I have a C10 truck with a LS1 BTR stage II cam, LS6 intake and headers. Otherwise it is completely stock. It has 354Hp to the rear wheels.
My goal is to reach 400hp at the tires.
To do that I want to change out the 339 head currently on the motor for a set of ported 243 heads that I own.

I have three options. Wondering what would be the best?

1. Option 1.
   1. Staying with the LS1 displacement and installing the LS6 style ported head.
   2. Compression would be about 10.7:1.
2. Option 2.
   1. Stroking the LS1 to 4"
      1. I would be running with 11.7:1 compression if I use the ported 243 heads.
3. I could use a better head for the stroker application like the 317 with 71cc chambers instead of the 64.5'cc ones the 256 heads have.

I really want to get it right as porting heads isn't something to have done twice. 11.7 seem too high for the street or it used to be.
What would you do?

BTW I don't believe the heads will ad another 46hp. But a Fast intake and ported heads may.
Thanks

1. 
   
   

 

Just remember. There’s a world of difference between static compression & dynamic compression. With the right cam, you could bleed off a lot of that cylinder pressure & get away with running it on the street. I try to shoot for no more than 175/180 psi in cranking (dynamic) compression for pump gas. You can get away with more if you use E85. These LS1 engines are very forgiving in regards to high compression on the street because of their excellent reverse flow cooling systems.

Not sure where you live, but. Have you asked Richard at West Coast Racing Cylinder Heads (Pro1) about making that extra 60 hp with just a head & cam swap? Hes in California & he’s got a whole range of cylinder heads & packages he sells specifically for LS1. He’s a really nice guy & has a world of knowledge when it comes to these things. Give him a call at 818-705-5454

Btw. If you wanted to compare static & dynamic compression ratios using the cam profile centerline, here’s a calculator to do that. You’ll see once you start playing with the valve lift & duration of cams you’ll see how you can get away with a lot of compression on the street.

www.gofastmath.com/Compression-Ratio-Calculators/Static-And-Dynamic-Compression-Ratio-Calculator

 

Thanks for the response. My plan is to have the heads ported before installing.

To clarify, I have two LS1's. One is running driving in a C10. The other is a bench motor. I have purchased a 4" stroker crank and am sorting out the to combinations.
I could install the 243 ported heads on either motor. Attempting to make up my mind on the best combination. Or the simple version which motor to install the heads on.

I did look up total engine airflow. Will see it the answer my email inquiry or if I need to call.
I did notice on there website the listed the combustion chamber size, on the ported 243's, as 67cc not the factory 64.5cc.
Expect they do some CNC work to the chamber which will lower my compression.
This changes everything.

Using the TEA combustion volume
The 4" STROKER MOTOR WILL HAVE 11.3 TO 1 COMPRESSION RATIO (with the ported heads)
THE 3.89 STROKER MOTOR WILL HAVE 10.35 TO 1 COMPRESSION RATIO. (with the ported heads)
The stroker compression number seems slightly more livable.
It's interesting as the TEA ported heads (with the 67cc chambers) bring the compression right back to the stock ratio on the LS1.
Removing the 1 point compression advantage of the 243 heads on the stock displacement LS1.
It would make them perfect for the stroker motor as they would bump the compression ratio slightly.

To recap:
Using the ported 243's on the LS1 I would gain airflow and not change the compression. I would loose the 2 to 3% gain from an extra one point in compression. This motor is an automatic and has a BTR Stage II truck cam.

Using the ported 243's on the Stroker LS1 I would gain airflow, and up the compression by approximately one point. I would gain the 2 to 3% gain from extra compression. This motor will also have a more aggressive camshaft as it will have a manual transmission behind it. The vehicle this is going into will be tire limited. Power isn't as much of a concern on this motor. It will be stupid power because of the tires anyway.

 

Id look into a ported tbss intake manifold and 90mm tb. You would pick up power across the board and likely get close to your goal with only the 243 heads and intake. This would have better low end torque and likely not give up much up top to a fast intake. Your cam isnt big and focuses on low/midrange so you might as well use its strengths especially in a heavy truck like that.

 

I like the idea and the price of the TBSS but not the look. I think $1200 for an Fast intake is credulous. That's without a Throttle body and one may still require injectors. However, you are exactly onto my goals.
Hope to make 400 at the wheels and I only need 46 more hp. I don't think just the addition of the CNC ported heads will get me there. But heads and an intake may put me slightly over my goal. I typically pick the cam I want and they purchase the next one down on the power list. Seems to work out well in the long run.
Thanks again for the comments.