A look at Stock Rod weights

[BogusSVO]

I needed a set of stock rods for a simple no frills short block.

I grab a set, press the pistons off and clean them.

I weigh each rod and find a difference of 7g from low to high.

I thought that was a fluke, so I grab up all the stock 6 bolt rods and press the pistons off.

23 rods weight out between 687g and 704g

(2) 687g
(1) 688g
(1) 689g
(3) 690g
(1) 691g
(2) 692g
(1) 693g
(2) 694g
(2) 695g
(1) 696g
(2) 697g
(3) 699g
(1) 702g
(1) 704g

I could tell some of the sets, what engine they came out of, average High to low difference was 5g to 7g

I was amazed on how far off the weights were in the same engine set.

So I went to a buddy's shop and picked up 10 more rods to weigh out.

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Back to the scale.

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In 10 rods I found a range of weights, The difference of 21g!!

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(1) 680g
(1) 687g
(2) 697g
(1) 698g
(4) 699g
(1) 701g

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Lightest rod found was 680.5g and the heaviest rod is 704.5g So that is a low to high difference of 24g in 33 rods checked

So after all this I was able to make up 6 sets of rods with close weights, 1 to 1.5g high to low differences.


So to the guys doing there own back yard builds, make sure you you have the weights of your rods checked, even more so if you are planning on doing a BSE in your build.

 

[habitatguy187]

Where on the rod would be the best place to shave weight off? And did you take them all down to 680?

 

[nitrouskris]

Great Info....Now I want to check rods I have around

 

[bastarddsm]

So to the guys doing there own back yard builds, make sure you you have the weights of your rods checked, even more so if you are planning on doing a BSE in your build.

Don't want to be a dickbeater, but a bse has little to do with balance. Ballanceshafts (silentshafts) take out that little bit vibration that occur in a 4 cylinder because they do not have symmetrical acceleraion profiles, up and down.

No matter if you do a bse or not you should always strive for equal weighing parts.

 

[bullettdsm]

Lol, Dale. I did the same thing with 420a rods one time. Its surprising the variances on one set of stock rods (we did up to 10 grams on a set). Keeping in mind that their expectations are that the engine will last 150 to 200k.

And yet, as we do a "build", our tolerances are within the .5 gram range.

The same goes for the stock flywheels. Spin one of them and see how far out they are.

Just fun facts.

 

[BogusSVO]

Where on the rod would be the best place to shave weight off? And did you take them all down to 680?

The best place is at each end, Ill get them balanced as I need them.
http://www.dsmtuners.com/forums/art...ss-fit-pistons-balace-rods-6bolt-1g-4g63.html

No They will not be taken to 680, I would weaken a rod if I had to take the 704 rod to 680

Lol, Dale. I did the same thing with 420a rods one time. Its surprising the variances on one set of stock rods (we did up to 10 grams on a set). Keeping in mind that their expectations are that the engine will last 150 to 200k.

And yet, as we do a "build", our tolerances are within the .5 gram range.

The same goes for the stock flywheels. Spin one of them and see how far out they are.

Just fun facts.

I have balanced a flywheel, IIRC the most I have seen one out is 50 odd grams

 

[fun kart kid]

On the subject of stock rods do you think side polishing would help any on these rods? And have you ever balanced any bigger diesel cranks?

 

[BogusSVO]

On the subject of stock rods do you think side polishing would help any on these rods? And have you ever balanced any bigger diesel cranks?

Polishing the beam of any stock rod will help strengthen it, and make it lighter. I have done several sets in the past, but it is not cost effective to have done at a machine shop. A new set of Scat, Eagle or Manley rods would cost less.

Now for balancing diesel cranks, I personally have not done any, but years ago when I lived in Mo. The shop I worked at would weld up crank rod throws and off set stroke grind and balance the cranks for tractor pull builds.