piston slap or lifter knock... problem solved, header bolts not tight enough

[silver]

So I mentioned in another thread that after my car sat for about 1 month the noise that I think is lifter knock is much louder then before and comes and goes during the rpm sweep.

I took a quick video which was mostly to record the sound it's a short clip and the knock is audible towards the end and seems to be coming from the passenger side.

Can anyone diagnosis this issue, is it a problem?  On my corvette everyone called it "piston slap" on many other cars I can hear it come and go and people call it lifter knock....2 different things which create very similar noises.

Any input is appreciated..I'm definitely not going to tear into the motor to find out what's making the noise...but I would like to know if someone has an opinion hopefully with some data or facts to explain the noise.

[positron]

Hard to tell with that quality of video/audio, is it coming from/around the blow by catch tank and do you have any excessive blow by when you pull the dipstick?

Does it go away once it comes up to temp?

Does it do it on both rev up and rev down?

[silver]

the unscientific answer is that it sounds as if it's loudest at the top of the motor like just under the valve cover.

It occurs at idle and then throughout the rpm range it will go away upon acceleration then return if let it return to idle. 

Sometimes it stays constant upon initial slower acceleration but under harder acceleration it goes away.

How do you check the catch can for blow by, I've never touched the catch can in almost 2 years of ownership.

[positron]

fastest way is to pull the dipstick out about an inch and have an assistant raise the throttle at different frequencies. ie some fast some slow. A little smoke/pressure is normal.

You should open and drain the lower petcock at each oil change, this will tell you the health of the engine. I've found that a paper plate folded into a V directed to a small water bottle is the best funnel.

[silver]

ok i went outside to check the catch can.....can't budge the lower petcock....am I supposed to turn that T-handle looking thing or just push it towards the floor...either way I'm not one to force things...and it ain't moving under finger power....so before I put more tension on it, let me know if I should just push down or loosen it or what?

[bolus]

that's either bitchslap or cockblock.  I cant tell

Mine used to do that until I replaced all the innards.  So it is either the pistons, rods, valves, valve springs, valve guides, valve seals or balance shafts

[silver]

You killed Kenny!!!! You bastards!

[positron]

It's a twisty water faucet thingy, I just checked mine and it's anticlockwise as viewed straight on to open.. Don't do it hot otherwise your guaranteed to turn it the wrong way/more open as you burn your hand..You should be able to put a small box end wrench over one of the wings and rotate. Once you get it unstuck you can spin by hand onto the V'd paper plate approached from the rear.. *cough* otherwise it goes everywhere.. again you will turn the wrong way to stop it thereby opening it more making a bigger mess.. can't image why I know this.. *cough*

Hand tight to close is sufficient.

It'll have some thin stinky oil regardless.

[maverick1]

[quote="Positron"]
It's a twisty water faucet thingy, I just checked mine and it's anticlockwise as viewed straight on to open.. Don't do it hot otherwise your guaranteed to turn it the wrong way/more open as you burn your hand..You should be able to put a small box end wrench over one of the wings and rotate. Once you get it unstuck you can spin by hand onto the V'd paper plate approached from the rear.. *cough* otherwise it goes everywhere.. again you will turn the wrong way to stop it thereby opening it more making a bigger mess.. can't image why I know this.. *cough*

Hand tight to close is sufficient.

It'll have some thin stinky oil regardless.
[/quote]
Thanks for the tip Dennis. I've never tried to empty mine. How much oil should we expect to come out?
cheers

[bolus]

[quote="maverick1"]

Thanks for the tip Dennis. I've never tried to empty mine. How much oil should we expect to come out?
cheers
[/quote]

none

[DarthChicken]

With all the work thats been done on your car Aaron... is it possible a nut or bolt got dropped someplace it shouldn't be?  I think you should take the valve cover off sooner than later, something is definitely not happy.

[positron]

[quote="silver"]
So I mentioned in another thread that after my car sat for about 1 month
[/quote]

oh that month you thought it was sitting... we've been meaning to tell you... Calscot, dp35 and I drove the crap out of your car ..   

but we brought it back full...

[bolus]

There are some engine rattle threads over on the cobalt forums.  Timing chains, broken timing chain guides and loose nuts on the timing chain guides are some common reports.  Hopefully that's not the case cause you would need to dismantle the engine. 

[CalScot]

Prior to my engine failing at Laguna Seca, I had a mechanical tapping come from the engine. At first I thought it was the valves. I re-adjusted all of them and all looked well. A leak down test showed cylinder # 3 was at 85% where all others were 100%. On the Honda, #3 is the one which fails most often on high HP forced induction engines due to it always having a firing cylinder next to it thereby gets the most heat of all 4.

I noticed it more when I had the quiet muffler installed. (The twin pipe exhaust was so noisy my wife could hear my car two miles away)  I had the local Honda dealer techs listen to it and Hytech and others. John at Hytech figured it sounded like a piston "slapping". The Honda dealer techs said that it was noisier than usual but some high strung motors like mine make "funny" noises and it was likely the valves.

Of course the engine failed with a spectacular cloud of engine smoke on track and when I pulled over, burst into flames from the oil on the exhaust. I thought the entire motor was trashed.

I finally got the engine out this week. I got it to Hytech and John stripped it down yesterday. The diagnosis is a piston ring on #3 broke.  The piston skirt was broken as well.  Overall the damage was limited to mainly one cylinder. The sleeve held up well but the scoring is just enough to require a rebore on that one only. Johns idea that the original noise was a "piston slap" was probably on the money. Of course, the collateral damage from broken ring pieces going through the valves and the continued running of the motor with chunky bits running through it have caused minor valve seat damage and the engine is getting a complete re-build. The block will be re-bored by Dan Benson in Idaho, the head is off to Endyn in TX for re-work and a set of new pistons are on order. We have ordered a custom set with thicker rings. All in all, it's not too bad for a small engine that puts out close to 500HP at the crank and has been thrashed for 5K miles.

There's not much I could have done to fix this ohter than what I am doing. I checked the valves for the noise and thats probably what you should do sooner than later. If its a piston, your choices are slim. Remove the motor and rebuild it or run it till it breaks. I reckon the damage from me running it have cost me an additional $750 to $1,000 over what it would had I stripped it down and fixed the noise. Then again, it has been rattling for about 2K miles so I got a lot of use out of it too. Also, in many respects, I was lucky as the piston was still mostly in one piece but was close to complete failure (pictures next week) and the collateral damage would have been $$$ more had it run just another minute.

Good luck with it and lets hope it's just the valves needing adjusted.

[bolus]

You could do a leak test pretty easily.  You can fit one of these in the spark plug hole.  Our cars are prone to loose #4
http://www.carcraft.com/techarticles/11 ... to_02.html