(100% my opinion only)
If I measured:
- all four cylinder bores, at 3 places each
- the skirts of all four pistons
- all 3 ring gaps, on all four pistons, several places on each gap, especially by the top two gaps, injector side
- wrist pin wobble, all four pistons
and everything was within spec, I might be inclined to reuse those pistons.
My guess, however, is that with that kind of erosion other things have also been going on in that engine... things that the measurements above may reveal.
Scratching head over head gasket?
Moderator: Fatmobile
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- Turbo Charger
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- Location: Edmonton, Alberta, Canada
Vince
Edmonton, Alberta, Canada
2001 silver TDI Jetta Malone Stage 1.5 , 2001 blue TDI Jetta SBIII 216s Malone Stage 3
1970 Bay Window bus
Gone but not forgotten: 1969/1971 Beetles, 1969/1974 Westies, 1979 Rabbit, 1986 TD Jetta, 1992 gas Jetta, 1994 TD Jetta
Here's a small collection of HOW-TOs
Edmonton, Alberta, Canada
2001 silver TDI Jetta Malone Stage 1.5 , 2001 blue TDI Jetta SBIII 216s Malone Stage 3
1970 Bay Window bus
Gone but not forgotten: 1969/1971 Beetles, 1969/1974 Westies, 1979 Rabbit, 1986 TD Jetta, 1992 gas Jetta, 1994 TD Jetta
Here's a small collection of HOW-TOs
balance pistons by weighing all individually ( after cleaning and no rings ) take the lightest and put aside ( your reference)
then take each other piston and grind away the bottom of the skits (by the wristpins) till you are within spec of your reference piston... smooth out any burrs .....
con rods repeat weighing as above to get reference ROD ... remove material from the SIDE of the rod between the big and small end till within spec ...
reassemble rods / pistons / wrist pins ( matching heavy rods with light pistons ... ) and re- weigh you should be within spec by now ....
then take each other piston and grind away the bottom of the skits (by the wristpins) till you are within spec of your reference piston... smooth out any burrs .....
con rods repeat weighing as above to get reference ROD ... remove material from the SIDE of the rod between the big and small end till within spec ...
reassemble rods / pistons / wrist pins ( matching heavy rods with light pistons ... ) and re- weigh you should be within spec by now ....
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- Turbo Charger
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That is a very "tight" specification. Probably that would be for a super high revving engine. My machine shop told me that within 1 gram is their standard for a passenger vehicle. Take into account diesels do not rev high compared to gas.82vdub wrote:I did a google search for balancing an assembly and one website said to balance the pistons to within .5 grams of each other....
Probably typo, and would be very difficult to make them match that closely. Probably impossible to grind off .05 grams. What would end up happening is you would grind off too much then have to grind off the others, then you would grind off too much... ect...82vdub wrote:... and another one (Ford engine) said to balance to within .05 grams of each other. I wonder if this last one is a typo, as it doesn't take much to equal .05 grams of weight.
The <a href="viewtopic.php?t=6550&start=15&postdays= ... ht=balance" target="_blank">Engine Pull thread</a> has my piston balance story... Last post on pg 1....
I would try to reuse them as well.Vincent Waldon wrote:..... everything was within spec, I might be inclined to reuse those pistons.
Richard
85 Jetta TD
ASE Certified Master Auto-Technician with L1 Advanced Engine Diagnostic Rating and Light Diesel certification
ATRA Certified in Rebuilding, Diagnosing & Installing Transmissions
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85 Jetta TD
ASE Certified Master Auto-Technician with L1 Advanced Engine Diagnostic Rating and Light Diesel certification
ATRA Certified in Rebuilding, Diagnosing & Installing Transmissions
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- Glow Plug
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Thank you for the info guys. I will get them weighed and see where things stand. Just to clarify... If I matchup the pistons and rods, I will be okay as long as I keep the pistons with their cylinder and the rod bearings with their correct crankshaft journal.
I had a broken ring in number 3. I am guessing the timing was off a little and I think the injectors were overdue for a tuneup. I already have new injectors.
I had a broken ring in number 3. I am guessing the timing was off a little and I think the injectors were overdue for a tuneup. I already have new injectors.
1991 gasser to 1.6n/a conversion
How worn are the cylinder walls and what is the clearance with the pistons and cylinders? To use the same pistons in the same hole probably isn't necessary, but I'd plan on doing it that way. You will have to hone the cylinder walls if you want the new rings to have any chance of breaking in properly. Keep that in mind when you determine your clearances, and make sure they are within spec.HOPPING DIESEL wrote:Just to clarify... If I matchup the pistons and rods, I will be okay as long as I keep the pistons with their cylinder and the rod bearings with their correct crankshaft journal.
I, personally, would not reuse rod bearings. I mean if they were nearly obsolete or $100 a bearing pair, then that's another story. But, you should at a minimum find out how worn the journals are, and have the crank turned or polished and use a properly sized new bearing. Do this thing up right. It will cost a little more money to get things back in spec and use some new parts, but why reassemble a used engine?
Everybody else lists their cars here - but not me.
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I have too many to count
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- Glow Plug
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