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General Category => Modifications => Topic started by: Burns on June 24, 2014, 09:13:48 PM

Title: give me head - Busa BJ
Post by: Burns on June 24, 2014, 09:13:48 PM
I read that the 'busa's bore/stroke are 81/63mm, and the FJ1314's are 81/63.8mm - leading me to wonder about bore centers and if the 'busa head can be transplanted onto the FJ1200 cylinders.

420 is legal is Washington.
Title: Re: give me head - Busa BJ
Post by: Pat Conlon on June 24, 2014, 10:26:58 PM
What makes you think so?   The piston bore and stroke have nothing to do with it.

The spacing of the pistons and head bolt pattern have more to do with your question, than bore/stroke.

Look at the 'busa's throttle body spacing for a hint.   FYI the carb spacing on the FJ is 77-85-77

Better yet....put down the pipe and go for a walk.
Title: Re: give me head - Busa BJ
Post by: Burns on June 24, 2014, 11:42:36 PM
Well, no pipe, just pipe-dreams.

There has been a lot of technology in head design since the FJ's blue prints saw the light of day.

The piece that I read  noted the 'busa similarities and reworked the FJ heads with very impressive flow-bench results.
The bore and stroke indicate very close displacement and fit of combustion chamber-to-the deck IF the center of the crank throws are the same - which is what you are calling "spacing of the pistons" and I am calling "center bores".  The crank throws could be a mile off for all I know. That number is the bottom line.

I don't follow the relevance of the FJ's carb spacing since that head would not be used. Unless it is a clue as to the crank-throw spacing.

Of course bolt pattern is an issue, but not necessarily insurmountable.

Just bench-racin'  but 190 hp from mostly off-the shelf parts is an interesting concept.
Title: Re: give me head - Busa BJ
Post by: fj1289 on June 25, 2014, 12:51:57 AM
Buy a head and see how far off it is!  Same way I did with the clutch for the dragbike.

Run it thru a band saw a few times and weld the pieces together where you need them.  And add a cam chain tunnel.  Bolt it to the top of a Hank Scott water cooled block....

Not being a naysayer -- that is exactly how I'd go about it.

Now, with all the CNC porting being done, I wonder how much welding it would take to CNC Busa ports and chambers into an FJ head?


Oh yeah, it's 63.75 mm without the rounding!
Title: Re: give me head - Busa BJ
Post by: fj1289 on June 25, 2014, 01:12:55 AM
Quote from: Burns on June 24, 2014, 11:42:36 PM

The piece that I read  noted the 'busa similarities and reworked the FJ heads with very impressive flow-bench

What piece is that?  Is it in one of the write ups on the FJ Mods site?
Title: Re: give me head - Busa BJ
Post by: FJ1100mjk on June 25, 2014, 05:17:06 AM
Quote from: fj1289 on June 25, 2014, 12:51:57 AM
Bolt it to the top of a Hank Scott water cooled block....

Didn't know about that. Wow!

The future is here...!

http://www.hankscottracing.com/HSRWC.html (http://www.hankscottracing.com/HSRWC.html)

Burns, don't put the pipe down  :yahoo: