Crate LS6 install problems (F-body)
I'm going to have to disagree with the dianostic of it's the stock tune. I ran my crate LS6 on my '98's stock tune for 3 years with no issues. Idled fine, ran great. I finally had a dynotune last summer and found out I was running VERY lean (14+:1) at the higher RPM's on the stock tune. I dynoed 375 RWHP on the stock tune and even after Vengeance worked their magic with my computer, Mike was only able to pull it up to 377RWHP, but got my AFR exactly where it needed to be.
I'm going to have to agree with the posts that think it's a vacuum or air leak of somekind somewhere. First thing I'd do is swap back over to the LS6 or even LS1 intake and see if the problem persists. Make sure all of the little gaskets are installed around each port too and all the bolts are torqued correctly and in the correct pattern. Make sure the 2 knock sensor harness fittings are also as flush to the valley cover as possible. That could prevent the intake from sitting flush and could cause the intake leaks.
Also, one of the biggest problems in installing an intake is the hose that goes to the back of the intake that you have to work around the oil pressure sending unit. Make sure that hose is ALL THE WAY on, but make sure you don't break the oil pressure sending unit at the same time.
I've got an LS6 crate installed in my '98 and I installed it with the help of a friend. I've been there, had minor problems that I had to work out, but it's been in my Z28 since the summer of '04 and I couldn't be happier!
Pics of my install as well as LS6 installation tips can be found at my website in my sig.
I'm going to have to agree with the posts that think it's a vacuum or air leak of somekind somewhere. First thing I'd do is swap back over to the LS6 or even LS1 intake and see if the problem persists. Make sure all of the little gaskets are installed around each port too and all the bolts are torqued correctly and in the correct pattern. Make sure the 2 knock sensor harness fittings are also as flush to the valley cover as possible. That could prevent the intake from sitting flush and could cause the intake leaks.
Also, one of the biggest problems in installing an intake is the hose that goes to the back of the intake that you have to work around the oil pressure sending unit. Make sure that hose is ALL THE WAY on, but make sure you don't break the oil pressure sending unit at the same time.
I've got an LS6 crate installed in my '98 and I installed it with the help of a friend. I've been there, had minor problems that I had to work out, but it's been in my Z28 since the summer of '04 and I couldn't be happier!
Pics of my install as well as LS6 installation tips can be found at my website in my sig.
Staging Lane
Joined: Sep 2008
Posts: 78
Likes: 0
From: West Chester, PA
I've also have a GM ls6 engine in my Trans Am. I did the swap over a year ago after my stock Ls1 died. I ran over a year on the stock Ls1 tune and never had an issue. I just had the pcm tuned and that was becuase of BandDirector's ( I think it was his, btw you get that thing down to the track yet, what did it run?) witeup of his Ls6 install, and how it went way lean in the upped RPM range. before he had it tuned.
I would be hunting for something along a vac. leak to start. Then go on from there.
I'm going to have to disagree with the dianostic of it's the stock tune. I ran my crate LS6 on my '98's stock tune for 3 years with no issues. Idled fine, ran great. I finally had a dynotune last summer and found out I was running VERY lean (14+:1) at the higher RPM's on the stock tune. I dynoed 375 RWHP on the stock tune and even after Vengeance worked their magic with my computer, Mike was only able to pull it up to 377RWHP, but got my AFR exactly where it needed to be.
I'm still having a hard time just finding time to drive it....I did my annual oil change a couple of weeks ago and I managed to only put a whopping 700 miles on my LS6 Z28 in the past 13 months...I need to start renting it out or something 
Red99TA, I didn't get a printout of the baseline, so I don't know how much the torque went up. However, I was surprised at the RWHP the LS6 put down on the stock tune. I was really expecting to be around 360 RWHP and then I figured the dynotune would pull me up around 380...I was surprised to find out how close I was on the stock tune.
I've now got the Powerbond underdrive pulley and a 180 degree thermostat, so I'm guessing I put down a solid 385 RWHP now. But I desperately want to get over the 400 RWHP mark soon. LT headers left a bad taste in my mouth after my last fiasco with them, so that's why I'm running Hooker shorties. I'm thinking about doing a cam swap to Thunder's TR224 w/114LS to get me over the hump or letting Vengeance have it back for one of their cam swaps. However, once you get the LS6 with Fast 90 intake dynoed, I am curious what that will do...
Red99TA, I didn't get a printout of the baseline, so I don't know how much the torque went up. However, I was surprised at the RWHP the LS6 put down on the stock tune. I was really expecting to be around 360 RWHP and then I figured the dynotune would pull me up around 380...I was surprised to find out how close I was on the stock tune.
I've now got the Powerbond underdrive pulley and a 180 degree thermostat, so I'm guessing I put down a solid 385 RWHP now. But I desperately want to get over the 400 RWHP mark soon. LT headers left a bad taste in my mouth after my last fiasco with them, so that's why I'm running Hooker shorties. I'm thinking about doing a cam swap to Thunder's TR224 w/114LS to get me over the hump or letting Vengeance have it back for one of their cam swaps. However, once you get the LS6 with Fast 90 intake dynoed, I am curious what that will do...
Teching In
Joined: Feb 2008
Posts: 18
Likes: 0
From: Lehigh Acres , Fl.
I put the gm ls6 long block part#89017653 in my 01 ss in march. I reused the old oil pan , ls6 intake , and swapped to the ls6 style pcv system. Engine fired right up and ran perfect on stock tune. I have put 7k miles on it so far with the only problem being my slp maf leaning the car out to much and damaging the driver's cat. From what you posted above I would have to say you have a vacuum leak. Try keeping the car alive by reving it light as possible and sparying carb/intake cleaner around the intake and vacuum lines. If engine rpms change when spraying in one area you have a leak. Rember that intake tourqe is very important and to follow the correct pattern to avoid cracking the intake. I hope this helps and you find a very easy/cheap fix.
