Topic: Compression test procedure

[Critterman]

Pistons have to be custom made because of the rod lenght (aftermarket).  It can take a long time to get them.  Ask Jimmybaja

[Arabas]

Pistons have to be custom made because of the rod lenght (aftermarket).  It can take a long time to get them.  Ask Jimmybaja

i thought there were direct replacement pistons and rods for our engine

[Critterman]

The aftermarket rods are longer, which requires a custom piston, with the mount higher in the skirt.

[Gentleman Jack]

The aftermarket rods are longer, which requires a custom piston, with the mount higher in the skirt.

Critter,
I have had a busy day already, so I will leave this one for SA.  But mounting higher up the skirt is not always a bad thing.  It really depends on the length of the skirt and the shape of the custom piston.  Those with aftermarket rods are usually a different breed, built for a singular purpose.  I'm not sure if that is going to apply in Jimmys case or not.  For him, it's going to be all about the protection.  He can't afford another mistake.

GJ

[tazz]

My vehicle is still under the extended GM warranty so I can't really go aftermarket right now and keep my warranty.  Also if they don't replace with stock parts I have to pay labor and they won't warranty the motor any more.

[Sol Asylum]

Critter,
I have had a busy day already, so I will leave this one for SA.  But mounting higher up the skirt is not always a bad thing.  It really depends on the length of the skirt and the shape of the custom piston.  Those with aftermarket rods are usually a different breed, built for a singular purpose.  I'm not sure if that is going to apply in Jimmys case or not.  For him, it's going to be all about the protection.  He can't afford another mistake.

GJ

If it was anyone else I would say that post is on topic, but since it's GJ I just know he's angling for something there.  I guess I had just better let it be or else Ivy might be upset with me again for picking on him.

[tazz]

When I get my car back will I have a "break In" period for the rebuilt engine since they are re-honing the cyl walls and installing new rings?  If so how many miles and do I change the oil filter and oil at let's at 500-1000 miles then go for the reconmended mileage that the DIC reads?

[LatinVenom]

Just like you wrote 500 miles or so would be a good time to change it.
I would also change both at 1500, then after that would go by what the DIC shows is time to change.

[tazz]

I get my car back tomorrow.

[Critterman]

Please let us know the results.

[tazz]

Will do.

[tazz]

Talked to the shop Mgr and he showed me the damage to #3 & #4 piston.  He didn't say anything on what might have caused it but my thinking is that detonation??? had to have occurred to do the damage on the pistons.  On #4 two "ringlands?" "areas between the rings" where toast where an inch chunk was cracked off but didn't score or dislodge since it was held in-place by the top ring and 2nd 3rd ring.  Im not sure what could cause that but it had to be detonation i would think.  On #3 the area between ring 1 & 2 had an inch chuck out of it but also held in-place by the rings.  He said that they way it cracked was strange and hardly ever happens that way where the crown of the piston is fine but cracks in the middle .  Also was extremely surprised that the cylinder walls were not scuffed AT ALL in those two cylinders and asked what type of oil I used and I said RP.  He said keep using it since it probably saved your walls and the fact rings didn't allow the chunks to really move anywhere since the walls showed no wear.  Since they had it tore apart they replaced the all the rod bearings just to make sure but they didn't even show wear Even the wrist pins on the pistons where nice and polished no scuffs.  I did not look to see if the rings where toast but I'm sure they where but still able to keep the chunks in-place.
I'm really not sure what happened but the car but it had been idling rough but not enough to set any codes months prior to the piston failure so I suspect the rings got damaged at some point.  Maybe allowing oil to combust in the chamber causing the engine to detonate bad enough to hammer the ringlands and cause them to crack.  Never heard any audible detonation and KR logs never showed any more less than normal until she started to smoke like a fog machine, so......I dunno.  I replaced the O2 sensor today though just as a precaution and it idles smooth and great now RPM stays within 10-15 of the set 800RPM at idle.  Used to about 25 RPM's of set 800RPM's within the last few months which gave it a bit a a rough idle.
2 new pistons, All new rings for each cylinder,new rod bearings for all the cylinders, deglaze all the cyl walls, all new head gasket/s and head bolts I think that was it according to the paperwork.  Said the head look great no nicks or chunks springs valves fine crank fine pan fine cyl wall great no scuffing or marring just basically the 2 cyl and rings toast.
Here is a pic I pulled off the NET that shows SIMILAR damage to what my piston #4 and less so #3 looked very similar but the rest of the piston looked brand new not like the one pictured and the rings had taken off. 

[Critterman]

Amazing what these engines will take.  Glad you are back on the road.

[Arabas]

damn, that must have been an ugly sight!
Glad you got it fixed under warranty and you are back on the road, tazz!!!!
the best thing is that the cylinder walls had no scratches.

[Kelu]

  Nice to hear you found the trouble and now the kappa is fixed 

[tazz]

Damn
When they put the hood back on they didn't align it properly also they put 1 scuff mark, one scratch, one very small ding in the fender panel and two small chips on each corner of the hood by the windshield.