Piston pins---Press fit or full floating?

[Chatt69chgr]

Whats the best way to go on a 6000 and below rpm 440 that I don't intend to run at the dragstrip.  The thought of a spirolok failing and destroying my engine worries me.  Is there anything wrong with going the press fit route (assuming I don't heat up the end of the rod with a torch to press fit the pin like they did on TV recently).  I'am assuming I can find good aftermarket rods that use the larger diameter pin. 

What are the pros and cons?  And by the way, I am planning on using forged pistons. 

[John_Kunkel]

There's absolutely nothing wrong with pressed pins for a setup like yours.  440source has some nice looking rods that take the press fit stock pin.

[firefighter3931]

I agree with John....Those will work fine in your engine. For years guys raced with Pressed pin TRW 6-pack pistons and stock rods and those engines were very reliable. I have them in my 446.


Ron

[Blakcharger440]

How often do spirolocks fail? I have not heard of any failures unless incorrectly installed. 

[Chatt69chgr]

I don't know how often they fail.  In a correctly machined engine with correctly installed Spirolox they would probably never fail.  While surfing the net, I came across an article describing the engine damage that results from failure of these.  It wasn't pretty.  Apparently, they can fail for reasons other than improper installation.  If the rods are slightly twisted, it puts forces on the Spirolox that cause it to fail.  I am not really sure what such a rod would do in a pressed pin installation.  I had been looking at the rods that 440 source offered and noticed that the good H-beam performance rods they have at a real good price ($419) is only offered in a 0.990 pin which means Spirolox.  From the part number, it appears that this is a Eagle rod although they don't say.  Interestingly, Eagle makes this same rod with the 1.094 press pin diameter.  Of course, your piston choices will also determine which pin you will use----may only be offered in one or the other.  I was just curious as to why the Spirolox system is used at all.  Must be so the piston can be changed without specialized equipment to heat the rod to allow insertion of the pressed pin.  Just guessing.  Or are there other technical reasons why floating pins are used?  All this is part of my decision matrix in picking a rod and piston to use.  I did notice that the 440 source lower cost forged rods don't use ARP rod bolts.  If you wanted to use those, you would have to add about $50 for the bolts but you would also have to have the big ends resized if you did things correctly adding more $$.  So the $419 H beams start looking a lot better.  And it seems to me that the most important fastener in the entire car is the rod bolt.  You don't want to skimp on those.

[superduperbee]

I don't know how often they fail.  In a correctly machined engine with correctly installed Spirolox they would probably never fail.  While surfing the net, I came across an article describing the engine damage that results from failure of these.  It wasn't pretty.  Apparently, they can fail for reasons other than improper installation.  If the rods are slightly twisted, it puts forces on the Spirolox that cause it to fail.  I am not really sure what such a rod would do in a pressed pin installation.  I had been looking at the rods that 440 source offered and noticed that the good H-beam performance rods they have at a real good price ($419) is only offered in a 0.990 pin which means Spirolox.  From the part number, it appears that this is a Eagle rod although they don't say.  Interestingly, Eagle makes this same rod with the 1.094 press pin diameter.  Of course, your piston choices will also determine which pin you will use----may only be offered in one or the other.  I was just curious as to why the Spirolox system is used at all.  Must be so the piston can be changed without specialized equipment to heat the rod to allow insertion of the pressed pin.  Just guessing.  Or are there other technical reasons why floating pins are used?  All this is part of my decision matrix in picking a rod and piston to use.  I did notice that the 440 source lower cost forged rods don't use ARP rod bolts.  If you wanted to use those, you would have to add about $50 for the bolts but you would also have to have the big ends resized if you did things correctly adding more $$.  So the $419 H beams start looking a lot better.  And it seems to me that the most important fastener in the entire car is the rod bolt.  You don't want to skimp on those.

Floating pins/spirolox reduce friction and weight, also make changing a piston at the drag strip easy. For a street engine the pressed pins are just fine.

[suntech]

I would not rule a set of rods out, because of made for full float.
In 2 strokes that is the only thing used, and if used correctly there are no problems with the lockers. There are ofcause, like with everything else, a bunch of stuff that needs to be checked. Correct groove, correct locker, and use it only once. Works great in two strokes doing 10K rpm + 
I like this better than a press fit.