ss.slp.ls1

I just installed a new LT1 w/ a cc503 cam and headers. I have 12" of straight pipe off of the headers temporarily until I get my y-pipe put in. I have a mail order tune from MadTuner.
The car starts up fine, idles fine, just doesn't have any power when I get on it. I have been given a couple of suggestions:
a) Fresh air hitting o2's causing a rich condition
b) Open headers causing false knocking which in turn pulls timing
No codes present.

Ok, now to the real purpose of this thread...if I unplug both the knock sensor and the o2's will that be sufficient to test if either/both a. and b. are the culprits to my lack of power? I also heard that I can remove the knock sensor module from the pcm so that no timing will be pulled.

bombebomb

If you unplug the o2's it will (normally) tell you if thats the cause, cause it will run in open loop instead of closed loop, where it would use the o2's.

I am somewhat skeptical its your o2's because you have 12 inches of pipe after it. But its something to check.

Green96Z

With open headers, or near open headers in your case, there will be a significant loss of low end power. It will feel kind of gutless at lower RPMs where you used to have your torque. Once you get the y-pipe on it will run like it should.

ss.slp.ls1

I was prepared for that, but I took the engine through it's entire power band, and it never picked up, seemed like it took a long time to go through the power band too, like it was hesitating/being restricted somehow. I know I'm being vague, but that's all the info I have right now, I will try to get some more soon.

ss.slp.ls1

Will a compression test confirm that I have the rockers adjusted properly?

If not, would adjusting poly locks with the engine on method simply consist of backing off each poly lock, turning it slowly until it stops, adding the preload, and setting the allen screw? Thanks.

Also I added 1/2 turn of preload, not 1/4, is that bad?

<Puck>

Open headers wont cost you power or torque unless the tune is way off. I suspect its just pulling loads of timing.

Everything is just a guess though until you data log it.

Green96Z

The engine running method is you set them to zero lash, start the engine, then set your preload until they stop ticking, then tighten the set screw. I set all mine to 1/2 turn preload and have no problems.

ss.slp.ls1

I don't mean to argue with suggestions, but aren't you supposed to back off the nuts with the car running until you hear ticking, tighten it till the noise goes away (zero lash) and then add the preload? My question is can I use the point at which the poly lock stops spinning as zero lash before adding preload while the car is running (cause I won't be able to hear when the ticking stops)?

bubba4

Unplugging the knock sensor and conneting the plug to one side of a 1/4 watt-4K resistor (radio shack ) and connect the other side to ground will bypass the knock sensor in the computer. This info came from F.A.S.T. but I would only use this for test purposes.
Big Bubba's Racing ,Drive it like you stoled it!
95 Z28 383LT1, AFR 190's,CC306,A4,3200 stall, 100 shot nos, and much more.

ss.slp.ls1

Good to know man. Thanks.

ss.slp.ls1

I hooked up an Auto Xray scanner to my car and drove it around a little. The car was running worse than ever.

The o2's were fluctuating from .1-.9 at idle
Long Term fuel trim was 25%
Map sensor at idle was ~11 in.Hg.
Ignition timing at idle was ~25*

Ignition timing under load was 30-45*
Map sensor under load was ~30 in.Hg.

I didn't have anymore time to get more data, it was getting dark and I didn't want to get my car impounded.

I am going to check the wires and maybe change the opti soon.

Injuneer

The 4Kohm resistor is the correct value for OBD-I PCM's (93-95). It is not correct for OBD-II (96/97).

Green96Z

No, you're right, I'm not sure what I'm thinking about.

If you have doubts about your lash, you can just go back and do it again. But I doubt it's your problem. I prefer the engine-not-running method myself.

ACE1252

I adjusted mine not running too. Went 1/2 lash and have had no problems. They are like a loud sewing machine, but the Pro Mags just do that.

This was my first time ever adjusting rockers and had no problems. However, I do have a background with mechanical things too. I just followed comps instructions. I also used a torque wrench to tighten the polylocks(use a wrench to hold the lock after the desired lash, then torque the allen with the torque wrench). 30 lb/ft. That guarantees uniform tight polylocks.

My CC503 install went fairly well, but I still have several bugs to work out...

1. Cooling issue(runs 20* hotter than normal....finally think it's a dirty cooling system.....coolant is dark orange....scale in it.....however looked clear orange when I drained it for the install... must have shaken something loose during install)
2. Wicked cam surge at low throttle
3. Engine vibration @ 4000 and up(new clutch plate balance issues).

......but the car is much stronger....it's picked up almost 4 mph in the 1/8. I pulled very hard on some bolt on LT1's. I was also out running the LS1's at the track that night too(bolt on LS1's). This is was through stock manifolds, stock y-pipe, and an old flowmasters catback.

My times suck, because I can't get the car off the line. I either bog it or blow the tires off......my rear shocks are also too hard for a good launch.

ss.slp.ls1

So no one can confirm that while adjusting the rockers with the engine on method, that turning the poly lock til it just stops, and then adding the preload is an acceptable procedure?