TheSamba.com :: View topic

Fri Feb 28, 2020 6:33 pm

Read plenty of posts for and against the WV service bulletin on notching the 2L GD connecting rods for better piston skirt lube, but couldnt find any pics of anybody doing this. Other than the the sketch in the service bulletin.

Decided that for Ryans engine rebuild, that I would do this mod and maybe throw some pics up for anyone else considering it. The bulletin has a rough sketch that shows a v notch with a depth of 1.5mm. Very non descript as far as location (other than a sketch), and dimensions. Mic’d up the original rod width at that point and notched with a hand triangle file, cleaned up with a jewelers round file, to 3 mm less than start width. Its not very precise of a measurement, but for hand filing to a tolerance of 1.5mm, i figure it will work.

We are fortunate that we have one of the few 2L cases that arent blown out and /or been rebuilt before. Standard bearings, no cut crank, and a modest cam replacement should bring this ole boy down the road feelin bad.

Mon Mar 02, 2020 7:20 pm

The mod is to get oil up into the piston and cylinder for added lubrication and cooling. I have decided that using a 3mm chainsaw file and making a "U" notch verses "V" makes sense.

Mon Mar 02, 2020 7:31 pm

Agree on the “ u “. In fact I think it was based on one of your older posts about this mod that you mentioned the less stressful edges of a “u” vs “v” that led me to run my round file to finish. May not look it, but the edges are smooth and radiused.

Tue Mar 03, 2020 3:30 am

I imagine they wanted the V cut for a mist/dispersion pattern?
.....But I digress & frown upon this barbarity. Can't look.

Tue Mar 03, 2020 9:01 am

It's also for piston cooling as it sprays oil up to the bottom of the piston.

Tue Mar 03, 2020 9:45 am

timvw7476 wrote: I imagine they wanted the V cut for a mist/dispersion pattern?
.....But I digress & frown upon this barbarity. Can't look.

There is very little pressure pushing the oil, it is mostly just the oil being thrown from the big end of the rod as the rod experiences acceleration towards the crankshaft over the top half of the stroke. All the notch does is encourage more oil to spin off towards the piston verses away from it.

FWIW a 1.5mm deep "V" cut has about 80% of the area of a 1.5mm deep "U" cut so there would not be much difference in pressure differential across the cut to do any misting.

Tue Mar 03, 2020 8:21 pm

Wildthings wrote: timvw7476 wrote: I imagine they wanted the V cut for a mist/dispersion pattern?
.....But I digress & frown upon this barbarity. Can't look.

There is very little pressure pushing the oil, it is mostly just the oil being thrown from the big end of the rod as the rod experiences acceleration towards the crankshaft over the top half of the stroke. All the notch does is encourage more oil to spin off towards the piston verses away from it.

FWIW a 1.5mm deep "V" cut has about 80% of the area of a 1.5mm deep "U" cut so there would not be much difference in pressure differential across the cut to do any misting.

It must be a safe mod, no one ever posted 2.0L rod failure @ the VW app'd
slot yet. : ) maybe I;ll do it to some 1800 rods first, wade intoit so to speak.

Wed Mar 04, 2020 1:11 am

Bleyseng wrote: It's also for piston cooling as it sprays oil up to the bottom of the piston.

That's almost ENTIRELY what the TSB was for. It wasn't about rod failure, oil temps, or piston temps. The stock 2.0L pistons could smear their skirts on the cylinder walls from heat expansion in buses. Deletion of the "head gasket" sealing ring allowed heat to transfer into the cylinder sooner, which helped it expand/clear the piston, and the TSB-recommended piston/cylinder clearance was increased as well.

The 1700/1800 engines did not suffer the same failures as the 2.0 bus engines, so those rods do not need to be notched. The notch-sprayed oil is purely intended to cool/shrink the 2.0L pistons.

Robbie

Wed Mar 04, 2020 2:01 am

This is how I found this engine when opened up. Maybe it helps avoid this from happening, along with the shim and piston clearance.

