Moparts Tech Archive

Motor General

Balance the motor ??

318Charger4bbl
Moparts Member
Posts: 983
From: Yarg!
Registered: Dec 2000
posted 05-12-2002 10:22 PM

Hey guys, the 383 will be going into the shop tomorrow afternoon for a rebuild. I'm replacing every frieking mechanical part of the engine with high performance parts. I'm running a 1969 (build date 8/68) 383 HP engine with stock rods, stock crank freshly ground .010 under, and Keith Black pistons in the fresh .030 over cylinders. My uncle insists that if I want the engine to last and run well (mostly street use, some very limited weekend warrior strip use) that I need to have the rotating assembly balanced. If balancing is really worth the money, I will go ahead and have it done. What do you guys think? I can't see building this engine past 400 flywheel horsepower at any point within the next 5 years. Thanks for your input!

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383-man
Moparts Member
Posts: 5382
From: Balt. Md. USA
Registered: Nov 2000
posted 05-12-2002 10:27 PM

Yes its always a good idea but I use all stock parts internally except the cam and I did not balance it and have no vibrations at all. Guess the factory did a good job on it but I dont ever see over 6k. Ron

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Brian_wo
Moparts Member
Posts: 11675
From: Omaha Nebraska wo23dodge@cox.net
Registered: Nov 1999
posted 05-12-2002 10:39 PM

it's amazing that factory engines didn't vibrate with as far off as they are,no way no how would I ever build one without balancing it.

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JDMopar
Moparts Member
Posts: 1524
From: Asheville,NC
Registered: Aug 2000
posted 05-12-2002 10:45 PM

Yes.

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DRAM
Moparts Member
Posts: 4806
From: West Palm Bch. Fl.
Registered: Jun 2000
posted 05-12-2002 10:47 PM

there is only one correct answer to your question, ****YES****

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Mark Nixon
Moparts Member
Posts: 5116
From: Just this side of reality, South 410 miles....In NEBRASKA!!
Registered: Jul 2000
posted 05-12-2002 11:09 PM

Balance it!!
I can't believe people have to ASK that question!!
Mark.

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JohnRR
Moparts
Posts: 10627
From: Ma.
Registered: Nov 1999
posted 05-13-2002 12:56 PM

when i did my 383 the rods were off by 25 grams from the lightest to the heaviest .
KB pistons are lighter than stock pistons also .

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GregZ
Moparts Member
Posts: 4373
From: Naples, Florida !!
Registered: Nov 1999
posted 05-13-2002 01:08 PM

Several machinists have told me that mopar engines have the worst factory balance jobs of any manufacturer.

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Don1
Moparts Member
Posts: 4812
From: Valley City, ND. USA
Registered: Oct 2001
posted 05-13-2002 01:14 PM

Contrary to the above opinions I am on the other side. If you are using the car for a driver with occational weekend blasts i would polish or cut the shaft and leave. If it is a good running engine no spun bearings and al the new bearings fit tight in the caps I would just replace the rod bolts unless you like padding someones pocket The remark has been made here that balancing is free horse power. I have yet to see a free balance job. There many thousnads of rebuild done daily that go for many thousnads of hard miles. The engines that are a prime candidate are high rpm drag engines and engines use at sustained Rpm's such as circle track or the like.
Locally there are 5 of us running Mopars only 1 of which is balanced and that is Hemi car that will run 8's. When we have torn down for yearly or everyother year inspections so far it has turned out to be a tear down of satifaction with no excessive wear. These are strip cars with weekly "Sunday Short trips".
If you want to spend the money fine I will spend mine some where else until such time as I decide to up the output of the engine to a Higher RPM faster ride which I don't see in this lifetime. 11's are quick enough for this old man.

I have rebuilt many engines in the years that I have been wrenching with out balancing. Ever see a engine shop rebuild an engine and balance it without a special request from the owner, do you thnk that rebuilt engines are balanced? Not. The also have new pistons in them. we've had to replace 1 or more pistons in an engine no biggy. If it were going to be a serious race engine and he can afford it I would say go for it but being a street car and sometimes bracket car I think it is a waste of good cash that could be used some where else.
The muscle engines of yesteryear,other than the Hemi, were not balanced and they took serious abuse.

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68MOPER
Moparts Member
Posts: 113
From: WRENTHAM,MASS. USA
Registered: Feb 2000
posted 05-21-2002 07:38 PM

I just rebuilt a street 383. Put KB pistons in it which are lighter than stockers. That leaves the assembly overbalanced at the crank which is the way to be. I was told by several people that for a motor that rarely goes above 5500 and for short blasts the factory balance is fine. I haven't put many miles on it yet but it runs nice and should provide many miles of street use. On a budget I'd spent the money on somthing else.

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Tim Moffett
Moparts Member
Posts: 1627
From: Rochester, NY
Registered: May 2000
posted 05-21-2002 09:29 PM

If it were my engine, I would balance it. My rods were WAY off from the lightest to the heaviest.

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Runner
Moparts Member
Posts: 3039
From: Lewiston, idaho
Registered: Nov 1999
posted 05-21-2002 09:37 PM

i didnt balance mine and i dont have any vibrations, however its not as smooth as another friends balanced 383. (mines faster though )
i was on a pretty tight budget when i did my motor, only had 1300 in the hole long block including machine work. but i can tell you that if i was to do it again the 2 things id change is #1 id put forged pistons in it and #2 id balance it.
its called piece of mind

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dusterjim
Moparts Member
Posts: 342
From: Stanfordville, New York USA
Registered: May 2001
posted 05-21-2002 10:39 PM

Are you prepared to build it again if you really have parts way out of balance? You'll kill your bearings and the motor will shake like a dog scratching fleas! My complete rotating assembly only cost $225 to have balanced. Do it!
Good luck,,

DusterJim

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