[Ruyguy]

Hey guys, anyone know what the height and width on the exhust port are supposed to be . I see just widen 3mm each side but that would not only most probably bust through the case but also would be wider than what i can make the exit of the port ( id bust through to the screw holes if i follow through widening 3mm . ) which i hear is bad.. i also heard something about having the exhaust port area 75% of the transfers , can’t remember why , anyway here are my current exhaust port specs. Height of it at the bottom is good matching up with bdc, i don’t really want to make it higher as to keep the power stroke as long as i can . Please show me the light lol
( the pencil outline is the inside of the port ,
The other measure of the bottom of the sheet to top of port , top of sheet = top of cylinder ( without head) so it’s probably not really tdc.

 

[Atvrunner2]

3mm is too big IMO. I always do 1mm on each side and football arch the inner roof. Taper all the inside edges. They the outside do whatever and try to match your pipe. I need to make my own headers like I read CAM2 always did.
Thats all foolproof. Properly done would be using a degree wheel and take it from there with proper measurements.

 

[MrKitty]

Yea if you go to big the fuel charge that you worked so hard to get to the top of the Piston will go right out the tailpipe

 

[Ruyguy]

3mm is too big IMO. I always do 1mm on each side and football arch the inner roof. Taper all the inside edges. They the outside do whatever and try to match your pipe. I need to make my own headers like I read CAM2 always did.
Thats all foolproof. Properly done would be using a degree wheel and take it from there with proper measurements.

do you also make the side sorta roundish to continue the football shape?
And yeah about the degree wheel and everything, i thought someone here already knew what the « right » specs , even with a degree wheel yes i could tell you duration and opening but i still would not really know what to do with those numbers

 

[Ruyguy]

Yea if you go to big the fuel charge that you worked so hard to get to the top of the Piston will go right out the tailpipe

And god knows ive been working hard on this one 🥲

 

[Ruyguy]

Oh and just to be sure we are talking radial when we talk about how much we widen right and not linaire right?

 

[Atvrunner2]

I just go 1mm wider on each side, leave the side flat but round corners and taper all edges so the piston doesn't catch. The football or arch is only for the inside roof.