ATCFLYBOY02

iTrader: (1)

What happens when you stick a internally balanced dampener on a externally balanced 383?

My pop had a 383 build at a local machine shop:

1. Ran GREAT on the stand w/ no vibrations
2. Put it in a boat and now we have a vibration.

It vibrates when it is in neutral AND when you have it in "drive".
When its in neutral the only things that spin are an input shaft, a U-joint and a sort of a gear selector in the foot...

My thoughts are that one of the pieces that spins when in neutral is slightly out of adjustment?

Thoughts??

Doc

vetteoz

iTrader: (13)

Did you change any motor parts with the install?
Exp
Install a crank hub for rear mount engine with V drive

AlkyIROC

An internally balanced engine such as a 383 would be using a 400 crankshaft. This needs an externally balanced dampener and flexplate/flywheel. If either have been removed or switched to neutral balance, the engine will hammer out the bearings very quickly.

Without knowing how it's set up in the boat, it's hard to make a suggestion on a remedy. If it doesn't have a 400 dampener and flexplate/flywheel attached, you'll need to correct that.

If the setup in the boat can't use a dampener and flexplate/flywheel then you can't use an externally balanced engine.

ATCFLYBOY02

iTrader: (1)

I think its internally balanced... It doesnt have a bad enough "shake" IMO... I talked to summit and they told me that if it was an external kit that Eagle would have sent the flexplate and balancer also.

I'm not exactly sure how it was installed, I didnt do it and I wasnt there when it was done. The fella that actually put the engine in has been doing it for 40+ years so its hard to say that he didnt know what he was doing. I'm just trying to get some ideas to float around.

Also, It has the 170cc, 62cc, summit racing heads (Made by Trick Flow)... we are getting what appears to be a oil leak from the head gasket... Everything is brand new, so I'm kinda stumped... PS: every time we have the motor taken out, its a whopping $600.00 ... and its a PITA to work on in the boat

basiccamaro

Does it mount flywheel forward (in relation with the transmission in the boat)? This is a common marine application, and it almost always runs with just a coupler on the crankshaft snout- using no balancer whatsoever. It sounds odd but it has been done by many manufacturers over the year with great success. Evidently the harmonics travel down through the prop shaft and prop and disapate into the water.
They do this for two reasons. One, it usually puts the flywheel farther forward in the boat allowing clearance for having the rear of the engine lowered into the bottom of the boat to get the angle to run the shaft out of the bottom of the boat. Not all boats need this, but some do. Secondly, it allows the boat to run a right hand prop without modifying any engine internals. And a right hand prop is like the human right hand world, a lot more stuff is set up for it.

So if you need the externally balanced harmonic balancer for your 383 crank, you will have no way to do this in a marine flywheel forward set up if the transmission coupler runs directly off the crank snout and key/keyway..

ATCFLYBOY02

iTrader: (1)

The flywheel bolts on just like u where hooking a T5 pressure plate to it. It does have a sort of cupler where the output shaft comes out. I did a search on Summit (where the kit was purchased) from what my dad told me about the kit: Eagle, 1 piece seal, 5.7 rod, forged, and a 4.0 throw, it came back with the internal balanced Eagle kit... So until I'm told differently, I am going with the internal assumption...