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2L GD connecting rod notch mod w/ pics
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Jetfxr69
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PostPosted: Fri Feb 28, 2020 6:33 pm    Post subject: 2L GD connecting rod notch mod w/ pics Reply with quote

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.



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Wildthings
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PostPosted: Mon Mar 02, 2020 7:20 pm    Post subject: Re: 2L GD connecting rod notch mod w/ pics Reply with quote

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.
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Jetfxr69
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PostPosted: Mon Mar 02, 2020 7:31 pm    Post subject: Re: 2L GD connecting rod notch mod w/ pics Reply with quote

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.
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timvw7476
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PostPosted: Tue Mar 03, 2020 3:30 am    Post subject: Re: 2L GD connecting rod notch mod w/ pics Reply with quote

I imagine they wanted the V cut for a mist/dispersion pattern?
.....But I digress & frown upon this barbarity. Can't look.
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PostPosted: Tue Mar 03, 2020 9:01 am    Post subject: Re: 2L GD connecting rod notch mod w/ pics Reply with quote

It's also for piston cooling as it sprays oil up to the bottom of the piston.
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Wildthings
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PostPosted: Tue Mar 03, 2020 9:45 am    Post subject: Re: 2L GD connecting rod notch mod w/ pics Reply with quote

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.
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PostPosted: Tue Mar 03, 2020 8:21 pm    Post subject: Re: 2L GD connecting rod notch mod w/ pics Reply with quote

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.
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airschooled Premium Member
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PostPosted: Wed Mar 04, 2020 1:11 am    Post subject: Re: 2L GD connecting rod notch mod w/ pics Reply with quote

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.

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Jetfxr69
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PostPosted: Wed Mar 04, 2020 2:01 am    Post subject: Re: 2L GD connecting rod notch mod w/ pics Reply with quote

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

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PostPosted: Wed Mar 04, 2020 7:37 am    Post subject: Re: 2L GD connecting rod notch mod w/ pics Reply with quote

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.
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PostPosted: Wed Mar 04, 2020 8:52 am    Post subject: Re: 2L GD connecting rod notch mod w/ pics Reply with quote

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. Smile

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