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[mommasGN]

I am in the process of doing a full engine re-build using a long rod stroker kit. I weighed all the parts( pistons, rod big end/small end, wrist pins, clips, ring pack, and bearings) and set up the bob weights, and got to help balance the crankshaft myself. The machine shop was trilled at how well the balance came out and how close to zero it was. Heres where i messed up. I was about to assemble the pistons/rings, and rods. and i notice 6 extra "rings" in the JE box. I never even realized that the pistons for a long rod require the extra ring below the oil rings because the wrist pin is so high. Dammit!

My question is, how much will the weight of this extra ring mess up the balance that was so close to perfect? and do i need to take it and have the balance checked again? I'm sure i already know the answer to my own question, just want other opinions. I will not be able to weigh the extra rings on the same scale i used for a couple day, but im guesssing they weigh 4-6 grams?

 

[Mr.Spool]

You already answered your own question

 

[TurboBuRick]

Really? How much does a set of rings weigh? Next to nothing.

 

[earlbrown]

Just run it. There's no 'perfect' balance number.

Or, if you're really anal, get a weight on the oil support ring, then remove that same amount from the piston/little end.

 

[turbodave231]

What balance factor did you use ? 36.6% or 50%? The Bob Weight formula uses either 36.6% or 50% of the reciprocating weight to calculate the Bob Weight. What is your bore size?

I have balanced MANY Buick V6's and here is my opinion: You will never notice the difference. Your reciprocating masses will be equal when you add the support rails. Good balance characteristics are created when the reciprocating masses are equal (and the forces generated cancel each other).

If you study the Bob Weight formula, you will see that adding weight to the reciprocating mass and keeping the bob weight constant, will change the balance factor. Engine designers change balance factors all the time to tune the engine to the mounts and chassis. Some engine builders claim there is horsepower to be found in racing applications by slightly altering the Balance Factor. (I don't buy that, but it's out there)

Bob Weight = (Rotating Mass + (Balance Factor * Reciprocating Mass)

Send me the info off your balance card. I have records for several builds that used oil ring support rails. I can tell you how the addition of the support rails affect your balance factor.

 

[Steve V]

You can not truly balance a Buick V6 spilt through crank. It's compromise. If it was so close to perfect(there's no such thing with these engines) the rail supports will not affect it one bit. Once oil starts slinging around it's out of balance. I have balanced may Buick V6's at RCG and now I do my own here. 2 grams or less is way better than the Factory let things go at. They where 30-40 grams out. Yikes.

One thing I notice is both balancers I have used(CWT and Turner technolgies) they all vary on each spin. They are close but very rarely come up the same.

When Buick added the balance shaft these things became balanced.

 

[Mr.Spool]

never even realized that the pistons for a long rod require the extra ring below the oil rings because the wrist pin is so high. Dammit!

When things should be there,then they should be there.but hey shortcuts are common,then again details are what separates

 

[TurboBuRick]

Bottom line, don’t worry about it. Put it together.

 

[TurboBuRick]

You can not truly balance a Buick V6 spilt through crank. It's compromise. If it was so close to perfect(there's no such thing with these engines) the rail supports will not affect it one bit. Once oil starts slinging around it's out of balance. I have balanced may Buick V6's at RCG and now I do my own here. 2 grams or less is way better than the Factory let things go at. They where 30-40 grams out. Yikes.

I respectfully disagree With the oil throwing it out of balance. The oil does not have a chance sticking to the crank when centrifugal force is at work.

Im not a pro balancer but my machinist is and I know the motors he balances are the smoothest running Buick V6’s you will ever feel. You would never know I have HR motor mounts. That’s for sure.

 

[mommasGN]

What balance factor did you use ? 36.6% or 50%? The Bob Weight formula uses either 36.6% or 50% of the reciprocating weight to calculate the Bob Weight. What is your bore size?

I have balanced MANY Buick V6's and here is my opinion: You will never notice the difference. Your reciprocating masses will be equal when you add the support rails. Good balance characteristics are created when the reciprocating masses are equal (and the forces generated cancel each other).

