tensecls1

i installed an ls6 manifold and 160 t stat in my 99 ss about 3 months and my car has just not felt the same. My car ran solid 13.7's at lacr with nothing but an air lid and a couple of gallons of 100 octane mixed with 91. But now i am having problems with the car doing 14 flat. I checked for air leak by pulling the iac connecter and spraying t- body cleaner around the base of the manifold to check for idle changes and nothing. my air to fuel ratio at full throttle is from 12.8 to 13.0 with no retard from knock. All vaccum hoses are connected and i check three times. The vehicle also has a slight heistation at idle especaily when it's cold. I know the cars lean out at idle for smog reasons...or so i heard from my friend that works at chevy. At idle the short term fuel trim ranges from -3.7 to 0 and nothing real abnormal in the long term fuel trim. I just replaced all the plugs with delco replacements and replaced the spark plug wires, fuel filter, cleaned my k and n and applied a small amount of oil to the filter, changed the oil, and cleaned my maf. The only thing i can think of next is that there might be something going on with the knock sensor or the knock sensor harness or my car needs to be tuned for for the the new manifold. I still have the egr intact i bought the slp manifold with the fitting installed. Any help would great so that i start working on getting parts to get my car going faster

Another_User

Mine is rich as a pig at idle when it's cold. Fine when it warms up though. You may have messed up your MAF. How did you clean it? It sounds like you are running on the low-octane spark table.

boomcase

What was the difference in the weather , can you post up the 2 timeslips, to many varibles, need more input on the track days..

I lost 3 tenths in track times with weather alone...

tensecls1

I cleaned my maf with an electronic parts cleaner something that i got from radio shack that is used to clean circuit boards for computers.. i also confrimed that it is safe by my friend who works at chevorlet( also known as rubbing alcohol). i cleaned it with a q tip

LS1LT1

iTrader: (16)

Yeah as long as you didn't bend any of the wires/sensors in there your MAF should be fine.
There's no reason the car should run worse with those two things on, even if you didn't reset the fans for the new t-stat.
Could be the knock sensors/sensor wires cut maybe?

tensecls1

i don't think so because i am getting voltage in the wires and my ground is good. The only thing i am thinking is that the sensor is failing. And the loss of track times have been constant.Since the last 6 times i have been to the track since the install over the past three months..a constant 2.1 60 foot

sawedoff

iTrader: (3)

I would put the stock thermostat back in, as there is no benefit to over cooling an engine, and it doesn't sound like you are going to be doing the Rolex 24 hours. An internal combustion engine will run better the hotter it gets, up to a certain point. They also become more efficient. There's no reason why any of your sensors would be goofing up, so nix that idea. When you swapped that new manifold, you changed the breathing of the engine. It sounds to me like it's A/F ratio related, and you would benefit from adjusting the A/F mixture to gain the real benefits from the new manifold. You would definitely benefit from a dyno tune, or you can do it on your own.

Another_User

Just an interesting point, at any temperature under 185 degrees F, the PCM pulls timing at part throttle. So your car would crappier around town. It pulls up to 8 degrees at some points at 167 degrees F.

dug

iTrader: (10)

Its a tough call. Most engines seem to run better with cooler thermostats. But my car typically runs the same back to back. If not better the second time.

tensecls1

I hooked up my scaner and got an engine temp of 205*f and average 210 after 3 or 4 constant track beatings. What do the cars normally run with the stock t-stat? I really feel the power loss on the top end of the track...it kinda feels like the valves are floating or it's not getting enough gas to keep it going. It will lanch out of the hole real good and constantly get the jump on my friends heavly built up ws-6. it also feels real strong half throttle to 3\4 throttle on the freeway. The other thing i was thinking about was the length of the runners. Going back to my third gen iroc the runners on the tpi where long and when you changed them to shorter ones you changed the personailty of the car. So my question is did i sacrfice my top end to pick more low end torque from my ls6...because the runners look bigger (duh) and a little longer. Or should get a new aftermarket t-body and maf that flow better to get the full benefit out of the manifold...maybe not getting air for the larger manifold?

LS1LT1

iTrader: (16)

I would consider a ported TB maybe but I wouldn't change the MAF, maybe descreen it if you haven't yet.

Joe Bronikowski

iTrader: (1)

Stock valve springs are not the best. I believe I was getting valve float because I had similarly bad track times (14.0 @ 102), and I could really feel acceleration lay down after about 5000 rpm - most noticable in 3rd gear. That seemed way too early for the stock power peak. So I swapped in 02 LS6 springs and now the power runs up to 5500+ rpm before it starts dropping off, and the dropoff isn't so abrupt. Compare this to a stock dyno graph and you should get a good idea of when the dropoff _should_ occur.

(Sorry, haven't been back to the track since. I know, not a thorough enough experiment. :-)

So anyway, if your timing and O2's look good in the upper rpms, but there's a noticable SOTP power loss way before 5500 rpm, that could easily be valve float.

Swap in some better springs and see what happens. BTW choose springs to work with any cam swap in your future :-) Doing springs now puts you half-way there.

tensecls1

thanks for the help thats kinda what i was begining to my car..i currently have 66,000 miles on the valve train. I wanted to do a cam install at the same time,replace lifters, and replace the timing chain with a double roller unit...unless are cars already have them?