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What is external vs internal balance?

fine69

Well-known member
Joined
Dec 12, 2004
Messages
975
Location
Maryland / D.C.
Corvette
'69 Convertible Vette; '72 Z28 Camaro Rally Sport
Merry Christmas All!

I have an opportunity to acquire a rebuilt a 1970 454 long-block engine (4 bolt main) from a local machining and engine rebuilding shop. It comes with a three year unlimited mileage warranty. I don't believe this is a hotrod engine or anything - but it is standard height block from a car, not a truck.

I realize that the 454 would not be "correct" for a 1969 vehicle, but I am seriously considerinng this purchase (plus I'm not really into the whole numbers-matching thing anyway).

I understand that the 454 and 427 are somewhat similar. The guy mentioned something about "internal" vs "external" balancing. What does this mean?

Thank you!

Ralph

:w
 

motorman

Well-known member
Joined
Mar 7, 2002
Messages
849
Location
pa
Corvette
2008 Crystal Red Tint Coat
Merry Christmas All!

I have an opportunity to acquire a rebuilt a 1970 454 engine (4 bolt main) with a three year unlimited mileage warranty. I don't believe this is a hotrod engine or anything - but it is standard height block from a car, not a truck.

I realize that the 454 would not be "correct" for a 1969 vehicle, but I am seriously considerinng this purchase (plus I'm not really into the whole numbers-matching thing anyway).

I understand that the 454 and 427 are somewhat similar. The guy mentioned something about "internal" vs "external" balancing. What does this mean?

Thank you!

Ralph

:w
the 454 will need a special front balancer and a special flywheel,both have a offset weight built into them to balance the rotating assy. because of the longer stroke there is not enought room inside the engine to get large enought counter weights on the crankshaft so the extra weight is added to the balancer and flywheel.
 

fine69

Well-known member
Joined
Dec 12, 2004
Messages
975
Location
Maryland / D.C.
Corvette
'69 Convertible Vette; '72 Z28 Camaro Rally Sport
the 454 will need a special front balancer and a special flywheel,both have a offset weight built into them to balance the rotating assy. because of the longer stroke there is not enought room inside the engine to get large enought counter weights on the crankshaft so the extra weight is added to the balancer and flywheel.

Thanks for the explanation. Does the flywheel and torsion balancer need to be custom-tailored specifically for the individual rotating assembly (i.e., is this something that the machine shop would have to do, or can I just purchase the balancer and flywheel made for the 454 ?).
 

Jack

Well-known member
Joined
Dec 27, 2000
Messages
1,825
Location
Florence, SC (Timmonsville SC)
Corvette
71 War Bonnet Yellow VERT 71 BH Blue CPE (SOLD)
Thanks for the explanation. Does the flywheel and torsion balancer need to be custom-tailored specifically for the individual rotating assembly (i.e., is this something that the machine shop would have to do, or can I just purchase the balancer and flywheel made for the 454 ?).
Buy a balancer/damper for a 454 ... same for flywheel. OR ... there is "balance plate" available that mimics the 454 flywheel's cast-in counterweight ... that balance plate is basically a thin eccentric shim that installs between the crank's fw flange and YOUR 350's internal balance (aka neutral balance) flywheel. FYI, there is room inside 454 for internal/neutral balance counterweights ... clearance has as much to do with how the crank's counterweights are configured & if/how much the rod throws are gundrilled. Plenty of aftermarket FORGED STEEL 454 cranks are internal/neutral balance and fit without clearancing block. AFAIK, most OE 454 cranks are cast iron. If you internal balance a 454 w/ an internal balance crank ... you use a 427 damper and 350 or 427 flywheel/flexplate. 427 and '85-back 350 are internal/neutral balance motors. See? ... several ways to skin that cat. About the only thing on your built 350 that'll fit a big block is the flywheel (with addition of balance plate) ... most likely no brackets & no pulleys will swap.
 

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