Hey guys. I've got a question about deleting the balance shaft to install a double roller timing chain on the 3800. I know you have to drill and tap the rear oiling hole to get the plug all nice and installed, but how would this affect the engine's balance? Would I need to get the engine rebalanced so it wouldn't vibrate at a lower RPM range? This is my daily driver so I would want something that doesn't shake a ton at idle at a stoplight, although I would accept something that isn't vibrating too crazy.. Let me know what you guys think, thanks!

 

You don't have to do it that way. I went with the 440 cam bearing option - you just install the bearing so the oil hole doesn't line up and it blocks the flow off. Drill and tap is fine too if you prefer, I just didn't want the shavings getting into the oiling system.

No. Its an NVH item for 2nd / 3rd order vibration- not for primary balance.

Actually if you look at the shaft, its actually 0 balance static down the centerline (has equal mass above and below) unlike something like the flexplate or balancer which have a large offset weight for balancing. Its dynamic balance (end to end) is where its intended to smooth out the naturally rough 3800 firing order.

Tons and tons of people have deleted it without issue without touching the bottom end.

I can't talk to that. Mine vibrates like crazy, but I've also got an IS3 cam w/ 1.7s, solid poly mounts, and a low (for a bigger cam) idle because I love the chop.

Id just stick with stock rubber engine mounts to start (frankly there isn't any kind of major performance increase there anyways), and keep the idle rpm up a bit to smooth out the cam and I'd bet it'll be more than smooth enough for a typical car enthusiast.

 

Cam bearing option seems like an easier path when deleting the balance shaft? You just lube up the bearing, pop it in with a rubber mallet, and you're done?

Sounds good to know. I don't have poly mounts or don't really plan to- so I'm sure the vibration won't be too bad.

 

I think its easier for DIY personally, but I'm sure a machinist with a nice set of bits and taps would disagree.

Unfortunately the 440 bearing isn't quite as easy as you'd mentioned. It is .004" over spec on the OD so it takes some force as it'll be an interference fit. I added a steeper chamfer with a hand file to the leading edge (to help get it started quicker/minimize how much cold it lost), put the bearing in the freezer to shrink it, put a little lube on the block bore, and then hammered it home with a hammer and appropriately sized socket.

Ideally you'd probably want to use a cam bearing installer tool as the socket marred the trailing edge a bit - but since its not actually being used as a bearing I didn't really care.