XJ Frankenstein

SO I have some ideas that have burning holes in my mind for years but I cant ever seem to get a hold of the proper specs to determine what is feasible and what isnt.

There are several different motors in the XJ lineup, and I'm wondering if anyone has ever attempted to swap around parts to build the ultimate XJ? On any of the four wheel car brands Im familiar with, there are many options among engine families for greater performance, swapping heads, crankshafts, intake manifolds or turbo manifolds onto N/As. So I would like to gather some information on what is possible with the XJ.

I know the XJ100, 900, and 750/650 mount a little differently and the bore spacing may be different. The most choice frankenstein engine would be as follows though half these parts probably wont be compatible-

XJ 700 head- 5 valves per head should flow better than the other heads in theory, but is this head compatable with the 750, 900 or 1100?

XJ 900 or 1100 block - theres no replacement for displacement. Larger bore would help unshroud the valves anyways.

XJ 650 Turbo manifold and Turbo - Once again I'm not sure bore spacing or port size would facilitate an easy swap to another head or displacement. I imagine a 750, 900, 1100 would breathe a whole lot easier with a 650 turbo or larger.

Finally a higher final drive ratio or chain driven setup may be preferable to being shaft driven. Who wouldnt want to be able to turn less than 6000 @ 60-70mph?


Let me know what your thoughts are, Ive been looking for this information for years and I'm finally posting this in hopes that someone has at least held one headgasket up to another in consideration of these swaps. Obviously carburetion would be a nightmare so a fuel injected solution would be required. Anybody is welcome to comment since this is kind of a pipedream thread

 

Can I use an XJ900 crankshaft in an XJ750 engine? The stroke is slightly longer, but otherwise looks possible.

 

Frank

There more to do than just swap cranks.

edy

Lots of info in the information overload hour....

https://xjbikes.com/forums/threads/the-information-overload-hour.27544/

 

Can you swap crankshafts if the cases are line bored?

 

Yes, but I believe you’d have to swap rods, and probably pistons, cylinders, and head....
I imagine Simmy or one of the other guys will chime in.....