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Hello all, I am new to the site, but I have been lurking and reading here for a while. I have an 88 Bronco which I bought without a motor. The original motor was a 302 and i bought a 351 for it that used to reside in a 96 Bronco (not 100% sure on the 96 part..but almost). I had the 351 installed, the engine starts, the truck runs fairly well and I'm pretty satisfied with it so far, although it still needs work before I get it to where I want it to be (I don't drive it around much yet...hence, "sittingbronco").
So after this long introduction comes my question. I have read on this forum that when a truck goes from a 302 to a 351 the flywheel also needs to be replaced because they are balanced differently. I'm not sure the 351 I bought came with the flywheel. I am mechanicaly challenged so I didn't do the swap myself and that's why I don't know. However, as I stated above, the truck starts, and runs fairly well. Can anyone tell me exactly why the flywheel needs to be replaced, or what will happen if its not? Thanks in advance.
 

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Well here is what I know. The flywheel comes in 2 different teeth counts. 157&164 are the ones for the SBFs. Now the engine should of had one on it when you got it seeing as it came from another vehicle unless it got removed in either case if there is no weird vibrations coming from the motor as you rpm the engine up I would say thats all okay. I,m sure somebody else knowS this stuff better than myself and hopefully they will chime in.
 

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If it had the wrong flywheel or dampner you'd know!


:brownbag Not that I've ever installed the wrong flywheel on my old '84 Bronco w/302 before :brownbag
 

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the teeth count is all well and good, what is really really important (for your engines sake) is the weight of the flywheel inbalance. All 351s regardless of years were balanced at 28 oz. so thats a 28 oz crank, dampener and flywheel. 302s however had a change to them as pre 82s were balanced at 28 oz as well but after that they went up to 50 Oz. So most likely if you dont have a 351 flywheel you got a 28 oz balancer, a 28 oz crank and a 50 oz flywheel(from 88 302) I would say its worth it to know what you got and make it right!
 

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Yes I would agree on that with only one slight exception he has no vibrations and if he did in fact have a mismatch of components then he would in deed be seeing some kind of vibration when increasing the throttle.
 
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