Engine Rebuild Note, Rod Notching

Post by **Amskeptic** » Mon Apr 16, 2007 7:13 am

From a PM:

mycoleptodiscus wrote:

why did VW say to cut an oil groove in the rods in their service bulletin. My machinist is VERY particular and won't just modify stuff. He wants to know WHY first.

Rod notching (1.5mm V-groove at exact top of crankshaft end of the rod's bore) is a critical improvement for cooling the pistons on 2.0 engines. Tell your machinist that hard hill pulls in hot ambient conditions have been noted to expand the pistons too rapidly, causing a rash of seizures particularly as engines get dirty over their operating lives. Tell him to also allow a little more cylinder/piston clearance than the factory minimum tolerance (if yours are near the factory minimum). It can be accomplished by extra honing of the cylinder walls, but be careful, if your top compression rings have the black moly stripe, he must use a finer grit hone than the usual aftermarket cast iron rings. This is important.
Colin

bottomend · Post by **bottomend** » Tue Apr 17, 2007 11:29 am

Please look into doing a "three groove rod". There are lots of T4 guys doing this with stock rods thesedays. STF or Jakes site should have the info.

satchmo · Post by **satchmo** » Wed Apr 18, 2007 6:28 am

My machine guy recommended two or three grooves on each side of the rod (he is a racer and has 35 years in the VW business, so I guess there is some credibility there). We ended up putting a 4mm wide groove 1mm deep at the top (toward the piston) and one at 180 degrees from there, so two grooves on each side of the con rod. We'll see how that works, but I really have nothing to compare it with since I have never had a 2 liter engine before.

Tim

Bleyseng · Post by **Bleyseng** » Wed Apr 18, 2007 6:44 am

OK, what is the reasoning for the two or three groves? Oil spraying backwards off the rod seems silly..oil spraying to the bottom of the piston to cool it make sense.

Is it to just bleed off oil pressure on the rods?

satchmo · Post by **satchmo** » Wed Apr 18, 2007 6:53 am

Total speculation on my part here, but I think this just sprays more oil around generally. How much this may or may not cool the pistons, I have no idea.

Tim

Post by **Amskeptic** » Wed Apr 18, 2007 10:49 am

Typical Idiotic American Excess.
Please, these are horizontal engines. If you start spraying oil all over the damn place, you will have oil consumption and carbon build-up. If you start tripling the bleed-off volume from the connecting rod oil supply, you will be screwing with oil pressure. For crying out loud. Do not screw with your engine's engineering unless you have already gone way off the path with super-dooper "Hi-Flo" performance oil pumps and total circle rings with Xtraa Oil Control Technology.
If VW said stick in a 1.5mm groove to settle down a slightly too expansive 2.0 piston, fine.
Colin

Bleyseng · Post by **Bleyseng** » Wed Apr 18, 2007 9:43 pm

thats why I said it sounded silly......

bottomend · Post by **bottomend** » Thu Apr 19, 2007 11:11 pm

All I'm saying is that it should be looked into. No need to get all dogmatic on my tail guys!

There are respected folks out there who have done this mod with good results and we're fountunate enough that they have also shared their info with the rest of us. If I could find the threads, I'd post em, believe me.

Now that I think about it, it might of been ray greenwood on STF.

germansupplyscott · Post by **germansupplyscott** » Fri Apr 20, 2007 1:41 pm

the other notches are to spray oil on the cam.

bottomend · Post by **bottomend** » Fri Apr 20, 2007 7:49 pm

... and we all know how well the original cams held up in these wonderfully balenced german engineered spaceship/futuristic time travelers, right?

Lesson here; research good. rebuff bad.

Post by **Amskeptic** » Sat Apr 21, 2007 6:03 am

bottomend wrote:... and we all know how well the original cams held up, right?
Lesson here; research good. rebuff bad.

And what is your research on original cams?
Since none of these performance people will use the original cams (bad breathing yada yada yada), why would they be notching the hell out of the rods? For their aftermarket cams? I think so. Which are known to have quite a few catastrophic instances of going flat with the crap lifters out there.

So what is your point?
Too many people dismiss the original engineering without looking at the real issues. Every worn original cam I have ever seen has come from neglected engines. I can only speak from personal experience as far as cams. My original cam gave 200K, the Bus Depot cam has 80,000 on it with a set of their Febi lifters already eaten up and replaced at 67,000 miles.

Notching the rods to lubricate the camshaft in a stock engine is completely over the top armchair engineering. Splash lubrication is splash lubrication. You can't Extra Splash splash-lubricate a camshaft. If the thing is drenched with oil, it is drenched with oil. The oil film is either there or it isn't there.

I will defer to those who modify their performance engines, because I can't even begin to chase down the changing variables of high-lift cams and heavy springs.
Colin

Bleyseng · Post by **Bleyseng** » Sat Apr 21, 2007 10:34 am

I agree with Colin.....bullsh*t engineering..

With high lift cams goes high spring tension and loads...extra oil splashing isn't going to help there.....revised lifter face grind does help.

bottomend · Post by **bottomend** » Sun Apr 22, 2007 1:13 am

I've yet to teardown an aftermarket high mileage cams and calculated wear patterns but I have torn down about a dozen high mileage stock cammed engines and everyone had the pretty pattern that indicates extreme cam/lifter wear. Does this have anything at all to do with scientific research? Nope. Does it have anything to do with me trying to sell something to someone who may not really need the glorified aftermarket part? Nope. Does it have anything to do with me bringing up something I read about on another repspected VW forum board and thinking it might be of discussion value here without fear of haveing words like "idiotic" and Bull* hit hurled at me ... YES.

I just feel like a bit of an attack going on here guys. I thought the harsh language was supposed to be left out of this forum board. If I'm perceiveing this ultra-sensitively here... than it's my bad and I'll chill out, but if there is something else going on, then please take that attitude somewhere else because using language like that does nothing to move ANY conversation forward. It sets up walls and is simply not respectful. Words carry weight. Please lighten the load a little....

Bleyseng · Post by **Bleyseng** » Sun Apr 22, 2007 7:38 am

=D>

That make you feel better?

Not trying to rainon your parade but I don't see the use for the 3 notches. The oil sump of a type 4 is bathing the cam in oil plus the oil from the crank/rods is flung all over the cam, that should be enough oil. I too have seen lots of stock high mileage cams with lots of wear esp hydro cams. The few aftermarket cams I have seen seem to have the same wear as the VW ones. I have yet to tear into a Jake cam'd engine to check cam wear.

bottomend · Post by **bottomend** » Sun Apr 22, 2007 12:06 pm

hormones kickin up... bills due... fridge is empty...flywheel seal leaking... need a shower....place is a mess...just cost $48 to fill the bus ( again!) Thanks for keeping this conversation above ground and polite.

Explainations are always better than expulsions.

Anyway, I wish I could find the thing about the notches. It made sense to me at the time I read it , but man I'm no enginner ( obviously) and again, I'm not trying to sell anything and I dont really have an adgenda to promote. Honestly, the best sounding engines I've heard to date have always been stock.

I guess the sarcasm I used when saying that the stock cams are "highly engineered and never had problems" ect. opened myself up for an attack. Touchee'!

Itinerant Air-Cooled

Itinerant Air-Cooled

Engine Rebuild Note, Rod Notching

Engine Rebuild Note, Rod Notching