acceptable tolerance for connecting rods???

Posted By: '72CudaRacer

acceptable tolerance for connecting rods??? - 01/26/10 02:46 AM

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

Posted By: 68 HEMI GTS

Re: acceptable tolerance for connecting rods??? - 01/26/10 03:12 AM

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.

Posted By: Mopar_Rich

Re: acceptable tolerance for connecting rods??? - 01/26/10 05:57 AM

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.

Posted By: '72CudaRacer

Re: acceptable tolerance for connecting rods??? - 01/27/10 02:50 AM

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

Posted By: mopardamo

Re: acceptable tolerance for connecting rods??? - 01/27/10 06:32 AM

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

Posted By: '72CudaRacer

Re: acceptable tolerance for connecting rods??? - 01/29/10 03:57 AM

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