Requirements for forged pistons...

[luigisho]

My understanding when I was on AIM with him yesterday was both. I have to agree with everything that has been said. Rings and lands don't just break, they break because of knock.

I have hard time believing that the pistons had any cracks before the turbo went on. In N/A form, there's not enough cylinder pressure for a knock event to crack pistons. Not only that, the stock pistons are a very robust pieces. I've been feeding mine 10 to 14psi on premium fuel for 3 years and 20k miles and I used 3.2 pistons with unknown history to boot.

x2.

As was stated in other posts, I would build another motor on the side, as money allows, and swap it in when it's ready with a balanced rotating assembly if you think it's worth the cost.
For now I would drop in stock slugs, drop the boost level, and try to figure out what's not working properly. Do you have charge cooling problem? fuel? etc.
The reason I dropped my SHO project was I didn't have the funds, or a second car, to rely on when stuff broke. Aside from not havign alot of $$$, if you don't have alot of wrenching experience and a place to tear the thing apart (garage/shop) it's really hard to have a daily driver be a project car. I know Paul can swap pistons in his sleep. I can't. Big difference. You need another beater to use when the SHO is down. That's the big expensive lesson I learned with my GenI. I'm still paying off credit card debt for a car I haven't driven in at least 3 years (and eventually had Paul and Ash tow it away because I was sick of looking at it).

I'm hoping for the best so you can really enjoy this car. Good luck!

 

[nik97]

Give up that quick?

Hahaha, never. I sort of lost track of this thread really. I had gotten what I need out of it though. I will begin construction on a forged 3.2 and have it ready when I want to make some big power. A cryoe'd/shot peened MTX is also planned. For now, I'm focusing on getting the fuel system setup appropriately and installing all of my parts to have a conservative tune. I will be using a methanol kit internally and externally as well.

BTW, I now have 4 broken pistons in the garage. #'s 1,2(x2) , and 6. I think the ring lands breaking is a result of fatigue and cast pistons supporting twice the load they are used to.

#2(from the 3.0 - lost of detonation)

#s 1,2 and 6.

Replaced dead pistond and began installing upgrades -42lb FRPP inj's.


Cleaned things up a bit


Trash...

90MM Lightning MAF...


Hovercraft conversion(increases effect of boost ).


Now to get back to work. Need to install 255 pump and clear out fuel supply line to make way for high flow setup.

 

[1995SHO9]

Thanks everyone for your advice. I ordered some 3.2 pistons from SHONUT performance today. I am going to do it 100% correctly after hearing all of your opinions. I'm going to tear it out and bore the block out. Balence the rotating assembly and get a great tune on it.

 

[SHOguy 92]

Thanks everyone for your advice. I ordered some 3.2 pistons from SHONUT performance today. I am going to do it 100% correctly after hearing all of your opinions. I'm going to tear it out and bore the block out. Balence the rotating assembly and get a great tune on it.

Here's more more thing that no one else has mentioned.

Boosting any car (SHO or not) is a lot of a fun and if done properly can be reliable. But it is a high powered vehicle and that will have a greater chance of breaking and if not a higher chance of minor things breaking, then when something does go it will not be minor.

And it does sound like you are using your SHO as your daily driver. Your first step should be to pick up a cheap DD and go from there. That way when the SHO goes down for work you have the time and maybe even can find a place to work on it.

Thats part of the reason I have never gone crazy with mods, it's always been my DD and when your DD breaks then your sol.

 

[yamahaSHO]

Hahaha, never. I sort of lost track of this thread really. I had gotten what I need out of it though. I will begin construction on a forged 3.2 and have it ready when I want to make some big power. A cryoe'd/shot peened MTX is also planned. For now, I'm focusing on getting the fuel system setup appropriately and installing all of my parts to have a conservative tune. I will be using a methanol kit internally and externally as well.

BTW, I now have 4 broken pistons in the garage. #'s 1,2(x2) , and 6. I think the ring lands breaking is a result of fatigue and cast pistons supporting twice the load they are used to.

#2(from the 3.0 - lost of detonation)

#s 1,2 and 6.

Replaced dead pistond and began installing upgrades -42lb FRPP inj's.


Cleaned things up a bit


Trash...

90MM Lightning MAF...


Hovercraft conversion(increases effect of boost ).


Now to get back to work. Need to install 255 pump and clear out fuel supply line to make way for high flow setup.

That was quick...

 

[NCTaurusSHO]

I was in his engine. Did a compression check and only 1 cylinders hit above 100 psi on the gauge. only 2 were broken and didn't make the gauge move at all, the other 3 hit barley 60 psi... the compression rings were stuck in the ring lands and completely FULL of carbon along with carbon all in the ring land areas... when boost is added to a worn out motor it will just deteriorate rapidly. it took a few hours of cleaning the pistons before they went back in. Started the car, and wow it sure ran a lot better then it did when he was first here. His car has the exact same set up and tune as our green one and were still boosting happily on stockers, but I started with all new rings and spotless pistons but i am waiting for them to brake eventually because they are not intended for boost and wont last. And john kept telling me all top speed joy rides he was giving every one so it wasn't babied and probably was banged off the rev limiter a few times unintentionally. I found out on my red turbo sho that hurts the pistons really quickly. Also, for those who say having the SAFC isn't a good idea. just remember, it has a wire that connects directly to the knock sensor to let you know when you are in the lean area. that never left 0. it DID NOT RUN LEAN because of the tune, it just wasn't letting the rings expand as they should.... how many times do we have to tell this same story.... You guys are filing his head with incorrect "theories" and while yes, those can be reasons for "burned up pistons, this was not the case by any means. we were in the motor, we saw what was wrong..not one burned up piston.... that was not the problem.
Paul/Ashley


PAUL

 

[NCTaurusSHO]

Hahaha, never. I sort of lost track of this thread really. I had gotten what I need out of it though. I will begin construction on a forged 3.2 and have it ready when I want to make some big power. A cryoe'd/shot peened MTX is also planned. For now, I'm focusing on getting the fuel system setup appropriately and installing all of my parts to have a conservative tune. I will be using a methanol kit internally and externally as well.

