Internally / externally balanced assembly
Thread Starter
Melting Slicks
Joined: Jan 2002
Posts: 2,238
Likes: 4
From: Milan
Internally / externally balanced assembly
Internally / externally balanced assembly
I Purchased a rotating assembly for my Corvette (’90 automatic transmission) .The car is stock except for k&N filter, airfoil, and no precats and an hi flow cat. converter.
The rotating assy is not here yet in Italy… I’m waiting Fedex…… with the package….
The rotating is:
Eagle cast crank (1 pc rear seal)
Eagle SIR rods
KB flap top pistons +.030 (1.560” compr. Height)
Sealed pwer moly rings
Clevite main and rod bearings.
I purchased this 1 piece rear seal assemby with the option “balanced”.
Now the tech question:
I don’t know if the assy is internally balanced or externally balanced.
I don’t know if a L98 ’90 engine is internally or ext balanced.
I don’t need to know if an internally balanced assembly is best than an externally balaned, I need only to know if I can install the balanced assembly with my stock 12 ¾” 153 th. Flexplate and with the stock 6 ¾” balancer without knowing the kind of balancing procedure of the new rotating assembly.
Another question…_
What’s a SFI aprroved harmonic balancers? Whats means SFI?
Thanks.
Beppe.
I Purchased a rotating assembly for my Corvette (’90 automatic transmission) .The car is stock except for k&N filter, airfoil, and no precats and an hi flow cat. converter.
The rotating assy is not here yet in Italy… I’m waiting Fedex…… with the package….
The rotating is:
Eagle cast crank (1 pc rear seal)
Eagle SIR rods
KB flap top pistons +.030 (1.560” compr. Height)
Sealed pwer moly rings
Clevite main and rod bearings.
I purchased this 1 piece rear seal assemby with the option “balanced”.
Now the tech question:
I don’t know if the assy is internally balanced or externally balanced.
I don’t know if a L98 ’90 engine is internally or ext balanced.
I don’t need to know if an internally balanced assembly is best than an externally balaned, I need only to know if I can install the balanced assembly with my stock 12 ¾” 153 th. Flexplate and with the stock 6 ¾” balancer without knowing the kind of balancing procedure of the new rotating assembly.
Another question…_
What’s a SFI aprroved harmonic balancers? Whats means SFI?
Thanks.
Beppe.
Burning Brakes
Joined: Dec 2000
Posts: 1,023
Likes: 0
From: Marietta, South Carolina, USA
Re: Internally / externally balanced assembly (conv90)
The engine in your car is internally balanced, if you got a stock 350 kit then it must be internally balanaced but if you went with 383 kit then you can have both because they have to use a 400 crank and 400 engines cam externaly balanced but some people do balance them because if you dont you have to use a 400 balancer and flexplay, I dont think the balancer will fit the corvette because 400 balancer is much bigger, I would call the people that sold you this and ask them how they did balance the rotating assembly.
SFI just means that it has been made, tested and aprroved for racing like NHRA and other.
Hope this helps a little.
Jay
SFI just means that it has been made, tested and aprroved for racing like NHRA and other.
Hope this helps a little.
Jay
Thread Starter
Melting Slicks
Joined: Jan 2002
Posts: 2,238
Likes: 4
From: Milan
Re: Internally / externally balanced assembly (MrJay)
What's the difference from a internally balanced assy and a externally?
Are you sure that a l98 engine is internally balanced?
I do a quick search in the archive and I can see only confusion about this ...
To balance a rotating assembly you need also the diameter/weight of the flexplate and balancer ??
If I use a externally balanced assembly on my 90 corvette (supposed to be internally balanced) using stock 153 th. flexplate and stock 6 3/4 balancer , what's bad for the engine?? It shake ?? it's not perfect balanced? I don't fits?? Please help me because I'm very confused...
Thanks
Beppe
Are you sure that a l98 engine is internally balanced?
I do a quick search in the archive and I can see only confusion about this ...
To balance a rotating assembly you need also the diameter/weight of the flexplate and balancer ??
If I use a externally balanced assembly on my 90 corvette (supposed to be internally balanced) using stock 153 th. flexplate and stock 6 3/4 balancer , what's bad for the engine?? It shake ?? it's not perfect balanced? I don't fits?? Please help me because I'm very confused...
Thanks
Beppe
Burning Brakes
Joined: Dec 2000
Posts: 1,023
Likes: 0
From: Marietta, South Carolina, USA
Re: Internally / externally balanced assembly (conv90)
Im sure all SBC are internaly balanced except 400ci it is externaly balanced, they had to do that because of the bigger stroke, I have a 91 L98 and it is internaly balanced.
You dont nead the diameter or weight of the flexplate or the balancer because a balancer and flexplate is nutrol balanced, but you nead to have it if you balance the engine externaly because the balancer and flexplate help balance the engine and you nead a different balancer and flexplate because they help balance the engine.
If you use a externaly balanced crank and you put on a internaly balanced balancer and flexplate your engine shake and it will mess up, it will mess up the bearings.
Hope this helped a little.
Jay
You dont nead the diameter or weight of the flexplate or the balancer because a balancer and flexplate is nutrol balanced, but you nead to have it if you balance the engine externaly because the balancer and flexplate help balance the engine and you nead a different balancer and flexplate because they help balance the engine.
If you use a externaly balanced crank and you put on a internaly balanced balancer and flexplate your engine shake and it will mess up, it will mess up the bearings.
Hope this helped a little.
Jay
Thread Starter
Melting Slicks
Joined: Jan 2002
Posts: 2,238
Likes: 4
From: Milan
Re: Internally / externally balanced assembly (MrJay)
I received your instant messages , but I lost it..
Yes MrJay, My rebuilt is a 355 rebuilt with a3.48" stroke new cast crank and 5.7 rods.
I don't remember (I lost your instant messages) when you say: " if you go with a 350 or 355 ..... you can use... "
I purchased the assembly to partscavengers.com, and they haven't asked the weight/diameter of the balancer I have in my car....so i can expect they balenced the crank internally??
If you say that all SBC are internally balanced, why a store/garage should balance an assembly externally???
Thanks
[Modified by conv90, 5:51 PM 7/19/2002]
Yes MrJay, My rebuilt is a 355 rebuilt with a3.48" stroke new cast crank and 5.7 rods.
I don't remember (I lost your instant messages) when you say: " if you go with a 350 or 355 ..... you can use... "
I purchased the assembly to partscavengers.com, and they haven't asked the weight/diameter of the balancer I have in my car....so i can expect they balenced the crank internally??
If you say that all SBC are internally balanced, why a store/garage should balance an assembly externally???
Thanks
[Modified by conv90, 5:51 PM 7/19/2002]
