12 replies to this topic

[Prospero]

Hey all,

I have been tearing down a built motor and am trying to figure out what these pistons are.

They have on the bottom, inside the piston the part number "243668" and "H3A" On the top they have "PM4" "F50" engraved in on the top. The top piston ring measures out at 1.2mm, 2nd ring at ~1.6 and the oil ring at ~3mm.

Top diameter is about 80.53mm and at the base below the wrist pin is 81.1mm.

Anyhow, I am trying to identify if these pistons are OE+1 or what. Tried searching the part number but get no hits.

In essence I am trying to determine if I want to use these pistons in my 2000 T5 engine that I'm replacing the rods in. They came out of a 98 block with LGSpeed rods attached. Someone spent a lot of time grinding the extra weight off of the pistons and the weigh out very close to eachother; so I wanted to use them if they will fit.

Also I am trying to figure out if this piston ring installation is kosher. To me it looks like the rings are simply the wrong size for the piston and it maybe why the PO had issues with blow-by.

Any help would be appreciated. Trying to do a budget rebuild and have the gaskets and bearings already. Now I need to figure out the rings that need to be ordered.

What do y'all think? These rings look like the right ones?

Thanks and cheers!

https://plus.google....CNSGlN-sx6X2wgE

[wizzard_al]

They look like OEM pistons, particularly where the spring clip goes into the piston to hold the piston pin (gudgeon to the English). But those have a letter on the top of them, and an arrow to say which direction they go into the block. Letter is usually A through D, to show piston size.

If I remember correctly,
94-98? rings were:
1.5mm , 1.75mm, 3.0mm

later rings, at least starting with my '01, and probably starting in '99
1.2mm, 1.5mm, 2.0mm

Unless you measured wrong, these are like later style ring syzes, except oil control ring is too thick.

Measure again, just to be sure.

[Prospero]

Wizzard_al, Thanks for the reply!

Okay, so I have re-measured the piston rings and here is a link to the album. The last few photos are the calipers on the rings with their related measurements. I'm super confused right now... these are mystery pistons or something! I've checked the rods, and they are 139.5mm from center to center... so at least that part measures out

https://picasaweb.go...feat=directlink

Sooooo damn confusing!

wizzard_al, on 20 January 2012 - 12:49 AM, said:

They look like OEM pistons, particularly where the spring clip goes into the piston to hold the piston pin (gudgeon to the English). But those have a letter on the top of them, and an arrow to say which direction they go into the block. Letter is usually A through D, to show piston size.

If I remember correctly,
94-98? rings were:
1.5mm , 1.75mm, 3.0mm

later rings, at least starting with my '01, and probably starting in '99
1.2mm, 1.5mm, 2.0mm

Unless you measured wrong, these are like later style ring syzes, except oil control ring is too thick.

Measure again, just to be sure.

[wizzard_al]

First, what engine is this? I assume B5234T3, but what year? VADIS and VIDA are terrible for determining ring thickness for earlier engines, but from about '99 on they give the actual dimensions.

What I would do is measure the groove for the ring, not just the ring. The diameter of the piston tells me it is an odd oversize, each oversize from Volvo is .4 mm larger, and you are showing .1mm larger, which is not a standard oversize. This could be custom pistons, or even OEM, but the rings throw me. Maybe they were orderd to fit the block, and that is why the odd oversize. Both the middle and bottom ring work out right at stock thickness, but the top ring is different. If these are the actual dimensions, then I'd go to Hastings, and order rings individually or in a set. They have a set of rings that might just work: 2C4993, but you need to confirm the size of the pistons again. This is a set of rings for 5 pistons, and has 1.2mm, 1.75mm and 3.0mm rings at 81.0 mm diameter piston. They will handle a slight oversize. Even a .010" oversize piston would be 81.25mm, so you see my confusion.

Your piston at 81.1 mm is slightly larger than stock:
81.0 mm = 3.189"
81.1 mm = 3.193"
are you sure it is not 81.01mm? VADIS and VIDA both say to measure the piston diameter 42 mm from the top of the piston.

