426 Conversion

Anyone do or know someone who has done a 400 to 426 conversion? Any problems like overheating or clutch slipping?

I did...haven't had any problems yet...runs kinda hot I guess, but only in city/stop and go situations...probably not any worse than the stock 400 (only had mine for a brief time before converting)

Thanks for your reply.

I have a plated YZ that I am in the process of installing a WR trans. This means I have YZ radiators which I think are smaller than the WR. I have installed the WR recovery bottle which should at least keep the coolant if it boils over. What kind of power increase can I expect and was it worth the extra cost of a new cylinder?

Thanks for your reply.

I have a plated YZ that I am in the process of installing a WR trans. This means I have YZ radiators which I think are smaller than the WR. I have installed the WR recovery bottle which should at least keep the coolant if it boils over. What kind of power increase can I expect and was it worth the extra cost of a new cylinder?

I needed to rebuild anyways, so it was a pretty easy decision to go with the 426 parts. I don't know if you're aware or not, but in order to convert, you'll need to change out the con rod to fit the 426 piston...

The power is definitely noticeable, but not a drastic change...I also installed a set of HotCams when I was in there, so that accounted for some oomph as well...

If I were to do it over again, I'd send my cylinder to Luke's, order the 444 kit for the top end (barely, if at all, more expensive than stock parts), and replace the crank assembly with an OEM 426 piece (con rod has a stronger small end bearing, driven gear is splined)....

Have you had any issues with the extra torque and smaller clutch? I haven't seen the luke's kit but I do like the Powroll stroker 440 kit. They have a parts list for the 426 conversion on their site. I thought the crank castings were the same 400 vs 426.

Does the 426 clutch basket fit on the 400 primary shaft?

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