piston sizes

drjurman · Post by **drjurman** » 30 Oct 2018, 15:33

Hi all

Toasted two pistons on my 850 turbo. The # 3 valve seat rotted out and the head gasket went boom. Got another head did a valve job, good as new. Block not sure about yet, pistons 2 and 3 melted to the rings. Back to the block, there is no wear ridge, it still has the crosshatching, however cyls 2 and 3 have some pitting or build up cant really tell. back to the point. The pistons are marked "E" with "516/95" stamped around it. It may just need a ball hone and back in business. The dealer has pistons that are marked "D" what is the difference? Should I just go Wiseco and get 81.5mm pistons. its a heck of a lot of money either way. Dealer $148/ piston.
Wiseco $850.00/ set. What is the difference between E, D ,G pistons?

Post by **misha** » 30 Oct 2018, 16:41

Are you sure that pistons are toasted?I had never seen that happened to these cars...in fact...never on one Volvo.
Maybe the rings are melted around pistons....that i had seen on these cars.
Unless the ecu is insanely re-mapped so the pistons can't withstand the new combustion temperatures...i don't see how they can be toasted.

Post by **JimBee** » 30 Oct 2018, 21:45

Give this company a call:
http://www.crankshaftsupply.com/

The tech who sold me a connecting rod when I rebuilt my 850 had shelves full of engine parts, including a bunch from Volvos.

drjurman · Post by **drjurman** » 30 Oct 2018, 22:23

misha wrote: ↑30 Oct 2018, 16:41 Are you sure that pistons are toasted?I had never seen that happened to these cars...in fact...never on one Volvo.
Maybe the rings are melted around pistons....that i had seen on these cars.
Unless the ecu is insanely re-mapped so the pistons can't withstand the new combustion temperatures...i don't see how they can be toasted.

attached is a picture. two you can see the rings

Post by **misha** » 31 Oct 2018, 06:02

Since you ask for Wiseco pistons...i would say that ecu is insanely remapped...causing original pistons to melt down....or it was overheated badly.

Post by **abscate** » 31 Oct 2018, 08:15

The letter sizes are tolerances on piston diameter which are pretty finely tuned to within 0.010mm (0.0004 inches)

Piston Marked C 80.980-80.990 mm
Piston Marked D 80.990-81.000 mm
Piston Marked E 81.000-81.010 mm

Post by **SuperHerman** » 31 Oct 2018, 12:09

abscate - good stuff. I looked for that a while back and could not find anything.

As to drjurman's situation I would start by dropping the oil pan and disconnecting pistons 2 and 3. Before trying to remove the pistons I would clean everything up as best you can and spay some solvents to rinse it all clean. (For the pistons you need to make sure you mark everything so it goes back together the same way - I believe the rods are cracked so they MUST be reinstalled exactly how they came out.) Next I would hit it with some PbBlaster or the like to free up any sticking and then oil the cylinders to limit any scratching.

After that you will have a good idea of what is going on. If I recall correctly the liners are iron, and the pistons aluminum. The substance you are seeing is probably the aluminum. The rings are steel. On a Range Rover, with an aluminum block and pistons I had a similar situation, but the block was toast. My conclusion was the issue was caused by lack of lubrication and cylinder wash.

My guess is the extra heat did some melting and you had some detonation plus some fragments and that caused the missing portions. On my old S80 that ran for 50k plus miles with a small head gasket leak I saw lots of signs of the Aluminum head balling - but I did not see any damage to the pistons or rings.

Once you have the pistons out you can take some measurements and try a rehone and see where you are at size wise and cylinder wall conditon. If the specs match the "E" I would source some used ones. Based on what abscate provided your pistons are "E" and are the largest size Volvo makes. If you are out of spec your only choice may be the Wiseco - but at this point a used engine could be the cheapest route.