If you study the Bob Weight formula, you will see that adding weight to the reciprocating mass and keeping the bob weight constant, will change the balance factor. Engine designers change balance factors all the time to tune the engine to the mounts and chassis. Some engine builders claim there is horsepower to be found in racing applications by slightly altering the Balance Factor. (I don't buy that, but it's out there)

Bob Weight = (Rotating Mass + (Balance Factor * Reciprocating Mass)

Send me the info off your balance card. I have records for several builds that used oil ring support rails. I can tell you how the addition of the support rails affect your balance factor.

im not sure what balance factor was used. I'll find out. Here is a shot of the screen on the final spin.

here are my weights

pistons 439g
pins 124g
clips 1g
rod bearings 42g
rings ( without oil rail support ring) 46g
rod big end 470g
rod small end 202g

 

[rag231]

Stock flywheel?

 

[mommasGN]

Stock flywheel?

internal balance crank, neutral flywheel and balancer

 

[Steve V]

Well, the forum is not letting me load pics.

Rail support part number #4 3812-173
Weighs 7 grams.

I see it took pics above, must be my phone

 

[Steve V]

I respectfully disagree With the oil throwing it out of balance. The oil does not have a chance sticking to the crank when centrifugal force is at work.

Im not a pro balancer but my machinist is and I know the motors he balances are the smoothest running Buick V6’s you will ever feel. You would never know I have HR motor mounts. That’s for sure.

No problem, I am not a pro either. Everything I have learned is from hands on and elders.

FWIW I still shoot for 2 grams or less on everyone I balance.

 

[turbodave231]

I have been balancing my builds to +/- .5 gram. I'm probably way overkill on the tolerance but my results are always good. I have taken factory assembled engines apart and checked the balance. Steve is right, it is not unusual to see the engine 30-40 gram out at the crank.

There is lots of opportunity to improve the balance of a factory engine. Most people aren't racing and will never notice

 

[turbodave231]

	Engine Type:	90 degree V6 Internal balance
	Number of cylinders	6
	Balance Factor	36.60%
	Date:		Jul-20
	Customer:	MammasGN
	Bob Weight	814.8
	Connecting Rod		Piston and pin	Total Reciprocating	Total Rotating		Rings and support rails	Bearings and Oil
Cyl	Small End	Big End	Rod Total	Piston	Pin	Total					Rings	Bearings	Oil	Total
										All	46.0	42.0	3.0	45.0
1​	202.0	470.0	672.0	439.0	124.0	563.0	819.0	515.0		Rails	7.0
3​	202.0	470.0	672.0	439.0	124.0	563.0	819.0	515.0		Clips	1.0
5​	202.0	470.0	672.0	439.0	124.0	563.0	819.0	515.0
2​	202.0	470.0	672.0	439.0	124.0	563.0	819.0	515.0		Total	54.0
4​	202.0	470.0	672.0	439.0	124.0	563.0	819.0	515.0
6​	202.0	470.0	672.0	439.0	124.0	563.0	819.0	515.0
Avg	202.0	470.0		439.0	124.0	563.0	819.0	515.0

 

[turbodave231]

I took your numbers and plugged them into my Balance Spreadsheet. What was the Bob Weight value you used? I can figure out the balance factor if I know the Bob.

 

[turbodave231]

[QUOTE Or, if you're really anal, get a weight on the oil support ring, then remove that same amount from the piston/little end. ][/QUOTE]

As you can see.....I'm anal when it comes to balance. FWIW: if the support rails weights 7 grams, that is a lot to take of the small end or the piston.

The Molnar rods have very little opportunity to remove weight. The same goes for a nice piston. Stock rods have lots of ugly material top and bottom that can be removed. The stock pistons are easy to weight match as well. I don't build many stock rod/piston engines anymore.

 

[750H.P.V6]

In truth you can balance a Buick V6 anywhere between 36.6% and 50% and it will be fine. We've balanced a number of them in and around 40-45% because it was a good compromise between adding or subtracting large amounts of weight from the crankshaft counterweights. It's all a trade off between horizontal and vertical imbalance. If the detail parts are all very close in weight it will be fine.

In a different instance where you needed replace a damaged piston for instance you would want to make sure it is the same weight as the others to keep all the bob weights the same. If you are adding 7grams to all 6 piston / rod assemblies the weight of all 6 is the same in relation to each other. You can check it on the balance machine if you like but it isn't worth worrying about.

Neal

 

[turbodave231]

Neal, EXACTLY!! Well said.