Switched from Lt to ls going slower

[lt1fc3s]

Hey guys been awhile since posting, took out the old leaking lt1 and swapped in a 04 4.8. Hooker swap manifolds, drive by wire, 5 wire maf, ls6 dorman intake, other than that basically stock. Problem is I went from 12.0s@112 in the lt1 to 13.6@99 in the 4.8.  is the ls6 intake slowing me down or do I need the tune looked at. Was hoping to be in the 11s

[1320king]

The ls6 intake is one of the best stock intakes. I would say your main issue is the tune. Also the 4.8 is not a high HP motor out of the box but that is easily remedied with a  cam (stock ls6 cam and springs work nice). You will see another 40-60hp just with a bigger cam! I would also ditch those hooker swap manifolds and get some long tubes. Here are some reff:

http://www.superchevy.com/how-to/engines-drivetrain/1503-how-to-get-384-hp-out-of-a-4-8l-engine-mini-mouse-part-1/

http://youtu.be/Y7_lSU3D0jw

[lt1fc3s]

I got the ls6 intake because I planned on doing a cam swap later , looks like it will be soon than later. Will surely be sending the computer out to be looked at in the mean time. I've seen that link before. One of the main reasons I picked up the 4.8. plus only payed $300 for it.

[screamin88]

Well, you're giving up 0.9L in displacement for one. The 4.8 has n/a potential only because of the heads. To unlock that potential you need a cam. The tune is also critical. Also going from the LT1 to the 4.8 you are giving up a lot of torque unless you boost it (where the 4.8 shines). I'd invest in a decent cam, valve springs, long tube headers and get it tuned accordingly and you should see high 11s.

[GuillaumeC]

took out the old leaking lt1 and swapped in a 04 4.8.(...) Problem is I went from 12.0s@112 in the lt1 to 13.6@99 in the 4.8.

That'll teach ya.   

[1320king]

I got the ls6 intake because I planned on doing a cam swap later , looks like it will be soon than later. Will surely be sending the computer out to be looked at in the mean time. I've seen that link before. One of the main reasons I picked up the 4.8. plus only payed $300 for it.

Find a reputable tuning shop with a dyno. I would not waste your time on sending the ecu out. From experience you are most likely leaving 10-15hp on the table with mail in tunes.

[screamin88]

Find a reputable tuning shop with a dyno. I would not waste your time on sending the ecu out. From experience you are most likely leaving 10-15hp on the table with mail in tunes.

THIS^^

And spend the money on a good cam and valve springs.

[wickedrx7]

Well, you're giving up 0.9L in displacement for one. The 4.8 has n/a potential only because of the heads. To unlock that potential you need a cam. The tune is also critical. Also going from the LT1 to the 4.8 you are giving up a lot of torque unless you boost it (where the 4.8 shines). I'd invest in a decent cam, valve springs, long tube headers and get it tuned accordingly and you should see high 11s.

^ This.

[lt1fc3s]

I was die hard lt1 for 8 years, 170,000 miles on the engine I had in the car till head gaskets and ignition demons got old fast.  East coast supercharging is only few miles from me, that will be my place to get tuned. Wait till after a cam install hopefully this winter. I do have all the parts to run it carbed but fuel injection is hard to beat after tuning.