Open question to the community, but specifically interested in responses from anyone who did NOT balance their engine as part of a rebuild. I have recently installed wiseco pistons with eagle rods and paired each rod/piston set to give consistency in weights. I was reading today that because the wiseco pistons and eagle rods are lighter than oem, the crankshaft will be inherently out of balance. I agree but only to an extent. So if I'm planning another rebuild in 3 years (new turbos, downpipes, exhaust, intercoolers) and only drive my Z occasionally (~5,000 km annually) will 15,000 km actually see a negative effect from not balancing the engine right now? Yes, I know it would definitely be BEST to have it balanced now but here's the deal: I'm in the middle of moving and there is no engine balancer near me. The closest one I could find is a couple hours away and has a 4 week wait... So, how bad could it be? If it helps, here were the weights of my piston/rod combos: 1: 936.5g 2: 936.5g 3: 935.5g 4: 936.0g 5: 936.5g 6: 936.5g As you can see, I paired the two out of sync weights to be in the center of the crank to minimize its overall effect.
Why not balance them yourself? It really isn't hard. You need to weigh each item individually to work out which item is holding the weight. Process goes something like this. Weigh each item and find the lowest. This is your target for the item. Go to each item and cut wight out until it reaches it target. There is some good youtube videos on where you can cut wight from. Checkout HP Academy, he has really good videos on how to do it, and where you can remove weight. I balanced the pistons on a non-VG30 rebuild I did. I got lucky and went into the ANU and used sensitive set of scales. It wouldn't check the weights of the rods as they were too heavy, but got a matched set of pistons, rings, and gudgeon pins. Once I get some more time Ill check the overall weights of the rods and ensure they are all the same. Then get the professional to do the crank. If I ever do a rebuild on my VG ill be getting it balanced for sure.
Unique Autosports has a great video on youtube. Showing it's not just overall weight, but where the weight is. I've added it below.
Engine balancing is not just about getting pistons, conrods, rings and bearings all being same weight. That's part of it. The most important part is to balance the crankshaft with the new lighter pistons rods etc. Standard cranks are balanced for OEM parts. Wiseco/Eagle replacements are up to 80grams lighter, so crankshaft has to be lightened to match. In my view the best way is to take it to a professional performance engine balancer that has a dynamic balancer and correct counter weights. Include as many rotating parts as you can ie, front pulley and flywheel/clutch etc. Number the pistons/rods etc so they are balanced in the same position as will install them Its a few years since I had a VG30 race engine balanced but it only cost ~$300 then.
Thanks for the good responses. The effect on the crankshaft like Martin mentions is what I'm most interested in. Again, I do agree it is best to have the engine balanced to all the new components. Given my circumstances, being in the middle of moving, I really dont wanna pull the engine back out, tear it down, wait 4 weeks for an opening at the performance shop, and then have to reassemble everything once I get it back. This process makes my garage look very undesirable and may deter people from buying my house... lol So, how likely is it that over a period of 3 years and only driving occasionally (<5,000km per year) would any significant damage to my engine occur (beyond bearing wear which I can replace in 3 years).
Also, you mention that you had a VG30 race engine built, which is kinda part of my question here. Since mine isnt a race engine and will be rebuilt in a relatively short amount of time, what's the probability of actually doing any real damage?
A bit more info for anyone who stumbles across this thread: I went ahead and weighed the stock pistons and rods out of curiosity into how much change has been made. Weighing these shows switching to wiseco eagle rod combo results in approximately 200g per pair lighter than oem which I believe is about 17% weight savings. My OEM numbers for the pairs: 1: 1135g 2: 1134g 3: 1135g 4: 1136g 5: 1134g 6: 1136g Just wanted to share, still interested in any thoughts on my earlier post. Thanks
Sorry, I must be missing something here! Why did you install forged internals? OEM internals have been proven to be reliable in the VG30 for close to 30years if used only within the manufacturers specs. Sure you have saved weight but your engine is now completely out of balance. My race engine was balanced to 0.5 gram, using your figures yours is close to 200grams, I'm sure you can imagine what extra stress is exerted on main/bigend bearings and crankshaft at 6000rpm!! Good Luck
Would have been my question exactly Unless you're planning to run 500-600rwhp+, just stick with stock internals.
Here's an article about balancing on my work's website http://www.gallowayengines.com.au/crankshaft-balancing As a engine reconditioner my suggestion is get it done, the weight difference is substantial, and you're not even considering where the weight is, as it might be heavier or lighter closer to the pin or the piston to a greater effect than the simple weight difference check especially on the link where it shows how much the unbalance increases with the revs...
