Inliners International Forums General Discussion Engines Pressed our bushed Connecting Rods?

Whats the diference?
What is better?
Do they require different type of piston pins?
Thanks a lot!

After you discover that you bought the wrong pistons and can't get the right compression ratio or valve clearance, bushed pistons allow you to remove them without damage. And perhaps salvage some resale value.

(grin)

regards,
Leon

So the only difference is that you can easily take the pistons off?
The bushed ones also have locks don't they?
Thanks again!!!

Yes the difference is you can take the piston pins out without a press or heat (normally anyway). You can use a retainer, like a spirolock or a round wire snap ring (whatever the piston is designed to recieve) or you can use aluminum or teflon thrust buttons on the end of the wristpin. Either way you have to keep the pin off the cylinder wall.

FWIW I prefer floating wristpins to pressed.

Hi. I was searching in the internet for some answers and found this:
Pin types article .

This article talks about fixed pin, semi-floating pin and full-floating pin. When you mentionated floating pins you were talking about something like the full-floating in the picture?

But we are talking about pins, pistons and I begin to think that the Connecting Rod is different for full-floating pin and fixed one. Am I right? Maybe the full-floating Connecting Rod has different clearances for this different type of pin?

I am a little bit confused. Because I asked about Rods (bushed or pressed) and I don't know if I understood. Can I say that bushed Connecting Rods are for full-floating pins and the pressed ones are for fixed pins?

I was taking a look at the Scat Online Catalog here:
Scat Online Catalog and I found this one interesting Rod:

CHEVY 6-CYLINDER

ARP 2000 7/16" CAP SCREWS
PART# 2-250-6000-2000A
SHORT# 66000206A
ROD LENGHT 6.000
CRANK PIN 2.000
WRIST PIN .927
B.E. WIDHT 1.050

Is this part for floating pins, right?

I am really sorry, but all this information I asked here are really important to help me choosing the right piston (and pins) & rod types.
And tips about JE forged dome 250 chevy pistons for using this 6" rod are also welcome.

Thanks a lot guys!

I have never seen (or heard of) the 'fixed pin' setup as is in the picture in your link where the pin stays in place in the piston and the rod rotates on it (learn something every day ).

I have only seen where the wrist pin is slightly larger than the wrist pin bore in the rod for a 'press' or 'shrink' fit. Between the two I prefer the 'shrink' fit (where you chill the pin and heat the rod) as it is more secure (in my mind anyway) and you are less likely to have a problem with galling as you assemble it.

The other two setups shown in the picture I have seen, the 'semi floating' type in various Flatheads, the 'floating' setup I have seen in Aircraft, VW's (air and liquid cooled), and Motorcycle engines stock.

If I am building an engine for performance (as opposed to a stock overhaul) I prefer the floating pin for ease of assembly, it also reduces the chance of the pin seizing in the piston on initial start up (rare, but I know a few people that have had it happen with pressed pins, they are all careful about using lots of assembly lube and oil).

FWIW a piston pin can be set to 'float' in a rod without a bushing. The Motorcycle engines I have worked on (FJ 1200 Yamaha, in line 4, Air Cooled) did not use a bushing in their rods. But you have to leave twice the clearance between the pin and rod when it's steel on steel. I guess that's fine, if you want that, I just prefer not to run steel on steel. You also need a way for the oil to get to the clearance between the pin and rod.


Hope that helps.

That oiling issue is a problem.
I will try to talk to Scat to see if the answer about it.
But anyone knows how can I lubricate the pin (if I need to)?
Thanks!

Greetings . . .

This topic has been discussed at length before in the engines forum:
G10-250\'s post on wrist pins circa 2006

regards,
stock49

stock rods dont have enough material in the small ends to go to bushings unless you have custom pistons made and run smaller o.d. wrist pins.

stock rods dont have enough material in the small ends to go to bushings unless you have custom pistons made and run smaller o.d. wrist pins.