PDA

View Full Version : midsize porting



river_ratj40
07-05-2005, 03:01 PM
does anyone have any info on cylinder porting for midsize motors from 40 to 70 hp. i heard that it really helps.

Fast Fred
07-05-2005, 03:31 PM
what do ya have, what are ya putin it on, hows much dose it weigh, what are ya lookin to do with it :cool:

river_ratj40
07-06-2005, 10:41 AM
i am building a 76 model johnson 40 hp motor. it will have a jet unit attached and be ran on a flat bottom boat. i have the bigger carbs and reeds and plan to shave at least 100-120 thousand off my head. along with some exhaust work. i didnt know about porting and how much it affected it.

Fast Fred
07-06-2005, 11:00 AM
the pump wants GRUNT, don't mess with the hights, put finger ports in thare,
the big carbs, clip the head to 14O psi per cyl, run 93 oct, hit it a 18deg btdc
max advance :cool:

river_ratj40
07-07-2005, 05:31 AM
if you would please explain the finger ports. what does it allow to happen inside that cylinder to increase your perfomance. can i do the work or do i need to have someone else do it.

thanks

Fast Fred
07-07-2005, 05:53 AM
a finger ports are two slots cut in to the cyl wall, in between the boost port and the side tranfer port, set them at the side transfer port hight,best to send it out
she will move more air and mix in to the chamber for more Grunt,
like 200$ or so should get it done from someone who knows what thay are doin :cool:

Fast Fred
07-07-2005, 05:55 AM
the pistons need to be drilled to feed them as well, DO NOT DRILL IN TO THE WRIST PIN BOSS OR THE PISTON WILL FAIL :eek: :cool:

river_ratj40
07-07-2005, 02:34 PM
thanks fast fred, you have been a big help!

Fast Fred
07-07-2005, 03:15 PM
mr. WIENANDT, i'm not big on 2cly's he'll make it f'in sing
Fond du lac WI 54937
920 921 2552 :cool: make sure ya tell him what your doin with it :cool: