False knock

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Mar 3, 2007 | 04:55 PM

NXSLT1

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From: Clarksville,Tn

False knock

It's a stock LT1 with a roots blower on it and it's seeing about 5-7 lbs of boost. I'm getting knock only in boost. I was getting knock with as little as 6-10 degrees of timing in boost with 93 octane so I put 102 octane in it and bumped the timing up to a max of 20 in boost and I'm still seeing knock. I'm gonna back the timing way off again with the 102 and see what it does but should 102 be enough octane for this setup?? I'm seeing knock just revving it up sittin in the driveway and that doesn't seem right. The blower gears are a lil noisy and I don't know if that's causing false knock or not. Any thoughts??

Mar 4, 2007 | 08:43 PM

NXSLT1

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From: Clarksville,Tn

So nobody knows a thing about false knock??

Mar 4, 2007 | 09:05 PM

Rob

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From: Diamondhead, MS

Have you tried an LT4 knock module?

More than likely false though if it does it without moving. Probably the exhaust touching the frame from torquing over.

Mar 8, 2007 | 10:22 AM

Xtnct00WS6

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From: Sterling VA

Check the torque arm too. Make sure that's not hitting the exhaust.

Mar 8, 2007 | 10:27 AM

Frost

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From: Richmond VA

Just use some good fuel and see if it goes away... VERIFY that it's false.

Mar 8, 2007 | 04:25 PM

NXSLT1

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From: Clarksville,Tn

I don't have a torque arm so that can't be hitting. I have an LT4 knock module. It amazes me the knock the laptop reports just from revving it in the driveway. It trips it all the way back to zero like it aint nothing. I ran some 102 octane thru it, I don't know if that's enough octane to be sure it's false but same thing happened with it. What makes me think it's not false is it only does it under boost. I mean the instant it crosses over I get knock and this is with 5 degrees max timing. The exhaust is really loud so I can't hear the knock if it is real. I'm pulling my hair out here.

Mar 8, 2007 | 07:08 PM

Frost

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From: Richmond VA

Hate to say it, but a leakdown test is in order now. Oil in the cylinder will cause lots of knock. What's you PCV setup like? Maybe you are drawing oil through there. I don't know the LTx stuff that well though, does the blower actually make a lot more noise in boost? Maybe it's just that. What do your plugs look like?