Piston Pins

**IACS_HSV** · 12-29-2008, 10:51 AM

I'm changing my stock pistons for forged Mahle items, but aim to re-use the standard rods - are there any special precautions I should take when removing the pistons from the rods (i.e. heating etc.), or do I simply press the pins out and hope that no damage occurs to the small-end?

**mark21742** · 12-30-2008, 02:58 AM

Originally Posted by IACS_HSV

I'm changing my stock pistons for forged Mahle items, but aim to re-use the standard rods - are there any special precautions I should take when removing the pistons from the rods (i.e. heating etc.), or do I simply press the pins out and hope that no damage occurs to the small-end?

find a buddy with a press or let a shop do it, I wouldn't use a hammer. with a press they will slide out pretty easy.
since you have it torn down I'd put a set of ARP rod bolts in too

**IACS_HSV** · 12-30-2008, 05:32 AM

Thanks Mark, already have ARPs to go in! Will extract using hydraulic press rather than by *percussion* press!

**bronko91** · 01-13-2009, 12:31 PM

I am assuming you have an LS1 press pin and not the LS2 floating pin. If you can, convert to floating and not press. I hurt a piston in the LS1 so I bought a stock piston and pin. While I did not use the tool in the book, I did use a press. I chilled the pin and heated the rod in an oven.

I was later told upon the next rebuild that the LS1 pin does not like getting pressed on except at the factory. My pin walked out of the piston and into the cylinder wall ruining the block.

The LS2 is a floating pin and far superior.

**IACS_HSV** · 01-14-2009, 03:04 PM

Thanks mate.

It's an LS1 with pins pressed into the small end of the rod. I'm hoping to re-use the stock rods with ARP's as discussed above. I've turned up a nice tool which supports the piston skirt correctly but I'm having difficulty getting the old pistons off the rods. The pins are so tight that my fly press will not touch them; however, I've got my local engine shop on the case now (they have LARGE hydraulic press)!

The Mahle's come with new pins and spiral locks. I wasn't planning on using the locks and was aiming to rely on the pressed in pins but you've got me worried now about walking pins! Perhaps I may use the spiral locks after all but to do this I'll need to be extra careful to get the pin in the correct position to eliminate any side loading...

Any one tried this before?

**bronko91** · 01-14-2009, 04:54 PM

If they come with spiral locks it they float. Mahle sells both but remember, the piston and pin is what is pressed, not the rod and pin. So yours float. You will be fine.

**IACS_HSV** · 01-14-2009, 05:17 PM

Originally Posted by bronko91

If they come with spiral locks it they float. Mahle sells both but remember, the piston and pin is what is pressed, not the rod and pin. So yours float. You will be fine.

No, my pins are interference fit in my stock LS1 rods - the stock pistons float on the pin... and so will the Mahle's

**bronko91** · 01-15-2009, 04:16 AM

Ah, I ran out and looked at mine and you are right, stockers are pressed pin to rod, however read this:

While stock GM pistons have their pins press-fit into the rods (thereby limiting how far the pin can travel out of the piston's pin bore), performance pistons use so-called "spirallocks" to hold the piston pin in place. This makes for a "full-floating" piston pin, which gives more bearing surface for the piston pin (in the rod and in the piston as opposed to just in the piston), reducing friction and thereby increasing component life. The spirallocks come as shown on the right, but must be stretched open like a slinky in order to get them ready for installation (left).

This came out of this article:

http://www.gmhightechperformance.com.../rod_prep.html