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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
(2477 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...
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mgb260
Jim Nichols
Sequim,WA
(2477 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

(108 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
(1375 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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