I have seen several threads with guys asking about gains or losses when doing cutouts or taking the cats off. Two weeks ago I had mine cut-off & went to the track to measure the difference. With nothing changed but the removal of the cats I gained .297 off my et.'s over prior week with same weather conditions. The other thing is that I did not loose any measurable low end touque based off my 60 foot time, I actually improved it .022!

Keep in mind this was on a 4.8 with 20 inch wheels & tires that weighed in @ a whopping 5493 lbs @ the track!

Last weekend I installed the Z06 hot cam valve springs & I must tell you that above 6000 rpms the truck not only pulls like bear all the way up to 6600 with NO VALVE FLOAT, but sounds wicked!

I am not telling everyone to go out & cut your cats off, but for my application it made a noticable improvement that was complimented even more with the valve springs. All things considered it is the single most seat of the pants improvement next to the cam/tune combo. I do believe that a new tune should be done based on the increased smell of hydrocarbons. I will know for sure once I get back to the dyno with the wideband.

 

Was this 1 freak run or an average of several runs? I still have cats since I was afraid of losing alot of lowend. Im thinking about getting them cut off now

 

this was a total of 4 runs back to back! it was the end of the night & I had this duramax that kept spanking my tail. we were basicly hot lapping.

I was afraid of the same thing me having the 4.8 and all, but it made a difference!

 

what were your overall times

 

15.44 with the stock tires, 15.81 @ 91.89 with 20's before spring install

 

The way your post reads, it looks as though you removed the cats and installed a Z06 cam over the course of 2 weks and then went back to the track and picked up nearly 3 tenths. From what I hear, the cam is good for about 20 rwhp or so, so that would make more sense.

Is this correct?

 

no I have a comp 212/218 cam, I installed the Z06 hot cam valve springs. I Ran a cople of weekends ago with the 20's on, the following thursday I had the cats cut off. The next day Friday went out to the track, gained et time over previous friday. The following day Saturday/Sunday I installed the valve springs.

just for kicks though this is the 3rd cam I have installed, I did have the Z06 cam @ one time & have dyno sheets @ 289 rwhp. Even degreed the cam was a dog on the bottom end.

 

Oh, ok.

 

I have gutted mine and ran a pipe through them so it looks like they are still there. I run 15.01 @ 90.54 with just exhaust and a tune on stock rear rims and my 17s up front.