[Land-speed] dumb Question # 4856 - Wrist pins

[Larry Mayfield]

Hey, all youse guys..thanks for the replies!  While some disparage 
Summit, I used them as reference because they sell a lot of aftermarket 
maker's parts.  I surfed for piston wrist pins and wrist pins and found 
tons of them in all shapes and sizes.  I did find a couple made by Ross 
that were side by side comparable, just different diameters. The price 
was exactly the same.  Naturally the slightly smaller diameter is a tad 
lighter, not enough to make a difference in my opinion. Big was 96 
grams, smaller was 94 grams.

I will say that the notion of the 0.927 RM diameter being most prevalent 
is true. By a long way. Still, every maker does have the Ford diameter 
and they run at virtually the same price.   So I don't think 
availability is the full reason.  And the pins no matter the diameter 
come in an almost bewildering array of lengths and materials and 
retention methods.

I asked the original question, not because I have rods with the ford pin 
diameter and whether or not I should go to the larger ones, but because 
I have a set of rods that have that diameter off the shelf.  Since they 
came that way, I was curious as to why since ford pistons come with teh 
0.912 diameter o begin with.  I suppose the very small difference in 
load bearing area in the aluminum piston might be a reason, but,  I 
dunno.  Since I need to have the pistons custom made anyway, I will just 
have them made to fit the 0.927 diameter and will also have the pison 
maker supply the pins as well. That way, they should fit and I know the 
retaining system will work.

Happy Turkey Day!

mayf

______________________________
drmayf
Worlds Fastest Sunbeam, period.
204.913 mph flying mile
210.779 mph exit speed


On 11/23/2011 9:35 AM, Larry Mayfield wrote:
> Ford uses a wrist pin diameter of 0.912 inches for the little end of the
> rod/piston.  GM has a wrist pin diameter of 0.927 inches. I see a number
> of  Ford products whether pistons or  rods offered with the option of
> using the GM wrist pin diameter.  I don't know if the Ford pin diameter
> is offered as an option for GM stuff though. Don't care, lol...
>
> What's up with that?  Is the GM pin lighter even though it is larger in
> diameter? Stronger for sure but is that the reason?
>
> So, the dumb question is:  "why switch from 0.912 to 0.927 inch diameter
> wrist pins?
>
> Keep it technical please...
>
> mayf