does it have weights on the flywheel if its a stick,or fleplate if an automatic? then it is external balanced
The dampner will be undercut on the outside on one side or it will have a cast or bolt in counterweight on the back if it is externally balanced.
All of the one piece rear main seal small blocks are externally balanced on the flywheel end only! This is to make up for the removal of the rear balance weight on the standard 350 flywheel flange. WARNING, They are not the same as the 400 S.B. They are only for the one piece rear seal engines only!
to be completely truthful, there are three setups. Any pre-'86 small block aside from the 400 was internally balanced, the 400 was externally balanced, having the flex plate with weights and balancer with one side under-cut as pictured above. The '86 and up engine is a hybrid of the two with a flex plate or flywheel having about half the weight but still using a neutral balncer with no under-cut. Besides checking casting numbers, the visible difference would be the one piece rear seal on the '86 up motors and small pattern to attach the wheel to the crankshaft.
and what ive come to learn is you cant take parts out of any 1pc seal engine and put it in an lt1 engine.. lt1's are a different breed also.
you think correct....look at the harmonic balancer , if it has "cut outs" it is externally balanced . A internal balanced small block has a smooth round balancer.
"LT1" doesn't really tell you much besides 350 cu in. That code was used for 2 generations. The LS1 and newer is completely different, but a few parts interchange on the LT1 from 1970 and 1992. http://en.wikipedia.org/wiki/GM_LT_engine
you cant mix and match parts, its either the whole rotating ***embly or rebalance.. if you use the rods from a regular old 350, the rods are heavier, same as pistons and crank (crank throws). so if you use just the rods, it throws it out of balance.. if you use just the crank from an older 1 pc seal engine, the throws are balanced different, so it throws everything out of balance.. example: if you get a new rotating ***embly get it internal balanced, and also get a neutral weight flywheel/flexplate.. a regular 1pc seal crank, will work in an lt1, you just have to get it rebalanced.. i have an lt1 tore apart right now, you can see the difference in the rods and pistons, and the crank throws.. plus the crankshaft in an lt1 is nodular iron, standard 1pc seal cranks (from say a truck) are cast iron.. they also have different part numbers..
Now you guys are getting into Gen 1 versus Gen 2. The Gen 1 consists of the pre '86 sbc, including the 1st LT1, the post '86 sbc that was produced through 2005, which includes the Vortec family and the 400 sbc of pre '86 variety. The Gen 2 is made up of the LT1 family that came after about 1990 in the vette, 1993 in the F-body and then was also used in the GM full size caprice, impalla and several buick and cadillac rwd vehicles. It is identified by it's lack of distributor above the intake as it was moved to the timing cover, cam driven waterpump and the aforementioned balance changes due to a lighter rotating ***embly. It was also the basis for the fast burn combustion chamber that found it's way to the Vortec and ZZ family. Now we have 4 small block chevy balance configurations.Early internal balance, Early external balance (400 ci), Late Gen 1 hybrid external balance, Gen 2 (LT1) hybrid external balance. I exclude the LS family because they aren't close enough to interchange much, though I have heard of a aftermarket block to put LS heads on a Gen 1 motor.
Not entirely true. My '99 Vortec motor has no under-cut on the balancer, but very much needs a counter weight on the flywheel (as do all '86+). This is a huge source of confusion in a catalog because people do refer to the engine as internally balanced, but then they say the flywheel is externally balanced. I had two shipped to me that were incorrect. The super simple small block chevy seems to be too complicated for many sales types these days.
Later 283's,307-350 are all external balance if ya think about it.The porkchop shape on the rear of the crank is a balance weight.The 86 and up one piece rear main seal SBC has a small weight on the flexplate or flywheel,but a round crankshaft end.The weight went from the crank to the flywheel,all the internal moving parts are the same design
Most folks think "internal balance" means the crankshaft has all the weight on it, and the damper and flywheel are neutral. and that "external balance" means there is offset weight on the damper and/or flywheel
squirrel has left the building! i was hoping for an answer on this one to, as a suppler is trying to give me the wrong flexplate.
sorry , but now your just trying to confuse the issue, as stated previously above, 283, 307 and 350 up to 1986 are all internally balanced. the the shape of the rear crank flange makes it a weight but is part of the crank(internal part). the weighted damper or flywheel are what make other engines external balance.
I made than comment a few years ago while ***embling a one piece rear main seal SBC.I'm an electrician not a pro engine builder so to me the fact the balance weight is "external" ,as in not inside the oil pan,I made the remark. I think it's an good observation actually although it may confuse pro engine builders
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