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phongshader
Justin Brown
Ca
(63 posts)

Registered:
02/19/2010 04:03PM

Main British Car:
Locost Lotus 7 2.3 Duratec

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con rod wrist pin bore
Posted by: phongshader
Date: March 22, 2024 12:37PM

I'm looking at some Nascar 6.125" con rods but the wrist pin bore is too small for the pistons I want to use. The pin bore is 0.787" but the pin dia is 0.866"...would boring out the rod pin bore to accommodate a 0.866" wrist pin weaken the rod too much, advisable? Floating pins, by the way.


mgb260
Jim Nichols
Sequim,WA
(2482 posts)

Registered:
02/29/2008 08:29PM

Main British Car:
1973 MGB roadster 260 Ford V8

Re: con rod wrist pin bore
Posted by: mgb260
Date: March 22, 2024 12:55PM

Depends on how big the top end of rod is. .048 bigger all around. EDIT: .0395



Edited 1 time(s). Last edit at 03/22/2024 05:39PM by mgb260.


phongshader
Justin Brown
Ca
(63 posts)

Registered:
02/19/2010 04:03PM

Main British Car:
Locost Lotus 7 2.3 Duratec

authors avatar
Re: con rod wrist pin bore
Posted by: phongshader
Date: March 22, 2024 04:57PM

I don't have the rods so I don'y know the answer on how big the top end of rod is. ".048 bigger all around" means what? The pin diameter difference is .079 larger...


mgb260
Jim Nichols
Sequim,WA
(2482 posts)

Registered:
02/29/2008 08:29PM

Main British Car:
1973 MGB roadster 260 Ford V8

Re: con rod wrist pin bore
Posted by: mgb260
Date: March 22, 2024 05:27PM

Divide by 2 for each side. Should be .0395 each side or all around if centered.

I don't know where the .048 came from.



Edited 2 time(s). Last edit at 03/22/2024 05:37PM by mgb260.


ag1234
Arthur Gertz

(119 posts)

Registered:
03/29/2023 08:26PM

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Re: con rod wrist pin bore
Posted by: ag1234
Date: March 24, 2024 08:58PM

Many engines using floating pins, steel on steel. Must lube the pin adequately. When you say weakening, meaning tension ?
To answer that, look at LS7 titanium rod.


DiDueColpi
Fred Key
West coast - Canada
(1384 posts)

Registered:
05/14/2010 03:06AM

Main British Car:
I really thought that I'd be an action figure by now!

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Re: con rod wrist pin bore
Posted by: DiDueColpi
Date: March 25, 2024 09:01PM

Depends upon the rod.
Lots of the Carrillo's have a relief around the big end and probably wouldn't tolerate that much of an overbore.
I would hunt down some Pankl's with the 0.827" pin bore and ream them out. They appear to have the beefiest small end. So a 0.039" overbore should be just fine.
On the other hand, depending upon what you're building, the LS rod might be a better choice. They are strong, cheap and have the 2.100" big end bore that you probably need. The small end is 0.927" so a bushing is safe and easy.

Live like you mean it
Fred


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