I have been having knock problems at WOT above 4800-5000rpms. At first I attributed it to noisy rocker arms(Cran 1.8's) but I relashed them and it did not help. So, I thought maybe my injector constants were off(I had changed them from 26 to 28lbers) so I set those back to stock and that did not help. I have been data logging(atap) for the last few days and everything seems to be good(I am actually a little on the fat side) but everytime I go WOT at 5000rpm it feels like I hit a brick wall and I get anywhere from 1.6* to 4* of knock retard. I am not sure what to do next...Please advise.

MODS
SLP LT headers
Flowmaster CatBack
Holley Manifold
Comp Cams 216/220
Cran 1.8 Roller Rockers
Underdrive pulley
Stock heads/ported and decked .030
3500 Stall converter
Transgo Shift kit

Thanks

 

I had the same problem with my GF's 02' Formula. I would recommend a good fuel system cleaner -especially the Redline SI-1. Use one whole bottle. The next thing I did was lean out the IFR tables on the very bottom end and fattened up the top some. Also, if you are running 28 degrees timing with the LS6 intake that may be too much. From my experience you make the most power going leaner with a little less timing. Try the Redline stuff with Chevron 93 in your tank. If that doesn't do the trick then try flatlining your timing @ 24 from 4400rpm on up and see how it runs like that. You should make more power leaner @ 24 degrees than being richer @ 28.

If you have any other questions feel free to e-mail me <img border="0" title="" alt="[Smile]" src="gr_stretch.gif" />

 

Thanks for the tips. I run cleaner through my fuel system about every 6000 miles and I have a relatively new filter so maybe it is my timing. I will try what you suggested and see what happens. <img border="0" alt="[burn out]" title="" src="graemlins/gr_burnout.gif" />

 

Some people have har KR problems with aftermarket underdrive pullies. If you switch it out with the stock one does it still pull timing?

 

I have not tried to change the pulley. But, it ran fine with the pulley for about a year. I can't quite pin down what I changed that caused this problem. Also, I changed the timing down to 24* and the problem did not go away. I am running rich, 24* of timing, MAF flow and frequency look good so I am stumped.

 

You have too much slack in your valvetrain. Our Rockers DO NOT require setting lash. You simply torque them to 22lbs-ft.

Here is the procedure from GM

</font><blockquote><font size="1" face="Verdana, Helvetica, sans-serif">quote:</font><hr /><font size="2" face="Verdana, Helvetica, sans-serif">Valve Rocker Arm and Push Rod Installation

Important
When reusing the valve train components, always install the components to the original location and position.

Valve lash is net build, no valve adjustment is required.

1) Lubricate the valve rocker arms and pushrods with clean engine oil.
2) Lubricate the flange of the valve rocker arm bolts with clean engine oil. Lubricate the flange or washer surface of the bolt that will contact the valve rocker arm.
3) Install the valve rocker arm pivot support.

Important
Make sure that the pushrods seat properly to the valve lifter sockets.

4) Install the pushrods.

Important
Make sure that the pushrods seat properly to the ends of the rocker arms.

DO NOT tighten the rocker arm bolts at this time.

5) Install the rocker arms and bolts.

6) Rotate the crankshaft until number one piston is at top dead center of compression stroke. In this position, cylinder number one rocker arms will be off lobe lift, and the crankshaft sprocket key will be at the 1:30 position. If viewing from the rear of the engine, the additional crankshaft pilot hole (non-threaded) will be in the 10:30 position. The engine firing order is 1,8,7,2,6,5,4,3. Cylinders 1,3,5 and 7 are left bank. Cylinders 2,4,6, and 8 are right bank.

Notice

Use the correct fastener in the correct location. Replacement fasteners must be the correct part number for that application. Fasteners requiring replacement or fasteners requiring the use of thread locking compound or sealant are identified in the service procedure. Do not use paints, lubricants, or corrosion inhibitors on fasteners or fastener joint surfaces unless specified. These coatings affect fastener torque and joint clamping force and may damage the fastener. Use the correct tightening sequence and specifications when installing fasteners in order to avoid damage to parts and systems.

7) With the engine in the number one firing position, tighten the following valve rocker arm bolts: Tighten

- Tighten exhaust valve rocker arm bolts 1, 2, 7, and 8 to 30 N·m (22 lb ft).
- Tighten intake valve rocker arm bolts 1, 3, 4, and 5 to 30 N·m (22 lb ft).

8) Rotate the crankshaft 360 degrees.

Tighten the following valve rocker arm bolts: Tighten
- Tighten exhaust valve rocker arm bolts 3, 4, 5, and 6 to 30 N·m (22 lb ft).
- Tighten intake valve rocker arm bolts 2, 6, 7, and 8 to 30 N·m (22 lb ft).</font><hr /></blockquote><font size="2" face="Verdana, Helvetica, sans-serif">

 

My rockers are not GM. I have the Crane 1.8's and they are adjustable.

 

TTT for you

 

</font><blockquote><font size="1" face="Verdana, Helvetica, sans-serif">quote:</font><hr /><font size="2" face="Verdana, Helvetica, sans-serif">Originally posted by NO CATZZ:
<strong> My rockers are not GM. I have the Crane 1.8's and they are adjustable. </strong></font><hr /></blockquote><font size="2" face="Verdana, Helvetica, sans-serif">The rockers are not, but the head you're installing them on ARE! The pushrods, which even though they may be aftermarket and stock length ARE!

I'm still trying to figure out how you even were able to set the lash. <img border="0" title="" alt="[Big Grin]" src="gr_grin.gif" /> My fingers aren't the biggest and even still I couldn't do it. But then again, that is a stock rocker setup.

Just telling you, LS1's are net of build...no adjustment necessary.

 

If no adjustment is necessary then why does the crane instructions give you a long drawn out process on how to set them???? I think the total time is like 2 hours to set them. Anybody out there used these before???