Octane knock test

[Paul Clark]

If I have alky and also use race gas, is it a pretty sure thing that any knock I get will be false?
Boost will be below 20 lbs.
I'm chasing a gremlin here.
Thanks

 

[Paul Clark]

No takers on this, huh? Must be because it's a no-brainer.
17 lbs. boost, 110 octane (alky shut off), 02s at 825, 17 counts of knock retard. SC numbers are fine. I'm thinking the knock is false, but the computer doesn't know that.
Think (fuzzy memory) this started with new body mounts and tranny.
It was 24 lbs. of boost on pump gas with alky before.
Anybody have suggestions that might narrow down my search?
Thanks

 

[QUIP'6']

your probably getting knock because there is something called a rich knock its like trying to compress a liquid from not enough air. you are defeating the purpose running the boost that low with such high octane. you should try lowering your boost to 14 and run pumpgas with xzylene from lowes or home depot then slowly turn up the boost

 

[Paul Clark]

Would lowering the FP accomplish the same thing?

 

[pacecarta]

do you have a cracked flywheel ?
loose converter bolts?
loose trans to block bolts? should be torqued to 50 ft lbs
loose motor mount through frame bolt? , they need to be torqued to 65ft/lbs

 

[NHRA Super Gas]

If I have alky and also use race gas, is it a pretty sure thing that any knock I get will be false?
Boost will be below 20 lbs.
I'm chasing a gremlin here.
Thanks

I agree with your statement above, especially if things were in tune before you made other changes. 17 is a lot....a normal number if you were on edge would be more like 3-5 on the high side.

 

[Blown&Injected]

This is strange. I believe if it real knock than if all is left as is except for pump gas in place of the race gas, the knock should be even worse - I bet it stays the same because 17 psi is not that much that 93 octane should not be able to mostly deal with.

I wonder if the new body mounts are causing something to hit.

 

[Paul Clark]

Yep. I put in the race gas because it was already knocking bad - even with the alky. The race gas isn't causing the knock.
It was fine at 17lbs. on 93 w/o alky before, so think I'm at least starting to figure out how to tune.
Time to put it up on the hoist and hopefully find something amiss.
Appreciate the suggestions.
Thanks