OkeeGuy

does anyone here know? :confused:

Teuffelhunde

When I was building my new engine I had it internally balanced and blue printed. I assume you mean crankshaft. I'm sure Chevy did the same in St. Louis.

GrandSportC3

What I've heared - 327's and 350's are usually internally balanced and 383's and 400's are usually external balanced.. However - you could balance any engine either way.. Stock Corvette engines are very likely internal balanced...

:cheers:

Olivier

Scott78

The ones that are externally balanced from the factory are the, 400 and 454
all others (V8) are internally balanced. NOw if your taking about a stroked 350 aka 383, depending on the crankshaft used it can be either. Hope that helps, oopss I'm not absolutely sure on the 305 but I think it is.

Scott

Clink69

My 383 is internally balanced which required a Forged Crank.. I much prefer Internal balance since its done once. If you have external balance and need flywheel work, well, you gotta do it again...

Chris :flag

OHSIXX

Mine is balanced, but what difference does it make if it is internally or externally? :confused:

norvalwilhelm

I would prefer internal balancing also but with my 454 it is too costly. Heavy metal internal balancing can run $500 plus easily if alot of heavy metal is required.
To keep the cost down I go with external balancing using a standard 454 flexplate. Hopefully if I had to replace it any stand 454 flexplate would work. You can also take a new flexplate/ flywheel and have it offset matched to the original.

wallyknoch

It all depends on the year and engine size. All C1-C3 small block cars are internally balanced engines. 265-350`s . Big block C2`s 396/427 are also internally balanced. Big block C3 427`s internally, and the 454 cars are externally balanced. To internally balance the 454`s would require a ton of heavy metal to do the crank. Not really worth the expense. :thumbs: :D

OkeeGuy

that was originaly my question too...
although my engine runs super, when you rev it, when the revs "come back down" im getting a vibration...also my shifter rattles at or around 4000 rpms.

so my mech/tech asked if when i bought my crank, if i bought an internaly or externaly balanced one and what was the engine originaly? aparently either way is ok but the crank and flywheel should be of the same type...
ie...
internaly balanced crank/internaly balanced flywheel...
externaly balanced crank/externaly balanced flywheel...

im not sure of what type the crank it is but i will find out today...
the other thing we're considering is the clutch...i bought a Ryno...
we're thinking that it may be the culpret...have any of you had any bad luck with Ryno clutches?
the rattle seems to originate from the bell housing area...and it is possible that it is related to the squeek we cant find... http://forums.corvetteforum.com/zerothread?id=475336

thanx to all of you for your help

'79ProwlerOrange

:iagree:

MRZ28HO

All SBCs (less the 400) up to 1986 (two piece rear main seal types) were internally balanced. Internally balanced means that only the crankshaft, connecting rods, and pistons were balanced together (basically all internal components). Where as an externally balanced engine needs to have the flywheel/flexplate and harmonic balancer installed to be properly balanced. If you are bulding a stroker, then internally balanced can get expensive (depending on the stroke and needed counter weights). SBC after 1986 (one piece rear main seal types) are consider late model externally balanced. This differs from the 400 and some BBC, how? I don't know that.


[Modified by MRZ28HO, 6:53 AM 1/24/2003]

fauxrs

Basicly if the crank you purchased was a reground original from a 400 sbc it is externally balanced and as you surmised requires the 400 flywheel which has an offset weight cast into its body - in addition you need a 400 sbc balancer which has a corresponding offset weight cast into it.

On internally balanced motors the flywheel and balancer are neutral (i.e. have no offest weight and therefore should be neutrally balanced )- however if you are balancing an engine it never hurts to throw the flywheel and balancer onto the machine at the same time as the crank/rods/pistons, because despite thier neutral balance status they are not perfect items and may throw balance slightly off. (a very very small amount).

Most mfrs of aftermarket cranks are now designing their stroker cranks to be internally balanced. Scat - Eagle etc.....

On the newer 1 pc seal rear motors the bolt circle on the flywheel is smaller so flywheels will not interchange. I dont know for a fact but have been told that factory engines are balanced by weight only - (in other words they weigh the rods and pistons individually to get as close a weight match as possible, their balance is not dynamic - spun up on a machine) this makes sense to me as doing a dynamic balance and the machining of rods and pistons to balance the system dynamicly seems too time consuming for a mass produced motor.


