cracked wiseco piston skirts!

[Razor_DSM]

i have a set of wiseco 86mm pistons w/ eagle H beam rods that i was wondering if they would be usuable in a fresh block with fresh rings and bearings.

there are 2 tiny cracks on the weakest point of the piston skirts, and the rings where worn .01 out of the service limit and there is minor wear on the sides of the skirts. im not really sure what happend here, i think they where overheated and swelled...

the cracks go up the skirt about .25 . the person running these before had nos and was hitting 31psi somwhere near 600 crank hp, thats a very harsh environment. ill be running all evo stuff with 550's, no where near what that guy ran.

what should i do, i really dont have money for any new pistons

there are hardly any miles on these they still look new other than that

 

[DSMJim]

I honestly don't think this is a very good idea. If the pistons are cracked they are not suitable for re-use.

 

[Maglin]

Yeah. Even if they are given to you don't use Cracked pistons. That is the one part that takes most all the beating in an engine. I've personally seen pistons split on the wrist pin, melt and cause total engine loss. The block wasn't even good after that. I'm guessing it too started out as a cracked piston from thermal stress. I was very young at the time but it has stuck with me. BTW pieces of the rings and piston was melted to the cylender wall which I couldn't remove.

 

[TSIfreek]

I agree about not using them. Why put a part in your motor that you spent good money on with machine work and all? You will thank us down the road when your motor is back in and running again and not have to worry about it.

 

[Razor_DSM]

they wernt free...

 

[rforres]

these are my old pistons, they have less than 1000 miles on them, they came out of a track car, i had no idea of the damage and im prepared to work something out w/razor dsm. the car was not overheated, it just developed blow by one day on the way home, i drove it to work every now and then on low boost/pump gas. i will call wiseco tommorrow, they have bben kind to me in the past.

 

[swordfish]

Definate DO NOT use those. Sounds like the seller is a good guy and willing to make things right. Nice to see DSM'ers do the right thing.

jeff

 

[Razor_DSM]

piston sizes measured at the skirts...


#1 ..... 3.3798
#2 ..... 3.3808
#3 ..... 3.3797
#4 ..... 3.3819

3.3865 is what they should be right?

maybe the machine work was poor on rforres block?

I just head a machinst friend of mine check the work done to my block with a bore gauge and it was way off spec.

Bore -.002 from 3.3865 in some areas
Taper .0008 max... mitsu limmit .0004

it was kind of a rough job untill i get the set of pistons ill be using, and they will fix it at that point, they better anyways

my main question is what exactly should i be reading for the perfect fit of an 86mm piston, of course these arent the same , but assuming new ones are made available are thay pretty much exact to 3.3865 ? if so then what should the bore size be 3.3885 at the max like mitsu says, piston to cylinder clearance .0012-.0020. i was under the impression that forged pistons like to expand and require more clearence, could someone give me a hand with the clearances, ive heard .0045 people have done on JE PISTONS. seems a little loose for my taste. is the added clearance required for expantion allready taken off the overall piston size so the factory spec is still good?

i just dont want the same thing to happen to a new set of pistons, so i have to look at this from all angles... rforres any idea what specs they went by when whomever did your block, with so little miles and the rings so far worn as well as the pistons, just seems like a real quick death


so if anyone can let me know what measurements i should be looking for....

-piston to cyliner clearance
-bore of the block for .040 over wiseco pistons
-ring gaps for wiseco rings .040 over
-brand new .040 over wiseco piston O.D. skirts

any other tips to avoid this situation in the future would be very helpfull

thanks again DSM masters

 

[Maglin]

ok as far as piston to cylender clearance goes every brands pistons have different clearances and those clearances are measured at different parts of the piston depending ont he manufacture. Wisco is measured perpendicular to the wrist pin on the lower side of the skirts which is the widest point on a Wisco piston. You will get all this information with your pistons provided you get them new. Don't go with Mitsu specs for these if you are useing forged pistons. They do expand quite a bit and so they are loose in the bores when they are cold. That is why you have to let them warm up before you put a load on them so they expand and fit properly to prevent damage "like a cracked skirt". To some this alone is enough of a hassle to stay away from forged pistons and go for quality cast and hyperxxxxx whatever the name is pistons.

