and rods? Thats kinda wreckless imo

Wreckless? totally. I have a set of new rods sitting in a box ready to go, but I also have 2 non running, complete motors coming, plus the motor that's currently sitting in the bay. These rods were less than $200 shipped to my door and will give me something to play around with and make mistakes without killing an expensive motor in the process.

TyCorr · Aug 1, 2015

Oh. Ok. I guess if thats your style of pain. I hate the thought of experimenting and trashing a block I may need someday.

Arisley · Aug 1, 2015

Many motors have been built with used rods and pistons. Do not believe anything that you were told by the previous owner.

Blown262 · Aug 1, 2015

Arisley said:
Many motors have been built with used rods and pistons. Do not believe anything that you were told by the previous owner.

But I was told the pistons were cast from angel tears and can handle 700 psi and 10000hp..... I tend not to belive what they say ever. The only thing I do believe is that they have low miles. If I had to guess, they have very low, VERY hard miles.

TyCorr · Aug 2, 2015

Id find truth to that but since many diesel shops cant keep even a 7.3 running after rebuild using new parts, i think we can skip the whole mythbusters episode comparing our two points.

Case in point, Jakes rebuild. Rainman could have built him a better longblock. For waaaay less coin.

co04cobra · Aug 2, 2015

I'll throw in my .02.

IMO total waste of time to put those rods and/or pistons in anything. What little I can see of them the pistons don't look that great and used rods that are showing signs of bearing wear..

$200 was the most they were worth. They're really not worth paying to have the machine shop check them.

A good used forged rod short block would put you miles ahead IMO.

Just seems like a lot of wasted time and effort, but if you like doing things over, go for it.

Magnum PD · Aug 2, 2015

Rods would be the only thing I'd use.

Blown262 · Aug 2, 2015

co04cobra said:
I'll throw in my .02.

IMO total waste of time to put those rods and/or pistons in anything. What little I can see of them the pistons don't look that great and used rods that are showing signs of bearing wear..

$200 was the most they were worth. They're really not worth paying to have the machine shop check them.

A good used forged rod short block would put you miles ahead IMO.

Just seems like a lot of wasted time and effort, but if you like doing things over, go for it.

Well my friend owns the shop and is reconning them for free. A good forged rod short block is still probably going to get blown up. It's not about doing things over, it's about educating myself without dumping a ton of money into something. If I can build up a block for less than $500, am I really behind anything? These are going in a throwaway motor that I can experiment with while I research and build a proper motor. I have 3 complete used engines and 2 more sets of rods. I am far from an expert on these motors, so why not teach myself, and if there's a catastrophic failure, oh well.

lincolnlocker · Aug 2, 2015

TyCorr said:
Id find truth to that but since many diesel shops cant keep even a 7.3 running after rebuild using new parts, i think we can skip the whole mythbusters episode comparing our two points.

Case in point, Jakes rebuild. Rainman could have built him a better longblock. For waaaay less coin.

lol.. prolly!

live life full throttle