3.2L Carrera Engine Balancing, IS THIS CORRECT? PLEASE HELP.
 

Hi everyone,

I've searched some old forums but I could not find clear instructions on how to properly balance my engine. I have an 84 Euro 3.2L and I'm near ready to reassembly and close case but I'd like to balance the engine if possible. I've attached some weigh data for your review and comment, please help.

Thanks everyone!

Alex

http://forums.pelicanparts.com/uploa...1162773365.jpg

EDITED to correct the rod weights.

Hey, cool spreadsheet.

What are the exact cc values of your heads and piston domes? That will influence their placement to balance the compression ratio in each cylinder and then everything else fits into that.

The other question to ask of the pros is which cylinders run hottest? Those will experience less charge density, right?

With regard to your rod placement, doesn't Wayne say in the engine book that you want to minimize the weight difference between opposite rods i.e. 1/4, 2/5, 3/6? Or did I read that incorrectly? Some more here: http://forums.pelicanparts.com/showthread.php?s=&threadid=89699&highlight=rod+wei ghts+opposite

Can't wait to hear a professional chime in on this.

John's right. The key is to have opposing cylinders with the least differential side-to-side. (ie it's better to have the heavier assembly across from another one, rather than each cylinder plane equal.)

Then put your heaviest group on the flywheel end.

Extreme example (numbers made up for demo):

WRONG:

3 - 200 6 - 400 = 600
2 - 275 5 - 325 = 600
1 - 225 4 - 375 = 600

Each "plane balances" which looks like what you've done?

BETTER:

3 - 375 6 - 400 = 775
2 - 325 5 - 275 = 600
1 - 225 4 - 200 = 425

So try and select weights to be most equal side to side. Then put the heavist assemblies across from each other, starting at 3/6, next heaviest at 2/5, next at 1/4

Great! Thank you both for your time. My pistons domes are Euro 3.2L, I did not confirm volume yet.

Alex

That looks to me like a set of rods that should be balanced.

That said, if you are ditermined to use rods that far out of balance I would suggest that you match opposing rods.
In a horizontally opposed engine, force opposing each other will cancel one another out.

Aktung, Henry is right, look at the deviation in weight. 3 grams, should be balanced to one another.

Henry mentioned on another thread that the goal with rod balancing is 0 grams, plus or minus half a gram, which is the LRQ (limit of reliable quantitization) of the measuring equipment. Put another way, don't let somebody tell you they balance to 0.0000 grams unless they work at Los Alamos and can back up those zeroes to the right of the decimal place!

Thanks Henry, John, and Chris.

If I understand correctly, proper balancing in my case involves matching rod weights on cylinders 1, 2, & 3 to within .500 grams. Same on 4, 5, 6 then placing the heaviest towards the flywheel and lightest towards the rear of the engine. Is this correct? Or, if I match weights on opposing cylinders which in my case they are close (<.550 grams) except across cylinders 2 & 5 which is over 1.0 grams it will cancel each other out like balanced rods? Finally, should my pistons and wrist pins also follow the same methodology? Thanks in advance for your time and support.

Best Regards,

Alex

Alex,

Remember that your piston and wrist pin is part of the assembly, so by combining different pistons and pins you can "adjust" the weight of each cylinder.

...and in a perfect world you want to balance ALL the rods to each other, meaning the lightest one. So if your lightest was 600.5 grams you would try and get them all to weigh that.

Now, assuming that the entire rod/pin/piston assembly isn't going to be perfect, you get as close to balanced independently as you can.

Then take the two heaviest and put them on 3/6, take the next two heaviest on 2/5, etc...

Got it! Thanks Chris!

ALEX

There is only one draw back when you balance in assemblies.

If you use a piston to compensate for a light/heavy rod then if you have to replace a piston/pistons the engine becomes out of balance.

Balance rods to each other, then balance piston to each other. You can use the wrist pins to make pistons match.

We quite often remove small amounts of weight from a wrist pin to balance a set of pistons.

Like Chris says, put them in pairs with the heaviest at the flywheel end. I think the factory spec is 7 grams difference!!! (but I may have to look that up to be sure)

Cheers

Once again, Thank you all for your time and advice. I greatly appreciate it, I'm near the end of my project.....if I could only get a hold of some of the Threebond sealants....I'm done.

Best Regards,

Alex

Supertec sells Three Bond products.

At least they list them on their web site.

supertecperformance.com

Try a yamaha motorcycle dealer, won't even have to pay the p-car premium!

Cheers

Thanks again everyone. I think supertec requires a minimum $100.00 order?

Alex

Update: I balanced my rods this morning.
 

Alright, I woke up early this morning and balanced my rods. Weights are minus bearings but rod and bolts included in total weight. Should I continue working across 1 and 4 cylinders or is it fine now?

Best Regards,

Alex

http://forums.pelicanparts.com/uploa...1163879506.jpg