just how offset are OE rods?

[BFB]

anyone ever measure or read about how much factory connecting rods are offset?
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"how am i supposed to torque the rear wheel nut to 250 ft lbs??? " - clonebug
An interesting thing happens in forums where everyone starts parroting the same thing and "common knowledge" takes over.
Most experts aren't.

[BFB]

I guess its one of those things that Berg didn't notate so none of the experts know...
_________________
"how am i supposed to torque the rear wheel nut to 250 ft lbs??? " - clonebug
An interesting thing happens in forums where everyone starts parroting the same thing and "common knowledge" takes over.
Most experts aren't.

[Dougy Dee]

You, too, could measure a stock rod...

I get 1mm...

[redhot]

According to a 1968 print.

Since February 1963.
34hp engines 1.0mm
Other engines 1.5mm

The print refers to rods otherwise of the types 25/30hp, 34hp, 1300ccm up to Jan.1966 and 1500cc up to Aug.1965 plus 1300, 1500 and 1600 otherwise.

So would assume all those are included in the statement (34hp and up).
If they later changed also the 34hp...?

[BFB]

[raygreenwood]

[Dougy Dee]

[BFB]

Im getting the feeling ya’ll are talking about the small end being offset side to side , not offset parallel to the big end’s center line ?

Im wondering if , say the stock wrist pin is off centered, is it just in the piston or the piston & rod both?
IE if you flip the stock rod so tang is down with using non-offset pistons, would it change the geometry of the crank & wristpin ? Or is the rod’s big & small ends parallel?
Theres always been talk of the rods needing to go tang up because their offset, but i got a feeling their not. And even if they were i dont see how itd matter aside from making a goofy off centered rod. Thats why im asking if anyone actually knows.
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"how am i supposed to torque the rear wheel nut to 250 ft lbs??? " - clonebug
An interesting thing happens in forums where everyone starts parroting the same thing and "common knowledge" takes over.
Most experts aren't.

[redhot]

My understanding is that there are two offsets with two differing objectives;

- connecting rod offset (in connecting rod itself): center the pistion in the bore engine lengthwise front to back. This I assume stem from how the engine block, crankshaft and piston bores all stack up packing wise including re-use existing forming tools, parts, optimizing tolerancese etc.. So one can move them over btw. sides without flipping them.

According to a search here, but not available on website anymore?

[modok]

How offset are the rods?

One would hope the right amount for the crank

So how offset is the crank?

The CASE did not change from 40 horse to 1300/1600
it was the crank and rods that changed offset, to have a thicker cheek between rod throws.

It just takes some time with dial calipers and a flat surface to figure it out with what parts actually exist. Aftermarket stroker cranks sometimes have LESS.

I figured out half of it before but I don't recall what that number was exactly for all brands of this or that.
GOood question. Good luck

[BFB]

wristpin offset in the piston should be easy enough to measure. but rod offset ( not side to side ) seems a different story to me, unless im overthinking it. the only way I could see to measure if theres any rod offset would be to mock a rod up on a crank with a piston that is known to not have any offset then see if when these parts are lined up 180 if the piston is at true TDC. or set the piston to TDC and see if the crank is off by any number of degrees.
I bet theres a tool for this somewhere....
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"how am i supposed to torque the rear wheel nut to 250 ft lbs??? " - clonebug
An interesting thing happens in forums where everyone starts parroting the same thing and "common knowledge" takes over.
Most experts aren't.

[redhot]

Exactly what offset are you chasing?

[redhot]

Would be interesting to see a follow up.

My uinderstanding is that rod is offset I guess what you call "side to side" (engine lenght axis) while pistion boss is offset "top vs. bottom" (engine vertical axis).

What would be interesting - but have been discussed before - is what the use of non offset rods then has towards either/both performance or service life. While worthwile back in major serial production, maybe not for most of recreational use. But maybe important for high performance.

Or said differently - when should one maybe use original rods for "normal use" due to a tolerance stack up in the case, crankshaft and piston bores?

