Flexplate Weight Identification
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Trailering
Joined: Jul 2023
Posts: 16
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Just an update (documentation of my experiments).
I bought both a 28oz harmonic balancer for an 85 351W and a 50oz harmonic balancer for an 85 302. Both Dormans.
I tried the 28oz balancer (perfect bolt on for the 302), vibration still present (no wonder because Crank is likely a 50oz imbalance). Vibration moved from the front of the motor to the inside, I can definitely see the air cleaner rattle more.
I did a compression test with all the plugs out to rule out a misfire or dead cylinder. Compression values all between 112 - 118 (pretty tight spread I would say).
Old plugs were the Autolite variety (the kind that is factory black threads) so it was difficult to determine condition. With all new motorcraft plugs I had in stock, the vibration is still present.
That leaves me with no choice but to pull the motor, confirm the crank casting numbers, and change the flexplate to 50oz.
I bought both a 28oz harmonic balancer for an 85 351W and a 50oz harmonic balancer for an 85 302. Both Dormans.
I tried the 28oz balancer (perfect bolt on for the 302), vibration still present (no wonder because Crank is likely a 50oz imbalance). Vibration moved from the front of the motor to the inside, I can definitely see the air cleaner rattle more.
I did a compression test with all the plugs out to rule out a misfire or dead cylinder. Compression values all between 112 - 118 (pretty tight spread I would say).
Old plugs were the Autolite variety (the kind that is factory black threads) so it was difficult to determine condition. With all new motorcraft plugs I had in stock, the vibration is still present.
That leaves me with no choice but to pull the motor, confirm the crank casting numbers, and change the flexplate to 50oz.
Last edited by viven44; Jul 22, 2023 at 11:28 AM.
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