evo 8 gsc raacing balance shaft VS stub shaft

Do you guys use gsc racing balance shaft or is it better to use stub shaft on 4g63? I have both and I dont know which one should I use. I used gsc racing shafts before on other engines and I had some vibrations on couple engines on higher rpm's not sure if it was because this racing balance shaft but the other engine with stub shaft did not had any vibrations. Which option do you guys use on high hp. Thanks

Hi. On high performance engines with short preventive maintenance time i use stub shaft but those aren't reving much above 8000 RPM. On daily drivers i use simular to gsc power-division balance shaft.

The balance shaft(s) are used to counter 2nd order vibrations - you should be fine without them but as they take neglible power and make the engines much smoother for the driver, might as well use them.

I will for sure remove them because I don't want to risk damaging timing belt etc. I just can't decide between short stub shaft that some people say is damaging oil pump housing vs racing balance shaft. I used racing balance shaft before with good results but engine had some vibration not sure if it was because racing balance shaft was there or because factory balance shafts were removed.

There are several guides to 2nd order imbalance, and why balance shafts are used, but this is a good introduction it it - https://www.youtube.com/watch?v=h1ytdRB1iSg

"short rod" engines are more susceptible to it than "long rod", because the acc'ns around TDC and BDC are a little closer.

Thanks a lot Gord for the link. I found something very interesting about gsc racing shaft. We put it in the special fixture to measure runout, and I found that there is .0015-.0017 runout on the large bearing surface and .0000 runout one the small side. I know this is not horrible a lot but I dont feel comfortable running it on high rpm engine especially when this shaft spinning 2x faster than crankshaft. I hope gsc will replace it with another one but if not I think I will run short stub shaft.

If you'll watch Andre's video about his experience with 4g63 he reckons that short stub will definitely lead to oil pump failure over time. But he was reving his engine well past 10 000 rpm as far as i remember...

https://www.hpacademy.com/previous-webinars/297-balance-shaft-removal-4g63/

Thanks a lot far a video. Yes my main goal was to use gsc racing balance shaft but after checking it for runout and having almost 2 thousand of an inch runout I would definitely choose stub shaft over not straight gsc shaft. I did contacted gsc to have a replacement shaft but did not hear anything from them just yet. I hope they can replace with a straight peace so I can run it. Also I found something interesting on Magnus motorsport website about those machined shafts or gsc racing shafts here this is from their website:

Don’t be fooled by others and their ‘shaved’ or ‘lathed’ original balance shafts. If your motor is spinning 10,000 RPM why would you want another bearing on the end of a shaft spinning at 20,000 RPM? That could cause problems especially since it is way beyond what the bearings were designed for, not to mention it is rare that anyone ever checks the clearance of this balance shaft. Eliminating the original balance shafts or lathed unit is good insurance on eliminating another point of possible failure.

So it's loose-loose situation) No matter what you'll install you are most likely to find troubles with oil pump if it's reving really high...

That's what it look like. I used gsc racing balance shaft in the past and I was reving it to 9500 but I did not measured it for runout, I just installed it and it was fine but now new gsc shaft for new eng has pretty much a lot of runout and that is making me nervous. Shaft spinning at 18000-19000 rpms with almost 2 thousand runout I just dont know how I fell about it. If the shaft would have 0.0005 runout I thing it would be acceptable. When your car rotors are warped at 0.003 ( three thousand of an inch) you can feel it at your brake pedal or sometimes at your steering wheel while braking but imagine what vibration shaft can make spinning so fast with similar runout. I just don't know what I am going to install at that point.