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Old 03-28-2014, 09:06 PM   #1
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Default Replacing con rod in engine??

So i have been reading a lot of things about con rod replacement on when to do it and such. Im coming up with a lot of different answers. I have seen some say after break in replace it. I have seen others say after a few gallons or so.

What do you guys think on when i should replace the con rod in my engine. I don't want a failure and it break something bad.
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Old 03-29-2014, 02:32 AM   #2
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You can replace it right after break in. With my engines I replace the con-rod after the first 2.5 litres. (not sure what that is in gallons). Plus I replace the con-rod after every 5-7 hours of running. Everyone has their own method of doing this procedure, but this is what has worked for me.
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Old 03-29-2014, 07:13 AM   #3
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I generally just inspect the conrod for wear/play after each days racing and replace as nessacery. As a back stop I'll change the rod regardless after 4 gallons to take into account fatigue. I don't replace it after break in just follow the above.
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Old 03-29-2014, 09:49 AM   #4
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yea i didn't know if you all measured it when it was new and just kept track of measurements and such. I got a used nova 353 M3 tuned with an extra con rod. Should i replace it before i do an heavy racing on it or let it go for a bit. The engine looks good and has lots of compression. Engine looks new inside. Just normal wear or discoloring (black burn look) to the top of the piston. Sleeve and ports look good.
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Old 03-29-2014, 03:10 PM   #5
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These Pro-Tips will show you how to check your engine and when to change your conrod.

http://www.teamorionshop.com/en/cont...des-champions#

http://www.teamorionshop.com/en/
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Old 03-29-2014, 04:23 PM   #6
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Quote:
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yea i didn't know if you all measured it when it was new and just kept track of measurements and such. I got a used nova 353 M3 tuned with an extra con rod. Should i replace it before i do an heavy racing on it or let it go for a bit. The engine looks good and has lots of compression. Engine looks new inside. Just normal wear or discoloring (black burn look) to the top of the piston. Sleeve and ports look good.
How much fuel have you ran through it?
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Old 03-29-2014, 09:20 PM   #7
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i haven't ran anything threw it yet. but i will check out the links and read up. I got the engine used but its in great shape
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Old 03-29-2014, 09:31 PM   #8
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ok watched the vids and was informative about checking the sleeve for wear. But are you just checking for play in the con rod and replace it on that only or are they any other factors that factor into replacement of the con rod??
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Old 03-29-2014, 11:24 PM   #9
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ok watched the vids and was informative about checking the sleeve for wear. But are you just checking for play in the con rod and replace it on that only or are they any other factors that factor into replacement of the con rod??
I check for play in the con-rod. The amount of play is very small but you can sometimes see the bottom of the con-rod "move" on the crank. Not only that the con-rod can stretch. If you can, ask the previous owner how much fuel has been through it on that con-rod.
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Old 03-30-2014, 07:50 AM   #10
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yea i knew about the stretching but didn't know if there was a way to really measure it. Do you just measure the length of a new one vs the one in the motor and how much stretch is acceptable. Yea i saw how to check the play. Ill have to ask him about fuel used.
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Old 03-30-2014, 03:36 PM   #11
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I don't like the 'change it after this much fuel...' statements that are made. There are so many variables into how the conrod will wear. For example you'll put more stress on the rod running on very bumpy tracks or tracks that have a very long straight. Driver skill in how hard your able to run your engine is also a big factor. I just keep an eye on the big end wear/play and change it when play is present at TDC. It's also important to measure the crankshaft pin as well to ensure it's within tolerance as a crank pin that's worn below limit will eat conrod bearings for breakfast!
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Old 03-30-2014, 03:49 PM   #12
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yea i get that. I was questioning that as well. I was looking for hard spec when to replace. Can the pin actually wear since its hardened steel and the conrod bearing is brass and that will usually wear first. Do you really see significant wrist pin wear ?
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Old 03-30-2014, 04:28 PM   #13
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Do you just measure the length of a new one vs the one in the motor and how much stretch is acceptable..
Yeah that's pretty much it. Just get yourself (if you don't already have any) a set of digital callipers and measure the difference. I haven't had a rod stretch on my yet as I change them quite often.
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Old 03-30-2014, 06:41 PM   #14
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yea i just went threw all 3 of my engines my xz rb m3 and 353 m3 and they are all good. All are good on the sleeve wear. the con rods in the the rb and xz are fine. The one in the 353 has just minor play in it. I think i might just leave it for now. I might race the xz for now and use the 353 thats in my nt1 as a complete back up car
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