Ok, my tuner (PCMforless) just got ahold of my data logs and said I have a TON of knock retard. My car has GM LT4 roller rockers, shorty headers, no cats, magnaflow catback, and is an 11:1 compression 383.

I tightend the rockers using this method:

http://www.fearlessperformance.com/installmain.htm

Anyone think the rockers are too loose, causing false knock?

I don't think the exhaust could be triggering the false knock either.

Here in Utah we only have 91 octane gas, but we are also 5,000 ft. above sea level. At such a high elevation I assumed 11:1 compression and 91 octane would work fine. Was I wrong? Do you guys think I should get some 100 octane the next time I fill up and see if it goes away?

How do I check to see if I have a faulty knock sensor?

Lastly, if it is real knock, what are my options?

 

You can determine false knock by running a few gallons of 100 octane unleaded with as little pump gas as possible. Log some data and if there is knock retard, its false. Some causes include exhaust hitting/rubbing somewhere, exhust leak at the header flanges and rocker chatter (self aligning rockers are bad about this.) With 11:1 compression, 91 octane is kinda pushing it in my opinion.

 

Thanks, any other idea's?

 

I looked at your website. It says you have a 226/226 cam. With 11:1 compression, you should be fine. That's only marginally more than stock (which is 10.5:1). Given the bigger cam, I'd say your dynamic compression ratio might actually be similar or less than stock. 91 octane shouldn't be a problem for you.

 

The specs I see says a hot cam for his car. But either way there is not alot of overlap, which is what bleeds down compression. Running 91 in a stock engine would be pushing it. I am not saying you can't do it, but it would be much better with 93.

 

Gasoline is a moot point, as there is only 91 here.

The website is a tad out of date, my new cam is 232/242, .565/.576 on a 114.