NightmareTA

iTrader: (20)

My turbo 5.3 previously made 540 rwhp on 11 psi with no meth. Now I am running meth and 15 psi and I made 560 rwhp. Pathetic. The dyno graph was very questionable after 5200 RPM and it appeared to be a sure sign of valve float. Put in some BTR dual springs, hardened pushrods, and trunion upgrade, and after a data log the AFR was spot on still, meaning I picked up no more power. I don't know whats going on but a 5.3 @ 15 psi with my setup should be well into the 6xx rwhp mark.

Not sure what to look for next and I'm pretty upset about it. I'm wondering if maybe the timing chain or lifters could be the culprit, but it's a 38K mile motor so I have a very hard time believing either of those is worn out yet. Anybody that maybe has some experience, please help me out here. Set up is as follows..

-2005 5.3
-317 heads
-LS6 cam
-LS6 intake
-BTR dual valve springs
-BTR hardened pushrods
-BR7 plugs gapped at .026
-Tnetics T76 ball bearing w/ .96 hotside
-alky control methanol injection single 14 gph nozzle
-3.5" turbo back exhaust through bullet muffler
-viper spec T56 w/ textralia OZ700 clutch

This combo has roughly 4K miles on it over 3 years. If anymore info is needed, I can answer any questions. I have a bunch of data logs but nothing looks out of place. Boost holds steady in HPtuners at 202 kpa which is about 14.7 PSI. Timing is 14* across the charts, and AFR is 10.8-10.9 across the entire pull with no knock at all. It seems like it runs pretty well in all honesty, except for the lack of power. I'm at a loss here...

got-a-ls1

iTrader: (12)

id start with a compression and or leak down test at this point

forcd ind

iTrader: (7)

did you read the plugs-what is the preload on the lifters
pretty rich AFR's, not sure how the meth affects it
a turbo spec. cam could add power
intercooler?

NightmareTA

iTrader: (20)

Worth a shot. Motor seems to run very well though. I've cracked ringlands before and I felt a noticeable skip at lower rpm.

Plugs always look perfect. Nice tanish color. No idea on lifter preload. Using 7.4" rods with a stock LS6 cam and lifters, so I would imagine it's what stock should be. Using a CX racing intercooler which doesn't seem to affect boost drop much at all. The AFR's are a bit rich but I don't think I'd pick up 50+ hp from leaning it out a bit.

oange ss

iTrader: (50)

unless the heads are decked the pushrods are too short, you could get by with NKG TR6 plugs at that power level

oscs

iTrader: (19)

How can you possibly know his pushrods are to short for his combo without measuring them... Every car is different and there are a lot of people with this same combo and doing just fine with 7.400 push rods.

oange ss

iTrader: (50)

LS6 cam has .050 smaller base circle, using standard GM parts would put the pushrods .025 too short.

oscs

iTrader: (19)

Correct but adding assumed measurements together is not always accurate, far from it in my experience. Ask any decent builder. There is only one correct way to determine pushrod length and that is measuring.

stevieturbo

What liquid are you injecting ?

And does the car feel any faster at 15psi than it does 11psi ?

Also, you're making new dyno comparisons with an old dyno run ? Same dyno ?

NightmareTA

iTrader: (20)

I had 7.4" pushrods on 11 psi and my dyno graph pulled fine up to 6500 rpm. Now suddenly it won't make power over 5200 rpm on 15 psi. Not sure what the issue could be. I have a full 3.5" exhaust with XR1 muffler but I would think that should be enough flow for it.

100% meth. Feels faster for sure but it did gain 60 lbs ft over my last dyno...just not much power so it's hard to tell in the upper rpms. The runs were on 2 different dyno's, but both were dynojets. My brother's car was on each dyno and it made within a few HP on each, so I know they read very close.

samdogmx

iTrader: (14)

sounds very conservative on timing and AFRs for such low boost.

HRD

iTrader: (1)

Try a pull without the meth. If you have 93 then you shouldn't need it at that level. I would add a degree of timing and pull some fuel to get it into low 11s. Im pushing 17 psi on 93 pump gas with no meth on a stock bottom end 2000 5.3l and have had no issues for several thousand miles now. 726 rwhp. At 14 psi I was at 650.

NightmareTA

iTrader: (20)

Unfortunately I need the meth. The third gen TA front bumper has no airflow at all because it's solid, so my IAT's before would get scary...like 150-160* in 4th gear. Now the IAT's stay around 65-75* but the car isn't making power. I have heard that meth cars like timing, but still, I don't see picking up another 60-70 rwhp on that alone which is where I should be.

stevieturbo

2-3 deg of timing could easily yield that sort of power release if the engine wants it.

Ron_Stoppable

iTrader: (1)

Tranmission/ converter slipping?

NightmareTA

iTrader: (20)

I normally would pick up 5 or so HP per degree of timing....seems excessive to gain that much but I guess it's worth a shot to add some and see how it feels. Easy enough anyways.

It's a T56 car with a textralia clutch. The clutch slipping was a possibility to me but it only has 4K miles on it and it spins my 295 MT drag radials in 1st and 2nd with ease, so I wouldn't think that would be the issue. Just so many possible things it could be...wish there was a clear cut answer! Really thought the dual valve springs were going to solve it.

blue99fbody

iTrader: (5)

post the dyno graph or video, a 4th gear pull on the dyno is about the hardest thing on a clutch with the kind of load it puts on it. slipping clutch will show there before slipping in 1st or 2nd on the street especially if your spinning the tires the clutch doesnt have the load on it.

Wicked69

Here is my .02. 317 heads on a 5.3=Dog. Several people to include myself have made tons of power with the junk 862 heads but everyone wants to run the 317's. I don't even run the 317's on a 6.0. 862 heads on a 6.0 gives it some compression and will run like a raped ape. So to me a 5.3 with 317's sounds about right as far as power goes. I just can't believe you will make any power at that low of boost and that rich an AFR with such low compression. When compression is low you make up for it by running more boost. Again, just my .02 cents.

MonmouthCtyLS7

iTrader: (6)

I was thinking the same thing here.

1bdbrd

iTrader: (12)

What lifters are in it? Could they possibly be part of the problem?