| [GMCnet] Piston rod stretch in the 455 [message #279831] |
Sat, 13 June 2015 20:06  |
glwgmc
Messages: 1014
Registered: June 2004
Karma:
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Senior Member |
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Hi Chris,
You may want to call S&J in Spokane and talk with the owner whose name is Johnson. I think you will find that they are well aware of these and other issues associated with remanufacturing Olds and other engines using numerically controlled machines. I would agree that it is hard to find really good machine work done manually with worn out tooling. I can’t imagine anyone would have still in-spec manual tooling for a low volume engine that has not been made for 40 years. That said, I would assert It is not hard to find really good machine work using state of the art computer controlled tooling. So long as the programming was correct to begin with, it stays that way.
Normal disclosures, no affiliation with S&J, no compensation, etc.
Jerry
Jerry Work
The Dovetail Joint
Fine furniture designed and hand crafted in the 1907 former Masonic Temple building in historic Kerby, OR
glwork@mac.com
http://jerrywork.com
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Message: 8
Date: Sat, 13 Jun 2015 15:37:20 -0600
From: Chris Tyler
To: gmclist@temp.gmcnet.org
Subject: Re: [GMCnet] Piston rod stretch in the 455
Message-ID:
Content-Type: text/plain; charset="utf-8"
Bob, I think you'd have to agree all GM rods arent the same. Your Chevy rods in your Yenko were a better design even before you massaged them I would
bet.
Olds rods arent the best, but at least they arent the cast junkers that Pontiac used. Ask me how I know.
Rod stretch is more of a problem with RPM, and more with free reving without a load from what I have seen
Id have to agree that lugging is a bigger problem for our application. Piston speed [discussed elsewhere today] is higher with a longer stroke, and
energy being a function of mass x velocity it goes up exponentially, but not a problem with our RPM range. True, there is more friction, but via more
leverage and a longer burn time, more torque.
When were talking about lugging, its really about preignition or detonation that spikes the cyl pressure or worse, creates too much pressure while
still compressing BTDC. Plays hell with rod bearings and pistons, especially cast
Once the bearing goes, the rod follows.
Guys that worked for GM I knew swore Olds engines were more precisely assembled than other GM marks. I would bet their tolerances were on the mark,
and most rod failures are either high milage or after a shoddy rebuild on the rod. The clearance is critical, and the bearing is held in place by
proper crush. I dont know if olds uses tabs, but I have seen a lot of poorly resized rods that were not recut correctly and failed
Hard to find really good machine work anymore.
--
76 Glenbrook
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Jerry & Sharon Work
78 Royale
Kerby, OR
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