Originally Posted by atcoscrazyest69
I understand the external balance points with 400s and 383 as it is on a 4 speed trans and i had to buy that plate that bolts between the flywheel and crank. I understand that the balancers are different for the externally balanced 400 and all the other internally ballanced motors. The whole reason for trying to make it internally balanced is i do not like having to run that balance plate. I just dont understand why the add says its balanced and a couple fellas on here are saying send all the brand new stuff out to get balanced. If i have to send it ourmt to get balanced either way then theres no need for me to get a whole rotating assembly the only reason i said id get the assembly is because it states its balanced. I just donot know what to do. But i do not want to do it again
That's reasonable; I'm not enamored of externally balanced engines, therefore, work hard to keep 400's and 383's internally balanced.
The kit you sight is internally balanced and will, therefore, require that you purchase a netural balanced flywheel and damper.
The raging argument about how well balanced is one revolving around how good is good enough. Some of these pre-balanced kits have been miles off. Sometimes this is the result of the manufacturer other times it's been the fault of the builder taking to much material from the rods or piston skirts in the pursuit of clearance. Frankly, I prefer SCAT to Eagle when it comes to budget bottom end parts and assemblies. But since you're dealing with Summit, they have a very good customer service reputation so I'd mentally lean on them with this provisio; if you have interference between the rods and cam or piston skirts DO NOT FIX IT. Call Summit and make arraingements to return it in the original packaging in a clean and unmolested state. That eliminates any argument over who did what and has blame. Grinding on the rods and or pistons will alter their weight destroying what ever level of balance they came with. Mayby not by much, but you don't want to get caught in "if you touched it, its yours".
One thing we see a lot of when sending parts to our balancer is that many things that are sold as balanced (including flywheels, flexplates, and dampers) are often well off any reasonable standard for a performance to competition level engine. So we do not even bother with pre-balanced kits. We procure things in pieces, make up assemblies, proceed to a mock-up build that trims parts if necessary, mark them as to where they go and who goes with whom, then have them balanced. This is tedious and adds some cost but the end result is a correctly balanced engine, whether that's spot on or over/under balanced by end use or customer desired requirement. For a mild performance street engine that doesn't go over about 6 grand of RPMs, spot on is the place to be no over/under balance games needed.