Hope this info helps you out slightly. Also doen't machine your block until all the internals have arrived so you can have it all done at the same time and get it right the first time.

 

[Razor_DSM]

any one have wisecos specs, i did'nt get any

 

[44pirate]

piston sizes measured at the skirts...


#1 ..... 3.3798
#2 ..... 3.3808
#3 ..... 3.3797
#4 ..... 3.3819

3.3865 is what they should be right?

maybe the machine work was poor on rforres block?

I just head a machinst friend of mine check the work done to my block with a bore gauge and it was way off spec.

Bore -.002 from 3.3865 in some areas
Taper .0008 max... mitsu limmit .0004

it was kind of a rough job untill i get the set of pistons ill be using, and they will fix it at that point, they better anyways

my main question is what exactly should i be reading for the perfect fit of an 86mm piston, of course these arent the same , but assuming new ones are made available are thay pretty much exact to 3.3865 ? if so then what should the bore size be 3.3885 at the max like mitsu says, piston to cylinder clearance .0012-.0020. i was under the impression that forged pistons like to expand and require more clearence, could someone give me a hand with the clearances, ive heard .0045 people have done on JE PISTONS. seems a little loose for my taste. is the added clearance required for expantion allready taken off the overall piston size so the factory spec is still good?

i just dont want the same thing to happen to a new set of pistons, so i have to look at this from all angles... rforres any idea what specs they went by when whomever did your block, with so little miles and the rings so far worn as well as the pistons, just seems like a real quick death


so if anyone can let me know what measurements i should be looking for....

-piston to cyliner clearance
-bore of the block for .040 over wiseco pistons
-ring gaps for wiseco rings .040 over
-brand new .040 over wiseco piston O.D. skirts

any other tips to avoid this situation in the future would be very helpfull

thanks again DSM masters

Good reason why a tourqe plate should be used when using forged pistons.

 

[autronicDSM]

Correct me if I'm wrong but you can't just take stock bore + 0.040" and bore it out. You need to measure each piston then add your clearence then do it.

 

[Razor_DSM]

bad bad bad wear

 

[Bd1000Eclipse]

send them back to wiseco

 

[rforres]

my specs were what wiseco reccomended for high boost/n2o application

.024 on the top ring
.017 on the 2nd ring
dunno the oil ring-std i think

i had a issue w/the older non-coated wiseco piston on another engine so i specifically asked what piston to bore clearance should i have the machine shop set up , they reccomended 4.5 thousandths, i had no piston slap when cold and the car ran perfect, for a month.

i am working something out w/razor about the pistons.

 

[Razor_DSM]

thank you very much rforres, ill keep you informed on the progress after the build.

 

[Brian Nutter]

Hi there, first off, this customer has been very helpful and we're getting the pistons back to analyze them. As one of our most popular and best selling sport compact part numbers, we're very serious about this sort of thing. We track failure rates, and this particular part has an extremely low percentage of incidence. This is the first incident of cracking and we will pinpoint the cause.

The skirts on this particular piston have worn/collapsed between .003 and .005 according to the numbers listed above. When the piston gets to .006 clearance (double what it's designed for), it acts as it's own miniature battering ram when at tdc and bdc. So the cracking is a symptom and not the cause. I've had previous contact with this customer so I know the clearances were within range. That leaves us with one other possibility.

Many engines using our pistons make quite a bit more horsepower than this particular one without issue. The difference is they have done so in a more linear fashion. Hitting the nitrous adds an huge instantaneous spike in cylinder pressure and therefore torque. When the piston is at tdc and the rod is directly over the crank, only two things can happen, the cylinder head lifts and all the pressure is applied into the skirt of the piston skirt. Retarding the timing helps the problem by delaying max cylinder pressure until there is an angle between the piston and the crank. Unfortunately with nitrous, the factory computer can not pull it out quickly enough if the nitrous is activated anywhere around torque peak. As such, I wouldn't be suprised if this particular engine saw loads of 250 ft lbs one millisecond and 800 ft/lbs the next millisecond with as much boost as was being run here. Basically an Gorilla standing on the skirt of our piston.

