454vs.427 - Team Camaro Tech
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post #1 of 7 (permalink) Old Jan 21st, 01, 09:28 AM Thread Starter
 
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I have a 454 with a 427 crank, crank i crossed drilled forged- TRW pistons, 11.25:1 comp. Ratio, the block is 4 bolt, LS6 heads W/ manley stainless valves, Offy Supersonic intake, Holly 1050 dominator,cam.500 lift,.515I. 340 duration, there is a TH400 trans, Question, do I need to check the balancer & flex plate for being balanced or not?
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post #2 of 7 (permalink) Old Jan 21st, 01, 11:32 AM
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Since it isn't a 454 anymore it does not require external balancing. But there are 2 steel 427 cranks, 1 for 3/8" rod bolts, another for 7/16". I'm not sure there is any way to visually id either so you really don't know which you have. Mismatching parts will create an imbalance.

You might want to have the motor balanced.
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post #3 of 7 (permalink) Old Jan 21st, 01, 02:10 PM Thread Starter
 
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Understood it`s not a 454, but the block will always carry those #`s, So I am safe to assume that either of the two cranks are balanced, and that the use of 454 balanced flex plate, and balancer, should pose no balance problem. The rod bolts are 3/8-
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post #4 of 7 (permalink) Old Jan 21st, 01, 02:17 PM Thread Starter
 
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[QUOTE]Originally posted by coketrash:
[B]Understood it`s not a 454, but the block will always carry those #`s, So I am safe to assume that either of the two cranks are balanced, and that the use of 454 balanced flex plate, and balancer, should pose no balance problem. The rod bolts are 3/8- Since as you say it is no longer a 454, it isn`t a 427 either, cut out at 120 what is it?
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post #5 of 7 (permalink) Old Jan 21st, 01, 07:00 PM
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Coketrash, that's not a safe thing to assume.

The 427 crank relies souly on the counterweights for it's ballance, and the flywheel and balancer for it have a neutral ballance. The 454 crank, in part, relies on offset weights on both the flywheel and ballancer for propper ballance. Using the 454 balancer and flywheel on a "balanced 427" crank will definately cause a vibration problem.

Any machine good machine shop will ask for both the flywheel and the harmonic ballancer along with your crank when they ballance it. This is so the whole system can be checked. I would strongly recomend using the 396/427 flywheel and balancer, and having the whole system checked together at a machine shop.

Good luck,

Keith
'69 RS/SS 502
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post #6 of 7 (permalink) Old Jan 22nd, 01, 02:24 AM
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Isn't a 427 crank the same stroke as a 396 in as you install 396 crank in 454 block and you get 427 cu. in. so are there 396 AND 427 cranks or are the the same castings or forgings?

------------------
69 rallye green X77 Z/28,1967 SS 396 Conv. 1974 c-10 454 swb
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post #7 of 7 (permalink) Old Jan 22nd, 01, 05:34 AM
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One should always have the moving parts balanced, from the harmonic balancer to the flywheel, including clutch cover. It wold be nice if balancing shops did Torq. conv, but you would have to pump fluid thru it while doing the balancing. Some T/Q have an horrendous amount of imbalance. This only destroys rear main bearings because of tooo much load at high RPM's. Be sure you get a balance sheet from the balance shop, this will aid you in replacement parts later.

Everett 68/350/PG/11.90
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