Balancing engine parts at home.

[NAES]

Hey guys, I'm gearing up to start an engine build and am curious about balancing parts at home vs sending them out. Specifically the rods and pistons.

The rotating assembly was already balanced by my engine builder which included the rods and pistons. Unfortunately he won't be building my engine so I have all the pieces now and am going to tackle the build myself.

The rods I have are rebuilt stock VW but I want to go with I-beams. Pistons are 94's but I'm using thick wall 92's instead.

Am I doing any harm by balancing the rod and pistons separate from the rotating assembly? I don't believe I would be but want to double check.

I have a scale that can get down to tenths of a gram and would need to fab a rod jig which looks simple enough.

Thanks everyone for the help, NAES
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Barndoor Mafia
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[Clatter]

Yep...

I do rods and pistons al the time at home now.
Don't bother sending them out and paying anymore.

Make sure to jig it up so all of the little ends of the rods weigh the same,
Then all of the big ends..
Then see that the overall weight matches on all four (of course).

A normal postal scale goes to a tenth of a gram typically.
Blow a tiny puff of air to see it react and get it within that, even.

Pics in the bus motor in my sig.
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[oprn]

The Machinist that balanced my last engine told me that he either balances it all or he will not take on the job. Simple quality control. If my work is bad and the engine runs poorly because of it then it's his reputation that's on the line not mine. I get it.

Interestingly, the pistons I gave him were a used set that I had balanced 25 years ago and run for many miles. He only changed the weight on one of them by 1/2 gram!

I have balanced my own rods and pistons for years. My feeling is that even if they are not perfect, any improvement over out of the box is good.
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[Cusser]

My Moresa 85.5mm pistons and wrist pins were remarkably close in weight when I assembled my engine in 2016-2017. I had new CB connecting rods, they were close too. So I didn't need to assign a connecting rod to a certain piston, and balance that way.
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[Chickensoup]

if you need general ideas for designing the con rod jig heres my thread,

https://www.thesamba.com/vw/forum/viewtopic.php?t=747672&highlight=
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[frenchroast]

I can't imagine balancing rods and pistons/pins separate from the crank and flywheel would pose any risk. I did it and my engine runs pretty smooth. This was my first time balancing everything and it was kind of a fun learning experience. I didn't have a way to balance the crank and flywheel so just left it as it came from the factory (flywheel and crank are original and never ground). Made sure to index the flywheel to its original position.

I balanced the pistons to the gram including wrist pins. I then made sure each was balanced with the corresponding rod. I made a rod balancing jig and balanced them end-to-end. There are a lot of examples here and also on youtube.

I also made this contraption to balance the clutch with the flywheel. It uses some bearings I found in my coffee-can-o-parts and I just shimmed them with tape to fit the flywheel and pressure plate holes. I used some claybar blobs to identify where I needed to remove weight from the pressure plate. I also found that the bolts and washers weight varied. Before I drilled anything, I first moved the bolts around and also repositioned and indexed the pressure plate. That made the biggest difference. In the end I only had to remove about 2 grams by drilling in the area where the factory balancing holes were. I got it to the point where it would stop rotating at a different point each time so I called it good. If there is a slight imbalance, the amount is less than that required to overcome the friction in the bearings (not much): https://youtu.be/6nLLmm9V6PU

[Ohio Tom]

I imagine you could balance them, then take them to the shop. He will discover that they are good and not have to charge you the labor to balance them.

I kind of understand the guys concerns. Many folks have no idea where and how to remove material to balance things. Take it from the wrong place, and you have weakened the part.

I saw a guy bring a set of Diesel rods for his pulling tractor to a shop for shot-peen and balance. The customer had done some "light weighting" to the rods prior. They looked pretty sketchy for a Diesel.

The shop owner put a big disclaimer on the bill.

[oprn]

[Chickensoup]

[nextgen]

There are alot of things that are important to do, the first on the list of a rebuild is balance the engine.

I have done the rods and pistons alone on my first builds years ago to save money. The pistons usually are very close, so taking off a bit of weight is no big deal.

I agree with Oprn. The cost of doing it correctly, crank, flywheel, clutch is the most expensive, adding on the rods is not going to break the bank.

Any issues fall on the machinist.

My guy even puts small wedges between the clutch and the flywheel, so nothing is moved when installing to prevent even the slightest removal of metal if parts scraped each other.
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[mark tucker]

[mark tucker]

[mark tucker]

and too add to toms deisel post....Ive seen some pure junk that somebody thought they had helped by doing their own handy work, lightening, surfacing,sand blasting, porting etc. you cant fix stupid. and almost as much shit like that cumming from other shops....yes cumming, as somebody for sure got fucked.

[oprn]

[spencerfvee]

[spencerfvee]

i have seen clutch pressure plates out of balance . a lot of guys over look balancing a clutch pressure plate . spencerfvee

[oprn]

My Machinist said of all the parts he balances the pressure plates are the furthest out as a rule.

Back to Balancing things at home, years ago I built a Rabbit engine, took the crank to have it balanced. The shop owner didn't charge me full price because he said he could not improve on the factory balance. I did the rods and pistons myself.

A couple years later we moved and I flat towed the car but I accidently left it in 1st gear. So it got towed for 1 hour at 60 mph in 1st gear before I checked out what my wife was saying about something not being right(she was driving the tow vehicle). I have no idea really what RPM that would be - 15,000? Anyway it ran fine for several years after that and I'm sure will still run if I were to start it back up.

There is an acid test for home balancing... not?
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[nextgen]

My guy high speed balances the crank, flywheel with clutch and marks each piece with and engraving tool with a small arrow.



My brother and I had exact same 1600 1968 bugs his was stock factory balanced and mine was was done at the shop.

You can easyerly feel and see the difference. Actually can feel a hp gain.
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[Dauz]

Isn’t it fairly inexpensive for an engine balance? Moonshine did my last one years ago and I don’t think I e spent more than a couple hundred

[nextgen]

Supply and demand, balancing is so important that you want recommendations .

Any one that rebuilds an engine and does not balance is, nuts.

That said you want the best, so much depends on balancing.

A couple of hundred sounds like a lot, but if I had no choice I would gladly hand over the money.
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