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Connecting Rod Revision

 
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Moparboy72  



Joined: 29 Jul 2014
Posts: 34
Location: Naperville, IL

PostPosted: Wed Mar 04, 2020 1:12 am    Post subject: Connecting Rod Revision Reply with quote

I am in the process of building a short block for my 931 using a spare 1977 engine as a base. It has been interesting finding out which parts carry over and which do not. The current PET/pdf parts catalogs only show current parts with no indication of previous numbers or supercisions.

One case I found interesting was through reading an old technical bulletin , number 78-01.

This bulletin outlines that the connecting rods have been updated and now have an oil spray hole to improve piston cooling (near the exhaust valve). The new rods were installed starting with XH 005 193 and XF 003 260.

The XF rods that I have are earlier and do not have the oil hole. Has anyone drilled this hole?

Thanks,

Andrew
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924RACR  



Joined: 29 Jul 2001
Posts: 8300
Location: Royal Oak, MI, USA

PostPosted: Wed Mar 04, 2020 3:22 am    Post subject: Reply with quote

I seem to recall that there is a boss through which this is drilled... presumably to add strength around the hole. Which makes me concerned about the idea of drilling the hole without reinforcement...

Edit - not the easiest to see, but here's a pic, and you can see the little bump for oil down at the base of the web on the big end...
https://www.facebook.com/photo.php?fbid=10212999630420297&set=a.10212999625340170&type=3&theater
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Vaughan Scott
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'79 924 #77 ITB racecar
'82 931 Plat. Silver
#25 Hidari Firefly P2 sports prototype
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Moparboy72  



Joined: 29 Jul 2014
Posts: 34
Location: Naperville, IL

PostPosted: Wed Mar 04, 2020 3:47 am    Post subject: Reply with quote

Thanks for the post and photo link Vaughan. I was searching around and could not see it as clearly as you show.

The tech bulletin shows a grainy black and white photo. I will double check but, I am quite certain the early rods are uniform in their forging, as in no bump/material for oil hole.

It seems the safest course of action would be to search out a later set of rods.

Thanks again,

Andrew
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Mike9311  



Joined: 14 Dec 2004
Posts: 839
Location: Chicago-ish

PostPosted: Wed Mar 04, 2020 7:34 am    Post subject: Reply with quote

There is a post around here somewhere where Dan slotted the rod for the same purpose ...

I don't find the post of all the tech discussion but you see it on this page

http://www.924board.org/viewtopic.php?t=31912&postdays=0&postorder=asc&start=60
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1980 931 since 1989
1981 Ideola 931 Club Sport
1982 931 Entwicklungsfahrzeug
1979 924 NA M650 Herausnehmbares Dach
1982 931 Red Resurrection - 951 IC
1982 931 parts car / resurrection?
1980 924 NA (R&D lightweight)
1982 931 wana-be GTR race car
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!tom  



Joined: 28 Aug 2006
Posts: 1898
Location: Victoria, BC Canada

PostPosted: Wed Mar 04, 2020 10:41 am    Post subject: Reply with quote

Lots of discussion about oil squirters, pros, cons, necessity, etc. here:
http://www.924board.org/viewtopic.php?t=23223&start=0&postdays=0&postorder=asc&highlight=
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Mike9311  



Joined: 14 Dec 2004
Posts: 839
Location: Chicago-ish

PostPosted: Thu Mar 05, 2020 12:24 am    Post subject: Reply with quote

That was the thread I remember!
_________________
1980 931 since 1989
1981 Ideola 931 Club Sport
1982 931 Entwicklungsfahrzeug
1979 924 NA M650 Herausnehmbares Dach
1982 931 Red Resurrection - 951 IC
1982 931 parts car / resurrection?
1980 924 NA (R&D lightweight)
1982 931 wana-be GTR race car
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Moparboy72  



Joined: 29 Jul 2014
Posts: 34
Location: Naperville, IL

PostPosted: Thu Mar 05, 2020 12:08 pm    Post subject: Reply with quote

Thanks guys! It is nice to see another solution to use these early rods ( by adding a slot). I did double check and the early rods are uniform (no bump).
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