AAZ Piston pin diameters

[CrazyAndy]

It's more likely than anything that you will not notice a difference.  But your engineer friend has 2 things confused, rod length and stroke length(get the giggles out before u continue reading).  A shorter stroke is better for higher rpm power.  The stroke length is determined by the crank shaft which you are not changing.  A shorter rod actually is better for lower end power because the rod gets closer to a 90 degree angle which produces more torque.  The down side is that the rod flops back and forth more so it is a bit weaker and not as safe at higher rpms,  but I don't think u will notice much if any difference and I don't think these slightly shorter rods will at all effect the life of your engine

I agree, but to chime in on terminology, the rod getting closer to 90 degrees when optimum fuel combustion takes place is known also as rod angularity.  It's one of the ways they got more torque out of the type 4 air-cooled engine, along with a longer stroke crankshaft.  But you are right about rod angularity limiting your top end and red-line, since it increases your reciprocating assembly speed.  Pistons move faster in their bores and have a little more side loading on the cylinders.  Overall, tough, I wouldn't worry about it at all as these engines can take the punishment in stock form (obviously).  You might also gain a little more torque out of the setup which would help you on those hills. 

And boost helps too.

P.S.  On your trans, what trans are you running?  I have been told by one Vanagon enthusiast the air cooled transmission actually had higher FD/high gear combo.  IDK, but feel free to chime in on that.

[Gizmoman]

Thanks for the giggles TrevOrbr -  I'm not worried about it really - just wondering if any torque curves existed for the two different rod length engines.
I agree with you and he also agreed about the crank journal offset being obviously the most significant to torque - I mentioned it as well. He was pointing out that the torque curve will be higher in the RPM curve - but won't torque (the peak of the curve) be lower with the shorter stock rods? It's not that there's more torque or less torque - just torque in a different place.

My van has the gasser four speed - what they refer to as the six-rib. I just went through it last fall. I also have 16" rims and the tallest tires I could stuff into the wheel wells (I'll post the size and final ratios tomorrow from the shop computer).
It seems to run around 3850 at 70-75 MPH on the speedo which is off due to the tire size. I was running 15 lbs on a K14 with the fuel screw in a bit. It ran at 10 most of the time and 15 plenty (Cal mountains).

What I'm hoping to hear is that the shorter rods will be better (even if I can't tell) for this application - not worse. I guess it a bear sh**t/woods sort of thing. One thing for sure, the stock pistons have more mass in them than the ones with the smaller pins. That should help handle a bit more heat than it did.

OK, I've proof read this till I confused myself - oh well, I'm posting it anyways!

[RabbitJockey]

i think power wise u would theoretically gain power through out the whole rpm range the down side is higher risk of failure, but there are a million other factors, which is why i think any noticeable difference will be minimal once the engines all back together

[Gizmoman]

As promised, here are my Vanagon gasser tranny ratios (1st to 4th):
17.2746   9.4142   5.6211   3.89364

My tires are 215/65R16

Revolutions per mile = 724 which should put the RPM's at 3500 at 74 MPH.
These numbers come from a Vanagon transmission ratio calculator I downloaded.
(Actual reality may differ)
I download the chart (excel) here http://www.google.com/url?sa=t&rct=j&q=vanagon%20transmission%20ratio%20chart&source=web&cd=1&sqi=2&ved=0CDcQFjAA&url=http%3A%2F%2Fmembers.shaw.ca%2Fvwdiesel%2FVanagonTransRatios.xls&ei=U2CuUMGMI6q22gXdxIHoAw&usg=AFQjCNG-1BX8XdmTAsHWdzGLZif-OtDcnQ