BTW, I now have 4 broken pistons in the garage. #'s 1,2(x2) , and 6. I think the ring lands breaking is a result of fatigue and cast pistons supporting twice the load they are used to.

#2(from the 3.0 - lost of detonation)

looks like that one leaned out and that is not what his pistons looked like at all.

 

[yamahaSHO]

Lean conditions aren't the only causes of knock. Heat will knock like a son-of-a... Combine heat with high timing advance and cracked pistons will happen regularly with these.

If the rings weren't expanding to seal the combustion chamber, I don't see where the knock is coming from to break the pistons. I do see lots of blow-by happening. I can put a piston in without a ring and it isn't going to break.

I'll ask again, what pistons broke???

 

[NCTaurusSHO]

sorry it was 4 and 3

 

[1995SHO9]

And john kept telling me all top speed joy rides he was giving every one so it wasn't babied and probably was banged off the rev limiter a few times unintentionally. I found out on my red turbo sho that hurts the pistons really quickly.
Paul/Ashley


PAUL

Just to clarify I never once hit the rev limiter driving. But I didn't baby it either, you are correct there. The new injectors should be here within a week. I'm looking forward to getting those put in. And when I come down i was wondering if you would be able to data log it with your laptop, I'm curious what the intake temps are. I expect they will be good. Oh, and PM sent to you...

 

[yamahaSHO]

I'm sure you're spirited driving wasn't much of a strain compared to the boosted SHO's running road courses Except for that knock issue you had...

 

[techi14]

Hey John man, this little project is really costing you some dough man. But Im glad your gonna do it right. Good luck man.

 

[1995SHO9]

Hey John man, this little project is really costing you some dough man. But Im glad your gonna do it right. Good luck man.

Yah, to be honest with you I got in way over my head on how much it is costing me to do all of this. But I will get it done, it just is going to take alittle longer. However, I've made some good friends out of doing this project and for that I am thankful. I would be screwed if it wasn't for all of the people that have helped with this project and I have learned a ton from it. So I consider it to be well worth it. In another 6 months it should be totally done if all goes well.

Johnathon

 

[ManySHOs]

My advice: Don't let your SHO ruin you financially. It's just a car. Know when enough is enough and walk away.

Ian

 

[Sho Amo]

Hovercraft conversion(increases effect of boost ).

now thats where its at

so how long does it take you to replace a piston on the sho now?

 

[nik97]

now thats where its at

so how long does it take you to replace a piston on the sho now?

lol, IDK, 5hrs maybe. Being a flat-rate mechanic helps tho.

Hopefully this is the last time. Even if it does not take long, it's a pain in the ass and I'm running out of pistons.

 

[1995SHO9]

My advice: Don't let your SHO ruin you financially. It's just a car. Know when enough is enough and walk away.

Ian

By no means is it ruining me financially buddy. I'm just in school and all in all it is costing more than I planned. Once I drop the forged in I will be done for awhile. Besides, I've gone to far to turn back now Ian.

 

[Sho Amo]

I'm running out of pistons.

lol good reason

 

[SHO NUT]

Not only that, the stock pistons are a very robust pieces.

Sorry, I gotta disagree on this one.

Take a look at this pic:

See where the ring lands broke off? Just below that is a long oiling groove. I broke 3 pistons with someone else's tuning, before doing my own tuning (no broken pistons since, lol), and each land snapped off just above that groove with a crack starting at the ends of the groove, and propagating up through the land. That long groove leaves the land completely unsupported. If you look at our forged pistons, you'll see that instead of a long groove, there's a series of holes, so the land is as supported as the land can be.



So our pistons have a weak spot. I like to call it a safety fuse - it cracks before something bad happens like a meltdown (at least for over-rich or undercooled, anyway ... )

BTW, as I alluded to above, I got cracks due to a) overfueling, and b) heat-soaking the Intercooler. Massive blow-by out my valley vent tells the story, but make sure that incorrect PVC plumbing is not pressurizing the crank case before blaming cracked pistons for excessive blowby!

 

[twr]

Sorry, I gotta disagree on this one.

Take a look at this pic:

See where the ring lands broke off? Just below that is a long oiling groove. I broke 3 pistons with someone else's tuning, before doing my own tuning (no broken pistons since, lol), and each land snapped off just above that groove with a crack starting at the ends of the groove, and propagating up through the land.

I quess my point was missed. For a stock piston they handle mild boost pretty well. I looked into putting a s/c on my Titan - first thing I found out was that the stock pistons are being pushed at 6 psi of boost. As I said above, I've been running 10 to 14 psi of boost through my engine for 2 1/2 years using a tune with a fairly mild timing curve, still 390hp and 308tq at the wheels. I see knock every once in awhile, usually under high load and just before the rev limiter. Your statement about someone elses tune and no broken pistons since doing your own does say a lot.

Are the stock pistons good for boost, no they were never designed for it. Will they handle mild boost (9 to 12 psi) - I would say yes - with a conservative tune.. Don't expect to be able to run more than 12 psi even with a good tune and hope that the pistons will stay in one piece.