Porting LS 243 heads.
well i finally got my 243 heads for my build.
I've ported them now and changed the combustion chamber to suit my dome top pistons. Yes i know i should have just got flat top pistons.
but the original heads were going to be 241 heads.
when I found the 243 heads cheap in Australia i just had to get them.

Heads will be fitted with ferrera 2.02" intake and 1.57" exhaust valves.
intake throat size is 90% of the 2.02" valves
Intake bowl is 99% of the 2.02" valves.
Intake ports are burr finish.
The bowl has been biased to the cylinder wall size.
The all important ssr has been widened and layed back for a great line of sight to the back of the valve.

Exhaust throat size is 86.5% of the 1.57" valves and the bowl is 109% of the 1.57" valves.
The bowl has been biased to the cylinder wall side same as the intake port.
The ssr has been widened and lowered of the cylinder wall side.
Port has been finished with 120 grit cartridge roll.

Thickness between the bowl of each port is .140", 3.5mm or 1/8" depending on what measurement you understand easily.

Valve guides have been narrowed in each port like normal.
intake ports rocker bolt bump has been removed like normal.

The exhaust ports valve guide behind the valve has been made into a vane to divert flow around the valve.
you can't see it in the photos but can feel it by touch.

Minimum port thickness is yet to be measured with an ultrasond thicknesses tool. From my measurements it should be no less than .120" on the intake and the same on the exhaust port.

Last thing to be done is to match port the Holley 300-137 intake manifold to the ports.
I will also port the intake manifold plenum area too.
The manifold will be topped with a 2" spacer plate to increase plenum volume size to slow the air speed volisity to make the turn into the runners.

I'm underside if I will raise the port floor of the heads and intake manifold.

Hoping the intake ports will flow at least 290cfm with excellent low lift flow and the exhaust ports flow 75 to 80% of the intake ports.

Chamber mods

Exhaust port throat bowl and valve guide.

Match port to my exhaust manifold primary pipe size.

Intake port throat bowl valve guide and rocker bolt bump removed.

Intake port line of sight to back of valve and ssr.

 

Nice work. I ported a set of 243 heads and installed them on my "01 Camaro. It was worth all the time and effort to learn to port ls heads because ported 243s flow so damnwell. I went 88% throat for the intake and 86% on throat for exhaust. I took out the swirl ramp and rocker stud boss, enlarged the exhaust port and few other tricks. I'm sure you'll make plenty of power.

 

People are scared to touch behind the intake valve guide and exhaust valve guide because of the thickness of the casting in that location.
I tracked down a cross section photos of the ports and cut up a 241 head for comparison. They all have the same port wall thickness except for certain areas that i noticed.
I used inside calipers and outside calipers to measure the ports before and after porting them. This way i could keep track of how much meterial was removed from any location.
I could have removed more meterial but it's a street car and therefore will be running for long periods of time.
Hp goal is for around the 530 to 550hp at the crank.
I've bumped the compression ratio upto 11.2 to 1 and with my cam intake closing at 69.44 degrees ABDC with 6.3" rods. The dynamic compression ratio should be a nice 8.55 to one when warmed up. Because at the block expands the pistons will go from being .006 out the hole to zero deck height. This drops the static compression ratio from 11.39 back to 11.21 to 1. This allows me to run E10 pump gas and live.
I've worked hard to maximise scavenging and thermal dynamics in the exhaust system.

Exhaust port cross section. Note behind the valve guide area is .200" thick. I removed just under .080 in this area to create a vane to guid exhaaust gasses around the valve guide.

Intake port cross section. Port wall thickness on average is .200" some areas are upto .360"

Intake port cross section

 

Yeah, here is a different look at the intake and exhaust for my 243s. I practiced on the 241s off my Camaro and a set of 862s since they're so cheap at the local junkyards. I didn't adjust the height of the short side radius on the intake, but I did widen the ssr. On the exhaust I increased the size of the port to gain area. Ported heads are a great deal better than stock ls heads, you should reach your hp goal.

 

The 241's have that weird sharp drop off on the floor of the intake port. The 243 have a gentle radius.

 

This is the dome top pistons to show why i had to reshape the combustion chamber.

 

Are you going to dyno your LS or are you going to just install and run it in the car? Update the thread when you get it running.

 

Definitely dyno tune

 

I’m looking at porting my 243’s to pickup a few more HP. I’m afraid to go that deep into them. In your first set of pictures. The intake bowl looks like there’s a small hole where the rocker bolt is? If that’s the case do you fill the hole with aluminum or brass? Should I leave a little bit of the hump just to be safe?

 

Buy a set of 862s and practice on those. They're cheap as dirt.

 

Removal of the boss is normal to do. The rocker post is just fitted with sealant on the threads. Benefit to flow to remove this is quite big. Some really good vids on YouTube about porting 243/799 cast heads that show before & after of where to remove material , plus flow numbers showing the improvements.

 

That will give you a basic idea of what to do for smaller gains than im aiming for.

 

Thanks guys! I’ll check it out

 

I have 706 and 241 for practice this winter So I'll look for good porting threads and follow along with you guys I want to give it a bit of a tune-up in the near future anyway since it's been so hot and hard on it this summer and I'm using mobile 1 again it's seeping at some of the gaskets after the hardest runs (superficial it's not hurting anything, it just gets a little messy) oil somewhere at the front when the water temperature gets over 230° I just need to look closer at it It could be just a bad front seal or I didn't get enough RTV in the bottom corners of the timing cover for me taking apart so many times also if the 5w50 starts to break down before this heat really breaks. I might try the 5W60 I mean the things constant wot 4-7.5k for minutes at a time now and I only want to push it harder. I want to believe smoothing out some of the rough edges in the stock castings would help the engine run cooler as well

 

You mind posting some pictures of the tools you use?

 

Great thread that fits my current needs to port the 243s for my Luddite build

 

I'd save the time and look for a used set of ported heads.

 

Here are some tools I use for LS heads.
Electric die grinder from Harbor Freight. Below are couple of bits, the small one for the final burr finish.






This is to control the die grinder, found on Amazon.

 

Here's some short videos of the intake and exhaust ports of each head from different angles.

 

well I decided to polish the exhaust ports with scotch brite. I used 240 320 600 800 1000 and finally 1200 grit.
the results speak for themselves. Extremely smooth and almost a mirror finish.
i cc all the exhaust ports and they all came up at 81/82cc. Not bad for a home job for consistency. All intake ports came up at 234/235cc. I will be filling the port floor at the manifold face to achieve my 2.2" square mcsa to maintain air volisity average speed.