Hi Guys, anyone seen this sort of piston crown damage before ? I have had a persistent problem for 1k miles with what I reluctantly conceded was excessively noisy valve gear, probably caused by a damaged camshaft profile. I have previously done the valve clearances (twice), replaced a slightly cracked header, checked the v-belts for slap & removed the aircon belt altogether. Ages ago when I got my cheap and cheerful boroscope, I examined the pistons and remember these marks which I pretty much dismissed as evidence of old damage as the car currently starts runs and idles just great but just has this noisy valve gear problem. The noise itself sounds like a tapping noise which is very evident when cold and diminishes significantly when fully warmed up. My question to you Guys is..... Can it be that the valves are only just interfering with the pistons causing the tapping noise but in such a way that the car still runs just fine ? Can the camshaft alignment be out by one tooth and cause this ? Note : Each piston has 4 marks but I couldn't get a pic with all of them in view. The unseen marks are directly opposite the marks that are seen suggesting all 4 valves are interfering. Any help or suggestion would be appreciated. Kind regards, Steve Image Unavailable, Please Login Image Unavailable, Please Login
Had 8 of em just like that. It was determined that valve float due to excessive rpms and loose belts? May have contributed. The valves had been replaced in the front bank which showed deeper gouges in the pistons. I suspect the noise you hear isn't valve/piston but may be valve train/ camshaft stuff. When all else fails read the damn manual. - wife
Hey Crowndog...thanks for the feedback.. Was hoping to hear that this was the "smoking gun" to substantiate why I have this cam knock / tapping problem...damn it. This may ultimately take me back to square one which is damaged camshaft profile. Do you know if there is any way to establish the integrity of a camshaft ?. Inspection of the lobes shows that they are fine with all being perfectly shiny with no discolouration (black on the heel of the cams) Cheers, Steve
I am no expert but are you having excessive valve train noise or are you just not sure of the usual noise that these engines make? Another thought: has the engine been rebuilt before with a valve job? I have read here where seats have been ground down too far, valve guides either worn or incorrect etc. these May or may not cause excessive noise. Also, there are other things that sound noisy, change with rpms etc. tiny holes in exhaust or exhaust components can be loud and seem to come from the valves. I would look very carefully for any leaks. These are loud and sound just like a clacking noise. When all else fails read the damn manual. - wife
Mine developed a ticking noise that at first I thought was a sticking valve/ something to do with the cams but turned out to be a worn A/C belt. It was arcing on the pulleys and the ticking noise was very loud when cold.
Hi, The valve train noise happened suddenly one day. The tapping was not there the previous week although I agree with you that these engines are usually noisy but there was a definite and noticeable appearance of a new noise. By the time I got home and the car was fully warm the noise had almost gone. 9 months later, the noise during warm up when idling at traffic lights is still there and embarrassing. Just changed the header as I did find a small crack where #1 pipe joins with #4 and so bought another header. This also turned out to have more serious cracks but in places which were easier to weld. I am pretty confident that the header is now sound. My stethoscope tells me that the noise is coming from the valve train area of #1 and #4 cyls and so just can not be belts or header. The car runs just great and has good performance which indicates that the problem is not compression valve seating or broken springs. I seem to be spending a lot of time and money fixing what I am convinced is the cause of the problem only to find no difference. My concern now is that If I buy new camshafts that this would cost me dear and I may still be disappointed.....hence my quest to find the smoking gun. The cracked header could have explained it or even the mark on the pistons as shown in this thread but seems not. Apologies if I sound negative or dismissive but I am almost out of options. Cheers, Steve
I feel for you but "throwing expensive parts" before a Dx isn't IMHO the way to go. If that noise is only during warm up it certainly seems more likely an exhaust issue. Perhaps a second opinion, second set of ears like an exhaust specialist to test for pin hole leaks? Cams are big $$$ . Best of luck to you whatever you decide. When all else fails read the damn manual. - wife
Hi Freddie, Thanks for the feedback...I have had a rubber hose to my ear listening to the belts and pulleys and the noise is definitely not the v-belts. I wonder if anyone has encountered a worn and noisy camshaft. I have been searching the forum and not yet seen and such problems. Also, what are the signs and symptoms of a sticking valve....surely this would result in a loss of performance and misfire ? Cheers, Steve
Completely agree...especially when there is a very high risk that the problem will not be solved. Surely a rubber hose to the ear will tell me if there is a hole/crack/bad seal in the header. Done it before and found nothing but now feel encouraged to do it again with the repaired header in place. Cheers, Steve
Why don't you post a video of the noise? Then someone could possibly pass judgement on whether it is normal or not? May save you a heap of cash!
Don't forget that with our insulated headers on the QV it might be hidden. There are also those pesky sampling tubes which are notorious for disintegrating. When all else fails read the damn manual. - wife
a very simple tool and dead easy to use can help a lot here........the humble vacuum gauge, one of the most important tools in the box. decent article with interactive script: How to Use and Interpret a Vacuum Gauge
Steve, just a thought here, but are you sure that the cam didn't jump a tooth on the timing belt? You might be just enough out of timing with the valves that they are making some contact with the pistons. Even though you set the valve clearances, etc., it might be worth checking the valve timing just to be sure.
If your cams were worn but your valve clearance was correct I think you'd not get any excessive noise. Cam clatter noises come from excessive clearance. You said you've checked that. You'd have less lift and probably terrible valve timing, but with correct clearance I wouldn't expect much excess noise. With marks on the pistons I think a compression test would be a good idea. In fact, this is an excellent opportunity to buy a leak down tester and learn how to use it. No matter what the noise is, making sure those marks don't mean a bent valve is a good idea.
QV's will rev until the rods hang out the side without floating valves. I have seen the needle stop on the 10k tach with no valve float. Your car at one time had a cam timing issue and was fixed.
+1 My pistons had the same marks (still have them) - the belt had slipped one tooth, noticed during a rebuild (see "While You're In There" - has some pics of the pistons)
I have intimate experience with those kind of pictures - you have valve piston interference - and its not going to get better - the gouges will develop hot spots carbon build up and then more damage ... My guess would be valve guides are rattling...
Sounds correct. We found that head was removed for probable valve replacement. But the question was "why did the pistons on both banks have the marks if the belt slipped on one cog?" Hence the theory of valve float which may have led to a belt slip all due to a over rev situation. Just a theory to try and explain all the findings. The other head had never been removed. It was mentioned that slightly bent valves can still operate by straightening during the stroke then going back to being curved afterwards. Curious if you have ever seen both belts slip at the same time?
Thanks to you all for your input....interesting stuff I am back home this weekend and will tackle some of the investigations suggested, namely the basic compression test and post a video of the engine running. Not equipped to do a leakdown or the vacum test. I am also embarrassed to say that I have never checked the timing since a major service over 18 months ago. Can the camshafts be out by 1 tooth and the car still run perfectly well. I have always assumed that it would run like a dog if this was the case. Here is the thing though......the pictures at the start of this thread show one of the marks on the piston being shiny, suggesting recent contact but the other marks have carbon deposits on them suggesting an old scar. However, if there had been contact as described then surely the tapping would have deminished over time once the valve had pounded and re-shaped the piston Regardless, need to check the timing. Cheers, Steve
This is astonishing....I too would like to know if anyone has hooked up a 308 and if so where / how.....I want one of these
