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Gen 4 rods and pistons in a gen 3 lq4?

Old 01-05-2019, 11:28 AM
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Staging Lane
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Default Gen 4 rods and pistons in a gen 3 lq4?

would I be able to swap in some gen 4 rods and pistons in my lq4? Id hate to run these skinny gen 3 rods with a turbo.

Would they need any crank cutting or balancing if I where to do so? Ive searched around but found no clear answer so far.
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Old 01-05-2019, 12:36 PM
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The rods are obviously heavier so you SHOULD balance the crank when you make the swap, but some people have said they did it without balancing and had no problems.
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Old 01-05-2019, 10:17 PM
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Will the engine run without balancing? Yes it will. Is balancing necessary? No. As KCS stated, you should have it balanced. Would I balance it? Absolutely. Balancing the assembly will make the engine last longer, due to harmful harmonics being removed from the balancing procedure. Harmonics will fight against what the engine is trying to do. Harmonics from the assembly is hard on the bearings. A balanced engine will make more power, easier. I’m a perfectionist, and I balance every engine I build. It’s the proper way to build an engine correctly. You’ll hear all kinds of opinions about balancing on this forum. I was told recently that balancing an engine gives you “fake peace of mind” on this forum. Whatever...
I raced nascar asphalt late models for several years, and obviously our expensive engines were balanced, but a great example of harmonics hurting performance was found with our tires. We found that by balancing our tires, to rid off harmonics, we picked up speed, and our times were almost a tenth quicker. The harmonics of the unbalanced tires fought against the car. We were fast on unbalanced tires. We were faster on balanced tires. Sorry for the long reply...
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Old 01-06-2019, 11:12 AM
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The Nascar guy's point is well taken. A balanced assembly will have all rods within + or - one gram of each other. The factory tries to maintain this variable. Rods are also balanced as a group, that is in relation to the other 7 rods in the motor. So, the question I would ask is whether the rods came from the same motor or were loose. If they came from the same motor, and you are using the same type crank for the new build, the balance will be OK because of the factory balance. Do not use loose rods of unknown origin without balancing.

While the factory does not spin balance each crank assembly with bob weights, it does select rods of equal weight. So, if money is a factor, and the rods where from the same factory motor, then the balance is probably doable. Otherwise, you will need a balance, which is usually about $200 or so by a competent shop.

Last edited by rednari2; 01-06-2019 at 03:29 PM.
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Old 01-06-2019, 12:00 PM
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What gen 4 piston and rod combo would you guys recommend for my lq4? Id like to keep the compression low like my original ones do. Im gonna get it balanced for sure before I put it all back together.
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