[Modified by fauxrs, 7:52 AM 1/24/2003]

Fevre

Always wonder how they balance with the rods and pistons dynamically, is there a block like assembly they put them so they can spin the whole assembly?

:party:
Just thought I'd throw the new icon on just for the hell of it!


[Modified by Fevre, 9:58 AM 1/24/2003]

fauxrs

The fixture basically is a machine that has all the main cap locations - they attach bob weights that weigh the same as the piston/rod assemblies - and spin it up. Usually the piston/rod assemblies are balanced seperately by weight and the crank is spun up. final adjustment can be done by adding/removing weight from the counterweights - also material can be taken off the small end of the rod or the inside of the piston.

Its a painstaking procedure but well worth the effort.

UKPaul

I regularly get the bike engines I built dynamically balanced. Here's how it works:
The complete piston assemblies (piston, rings, pins & circlips) are accurately weighed & metal removed from the lower edge of the skirts to weight match them all (metal can be removed from the wrist pin if need be). Next the conrods are matched. This isn't the overall weight, but the weights of all the small ends are equalised & the weights of all the big ends are equalised (including big end shells, rod bolts & nuts). Metal is removed from the very top edge of the rods to equalise the small end weights & removed from the end caps to do the big end weights. Then it gets vague (he wouldn't tell me!). The crank is mounted in the balancing machine with bob weights clamped to the main journals. The mass of the weights depends on the balance factor to be used (63% or 85% on the engines I do). As far as I thought, the figure is the %age of the total mass of a conrod & piston assy, but he said it wasn't quite that simple. The crank is then spun & the machine (like a tire blancer) indicates where weight is to be removed (by drilling holes in the flywheel) or added (by drilling holes & inserting Tungsten slugs). The difference is incredible. My 500 was perfectly balanced statically, he told me, couldn't have been better, but across the flywheel (along the axis of rotation) variation in metal density, etc, was causing a rocking effect. Drilling holes one one side of the flywheel on the "top" side & another line of hole on the other side on the bottom side (hope that made sense!) corrected the balancing. The engine now runs smoother than an in-line 4 (it's a vertical twin)!
The guy who did the balancing was doing an Indy car when I picked mine up (ever felt that your crank was a bit small? :lol: ) & said that even though a V8 was pretty good statically balanced, it was far, far better to have it done dynamically.
:cheers:
edit: I took to long typing. Not only has fauxrs explained it in less words than me, he's also thrown a party :D


[Modified by UKPaul, 6:47 PM 1/24/2003]

lars

Gary -
Here's the deal:
The 400 and 454 Chevys are externally balanced from the factory. This means they have a crankshaft that requires a counterweighted balancer and a counterweighted flywheel (or flexplate) to offset the balance of the crankshaft itself. All of the internal engine pieces, like the rods, pistons, etc. are still individually balanced, but the crank balance must be offset through the use of the counterweighted balancer and flywheel. Likewise, a "383" engine, which is a 350 with a 400 crank in it, is usually externally balanced, using the 400 pieces on the ends of the crank.
The 350, 396 and 427 engines are all internally balanced, meaning that the crank is neutral balanced, and the flywheel and balancer are not counterweighted. It is possible to internally balance a 400 (or 406), but it is VERY expensive to install the heavy metal into the crankshaft to obtain the neutral balance. It is possible to procure an internally balanced crank for a 400, but these run about $1200-$1500. Some people claim that the internally balanced engines will last longer, but that's certainly up for debate...

Brettmc

If you had a 283, 327, 350, etc flexplate and balancer on a 400 crank, or vice-versa, you would certainly know it. When I was in college, I had a guy put a 350 in my daily driver in which the old engine expired. Don't know how, but it had a 400 flexplate and balancer on it. It shook very badly on the test drive. After swapping for the correct pieces, it was smooth running.

OkeeGuy

i bought a Scat crank so im assuming that it is internaly balanced as is my original 350 flywheel...correct?
anyone have any idea why im gettine that slight vibration when the revs are on there way "back down"?
what about the clutch? im using a Ryno and im thinking that it might be that...
thanx to all of you that responded...