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Old 08-11-2020, 02:23 AM   #1
Brendan1959
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Default Can rods be checked for straightness without special equipment?

Can rods be checked for straightness without special equipment?

I searched but have not found any thoughts on this.

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Old 08-11-2020, 07:12 AM   #2
wwirz
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Default Re: Can rods be checked for straightness without special equipment?

In my years if experience on piston compressors you need a Marble, accurate dial indicators, feeler gages and jobe blocks - calibrated.
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Old 08-11-2020, 08:01 AM   #3
Jack Shaft
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Default Re: Can rods be checked for straightness without special equipment?

You have a mis-matched set of rods to begin with any balancing might be an issue.Are there any witness marks indicating a bent rod?
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Old 08-11-2020, 08:29 AM   #4
BRENT in 10-uh-C
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Default Re: Can rods be checked for straightness without special equipment?

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Originally Posted by Brendan1959 View Post
Can rods be checked for straightness without special equipment?

I searched but have not found any thoughts on this.


Brendan, I guess the true answer to this is what do you call 'special equipment'?

I guess one way is if you have a good lathe and a knee mill, you can machine a mandrel for the big end of the rod that will be an exact fit (-not just the machined diameter of the crankshaft journal pin). Then insert the wrist pin on the small end of the rod, and using matched 1-2-3 blocks under both sides of the wrist pin, you will clamp it down to the table on your mill. With your mandrel located on your big end, use a Last Word indicator to sweep the top of the mandrel on both sides to check for twist.

To check for being bent, sweep the front of the wrist pin on one side and measure the distance back to the front edge of the mandrel. A DRO will make this WAY easier. Then repeat this op on the opposite side of the beam and see if your measurement repeats. A secondary method for this would be to use a large micrometer to measure between the mandrel and the wrist pin.

I guess my point is there are ways around specialized equipment like the rod checker however you really need the basic machine tools to get you started.
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Old 08-11-2020, 08:30 AM   #5
Kurt in NJ
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Default Re: Can rods be checked for straightness without special equipment?

if they came out of running engine a reasonable guess can be had by looking at piston wear patterns
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Old 08-11-2020, 10:06 AM   #6
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Default Re: Can rods be checked for straightness without special equipment?

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-------
Deleted, was thinking valves etc, not connecting rods.

Last edited by 30 Closed Cab PU; 08-11-2020 at 10:27 AM.
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Old 08-11-2020, 10:25 AM   #7
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Default Re: Can rods be checked for straightness without special equipment?

One of the most important "special tools" would be a purpose made surface plate. Some large measuring devices and some accurate gauge blocks to check lengths & distances between. A good height gauge for the surface plate would be required. I would consider this minimal.

There is no way to accurately check things like this without some equipment whether it's 'Special" or not.
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Old 08-11-2020, 06:54 PM   #8
Brendan1959
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Default Re: Can rods be checked for straightness without special equipment?

Thanks for the replies
I have a small lathe and a Mill/Drill, not terribly accurate.
I had to look up what a last word indicator was, seems to be a dial indicator with a little leg on it, I think I have one. I don't have any "V" blocks.
I don't think my skills and machines are are up to the required standards.
Some ideas to think about.

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Old 08-11-2020, 07:31 PM   #9
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Default Re: Can rods be checked for straightness without special equipment?

There are several different brands of testers to check for bent rods, this one is a K R Wilson. There are three checks that must be made, Offset, Twist and Parallel. Rods bend very easy, you can put the small end in a vise to hold it while you remove a tight nut on the other end and it will twist your rod, you will not be able to see the twist just by looking at it but it will show a twist in a rod tester.
It would be very difficult to check a rod without a tester.


You do not need any special equipment to straighten a twisted rod because they bend very easy, This K R Wilson tester is bolted down to the workbench so most of the time all you have to do is put a steel bar about 1 or 1 1/2 foot long in the wrist pin hole and pull on it with your hand, it will bend very easy.


If a rod has a bend in it that you can see just by looking at it, I put it in the trash and get another rod.
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Old 08-11-2020, 07:47 PM   #10
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Default Re: Can rods be checked for straightness without special equipment?

Your local engine machine shop has the tools. Cheaper to pay them then to try and do it yourself.
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Old 08-11-2020, 08:36 PM   #11
Brendan1959
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Default Re: Can rods be checked for straightness without special equipment?

Not many local machine shops left and all closed due to covid lockdown.
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Old 08-11-2020, 11:15 PM   #12
Bruce Newbery
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Default Re: Can rods be checked for straightness without special equipment?

A real easy way to check rods is to instal crank ,torque mains to spec.Instal all four rods and pistons. Torque rods to spec.Turn engine upside down in engine stand. Rotate engine a few times and observe the position of the rod in the piston. They should all be in the centre of the piston.If they are all centered you have no worries. If they are not any reputable engine rebuilder can straighten them. They are easy to straighten
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