Wed Mar 04, 2020 7:37 am

asiab3 wrote: Bleyseng wrote: It's also for piston cooling as it sprays oil up to the bottom of the piston.

That's almost ENTIRELY what the TSB was for. It wasn't about rod failure, oil temps, or piston temps. The stock 2.0L pistons could smear their skirts on the cylinder walls from heat expansion in buses. Deletion of the "head gasket" sealing ring allowed heat to transfer into the cylinder sooner, which helped it expand/clear the piston, and the TSB-recommended piston/cylinder clearance was increased as well.

The 1700/1800 engines did not suffer the same failures as the 2.0 bus engines, so those rods do not need to be notched. The notch-sprayed oil is purely intended to cool/shrink the 2.0L pistons.

Robbie

I see zero harm in notching the 1700 and 1800 rods, if doing so gives a 5°F cooler piston at the top of a long western climb, it is worth it in my book.

Wed Mar 04, 2020 8:52 am

What about the increased heat in the oil cast off the pistons afterwards? The smaller Type 4’s typically run at a higher RPM which can result in higher oil temperatures. No science here, just speculating on the internet. :)

Robbie

Mon May 09, 2022 11:24 am

myself and colin K just disassembled my 2L fi bus engine to find 1- 3 scored cylinders that were apparently causing quite the noisy ruckus and 2- 4 un-notched connecting rod re: tsb # whatever could that be the cause and effect?

oh and i forgot to mention the engine had been assembled by our local 'expert' vw engine builder and it only had 2100 miles on it

Mon May 09, 2022 11:40 am

that problem is most likely too much heat related. Mixture, timing, amount of air cooling the fins etc.. Lack of all the tin can do it too. Pushing the engine too hard in a sustained manner can also do it. or the guy who put it together could have not been as clean as needed. I do have to wonder, was that the bottom side of the piston? If so were the under cylinder tins in place? Were the piston arrows in the correct direction?

Mon May 09, 2022 1:14 pm

Is that 1 thru 3 or 1 and 3, meaning 2 and 4 were ok?

Looks like lack of lubrication and/or like SGK said, heat. Maybe a mouse nest on that side of the engine or something blocking airflow.

How do the rod and crank bearings look?

Mon May 09, 2022 2:05 pm

still tearing into the rest of the engine, only 1 out of the 4 cylinders was not scored, # 3 was the worst- there were no omissions of the oem tin and related parts, the engine was not clogged or dirty- it did run a bit rich based on the tail pipe but based on oil temp it was in the normal range as far as i can remember.....the other side of the barrel of all 3 was damaged, in general one side was worse

Mon May 09, 2022 3:36 pm

Maybe someone fired it up without oil at some point? Could also have been an engine low on oil that was pumping a lot of air through the galleys and there just wasn't enough lube reaching the pistons. If your crankcase ventilation clogs and pressure builds up in the case, most all the oil can be blown out within minutes.

Sun May 15, 2022 3:49 pm

would you notch only one side of the connecting rod?

Sun May 15, 2022 4:27 pm

I did both sides. You don't go deep enough to compromise the bearing. The oil coming out of the bearing will tend to exit more toward the piston. I did not leave a V but rounded the bottom of the V so that it lessens the chance of a crack forming at that juncture over time. VW never thought these engines would be going thru multiple overhauls.

Sun May 15, 2022 6:55 pm

blatzer wrote: would you notch only one side of the connecting rod?

The idea is to get the oil that goes through the bearing to be thrown in mass towards the piston. The notch has nothing to do with the bearing itself as the oil has already done its job there. All it does is cause a higher percentage of oil to be thrown towards the underside of the piston, thus giving a bit of cooling and assuring the piston has sufficient lubrication. I see nothing to be gained by only doing one side of the rod. FWIW, I would notch the rods on 1700 and 1800 engines along with 2000cc ones. I don't believe there are any negatives to doing this.

Mon May 16, 2022 7:07 pm

skep, you wanna chime in here?