AA type 4 pistons - wrist pin offset?

purity

I've searched, but couldn't find an answer to this: Does 94mm flat-topped pistons for a Type 4 engine, from AA Performance have offset wrist pins? I've measured in every possible way, but couldn't seem to find any difference between left and right. How much is the offset supposed to be?
_________________
- '67 1300 (Original)
- '71 1302 (Daily driver, TIV-engine going in)

The Noof · Samba Member Joined: January 25, 2005 Posts: 4346

If the pistons have a direction arrow, it's for that reason:pin offset.

MRRAGPICKER · Posted: Mon Mar 09, 2009 6:54 am Post subject:

My AA pistons had the arrows and valve reliefs. The arrows were all the same. If I had installed them by the arrows, one side of the engine would have had the valve reliefs 180 degrees off. I contacted the vendor and they said to go by the valve reliefs, that the arrows were wrong and that they were aware of the problem and were making sure none go out like that again.

The Noof · Samba Member Joined: January 25, 2005 Posts: 4346

Viande · Posted: Mon Mar 09, 2009 7:22 am Post subject:

purity · Posted: Mon Mar 09, 2009 7:54 am Post subject:

Mine have no arrow, but they have "STD" on the lower half (seen from above), and valve reliefs (extra material for cutting valve pockets). The reliefs and "STD" are on the same piston-half.

I've tried measuring them, but can't seem to find any big offset. How big is the offset supposed to be?
_________________
- '67 1300 (Original)
- '71 1302 (Daily driver, TIV-engine going in)

miniman82 · Posted: Mon Mar 09, 2009 2:12 pm Post subject:

purity · Posted: Tue Mar 10, 2009 3:18 am Post subject:

I was just wondering, because someone mentioned that the offset would end up the wrong way on two of the pistons if the offset had the same direction in relation to the reliefs on all pistons.

This makes sence when I think about it, because the rods "enter" the cylinder from the bottom on #3 and #4, but from the top on #1 and #2. As far as I've understood the offset is there to compensate for this?

I'll try and measure some more, but in what direction is the wrist pin supposed to be offset on say cylinder #1, towards the top or the bottom of the engine?
_________________
- '67 1300 (Original)
- '71 1302 (Daily driver, TIV-engine going in)

Type 5 Joe · Posted: Tue Mar 10, 2009 5:10 am Post subject:

I know of no aftermarket piston that features wrist-pin offset.... Besides Mahle / Cima.

I would doubt if AA is doing this based on price and Country of Origin.

I don't remember which way the factory off-set is , but you just need to check a stock piston.

If the extra valve relief material is larger for the intake valve, then there should be no question as to how they are installed.... Mark your own arrows, and ignore any that are Factory. Nice. Rolling Eyes

Why does AA not answer these questions? I would contact them, and post the answers given here.

lostinbaja · Posted: Tue Mar 10, 2009 5:11 am Post subject:

Why would you want anything that was made in China, if you have a choice?
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Type 5 Joe · Posted: Tue Mar 10, 2009 5:29 am Post subject:

I would like to use those pistons as a projectile, and shoot them back at the Chinese given our recent scuffle with their Navy. Twisted Evil

westcoast-paul · Posted: Tue Mar 10, 2009 12:55 pm Post subject:

don't throw them away - keep the cylinders, use KB pistons from eurosport. Laughing

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- Paul

Lionhart94010 · Posted: Sun Jul 31, 2011 1:03 pm Post subject: T1 Wrist-pin offset

Although this thread is quit old, I haven’t had much luck searching for what the stock wrist-pin offset is for a T1 based engine, I asume all Cima/Male & Stock will use the same offset…

I’ve found a reference that piston pin offset is still done to reduce slap - but typically in the 0.25-1.0mm,

On the Gene Berg website he refers to:

modok · Posted: Mon Aug 01, 2011 12:06 am Post subject:

there is no vw spec, it is up to the piston manufacturer

1-2mm is probably correct
It is easily measured with calipers

offset rod? nope
rod offset refers to how the rod bearing is not centered undeer the piston fore and aft. It has nothing to do with pin off-set

craigman · Posted: Mon Aug 01, 2011 9:04 am Post subject:

Isn't the offset on the bottom of the centerline of the cylnder?

RockCrusher · Posted: Mon Aug 01, 2011 12:57 pm Post subject:

Lionhart94010 · Posted: Tue Aug 02, 2011 12:19 am Post subject:

Thanks for the input, I did a bit more searching and have come up with a better visualization, now just need to measure the offset with a vise and a 90 degrees strait edge…

Measuring Wrist Pin Offset, they say a picture is worth a 1,000 words, now if some one would put up a picture of the measurement being taken, that would be cool :0)

Image may have been reduced in size. Click image to view fullscreen.

_________________
Current VWs 71 T2 Westy SO-72/6(Miami), 71 Crew Cab, 2015 GSW TDI
Other owned VW’s 59, 68 1500s, 69 & 71 Bug’s; 72 & 73 S-Bug’s; 67 Westy, 67 Deluxe, Other 71 DC, 72 KG GT that now lives in Australia, 12 JSW TDI, 2015 GSW TDI, 2023 Tiguan
VW technical information sights
thesamba - www.ratwell.com - www.shoptalkforums.com/ - www.vw-resource.com - http://www.type2.com/
http://bobhooversblog.blogspot.com/ - www.aircooled.net/gnrlsite/resource/articles.htm

modok · Posted: Tue Aug 02, 2011 2:07 am Post subject:

I don't think a pic is needed

-place piston upside down on table with pin in it
-with calipers, measure from the outside of one skirt to the far side of the pin, write that down
-then measure from the other skirt to the far side of the pin, write that down

the difference/2 is the offset

Lionhart94010 · Posted: Tue Aug 02, 2011 9:00 am Post subject:

Thanks Modok,

That is a simpler way to do it than using a vise and a striate edge as I had read on the web, I was able to do as you suggested with my digital calipers…

52mm and 55mm on both COFAP(2009 Piston) and Mahle(1970's Piston) = 3mm, /2 so the offset is 1.5mm on each :0)
_________________
Current VWs 71 T2 Westy SO-72/6(Miami), 71 Crew Cab, 2015 GSW TDI
Other owned VW’s 59, 68 1500s, 69 & 71 Bug’s; 72 & 73 S-Bug’s; 67 Westy, 67 Deluxe, Other 71 DC, 72 KG GT that now lives in Australia, 12 JSW TDI, 2015 GSW TDI, 2023 Tiguan
VW technical information sights
thesamba - www.ratwell.com - www.shoptalkforums.com/ - www.vw-resource.com - http://www.type2.com/
http://bobhooversblog.blogspot.com/ - www.aircooled.net/gnrlsite/resource/articles.htm

PlacerPuma · Posted: Sat Dec 15, 2012 7:56 pm Post subject:


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