Exhaust port, D-shape or round?

Message

wistech · #11 Post by **wistech** » Thu Jan 22, 2009 10:36 pm

Although I wouldnt call that extreme porting I would say you have at least an easy 5 horse right off the bat. The injector bungs are a concern but if the injectors fit fine then your good to go. Good job for a first try . Dyno it.

As far as chads work Id say it speaks for itself. Fun stuff

peterock · #12 Post by **peterock** » Thu Jan 22, 2009 10:42 pm

I know some aren't going to agree...........but you may be better off leaving the injector bung in place instead of shaving it off. Tapper and smooth it to create a nice flow around it though. Reason being is as you look down the intake, you can see the air is going to slam right into the bottom side of where the injector would sit. You would think this will cause some turbulance????

[attachment=7988:20012009405.jpg]

claas900 · #13 Post by **claas900** » Thu Jan 22, 2009 11:43 pm

QUOTE (Speed 1B @ Jan 22 2009, 02:32 PM) <{POST_SNAPBACK}>

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.

I think he was saying his race gas 500cc was 67 hp? Over on exriders.

Happyboy · #14 Post by **Happyboy** » Fri Jan 23, 2009 12:05 am

I don't know if anyone shaves the bungs off completely, at least not anyone with sense. What I have done in the past as well as the others is to clean them up as much as possible. Put the injector in and see how far you can shave them. Cut them down to as small as possible but still covering the injector.

MX Quad Dad · #15 Post by **MX Quad Dad** » Fri Jan 23, 2009 12:27 am

That exhaust port stepping goes aginst everything I have read or been told about any type of porting.

I also left the inner part of the bung in place, just trimmed them back a little.

I also polished the exhaust port and everything above the injector bungs

wistech · #16 Post by **wistech** » Fri Jan 23, 2009 1:32 am

I would just use whatever works for your particular engine setup. For every article that says you need a 5 degree valve job for perfect power I can find someone who say a 2 degree valve job is for max power. I think its all in the perfection of a particular method on each design. You can get power out of all of it. One thing you need to take into consideration is some of this stuff is for carbs that require a vaccum signal to pull fuel out of the bowl. EFI porting gives much more leway to do what you want. You can deal with reversion in several ways. One is cam timing and another is a stepped exhaust system, or exhaust tube length and silencer design. Most of this stuff turns out to be gimmicky and virtually impossible to prove but most sales are about the pitch than real world results. Tornado anyone?

Speed 1B · #17 Post by **Speed 1B** » Fri Jan 23, 2009 2:52 am

QUOTE (claas900 @ Jan 22 2009, 11:43 PM) <{POST_SNAPBACK}>

I think he was saying his race gas 500cc was 67 hp? Over on exriders.

Ive seen his charts, ive seen his bikes. They run good. He was the closest guy to me last year. I run about half a second faster than him in 500ft.

thedeatons · #18 Post by **thedeatons** » Fri Jan 23, 2009 3:34 am

So what you're saying is that Timbo still ports the best head (compared to the other make's porters)...

peterock · #19 Post by **peterock** » Fri Jan 23, 2009 4:54 am

or he weighs 5 pounds less...........................................

SlOoT · #20 Post by **SlOoT** » Fri Jan 23, 2009 7:07 am

On the picture with the TB installed you can see there is still something left of the injector bung to guide the air over the hole, they are not completely removed.

Actualy this is the second head I have ported. But the first one was more of a cleanup job.

This one will for sure go on the dyno, there is one 10 miles from here, so it would be stupid not to dyno it. I am hoping to get around 50HP on the rear wheels.