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#1 |
Registered User
Join Date: Mar 2008
Location: Tullahoma, TN
Posts: 406
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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? |
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#2 |
Senior Member
![]() Join Date: Mar 2003
Location: Colfax-California
Posts: 8,522
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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 |
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#3 |
Proprietor of Dale's Corner
![]() Join Date: Nov 2012
Location: Vacaville , CA
Posts: 16,096
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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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"Some Days Chickens And Some Days Feathers" Dale XNGH ECV Sam Brannan 1004 R.I.P. 67ChevyRedneck R.I.P. Grumpy Old Man |
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#4 |
Registered User
Join Date: Mar 2008
Location: Tullahoma, TN
Posts: 406
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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! |
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#5 |
Proprietor of Dale's Corner
![]() Join Date: Nov 2012
Location: Vacaville , CA
Posts: 16,096
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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 |
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#6 |
Registered User
Join Date: Jan 2011
Location: Chattanooga, TN
Posts: 2,149
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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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'83 K20-TPI '73 C10 '79 C10-ex-diesel(SOLD) '07 Tahoe(Son driving) '14 Suburban-DD '71 C10-current project |
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#7 |
The Older Generation
![]() ![]() ![]() Join Date: Aug 2006
Location: Montezuma, Iowa
Posts: 25,483
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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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Leon Locksmith, Specializing In Antique Trucks, Automobiles, & Motorcycles (My Dually Pickup Project Thread) http://67-72chevytrucks.com/vboard/s...d.php?t=829820 - |
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#8 |
Registered User
Join Date: Oct 2005
Location: Overland Park, Ks.
Posts: 5,216
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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. |
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#9 | |
Registered User
Join Date: Sep 2011
Location: Ark City, Kansas
Posts: 3,332
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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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#10 |
Registered User
Join Date: Dec 1999
Location: Austin, TX, USA
Posts: 7,717
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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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