.005 piston clearance causing slap and perhaps causing false knock ....any cure?
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Joined: Feb 2001
Posts: 1,081
From: Charleston, WV, U.S.
Re: .005 piston clearance causing slap and perhaps causing false knock ....any cure?
Originally Posted by jonaddis84
I dont know the expansion properties of the pistons you are running, or even pretend to. But if you cant get rid of the knock, try running the engine hotter, like at factory temp, assuming you probably have a 160stat in it.
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Joined: Oct 1998
Posts: 43
From: Frederick, MD
Re: .005 piston clearance causing slap and perhaps causing false knock ....any cure?
I am helping Charlie sort out this new combination, and I wanted to post the solution to this one.
It is true that the shortblock has audible piston slap particularly cold, and since the builder didn't check it, we have no way of knowing what the actual clearance is, but fortunately that was not the issue.
The car also had an ABS and airbag light when it came to me that I hadn't really tried too hard to find. Yesterday, the abs and airbag lights went off, but the scanmaster reported knock also went away at precisely the same time.... All three issues returned next time I started it.
I did a search for abs and airbag lights, and got a thread directing me to the chassis ground on the right inner fender. Sure enough it was all connected, but not securely.
The lights are off, and the retard is gone. Millivolts are funny things sometimes. The poor ground must have caused a backfeed into the KS circuit. I will look at the schematics tonight and try to fully understand it, but I wanted to post this under the category of "first time I've seen that" for you guys to file away mentally for future use.
Roger
It is true that the shortblock has audible piston slap particularly cold, and since the builder didn't check it, we have no way of knowing what the actual clearance is, but fortunately that was not the issue.
The car also had an ABS and airbag light when it came to me that I hadn't really tried too hard to find. Yesterday, the abs and airbag lights went off, but the scanmaster reported knock also went away at precisely the same time.... All three issues returned next time I started it.
I did a search for abs and airbag lights, and got a thread directing me to the chassis ground on the right inner fender. Sure enough it was all connected, but not securely.
The lights are off, and the retard is gone. Millivolts are funny things sometimes. The poor ground must have caused a backfeed into the KS circuit. I will look at the schematics tonight and try to fully understand it, but I wanted to post this under the category of "first time I've seen that" for you guys to file away mentally for future use.
Roger
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Joined: Jul 2004
Posts: 195
From: Palm Bay, Fl
Re: .005 piston clearance causing slap and perhaps causing false knock ....any cure?
It always amazes me how many problems can be caused by poor electrical connections...and as you mentioned especially when dealing with mv. Thanks for the heads-up on the fix.
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Registered User
Joined: Feb 2001
Posts: 1,081
From: Charleston, WV, U.S.
Re: .005 piston clearance causing slap and perhaps causing false knock ....any cure?
Originally Posted by 94LT1_89TTA
I am helping Charlie sort out this new combination, and I wanted to post the solution to this one.
It is true that the shortblock has audible piston slap particularly cold, and since the builder didn't check it, we have no way of knowing what the actual clearance is, but fortunately that was not the issue.
The car also had an ABS and airbag light when it came to me that I hadn't really tried too hard to find. Yesterday, the abs and airbag lights went off, but the scanmaster reported knock also went away at precisely the same time.... All three issues returned next time I started it.
I did a search for abs and airbag lights, and got a thread directing me to the chassis ground on the right inner fender. Sure enough it was all connected, but not securely.
The lights are off, and the retard is gone. Millivolts are funny things sometimes. The poor ground must have caused a backfeed into the KS circuit. I will look at the schematics tonight and try to fully understand it, but I wanted to post this under the category of "first time I've seen that" for you guys to file away mentally for future use.
Roger
It is true that the shortblock has audible piston slap particularly cold, and since the builder didn't check it, we have no way of knowing what the actual clearance is, but fortunately that was not the issue.
The car also had an ABS and airbag light when it came to me that I hadn't really tried too hard to find. Yesterday, the abs and airbag lights went off, but the scanmaster reported knock also went away at precisely the same time.... All three issues returned next time I started it.
I did a search for abs and airbag lights, and got a thread directing me to the chassis ground on the right inner fender. Sure enough it was all connected, but not securely.
The lights are off, and the retard is gone. Millivolts are funny things sometimes. The poor ground must have caused a backfeed into the KS circuit. I will look at the schematics tonight and try to fully understand it, but I wanted to post this under the category of "first time I've seen that" for you guys to file away mentally for future use.
Roger
Rog is humble but he's truly a "guru" at design and troubleshooting (among other talents).
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Joined: Oct 2002
Posts: 6,518
Re: .005 piston clearance causing slap and perhaps causing false knock ....any cure?
Wow good find!, we should sticky this thread.
No fix that we should have a thread archive.... maybe a good place to put the really good formal posts so that we could rehash old topics over time too.
No fix that we should have a thread archive.... maybe a good place to put the really good formal posts so that we could rehash old topics over time too.
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