Exhaust port, D-shape or round?

Message

SlOoT · #1 Post by **SlOoT** » Tue Jan 20, 2009 12:15 pm

I am now very close to finishing my "extremely" ported head. And am now wondering what will happen if I make the exhaust ports round.

Thanks

cannondale27 · #2 Post by **cannondale27** » Tue Jan 20, 2009 12:37 pm

You will lose power.Continue the D shape all the way down.

SlOoT · #3 Post by **SlOoT** » Tue Jan 20, 2009 1:42 pm

Thanks. I will leave it as it is now. Will post some pictures later. I think it turned out very nice.

wistech · #4 Post by **wistech** » Tue Jan 20, 2009 4:17 pm

What size engine and what are you building power for?

SlOoT · #5 Post by **SlOoT** » Tue Jan 20, 2009 5:30 pm

Right now I am planning on a stock bore and stroke (cheapest). But might go to 450cc in the future.

I am looking for mid- to top-end power for MX racing.

polyesterpig · #6 Post by **polyesterpig** » Tue Jan 20, 2009 8:05 pm

Here is a little info on exhaust D-ports

http://books.google.com/books?id=LswdRd2Zm...3&ct=result

wistech · #7 Post by **wistech** » Tue Jan 20, 2009 8:41 pm

[quote name='SlOoT' date='Jan 20 2009, 11:30 AM' post='201591']
Right now I am planning on a stock bore and stroke (cheapest). But might go to 450cc in the future.

I am looking for mid- to top-end power for MX racing.
[/quote
For stock displacement and low /mid range max torque I would widen(oval) the ports and not cut the floor of the port much. For a high rpm max power/large displacement engine then we dump the d porting to get least resistance. Just be careful on exhaust ports as it is very thin between the two runners where the water jackets is. Plug off the the 4 slits in the head and fill with water through the water pump hole to check for leaks when done.

SlOoT · #8 Post by **SlOoT** » Thu Jan 22, 2009 8:58 pm

Intake is very rough. It's 46mm at the top, and the runners are also made larger, also much larger around the seat and transfer very smoothly into the seat.
Also got the TB bored to match, lines up perfectly when hoseclamps are tight, on the picture there are no hoseclamps so it looks like it does not line up perfectly.
Stock injectors can be used with some O-rings as spacers.

Exhaust ports still have the D-shape.

claas900 · #9 Post by **claas900** » Thu Jan 22, 2009 10:10 pm

What do you guys think about this http://www.chad502ex.com/index_files/porting.htm

Speed 1B · #10 Post by **Speed 1B** » Thu Jan 22, 2009 10:32 pm

I know that DRG guy. He has been trying to beat my drag bike for 2 years.

He got a little closer last year but hes still pretty far off.