What defines Good and Bad pistons

[eldiabloz13]

Now im rebuilding my 91 tsi awd. Im probly going with a SB rebuild kit but no one has ever givin me straight answers on it so i just deleted my threads and said forget it. Now I have 1g pistons with 180XXX on them. Now here are my choices

1.Re-use the 180XXX 1g pistons
2.Buy my friend 100K 2g pistons for 50 bucks and buy rings from a company and re ring them
3.Get the top line rebuild kit from some damn placed i mentioned before and use the 8:0.1 pistons they give you. That also comes with rings.

Now i was woundering what really decides if pistons are good or not. Now the first 2 choices have a lot of milage on them. 100k for me is crazy used milage. Although what decides if a piston is no good anymore or not. Is it the piston wall?the ring seats(i dont know the actual name) where the ring is insterted. Mileage? I know the actual top of the piston plays abig role but what is the main part.

Say i were to give any one a set of pistons and have them tell me if there good or not what would you guys check. Would you take them and say ohh well the wall is good but the ring seats have a crack between the 2 gaps. So that gap will break more and probly break apart the piston. Now how can you tell a difference between pistons anyways. I have my 1gs and my friends 2g's and they look about the same. But i saw these in semi-lighted area at his house.

 

[95talon_in_ma]

Pistons are funny creatures. Some manufacturers stock ones are better than others (5.0 are forged from the factory). If you calculated how many engine cycles those things have been through and realize that metal eventually fatigues and weakens along with the wear on the side skirts, reusing the used ones is a bad idea. Unless your getting rid of the car right away. Otherwise the stock replacements are fine if the motor is staying stock. But make sure your block doesn't need boring first. But if you plan on doing any upgrades, get the forged pistons.
Better yet, do what I'm doing, drop the thing off at a machine shop and have them do the whole lower end. Align honed and balanced, you can sing that thing to 8000 rpm's when you get a turbo to support it... It might be a few extra bucks but well worth it..

 

[GVR4592]

If you're rebuilding there is no reason to re-use anything. If you want an inexpensive proven piston, get a set of stock mitsubishi pistons.

 

[Defiant]

^^^ Over the life of an engine, the cost of pistons in very trivial. However, a decent machinist can measure used slugs for you and make an accurate determination. The shop manual explains what he'll be checking.

 

[eldiabloz13]

I dropped off my bock and head today. 140 bucks for the head to be planned,revalved, and check for other stuff and one more thing. Now the block he looked at for a second and said it needed to be honed for sure. Then he said .20 over i was like honed? why would it be 20 over and he said the engine had been rebuilt befor with king rod bearings and didnt do something right where they came off. I caught it just in time before they caused some damage. Now how much do you think a honing and boring would be. I have a feeling there going to hand me back a receipt and im going to have a 500+ bill. Soon as i got there he was like alright alright yada yada. Then he looked at the pistons intently. Checked everything on them and said he will have to see further on them. Then i told him i might have had lifter tick and he then said 3g lifters and then pulled the rod bearing off and said ohh maybe these also. So i have a feeling that when i get my bill ill see 3g lifter(which i wont really mind if the head it completly set) new rod bearings and .20 over rings on my old pistons.....probly all set back in place. I told him about buying a SB rebuild kit and he said wait on that to see. Do you guys think i should just buy 3g lifters and give the to him to install. Cause i know i can get them for cheaper off here in the classified but i cant find them anywhere online. Does anyone know a site that sells them. There the 3rd gen lifters? So wouldent mitsubishi have some on a site. What engine does these go in anyways.

 

[95talon_in_ma]

Usually engine builders like to to do their job. If you try to tell them how to do it, you might pay the price....
If it comes with a warantee, be proud to display what they give you. (Usually). In other words, if you pay $50 more for lifters, it's worth the weight in gold. cheaping out leaves your builder with no profit. And that's just bad business.
Spending an extra hundred or so is better than pounding sand later on down the road.
Make sure you don't get screwed, but be open to spending a little more to get what you want....

 

[eldiabloz13]

hey gave me a 400-600 buck quote. Thats a little high people. 140 for the head and i baught lifters to put in and the rest to bore and hone the block. No damn way

 

[dsmputz]

Do not cheap out on your shortblock, internals get the shit beat out of them with a turbo.
I just spent $1030.46 on machine work for my bottom end. I had it magna fluxed, decked, bored 20 over, line honed, hot tanked, completely assembled (all mic no plastiguage) and had the rotating assembly balanced. I can rev to the moon

 

[GVR4592]

I think there is a lack of communication on his part or a lack of understanding on your part. Ask him to give you an itemized list of what work is being done and the price for each item on the list.

