Deckhand

iTrader: (1)

Or, just get some 104 Unleaded race fuel. Over here in South TX, its 4.50/gal.

Black Blown 02

Can't say if it will burn the cats,I wouldn't think so(there is some xylene in regular pump gas) but I've used it a few times before and it didn't hurt my 02's.

Flyer

iTrader: (1)

I read somewhere, maybe in the PCM forum, or a white paper posted in there, that the knock sensors are engine specific. They are specially tuned for the harmonics of each engine. If this were the case I would think that it would be consistant, even when you don't hammer into it. Have you checked to make sure there isn't anything banging up under there. That will definantly set off the knock sensors.

If you aren't already, I would use 93 octane gas with that kind of compression.

Check your headers out. Look at them and have someone rev it hard while you're looking. That should get the motor moving on those mounts enough to see if something's banging.

BigTex

iTrader: (16)

I would verify that the knock sensors are the same part number between the two motors. Worst case, put your originals back in.

BigKID

iTrader: (5)

The sensors came out of another 2000 5.3 motor so I dont see why the wouldn't be the same??

I took it out this evening to do some more loging and listening. I am still leaning towards something hitting under the truck because it sounds like hell.
HERE is an Excel file with two 10-15 min logs from this evening and copy of the stock 02 timing table I have in the truck. I cannot see a pattern with the kr at all.

Candy

Kenny,
Allan is going to give you a call in the morning. He was wondering if you checked the lifter preload?

Ryan23silverado

iTrader: (1)

It would be nice if the knock sensors were accurate -I have the worst year of them.
You weren't kidding about getting that full 8* knock retard right off the bat, geez. I remember when I ran the Crane 208/216 cam and 918s it registered a ton of false knock (as determined with race gas) The seat pressure for that low of a lift (.500/.500) really pulled the valves into the heads pretty hard. I think that is where most of the false knock came from.

You said it is fine running in neutral. Did you log a sweeping rev in neutral? You also said it sounds like hell when you gun it. Is the engine actually detonating? Or is it pretty indistinguishable from the part it might be hitting? Good luck man. I am really betting it is false knock as 10.25:1 is not that high. But definitely before you lower that knock limit number do the race gas test. I hope you find it soon.

BigKID

iTrader: (5)

Candy... I did not check lifter preload. I was pretty confident in my pushrod length calculations and Allan seemed to agree. Ask him to call me at work 228-935-8866 as my cell (number you have) does not work in my building.

Ryan... I have not loged a sweeping curve in neutral but I get no kr on a 5k rev. If I brake stall it I can get it to intermittantly do it around 2100 rpm but I dont hear the sound I hear when I am on the road. It sounds like an old Ford with straight pipes but it also sound almost identical to how it sounded this last time I had the exhaust reworked when one of the pipes was hitting a small bolt comming from the bed.

I am soo confused and at a loss at this point. :help:

BenKey

iTrader: (1)

We've all been there. You'll figure it out.

James B.

iTrader: (1)

Can the heads really handle a 40 thousandths drop? I recall reading that GM was having problems with pistons knocking the heads from just carbon build-up resulting in something sounding similar to piston slap but distinguishable by the change in characteristic with RPM increase...