Moparts Tech Archive
Balance the motor ??Is it worth getting the rotating assembly balanced??
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!
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
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.
there is only one correct answer to your question, ****YES****
when i did my 383 the rods were off by 25 grams from the lightest to the heaviest .
Several machinists have told me that mopar engines have the worst factory balance jobs of any manufacturer.
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.
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.
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.
If it were my engine, I would balance it. My rods were WAY off from the lightest to the heaviest.
i didnt balance mine and i dont have any vibrations, however its not as smooth as another friends balanced 383. (mines faster though )
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!