jamunm90 Posted October 10, 2008 Share Posted October 10, 2008 Quick question. Is a stock flywheel/pressure plate assy. that is 33 grams off considered significantly out of balance? Just finished my n/a to turbo conversion on my 80 zx after 400,000 miles, so that engine was tired!! (No cylinder bore cross hatches visible on this engine!!) Anyway, after rebuilding a turbo motor and putting everything together, the engine and car vibrates at 1500 to 2K rpm, engine loaded and unloaded, clutch in or out, moving or stationary, it doesn't change this vibration. All plugs are even colored, and compression is equal within 5 psi. Also valve train is adjusted to specs. The 5 SP non-T5 gearbox was swapped over from the old car, so I know it's fine. Bought a used 240mm flywheel on ebay and a new turbo clutch and pressure plate assy. After pulling out what little hair I have left, I decided to pull off the clutch and flywheel and check the balance. The machine shop stated it was off by 33 grams. Is this significant and could this be the source? A co-worked stated that compared to the weight of the flywheel, it wasn't much and likely wasn't the culprit, at least not entirely by itself. Do any of you have experience with a flywheel off by this much? Did it cause an issue? Thanks!! BTW...The pulley/harmonic balancer is the same one that came on the turbo engine, so I've eliminated that. Quote Link to comment Share on other sites More sharing options...
janaka Posted October 10, 2008 Share Posted October 10, 2008 33grams sounds like a lot to me. remember its not the weight while stationary but moreover the rotating mass. 33grams becomes a lot mo re when spinning at engine speeds. Quote Link to comment Share on other sites More sharing options...
woldson Posted October 11, 2008 Share Posted October 11, 2008 Might be wise not to assume that the turbo balancer is fine, unless it was off an engine you know. Once I had a problem with mine and I was farting with something and my brother was under the hood watching and was like whoaaaa. Harmonic balancer had become loose. Quote Link to comment Share on other sites More sharing options...
Clifton Posted October 11, 2008 Share Posted October 11, 2008 Damper, not balancer. 1 fast Z had to rebalance a pressure plate that was causing him problems. I don't know how much it was out by though. Quote Link to comment Share on other sites More sharing options...
dr_hunt Posted October 11, 2008 Share Posted October 11, 2008 33 grams is significant when dealing with something so large in diameter. Quote Link to comment Share on other sites More sharing options...
woldson Posted October 11, 2008 Share Posted October 11, 2008 Damper, not balancer. 1 fast Z had to rebalance a pressure plate that was causing him problems. I don't know how much it was out by though. I'll make a note of that thanks:) Quote Link to comment Share on other sites More sharing options...
Tony D Posted October 11, 2008 Share Posted October 11, 2008 If memory serves, a Volkswagen Flywheel that was supposedly never designed to be run above 5000 rpms was only allowed 1 gm/cm imbalance. Then again, they were forged chrome-moly too...those crazy Germans! That sounds like a lot to me, but I'm suprised it's in the flywheel and not the clutch-cover. Usually the flywheels are pretty stable and don't 'go out' unless something is coming apart. I would not not use it unless it was penetrant checked or magnafluxed. Quote Link to comment Share on other sites More sharing options...
jamunm90 Posted October 12, 2008 Author Share Posted October 12, 2008 If memory serves, a Volkswagen Flywheel that was supposedly never designed to be run above 5000 rpms was only allowed 1 gm/cm imbalance. Then again, they were forged chrome-moly too...those crazy Germans! That sounds like a lot to me, but I'm suprised it's in the flywheel and not the clutch-cover. Usually the flywheels are pretty stable and don't 'go out' unless something is coming apart. I would not not use it unless it was penetrant checked or magnafluxed. Thanks for the input everyone. I was suprised it was this off, and the shop told me the clutch cover actually helped it a little, which didn't make me feel much better. Anyway, as my luck goes, they're backed up and won't get around to it for about another week. I'll also eye that harmonic damper...I ASSumed it was ok...damn it, I did that again! Thanks Tony for the advice to check for cracks. I actually have a Ardrox Penetrant Dye kit that I need some more practice on, so I'll check it with that too. Drool...I'd love to have a forged chrome-moly flywheel, lightened of course! Now I'll think about that everytime I see a VW bug putter by on 45 bhp, and smile. Quote Link to comment Share on other sites More sharing options...
Doug71zt Posted October 12, 2008 Share Posted October 12, 2008 My stock L28ET rotating assy was 4 grams out from the factory. Any L-series rotating assy that I have balanced was around this number. When I built my LD28 cranked current engine, the crank was out a gram, the L24 balancer was out 3 grams, but the lightened flywheel was out by 15 grams. Personally, I would balance it down as low as you can get it. Quote Link to comment Share on other sites More sharing options...
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