Talk to Hasings about what ring to use, they have a very helpful tech support staff. I spoke to a woman who has been doing this for years, and she can rattle if off. Most ring sets come in oversize sets, and that is what you might need here, but the size difference is odd. Measure each piston to see if they are all the same.

[andyb5]

According to Heavyiron's posts on Swedespeed, they're Volvo OS1 pistons.
See here: HeavyIron's for sale thread

[wizzard_al]

OK, then measurement is just slightly off. Still, the stock Volvo sizes don't quite match the measurements, but if the top ring groove is wide enough, then stock ring sizes will work.

[Prospero]

Andy and Wizzard_al, thanks both for the help.

Measured the pistons again... this time while sitting and taking my sweet time. 81.11mm @ 42mm from the top, as per your comment. The help is insanely cool! Much appreciated again guys.

Yeah, for the life of me I can't figure out what is wrong with this motor. It had a serious blow-by issue and the pictures in my album of the motor... I really think that the way the pistons are fitting in the cylinder are to blame. They looked to be offset and there is way more piston ring showing on HeavyIron's motor than say on my stock GLT motor sitting next to it. Does this look strange to you guys as well? The link in the first post has the picture album; the pistons in the cylinder images start about 5 pics in...

Thanks guys! I'm pulling the stock pistons out of the 2000 motor tonight and will take a good look at them and compare them to HeavyIron's motor. Not sure if his build used new style pistons or what... but the ring differences are just funky.

Gonna finish pulling my head off the 00 motor tonight. Hope to have bent rods in my hands by dinner time. Fun, real fun

[Johann]

Measure the bore of the block the pistons were used in.

If the pistons aren't OEM there is a change they need to be measured at a different height.
It looks like an oversize 1 bore, 81.2.

[wizzard_al]

^^^^
What Johann said. Just going to say the same thing.

[Prospero]

Johann,

Long time no see man! It's been what, 4 years? Good to hear from you bro!

Yeah, I will measure the block later today since there are more questions than answers at this point.

Appreciate all the input all!

So a little update on my slavery last night. Spent about 12 hours pulling off all of the bits and got to the pistons in my 2000 motor. Found something that shocked the hell out of me! Get this, the bores look like they were honed yesterday. I've added the photos to my album in the first post. Take a look! It's insane since this motor is supposed to have 100k miles on it. Oh, and seafoam FTW. Intake valves and running bits are clean enough to eat off of!

Cheers, gonna go soak in a hot tub and get the soreness out of the back!
M@

Johann, on 20 January 2012 - 09:16 PM, said:

Measure the bore of the block the pistons were used in.

If the pistons aren't OEM there is a change they need to be measured at a different height.
It looks like an oversize 1 bore, 81.2.

[lookforjoe]

Prospero, on 21 January 2012 - 02:57 PM, said:

Get this, the bores look like they were honed yesterday. I've added the photos to my album in the first post. Take a look! It's insane since this motor is supposed to have 100k miles on it.

That's normal. Look at the wear in the top of the bores; that's why you need to measure for wear/out of round. You can see the banding where the wear is taking place.
It would be easier if you just post the pics here, instead of us having to go through the album to figure out which one you are referring to at any given time.

[TRACStar]

When I built my bottom end I ordered stock sized rings in case the bores needed a quick hone. My block had <70K and looked brand new and measured out fine. I didn't even need a reamer for the carbon lip at the deck, a little 2+2 and a rag took it right off.

[Prospero]

Thanks all for all the help and good input!

Spent a bit of time today and ended up swapping my original pistons onto the new rods. Seems that the OE+1 pistons wouldn't even fit into the bore period. I tried to measure the running gap and hell, couldn't get the skirt into the engine after pulling my OE stuff. So, that made my job easy. No need to worry about the OE+1 pistons any longer. Kinda bummed since they were all balanced; but screw it. The rods #1 and #2 were bent so bad when I pulled them out of my motor; I'll be happy just to drive the car again.

Anyhow, now I need to take an easy-out to a broken pan bolt out tomorrow. Exhausted from all this work. (also installed a turbo back system on a friends WRX, oil change, diff oil change, and Cobb access port tune.)

Time for pain killers and sleep!

Cheers,
Matt