657x to 657 swap

[Dmpaul89]

So my X motor blew in my 95 gtx. I have now a standard 657 that I am preparing to install. My question is, should I use my old flywheel and stator, or not. I read on an old post that the keyway may be in a different location on the crank, wouldn't that screw up timing with the rotor valve? Also should I change the timing to match the 657x spec? Or leave it alone.

To be clear I am going to have a standard 657 engine with 657x intake, carbs, and exhaust on it.

Thanks for any help.

 

[Dmpaul89]

Does each engine share the same stator? They are both 4 wire.

 

[mikidymac]

I hate to direct you off our site but here is some really good reading on the differences between the 657 and 657X. 657 vs. 657X

 

[IDoSeaDoo]

I heard the 657 was weak in a critical spot and that's why they went to 657x. You should have went up to a 720. Would have been a closer match. They're only 5hp different.

 

[Dmpaul89]

Just looking to get back on the water asap. This was all I could find that was reasonably priced. In the meantime I have my original engine boxed up ready to ship for rebuild which could take months

 

[Dmpaul89]

Got the "new" motor in and running. I left the rotor valve alone on the 657. I started to think about it and the reason the rotors are different between the 657 and 657x is due too the larger ports, so I don't believe they could interchange. I also had to have the standard 657 flywheel housing. flywheel and stator are off the new motor as well although that probably would interchange. So I now have a 657 running with 657x carbs and exhaust. We'll see how it does in the water but so far so good. Fires right up . Now I just have to put the jet back on and she's done.