header size for LSA 5.3

[69cutlassrkt]

I ordered an LSA blower for my 5.3. Going to use cathedral to rectangular port adapter plates.
What header primary size do y'all recommend? The current ones are dougs 1 3/4 with a 3" collector.
The 799 heads are going to be ported also.

[andrewb70]

I would do 1 7/8" primaries with 3" collector.

Andrew

[68Formula]

I honestly think what you have now will work great with that engine and positive displacement blower.

[69cutlassrkt]

Thanks for the replies. I may keep the headers especially since most headers now are 1000-1200 USD. My dougs headers were 500-600 dollars, but that was around 10 years ago when purchased.

[badazz81z28]

In perspective, people are using 1-3/4 and 1-7/8 primaries will larger displacement engines. A stock 5.3 with the LSA SC isn’t going to make massive power.

[65 drop top]

I’d keep the 1 3/4” since you already own them. It’s not worth $1,000 for a few ponies up top. Now if you didn’t already have headers, it would make sense to calculate for the proper size.

[69cutlassrkt]

In perspective, people are using 1-3/4 and 1-7/8 primaries will larger displacement engines. A stock 5.3 with the LSA SC isn’t going to make massive power.

I'll be shooting for 600rwhp. Ls1 guys see decent dyno results though with the 1 7/8th primaries.

[68Formula]

I'll be shooting for 600rwhp. Ls1 guys see decent dyno results though with the 1 7/8th primaries.

With a positive displacement blower, the headers are less critical. This is because during valve overlap, the manifold boost actually helps scavenge the exhaust out of the cylinder better.

As an example, with a much bigger blown 427, comparing bone stock truck manifolds to full length 1 7/8 headers on a 427 and only saw a 20hp difference for engine making 840-860hp. That's only 2.3% from restrictive manifolds to long tube headers.

http://www.superchevy.com/how-to/exhaust/1705-headers-vs-exhaust-manifold-supercharger-ls-engine-dyno-test/

Had they tested 1 3/4 with that combo, the difference would be in the single digit range. Scale that down to your engine displacement and hp target I doubt you'd see any difference what so ever. If you're not meeting target, it's not the headers holding you back.

That being said, I do think your goals are a little lofty for a blown 5.3l even with ported heads. That means ~700hp at the crank. Not sure if you can do that with an LSA blower. It's going to require a lot of boost (at least 15psi), careful cam selection, a lot of rpm, race gas (or E85), FAST Intake (or similar flowing), big throttle body, and a heck of a tune.

Let us know how it works out.

[69cutlassrkt]

With a positive displacement blower, the headers are less critical. This is because during valve overlap, the manifold boost actually helps scavenge the exhaust out of the cylinder better.

As an example, with a much bigger blown 427, comparing bone stock truck manifolds to full length 1 7/8 headers on a 427 and only saw a 20hp difference for engine making 840-860hp. That's only 2.3% from restrictive manifolds to long tube headers.

http://www.superchevy.com/how-to/exhaust/1705-headers-vs-exhaust-manifold-supercharger-ls-engine-dyno-test/

Had they tested 1 3/4 with that combo, the difference would be in the single digit range. Scale that down to your engine displacement and hp target I doubt you'd see any difference what so ever. If you're not meeting target, it's not the headers holding you back.

That being said, I do think your goals are a little lofty for a blown 5.3l even with ported heads. That means ~700hp at the crank. Not sure if you can do that with an LSA blower. It's going to require a lot of boost (at least 15psi), careful cam selection, a lot of rpm, race gas (or E85), FAST Intake (or similar flowing), big throttle body, and a heck of a tune.

Let us know how it works out.

Thanks 68formula. I did not know that about headers size with a positive displacement blower. That's good to know. I know the hp goal is a bit high for a 5.3 with an lsa.

[nicks67camaro]

What is your cam selection? Do you have an upgraded heat exchanger? Will you run an overdrive pulley? The LSA on 6.2L (LSA) bottom ends make 650-700HP at the wheels pretty constantly with the right supporting mods. You will need to open up the entire induction system to get close to your HP goals. If you don't have all the "other goodies" header size isn't as critical.

My LSA build is a 6.2 LSA with ported heads, snout, blower case, 22.5% overdrive, Cam, HX reinforced and all the other supporting mods including 1 7/8" primary tube headers. I am shooting for 700 at the wheels. We will see.

[69cutlassrkt]

What is your cam selection? Do you have an upgraded heat exchanger? Will you run an overdrive pulley? The LSA on 6.2L (LSA) bottom ends make 650-700HP at the wheels pretty constantly with the right supporting mods. You will need to open up the entire induction system to get close to your HP goals. If you don't have all the "other goodies" header size isn't as critical.

My LSA build is a 6.2 LSA with ported heads, snout, blower case, 22.5% overdrive, Cam, HX reinforced and all the other supporting mods including 1 7/8" primary tube headers. I am shooting for 700 at the wheels. We will see.

I'll probably start a build thread once it gets going. First gotta get things worked out with the 4l80e and trans tune. I have an EPS 222/226 112 LSA cam in it right now. Gonna see how it does. I bought a 4 bolt ls7 throttle body. I plan on buying the 10% overdrive crank pulley and a 2.45 supercharger pulley. I ordered an upgraded heat exchanger and the zl1 lid. Was also think about getting a ricks vaporworx tank.

When are you expected to have yours completed Nick?

[nicks67camaro]

Right now i am rewiring the car and in reassembly. Im waiting on my rock valley tank set up for the ctsv pump and vaporwox controller (highly recommend). Im hoping for a first start in 4 or so weeks when the tank arrives. I'm thinking full dyno tune before thanksgiving.