[BFB]

I dont think the rods are offset at all , i think it’s just in the wristpin. If you think about it, offsetting the small end to the big end would only make a weaker rod.
The small end does seem to have a little more meat on one side ( fore & aft ) but i dont see that making any difference and dont see why itd be done other than maybe production process. Theres so much room for the rod inside the piston that it’s not like a little more / less meat on one side or the other provides some clearance or something.
_________________
"how am i supposed to torque the rear wheel nut to 250 ft lbs??? " - clonebug
An interesting thing happens in forums where everyone starts parroting the same thing and "common knowledge" takes over.
Most experts aren't.

[RWK]

Ther is a pic of the offset in the 61-65 Bently workshop manual.
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73 Type 181
63 Type 113
63 Type 261- 428 071
62 Type 241-378 025 178 530

[Dusty1]

[BFB]

I think yall are making the assumption that because a wristpin is offset that the rod is too. the term rod offset is just used synonymous with wrist pin offset and again, ppl assume that the rods are offset because of a tab. and somewhere along the line its become common knowledge that they are offset but not a single person so far actually knows for sure.
all ppl know it that the casting tab goes up on OE rods which means bearing tangs go down, so then by that, all other rods missing casting tabs still need bearing tangs to face down as well too. why? apparently just because thats how its been done so we do it that way and were gunna keep on doing it that way because its been done that way, and if we do it that way there must be a reason and that reason must be because the rod is offset otherwise it wouldn't matter, but it does matter because thats the way we do it. so therefore thats why OE rods are offset. maybe not aftermarket rods but they still need to go the same direction as OE regardless...
_________________
"how am i supposed to torque the rear wheel nut to 250 ft lbs??? " - clonebug
An interesting thing happens in forums where everyone starts parroting the same thing and "common knowledge" takes over.
Most experts aren't.

[redhot]

It is in a VW publication, that the rod itself has a side-to-side offsett... With a drawing - of the rod.

[BFB]

ok, so rod offset is just common knowledge bullshit.
yes the small ends do seem to be thicker on one side than the other as far as front to back of the engine, but as I said before thats not what im talking about nor would that even affect anything because of the floating wrist pin.
what im talking about is small end offset to the crank, what ppl seem to confuse or correlate with the wrist pin being off centered in the piston. and that because OE pistons have a tang , that the tang must serve as the same purpose as the arrow on the piston, giving direction as to how its supposed to be mounted.

SO, I drew up and printed a mock crank that spins in a base with a wrist pin that slides up & down to mimic a vw, and yes it is spec correct so I can put a vw rod on it. I havent yet as I forgot to bring one home but in all reality, it's a moot point anyhow.
I also drew up & printed several connecting rods, all 137 mm from center to center, but with 0, 1, 2, and 10 mm offsets.

my conclusion, there is no such thing as ROD offset because its either 137mm center to center or its not. ie, if you offset the end of the rod but its still 137mm then you just made a dog legged rod is all you did. if it varies from 137mm then all you did was make a longer or shorter rod, and we know what that does.
as you'll see in the pics below, the altered offset doesn't change any positioning and matter of fact you can even use the 0 offset and the 10mm offset together , as in on the same journal, and theres no binding. fyi, theres .5mm gap between main 'journal' and the big end of the rod, not enough play that it'd allow for binding otherwise.

so you can mount your rods tang up, tang down, makes no difference other than your OCD and doing things the way they've been done because thats how we do it.
enjoy the pics....

_________________
"how am i supposed to torque the rear wheel nut to 250 ft lbs??? " - clonebug
An interesting thing happens in forums where everyone starts parroting the same thing and "common knowledge" takes over.
Most experts aren't.

[EVfun]

The rod offset that comes to mind for me is how the center of the rod journal is not the center of the cylinder bore. I think VW added a little extra metal between rod journals 1 and 2, and also between 3 and 4. This shifted the center of the rod journal off of the center of the cylinder bore. I'm not positive about this on the VW engine, but I have seen it on other engines.
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