Also take a look at your first post, compared to your second post. The first was organized and pretty easy to understand, the second post wasn't. If it's easier for us to read and understand, then you are more likely to get an accurate response.

 

[eldiabloz13]

Yes i think it was a communication or lack of understanding. I told him i just brought the pistons to be check to see if there .20 over or the stock ones. And i think he thinks i was trying to say i want .20 over. Becuase he said yeh you'll need .20 over. 600bucks is expensivveee. This shit better last me 100k miles w/o haven to be re-honed and so on. I dont have that kinda money right now iu just baught another 91 tsi awd for commuting. My rents are sayen take it back b/c the 3' turbo back exhaust wont pass inspec. Then there sayen the cams sound wayyy to agressive and i said thats how they always sound.

Now moving on. What do i NEED to get done. Nothing more. Just bored and honed?

What is deckking. Is it like plaining?

Hot tanking? I hear a lot of people doing this. Does it clean and treat the block to endure more heat or what.

Should i get my crank balenced to hold those rpms to the moon like someone else has here . If so how much more does that cost. I just want my head done for 140 and honing to make shit smooth and bored if needed. Then im going to topline the engine with the SB rebuild kit or a advanced auto one.

 

[drivemusicnow]

And this is why no one should start the rebuild process without having a good understanding of A) how much things cost, and B) whether they really need to do it.

First things first, Is this a stock car? what type of power are you going to be eventually pushing through this motor?

"decking" is the head and block surfaces. This cleans them up, makes sure they are exactly level, and machined to a finish that is suitable for your headgasket.

Boring is neccesary when the cylinder walls are not entirely round. Typically a car with 180K miles will not have perfectly round cylinder walls, thus making it neccesary. This also requires you to buy new, 20 over pistons. I would recomend OEM, as they are proven to take a hell of a beating.

Honing is required whenever you are installing new rings, and thats basically anytime you remove the piston from the cylinder.

Hot tanking is a cleaning process that removes oils and such from the block. Something most people don't realize is that greases/oils penetrate INTO the metal.

Your end bill for everything will depend on whether the machine shop is assembling the shortblock, whether you use the 3g lifters... etc.. 4-500 sounds reasonable for that type of work.

Remember. This is where going cheap can result in catastrophic failure later. Make sure your machinist knows that you are wanting this for a high mileage application.

 

[eldiabloz13]

Well i am doing the other work myself and with a friend. Personally i dont trust myself doing the rings so i will have him do them. Now I just origionally wanted to give him my head and say do what you did to my friends head that cost 140. I baught 3g lifters and told him i will bring them by for him to put in.

Now as for the rest i understand its not cheap but to hone and bore a block shouldent cost 400 bucks usually. Thats like 100 for each cylinder.

Now OEM parts. Im going to buy the SB rebuild kit cause its a very good deal. New pistons with rings all those or tiny parts that should be replaced. If i went and got 2g OEM pistons new that would be like 170 then rings. Then machining some more. Then i still have to get a full gasket kit. Bearings and all those much needed small parts.

Thanks for answering all my other questions.

Now for the fun part. This engine will be built to handle 450 if i WANTED it to. I will not run that much. It will see 350 with a 50 trim turbo and all supporting mods. Now im sure i will get everyone saying. If thats your goal stop being a cheap moron and do it right. Well i know whats needed and some crap he said wasent going to help my engine. I want it bored and honed then maybe hot tanked(how much does hot tanking cost?) rods check and crank checked with my 140 buck head being done with the 3g lifters. Thats all. I know it can handle 400+ with new pistons. I was actually going to buy my friend 2g pistons and get new rings but they have 100k on them. So i dont trust them. The sides of the pistons like brand new just the top was black but still. OHh and the top plained. That sounds important. So i said w/e to that.

 

[drivemusicnow]

True, but figure 140$ to clean up the head, then 60 to install lifters, 200 for bore and hone, and 50-100 to deck.

Good machine work costs... just the way of life

 

[eldiabloz13]

true^^

 

[Talonman92]

The first and foremost factor in your decision is how much money you have. Usually for me its not a lot.

180k is high miles for a car period, I wouldn't use those pistons.

100k isn't as bad. Pistons in a correctly running engine never really "touch" anything. There should be good clean oil separating the pistons from the cylinder. The rings are what isolate the bottom end of the engine with the combustion chamber. As long as the 100k mile ones were from a decently maintained car they should be OK to use in a stock rebuild with new rings.

Then of course you have just new stock replacements. Rings cost like $70, for $100 more you can get brand spankin new pistons. But then the money factor comes into play. (and like stated above, machine work is never cheap.)