Exhaust on the HD SE Hipo heads

[nw_guy4_fun]

Been a lot of chat lately about the exhaust side.
If you think they flow so bad reverse it, they make a good intake, quiet!

I understand what HD did and the philosophy. The flow bench does not tell the whole story here and to get them to work you have to do some out of the box thinking (not welding).

[Mother]

That's exactly what my head porter Larry Long said! To truly test the exhaust you pull through from the end of the port to the chamber(reverse of the intake)

[INDEPENDENT 1]

I haven't had one on the flow bench but I was told 150/160 on a good day. What would you do on these, Don?

[nw_guy4_fun]

Fix em
Each of the HD castings have their unique challenges
The flow numbers are not all telling.

[TXCHOP]

Will these fixes also translate to the MVA heads? Would they benefit as much as a hurricane would? Se110?

[nw_guy4_fun]

Well the concept is the same. The treatment is a little different for the individual heads. Seats, valve shape, throat, inlet(chamber). I credit David Vizard primarily, Roger Helgesen, Arne Atwood and Mike Roland to a smaller extent plus some of the more open and knowledgeable folks on Speedtalk with the help that changed my way of viewing the exhaust side. Plus countless of testing seat and port shapes. The motors we are building are a Big Block, we need to keep that in focus. They have high exhaust volume needs and if we used the flow bench completely we would be chasing our tails. Hell a 96" stock head flows darn near as good as a stock MVA at 28". Don't dice this or take it out of context my bench is highly used and will go to 60" and I do test there. Plus I am not all knowing, I am humble and learn more every day.

Along the path I learned the percent of intake theory was BS and then also realized there was a lot more to the exhaust story than the flow bench. Sometimes you have to step back and just look at the damn thing, from chamber to outlet, and analyze it compared to a perfect nozzle. How would an ideal port look? We can improve them but really to get it right you would have to weld it up and start over. There are better heads native to start with. Sachs used to mess with the Ultimas. I don't have any experience with them but my guess is they are pretty decent when worked, the Wild Things head another possibility and the S&S Super Stock. Of course for the maximum effort motors the B-2.
As with all of these parts optimizing heads is just one component of the assembly and with respect to the exhaust side the cam and pipe are also equally heavy hitters. A cam can't fix a bad port but the right timing can help especially as we see such high intake flows. That dual pattern cam starts to look better and better, added exhaust duration.

[C-Cat]

Originally Posted by nw_guy4_fun

Well the concept is the same. The treatment is a little different for the individual heads. Seats, valve shape, throat, inlet(chamber). I credit David Vizard primarily, Roger Helgesen, Arne Atwood and Mike Roland to a smaller extent plus some of the more open and knowledgeable folks on Speedtalk with the help that changed my way of viewing the exhaust side. Plus countless of testing seat and port shapes. The motors we are building are a Big Block, we need to keep that in focus. They have high exhaust volume needs and if we used the flow bench completely we would be chasing our tails. Hell a 96" stock head flows darn near as good as a stock MVA at 28". Don't dice this or take it out of context my bench is highly used and will go to 60" and I do test there. Plus I am not all knowing, I am humble and learn more every day.

Along the path I learned the percent of intake theory was BS and then also realized there was a lot more to the exhaust story than the flow bench. Sometimes you have to step back and just look at the damn thing, from chamber to outlet, and analyze it compared to a perfect nozzle. How would an ideal port look? We can improve them but really to get it right you would have to weld it up and start over. There are better heads native to start with. Sachs used to mess with the Ultimas. I don't have any experience with them but my guess is they are pretty decent when worked, the Wild Things head another possibility and the S&S Super Stock. Of course for the maximum effort motors the B-2.
As with all of these parts optimizing heads is just one component of the assembly and with respect to the exhaust side the cam and pipe are also equally heavy hitters. A cam can't fix a bad port but the right timing can help especially as we see such high intake flows. That dual pattern cam starts to look better and better, added exhaust duration.

Would a dual pattern cam heavy on ex duration be your choice on a 120 or 124 using Hurricane heads set to your liking, along with the correct exhaust? If so, any cams that come to mind? Thanks in advance!

[mccycle]

Funny how all this works .I was pretty much called a fool on another forum for saying much the same, in perhaps different wording on another forum.Hell all you need is a couple thousand inches of water pressure to check some blowdown lift areas.People were quick to laugh without any thought given to the two vastly different exhaust events.

[Knighty-Knight]

Nothing to add but this will be a great thread to follow.

[nw_guy4_fun]

Interesting to look at the RX267 cam and see where the factory engineers were at with timing. Especially the exhaust open. I am not saying that would be my cam of choice but would be in the ball park on the LSA and LC.