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03-11-2020, 11:15 PM | #1 |
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Join Date: Mar 2008
Location: Tullahoma, TN
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454 Flexplate question
71 GMC with Inline 6 and power-glide tranny - I pulled the I6 and put in a 1989 454 from an RV. I have not started the engine yet, still waiting on a carb and a starter. The flex plate on the 454 would not bolt to the torque converter on the power-glide, so I just used the flex plate that was on the I6. But now I've learned that the 454 is externally balanced and uses a special flex plate.
Here are my questions: 1. Do I need to take the I6 Flex plate off and get the correct flex plate? 2. What will happen if I run the I6 Flex plate? 3. Can I buy a 454 flex plate with a hole pattern that will fit the PG torque converter? 4. Will a 454 flex plate fit in the bell housing of the PG? |
03-12-2020, 12:51 AM | #2 |
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Join Date: Mar 2003
Location: Colfax-California
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Re: 454 Flexplate question
Yes you do.
It will create an engine vibration being out of balance. A new 454 plate from Summit should have a dual bolt pattern It should clear but if it does rub, minor grinding can make it clear the aluminum nubs inside the bell |
03-12-2020, 09:16 AM | #3 |
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Re: 454 Flexplate question
If you run it with 6 cyl flex. You will shake the main and thrust bearings out of it in minutes. Probably ruin pump in the trans too.
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03-12-2020, 10:20 AM | #4 |
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Re: 454 Flexplate question
Ole Blue,
Within minutes??!! You got to be messing with me? I figured it would cause issues over time? If you're serious, I'm glad I haven't tried to fire it up! |
03-12-2020, 01:00 PM | #5 |
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Re: 454 Flexplate question
It took about 10 minutes to screw up a fresh small block 400 / turbo 350.
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"Some Days Chickens And Some Days Feathers" Dale XNGH ECV Sam Brannan 1004 R.I.P. 67ChevyRedneck R.I.P. Grumpy Old Man R.I.P. FleetsidePaul |
03-12-2020, 01:47 PM | #6 |
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Re: 454 Flexplate question
Agree. 400SB and 454 have unique flywheels/flexplates. You do not want to run external balance style on them.
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03-12-2020, 02:30 PM | #7 |
The Older Generation
Join Date: Aug 2006
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Re: 454 Flexplate question
-
Don't they make a separate bolt on balancer plate that will compensate for that? LockDoc
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03-12-2020, 03:28 PM | #8 |
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Re: 454 Flexplate question
If they are the same diameter, drill holes in the 454 plate to match the converter.
It will have a horrible vibration if you use it. I had a customer onetime that had put a sb400 plate on a 350. It didn't damage anything but had a bad vibration. I went up through the opening on the bottom & knocked the weight off. It saved tearing it down & worked fine. |
03-12-2020, 04:46 PM | #9 | |
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Location: Ark City, Kansas
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Re: 454 Flexplate question
Quote:
Concerning the good olden days of Chevrolet V-8 engines, the largest displacements of the small block (400) and the big block (454) were externally balanced at the harmonic dampener and at the fly wheel/flex plate, AND I believe the 454 and 400 fly wheels are different.. There's nothing to buy to add to a neutral balanced flywheel... A person COULD have a weight added to a neutral balanced flywheel. It would have to be the exact precise weight and in the exact precise location...all this would cost more than buying the correct needed fly wheel/flexplate... |
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03-13-2020, 07:33 AM | #10 |
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Join Date: Dec 1999
Location: Austin, TX, USA
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Re: 454 Flexplate question
Most aftermarket flexplates are dual drilled for both patterns. $60 gets you an SFI certified one from Summit, Jegs, Amazon, etc. that is externally balanced for your 454.
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