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Author Topic: 1969 z/28 connecting rods  (Read 3134 times)
asm69
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« on: May 28, 2006, 12:32:56 PM »


I'm trying to find out some information regarding z/28 connecting rods. I have a 1969 z/28 camaro
that I'm starting to restore. Upon removing the pistons and inspecting the connecting rods I noticed
that on the bottom of the connecting rod end cap their were the raised letter 'O' which is correct for the
pink rods for a 1969 z/28. But, what has me confused is that the wrist pins are pressed on. My question
is did the 1970 z/28 camaro with the LT1 use connecting rods that had raised letter 'O' on the bottom
of the connecting rod but used pressed wrist pins. Or in my case did someone convert the full floating
pins to pressed pins?

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william
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« Reply #1 on: May 29, 2006, 10:21:09 AM »

Others with more knowledge should jump in.

First of all "pink" rods are not all that special. They are standard sb forgings shot-peened to eliminate stress risers and then magnafluxed to check for cracks. They were then coded with pink paint to differentiate them in production. In addition to the processes mentioned mid-68 and all 69 302 rods were machined for full floating pins. All 67 and early 68 302 engines had press-in pins. I believe 70-up LT1 engines used press-in pins.

What I do not know is if pistons designed for floating pins can be used with press-in pins.
If not you may have 67 style pistons. Standard bore 69 302 pistons were out of production for some time and perhaps the engine was simply rebuilt with 67s. Or, worst case, it is no longer a 302.

If this is a restoration-rebuild I wouldn't concern myself with having correct "pink" rods with full-floating pins. If the engine is to see hi-perf usage there are aftermarket rods way better than the stock stuff. We did a 69 302 rebuild from scratch almost 20 years ago and the rods we found back then were junk.

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asm69
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« Reply #2 on: May 29, 2006, 11:00:04 AM »

You are correct 70 LT1 engines used pressed in pins and used  large journal rods. The rods I have are also large journal and they have the raised letter 'O' on the bottom of the rod cap (69 z/28 rods have a raised letter 'O' on the bottom of the rod cap, 67 and 68 z/28 are small journal rods, dont know if any letters are on the bottom of the rod cap for 67 or 68). The gentleman I purchased my car from over 20 years ago informed me that he road raced the car. I'm trying to determine if my rods were modified to accept pressed
pins or may be 1970 LT1 connecting rods. The key question is that did 1970 LT1 connecting rods have the raised letter 'O'
on the bottom of the rod cap. If the 1970 LT1 engines did not use the raised letter 'O', then by deductin these are 69 z/28
rods, though modified.

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RAfbody
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« Reply #3 on: May 29, 2006, 03:00:58 PM »

The 96 style 302 pistons can be used with the pressed pin rods.  I would say that is what you have if it is a 302.  Do the pistons have the grooves in them where the keepers go for the wrist pin? 

The 67 302 was small journal but the 68 was large journal.
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Russ
asm69
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« Reply #4 on: May 29, 2006, 04:08:02 PM »

Thanks for your comments. Some background on the vehicle. I purchased the car about 20 years ago from a gentleman
who said he was road racing the car. Though the engine in the car was not completely stock. I have verified numerous 302
engine components, suspension components, interior components and exhaust components. The engine has been dissambled.
The pistons are trw with grooves for wrist pin retainers. But the pistons are not stock 302 pistons. The connecting rods have
the raised letter 'O' on the bottom of the connecting rod caps. There are some numbers (3 digits) around the cap bolt bosses. The
question I have  did the 1970 LT1 Z/28 have connecting rods that had the raised letter 'O' on the bottom of the connecting
rod caps?
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JohnZ
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« Reply #5 on: May 29, 2006, 06:04:07 PM »

Yes, as far as I know, the LT-1 rods had the "0" in the cap end of the forging. The small end I.D. of a pressed-pin rod is smaller than the I.D. of a floating-pin rod; the same piston pin diameter is used for all pistons (.9270"-.9273"), but that pin is a .0018"-.0016" interference fit in a pressed-pin rod, and is a .0001-.0008" clearance fit in the floating-pin rod. The pin hole is drilled larger in the floating-pin rod, that end of the rod is coated with copper babbitt bearing material, then it's finish-honed to the proper oversize to ensure .0001"-.0008" clearance to the pin to provide for lubrication.
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'69 Z/28
Fathom Green
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asm69
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« Reply #6 on: May 29, 2006, 06:34:59 PM »

Thank you. Thanks exactly the information that I'm looking for. When I press out the pins I will measure the openings. Then
I will draw my conclusions as what to do for my restoration. How is the lubrication to the floating pins accomplished. Are they
under oil pressure or just simply splash lubrication.

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JohnZ
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« Reply #7 on: May 30, 2006, 11:14:54 AM »

Thank you. Thanks exactly the information that I'm looking for. When I press out the pins I will measure the openings. Then
I will draw my conclusions as what to do for my restoration. How is the lubrication to the floating pins accomplished. Are they
under oil pressure or just simply splash lubrication.



Just splash lubrication - the only pressure lubrication in the crankcase is through the cam journals to the crank main and rod journals.
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'69 Z/28
Fathom Green
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