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what is the better option. I’m doing a 454 30 over with a stroked displacement of probably 489 and read that stroked cranks are better externally balanced but don’t quite know if I’m understanding the pros and cons completely.
what is the better option. I’m doing a 454 30 over with a stroked displacement of probably 489 and read that stroked cranks are better externally balanced but don’t quite know if I’m understanding the pros and cons completely.
The Chevy engineers who designed the original Gen IV engine chose to balance it externally (weights on the flywheel for manual and on flexplate for auto trans) for some reason that must have related to performance or manufacturing issues. Balancing it internally requires drilling the crank counterweights and adding heavy metal. I would suspect unless you are going to try to rev the motor to well over 6K rpm (difficult with your stroked motor) that the external balance method will be easier and cheaper.
The Chevy engineers who designed the original Gen IV engine chose to balance it externally (weights on the flywheel for manual and on flexplate for auto trans) for some reason that must have related to performance or manufacturing issues. Balancing it internally requires drilling the crank counterweights and adding heavy metal. I would suspect unless you are going to try to rev the motor to well over 6K rpm (difficult with your stroked motor) that the external balance method will be easier and cheaper.
It seems like the externally balanced assemblies are more expensive....are they just cheaper in the long run?
My machinist suggested to purchase a good quality crank and balance it internally. He said a good crank will need very little balancing. Plus he told me that if you every have a flywheel, flex plate or balancer issue you won't have to get either balanced and can just remove and replace.
It seems like the externally balanced assemblies are more expensive....are they just cheaper in the long run?
396-427's were internal. as stroke gets longer, it gets harder to balance. so cheaper and easier to add weight farther outboard, like on flywheel. if internal was cheaper, all manufacturers would do it. you want to internal balance, stop looking at eagle and scat. but the crank will cost more than the whole eagle rotating assy. I think what you are planning on doing with this motor, a round port or L29 head 454 with a little bit of cam will be fine. this is a car show and sunday driver, right? you are not trying to get into the low 10 second club?
Last edited by derekderek; Dec 19, 2017 at 05:33 AM.
396-427's were internal. as stroke gets longer, it gets harder to balance. so cheaper and easier to add weight farther outboard, like on flywheel. if internal was cheaper, all manufacturers would do it. you want to internal balance, stop looking at eagle and scat. but the crank will cost more than the whole eagle rotating assy. I think what you are planning on doing with this motor, a round port or L29 head 454 with a little bit of cam will be fine. this is a car show and sunday driver, right? you are not trying to get into the low 10 second club?
No but that sure would be cool. But yes if I’m being honest with myself I probably will rarely see strip plus I just heard Rocky Mountain raceways propert got sold and by next year will be no more😭
Better for you and "better" are two different things. You will get a lot of people on here to tell you to throw more money at it for the "better" option. But that doesn't mean it's better for you. As already said, think about what your turning RPM wise.
Or better yet, call Eagle and Scat and ask THEM. Nobody on this forum knows as much about those assemblies as the companies that make them. People tend to overbuild street motors because "nascar" or "the pro's" do this and that. Or the better claim I see all the time "That assembly won't handle what they say it will, you need to buy the higher end one". It makes me laugh every time. Following this advice is perfectly fine for folks that need the best of the best and the sense of a safety net on their performance caps. If you find yourself at anypoint weighing your options based on cost, I think you are likely not that and more like majority of car enthusiasts who really just want a good solid street/strip build that will never see over 6k at the best price possible.
Call Eagle or Scat and just tell them exactly what this motor will be used for, let them make a suggestion.
-Stroke
Last edited by Strokemyaxe; Dec 19, 2017 at 10:29 AM.
Sounds like you are buying the complete assembly. Probably not a big deal either way, but I would probably stick with internally balanced setup from the manufacturer.
Just make sure whatever route you choose, to match your parts... Internal balanced crank,internal balanced flywheel and balancer, if not you will have a lot of vibration...
Definitely internal. get the right crank. External was done only because it's cheaper at factory to not make a new crank forging. And get center counterweights. Cost is similar.
Don't use any fluid type damper either.
Jim
Last edited by 427Hotrod; Dec 19, 2017 at 11:44 AM.
I'm pretty sure the only reason the factory manufactured externally balanced engines is to control costs. If balancing the crank requires the addition of Mallory metal, then the cost goes up substantially. Cheaper for them to achieve balance with the flywheel and vibration damper. Therefore I am pretty sure internal balance is better. Not sure how related it is but the 383 I built about ten years ago was externally balanced. Internal balance wasn't common in those days. It was also a cast crank. Last summer I broke the crankshaft. Not sure the external balance had anything to do with it. More sure the cast crank was a weak link. My advice. Go internal balance, and definitely go forged crank.
internally balance vs externally balanced.
