[PRAY]

I showed some results for my ported intake runner a bit back. I am still working on it some but with the low flow capability of my bench and flowing it on a 4" bore gains are hard to come by. I should have kept one of my valves stock (I do a custom 3 angle valve job on my valves) so I could do back to back testing. With my current weather situation over all flow is down but gains are up. I don't have an apples to apples for today but you can basically add 10cfm to the .3 and .4 number.

Today I worked on the exhaust port a bit. There is another 5-10cfm in the exhaust for sure. I had some spare time so I took a whack at it. The exhaust gains are really good but the port is overall down to my LS2/3/7 heads. This exhaust port is a unique critter for sure.

As soon as I finish up some LS2 heads I am doing I will take this LT1 head up to the local SF600 bench I use and get some 28" numbers against the stock ports.

The overall goal for these heads is to be a direct bolt on with the stock cam and gain 20rw over my numbers with my ported IM/TB, CAI and Headers. Swapping heads is easy and is really just a day job for the DIY'er. I will eventually match them with a cam line.

[oldman]

really good exhaust gains..

[cmitchell17]

Originally Posted by PRAY

I showed some results for my ported intake runner a bit back. I am still working on it some but with the low flow capability of my bench and flowing it on a 4" bore gains are hard to come by. I should have kept one of my valves stock (I do a custom 3 angle valve job on my valves) so I could do back to back testing. With my current weather situation over all flow is down but gains are up. I don't have an apples to apples for today but you can basically add 10cfm to the .3 and .4 number.

Today I worked on the exhaust port a bit. There is another 5-10cfm in the exhaust for sure. I had some spare time so I took a whack at it. The exhaust gains are really good but the port is overall down to my LS2/3/7 heads. This exhaust port is a unique critter for sure.

As soon as I finish up some LS2 heads I am doing I will take this LT1 head up to the local SF600 bench I use and get some 28" numbers against the stock ports.

The overall goal for these heads is to be a direct bolt on with the stock cam and gain 20rw over my numbers with my ported IM/TB, CAI and Headers. Swapping heads is easy and is really just a day job for the DIY'er. I will eventually match them with a cam line.

Attachment 853007

Have you ever taken a look at the SAE paper GM published for the LT1 development? I had it around somewhere, it mainly talks about the trade offs they made to keep tumble and swirl up that sacrificed flow in areas for combustion efficiency.

[thescreensavers]

Originally Posted by cmitchell17

Have you ever taken a look at the SAE paper GM published for the LT1 development? I had it around somewhere, it mainly talks about the trade offs they made to keep tumble and swirl up that sacrificed flow in areas for combustion efficiency.

Yep, port velocity has a lot to do with that, making the port bigger you are lowering port velocity. While it may downflow great it might also hurt performance in other aspects and you undo the engineering work GM did for combustion efficiency but at the end of it the engine is an air pump make it easier to pump air you'll gain some power.

http://papers.sae.org/2013-01-1732/
http://www.c6registry.com/pdf/LT1%20...%2024OC12a.pdf

[PRAY]

I hardly ever increase cross section either horizontal or vertical if the head is not going on a larger motor. 99% of the time I only remove material from the short turn, hook wall, rocker boss, and valve guide area. I will make slight adjustments to the chamber as needed around the valve seat. All I did in this head was remove the obstructions in the intake port and reshape the short turn a bit. There really isn't much material around this port to take much out. Considering this is a dry head and I am only moving air I wasn't concerned with having to move fuel with it. Since it is DI as well and the fuel is coming out of the injector basically atomized I was more concerned with swirl. It is just a little difficult with this head since the runner is "backwards" and there isn't much material available to remove on the hook wall or short turn on that side. In the end, I didn't really change what GM did. I just removed some of the restrictions and cleaned things up. I also wanted to keep the port from crashing at .550. I didn't see it on my bench due to only being able to reach 7" stock and 5" ported. But I have done enough heads now to know what my short turns need to look like to stop flow seperation of the short side at 28". On the next port I may leave the entire bump around the push rod in and see what is does to port velocity on the hook wall side over the short turn. Kind of use it as a swirl generator and get the air off the straight wall. On the exhaust most of the gains were made in the valve seat and bowl area. But that is the evacuation side so not so critical. I just wanted a certain amount of volume. I did what was needed to get the numbers I was looking for.

[PRAY]

Thanks for the links. I will read up on it as soon as I have time.

When I get home today day I am going to bust out the Pitot tube and check some stuff. I used some of my other home made tools to show me where the air is going and the shape it is making down in the bore. I did not check the velocities around the entire valve though. I am also going to CC the runner to see how much was actually removed.

[PRAY]

Stock runner checked in at 300cc's mine is 313cc. The flow over the short turn is twice the speed of the long turn. The air across the short turn on the hook wall and straight wall are almost even. There is a little more velocity on the hook wall side. There is definitely no flow separation on the short turn. I just don't have the velocity to take advantage of the shape. I can only push so much air through a 1.895" throat at 5"hg. Nothing much else I can do in there. I tried a bunch of stuff today. Depending on the bore I used to test the head on the results varied. I think I am pretty much done on the intake. Now time to work the exhaust a little more.