So the particular customer has a few options. He can choose to slow down by getting rid of the nitrous, but that's un-American. He can retard the timing with a auxillary nitrous retard and that will help. He can also order some custom pistons that we make especially thick. These pistons will be quite a bit heavier, but that's what mother nature demands in this case.

I'll work with customer to see what can be done. -Brian Nutter-Wiseco Piston Co.

 

[bastarddsm]

Thats what 5hp/ci will do to ya, welcome to the would of race cars.

 

[Bd1000Eclipse]

Hi there, first off, this customer has been very helpful and we're getting the pistons back to analyze them. As one of our most popular and best selling sport compact part numbers, we're very serious about this sort of thing. We track failure rates, and this particular part has an extremely low percentage of incidence. This is the first incident of cracking and we will pinpoint the cause.

The skirts on this particular piston have worn/collapsed between .003 and .005 according to the numbers listed above. When the piston gets to .006 clearance (double what it's designed for), it acts as it's own miniature battering ram when at tdc and bdc. So the cracking is a symptom and not the cause. I've had previous contact with this customer so I know the clearances were within range. That leaves us with one other possibility.

Many engines using our pistons make quite a bit more horsepower than this particular one without issue. The difference is they have done so in a more linear fashion. Hitting the nitrous adds an huge instantaneous spike in cylinder pressure and therefore torque. When the piston is at tdc and the rod is directly over the crank, only two things can happen, the cylinder head lifts and all the pressure is applied into the skirt of the piston skirt. Retarding the timing helps the problem by delaying max cylinder pressure until there is an angle between the piston and the crank. Unfortunately with nitrous, the factory computer can not pull it out quickly enough if the nitrous is activated anywhere around torque peak. As such, I wouldn't be suprised if this particular engine saw loads of 250 ft lbs one millisecond and 800 ft/lbs the next millisecond with as much boost as was being run here. Basically an Gorilla standing on the skirt of our piston.

So the particular customer has a few options. He can choose to slow down by getting rid of the nitrous, but that's un-American. He can retard the timing with a auxillary nitrous retard and that will help. He can also order some custom pistons that we make especially thick. These pistons will be quite a bit heavier, but that's what mother nature demands in this case.

I'll work with customer to see what can be done. -Brian Nutter-Wiseco Piston Co.

wow thats a company that stands behind their product.

 

[heavyD]

wow thats a company that stands behind their product.

Yeah that is a pretty impressive response. I like how he didn't point fingers and understands that people that buy their products plan to abuse them.

 

[rforres]

thankyou brian, excellent customer service and im sure all the dsm'ers here will definitely buy from a vendor who stands behind their product. i will not hesitate to use wiseco pistons in my next project .

again, thx for all the help and technical support

 

[n3gativerr0r]

Everytime Wiseco pistons are discussed whether good or bad this guy is in here with good responses taking care of customers. I dont know about anyone else. But when it comes time to stop abusing my stock shortblock and go with a forged setup I will be definately going with Wiseco pistons. Only thing better than a great product is a great product that is 100% backed by the manufacturer.

 

[Razor_DSM]

wisco is great! not only was the problem taken care of, he offered to make me custom pistons with wider skirts. i passed due to a time line. like he said this isnt an everyday problem and i cant see it happening again, esp with a toned down setup


thanks again everyone and brian keep up the good work there at wiseco

 

[2.4 turbo Hyped]

Just an fyi, Im using wiseco pistons in my stroker 2.4 g4cs and I absolutely love them. I think wiseco is one of the only companies that offers a drop in stock bore piston for this setup. This is especially nice if you find a block with no wear on it as mine was. Thanks wiseco!!

 

[evil_eagle]

sorry to bring this thread back up, but my 2.3L stroker motor with weisco pistons did this same damn thing, ON ALL 4 OF THEM!!!! same spot as the picture above, 900 miles, go figure . Not very pleased with these pistons at all. So I am going back to ross pistons due to this problem.

I think weisco needs to really look into this problem as I could not beleive my eyes when i seen this thread as my pistons did the same thing..

$500 down the drain, my stock pistons took more abuse then this!!