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acceptable tolerance for connecting rods??? #594134
01/25/10 10:46 PM
01/25/10 10:46 PM
Joined: Aug 2009
Posts: 2,036
Mooresburg, Tn
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'72CudaRacer Offline OP
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'72CudaRacer  Offline OP
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Joined: Aug 2009
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Mooresburg, Tn
Just received new H-beam rods and started measureing them.
What is the acceptable tolerance for length (c-c)
Whats needed for clearance in the bushed end w/.990 pins? .0015"?
Also what is max side clearance on big end. I measured these (big end) and they are approx .006" "thinner" than a used stock LY rod w/ 100,000 plus steet miles ('69 New Yorker)That means my side clearance is going to .012" more than stock. Is this a bad thing, or acceptable?
Thanks, Brian

Re: acceptable tolerance for connecting rods??? [Re: '72CudaRacer] #594135
01/25/10 11:12 PM
01/25/10 11:12 PM
Joined: May 2009
Posts: 511
Temperance, MI
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68 HEMI GTS Offline
mopar
68 HEMI GTS  Offline
mopar
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Joined: May 2009
Posts: 511
Temperance, MI
i usually run the bushed end right at 0.0010" for "normal" use. usually aftermarket rods give you more side clearance, doesn't really seem to cause an issue if there a little loose. i would think new "quality" rods the CC should be right on.

Last edited by 68 HEMI GTS; 01/25/10 11:13 PM.

68 Dart GTS "HEMI" 10.30 @ 131 pump gas street car 3780#
69 Roadrunner 511 six pack 10.92 drive to track street car
Re: acceptable tolerance for connecting rods??? [Re: '72CudaRacer] #594136
01/26/10 01:57 AM
01/26/10 01:57 AM
Joined: Jan 2003
Posts: 1,938
Sonora CA
Mopar_Rich Offline
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Mopar_Rich  Offline
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Sonora CA
Quote:

What is the acceptable tolerance for length (c-c)
Whats needed for clearance in the bushed end w/.990 pins? .0015"?
Also what is max side clearance on big end.





C-C should be within .005
Pin fit should be .0010 - .0015
No max on side clearance although a really loose number (> .035) will affect the oil pressure slightly.

Re: acceptable tolerance for connecting rods??? [Re: Mopar_Rich] #594137
01/26/10 10:50 PM
01/26/10 10:50 PM
Joined: Aug 2009
Posts: 2,036
Mooresburg, Tn
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'72CudaRacer Offline OP
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Posts: 2,036
Mooresburg, Tn
the rods that I purchased are Ohio Crankshafts (made by whom?) are .002" from short to tall, but all are short (6.760" rods) from 6.7572" to 6.7592"
Just had a talk with my machinest, and was told not to over-think this. It's not a pro stock engine, the crank, pistons, block ect. are all going to be 2-5 thou off some where. I'm not going to spend enough to make it "perfect".
Guess he's right. Dang.
How close have you guys found your new stuff to be?
Thanks, Brian

Re: acceptable tolerance for connecting rods??? [Re: '72CudaRacer] #594138
01/27/10 02:32 AM
01/27/10 02:32 AM
Joined: Sep 2005
Posts: 1,328
St. Louis, MO
mopardamo Offline
pro stock
mopardamo  Offline
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Posts: 1,328
St. Louis, MO
Hello,

Your machinist is correct. The spec you gave are fine. Noting is that perfect in that price range. It will not cause problems. I know the apparent large increase in the side clearance appears to be a concern. Many have found out that it has turned out to be a non-issue. Have some fun.

Damon

Re: acceptable tolerance for connecting rods??? [Re: mopardamo] #594139
01/28/10 11:57 PM
01/28/10 11:57 PM
Joined: Aug 2009
Posts: 2,036
Mooresburg, Tn
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'72CudaRacer Offline OP
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Thanks for the replys folks.I guess I was expecting new 6.760" rods to BE 6.760"
But I know that EVERYTHING has a tolerance (+/-).
At least my confidence is back.
Brian







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