Does it sound like something knocking or bumping the valve cover? I ask because it sounds like something is knocking on my valve cover. Thanks in advance.
I thought I had the same problem a while back, there was this tapping sound which I thought was comming from the valves but turned out to be an exhause leak. Take it to a mechanic at least to make sue
An exhaust leak can sound very similar to a valve tapping. Also a valve should not be a knock. The sound comes from the rocker arm being to loose and i think tapping against the top of the valve. it is kind of a rattle sound or a sound of 2 pieces of metal being tapped against each other. It is hard to explain the sound really. I had problems keeping my valves tight for a while so i know the sound but not how to explain it. I would fix the exhaust leak first if you know you have one and then if the sound is still there adjust the rocker arms.
If you don't have an automotive stethiscope (spelling?) an old timers trick of using a length of fuel or vacuum hose, one end in your ear and the other poking around up and down the valve cover or whereever can help you locate the precise area. I've even used a piece of broom handle placed against the ear and the valve cover or exhaust manifold. I know, I'm an old timer (fart).
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Early '66 GT-350, purchased April '69
Last edited by cushman350; 04-29-2009 at 08:19 PM.
Reason: duh
Ok, next question. What causes the valve/ or lifters to tap. When my car idles in park, if you listen really hard, you can hear a very tiny tap. How do I fix it if it is a valve tapping?
I thought I had a lifter problem and used a two foot piece of dowel rod as a stethescope -- one end at my ear with hands cupped and the other end again the valve cover, intake manifold, exhaust manifold, and against any solid surface on the engine. I could not find the source. After weeks, a friend came over and lifted the vacuum line from the rear vacuum port on the intake manifold and we spotted a crack on the underside of the vacuum line. I cut away the split, stuck it back on lost the tapping, my rough idle, and it runs soooo much better...drivers license threatening better. If you have a stuck lifter or rocker arm problem you probably have a noticeable miss especially at idle. If you haven't been running over redline rpm or punishing the engine in some other way, I would look for a simpler solution.
Last edited by Phastback; 05-23-2009 at 04:05 PM.
Reason: forgot the "not"
I still have it, but we found out what is wrong. It was originally caused be a damaged headgasket. So I replaced the head gasket. I should have known there was something wrong because it leaked. But, the problem is, when I fixed the leaking head gasket, I found out that at least one of the rings on cylinder 6 is damaged, because I now have blowby from the oil filler cap and the oil dipstick tube.
Hi! dne' here, After reading your profile, I see you have a 6cyl(200). I think most people that have responded to your question may think you have a V8? Now after having read your last post about increased blow by after having replaced the headgasket, have you performed any testing to find out what your compression is? leak down test to determine where your compression is going? Did you change your oil after replacing your headgasket, to get out all the water, anti-freeze out of your oil? I think there is an acceptable amount of blowby to be expected(unless it's a ridiculous amount), and does your motor have a PCV valve, if so, is it working?(positive crankcase ventilation valve). If tapping is coming from your valve train for sure due to a slack in your lifter,pushrod to rocker arm, I was reading in my manual that there is/was oversized pushrods(lengthwise) to "adjust" the clearance. Well, that's about all I can offer. dne'
Quote:
Originally Posted by 66Sprint200
Does it sound like something knocking or bumping the valve cover? I ask because it sounds like something is knocking on my valve cover. Thanks in advance.
I talked to the shop that rebuilt my engine about 2 years ago. They said that odds are the rings on cylinder 6 got messed up when it blew the headgasket, because we found it was cylinder 6 that caused the damage. I have a set of moly .o3 over rings on the way. They bored the engine out to .o3 over, and we had all 6 cylinder walls checked for damage. There is no damage what so ever other than the cylinder leaking. My car does have a PCV valve. I replaced the original just in case it wasn't working. The oil was changed, and I will change it again when I re-ring it.
I hope you don't mind me asking additional questions and questioning things I'm hearing. can you explain to me how the rings on #6 cyl got messed up when it blew a headgasket? Obviously it would be a bad gasket, defect in the heads surface or block(a low spot needing milled). Before you pull your engine apart, I just about beg you to at least spend time doing some easy to do tests. A compression test on all 6 cylinders, then a leak down test, but the compression test should tell you a lot. Would you be implying that when it blew the head gasket, "something" damaged the rings? Just sounds highly unlikely to me that something could actually damage the rings unless they were installed incorrectly from whomsoever overhauled it or the engine just resulted in a mechanical failure of a particular component. I just know that before I would be having to take my motor apart again, I would at least establish a baseline of what my compression is. So answer me this: Do you know what the compression of each cylinder right now?
Quote:
Originally Posted by 66Sprint200
I talked to the shop that rebuilt my engine about 2 years ago. They said that odds are the rings on cylinder 6 got messed up when it blew the headgasket, because we found it was cylinder 6 that caused the damage. I have a set of moly .o3 over rings on the way. They bored the engine out to .o3 over, and we had all 6 cylinder walls checked for damage. There is no damage what so ever other than the cylinder leaking. My car does have a PCV valve. I replaced the original just in case it wasn't working. The oil was changed, and I will change it again when I re-ring it.
I know it sounds confusing, but here is what I think happened. My head gasket was always leaking oil, so odds are it was also leaking compression. I think that maybe the rings weren't put on cylinder 6 properly, but if it was leaking compression then the rings might not have been affected. One day after a forced downshift, my engine didn't seem to recover. It struggled to continue idling. So I figured maybe something was wrong with the rocker assembly. Took off the valve cover and found that they had put some of the rocker support shafts on wrong. So I rebuilt the rocker assembly using my original 1966 shop manual (holy bible of restoration). Well, it was still idling poorly, so I thought maybe a lifter was stuck. I pulled up each push rod, and I accidentally pulled the 2nd lifter on cylinder one out. That forced me to take off the head. By the way, 6 cylinder heads are REALLY heavy. When we got it off, we found that the head gasket had been literally evaporated and burned away between cylinders 5 & 6. So, I had a friend with all the tools known to man examine my head. He said that it wasn't damaged and that it was flat. So, we got a new head gasket and exhaust manifold gasket, used this as a chance to repaint everything, and put everything back together and torqued everything to factory specs. The head gasket didn't leak anymore, but I think that by fixing the leaking head gasket, the compression may have blown out the cast iron rings that were most likely not installed properly.
Good writeup, but I'd still like you to do a compression test please! I had an Maverick with a 6 (200), and I was running it kind of hard one day, and began missing aftewards. I found that one of my exhaust valves was not closing all the way. I removed the valve cover and located the valve, tapped it with a hammer and it popped closed, and then ran fine. Anyway, no extra charge for my story! lol But I like problems like this, keeps me thinking! Any good mechanic would do a COMPRESSION TEST . Do it for me. And one more thing! If you're going through this much work, why not have the head checked out, a 'valve job'? Unfortunately, the little 200's just aren't the greatest motors in the world, but it's all you have right now, so give it your best shot! me I would love to talk to you about it. 832-607-9116
I will find someone to help me with a compression test. I too thought maybe it was a valve, but all the valve seals are ok, and just to make sure, I tapped each of the valves with a mallet (not smashing them, but enough to seat them if they weren't) but nothing changed. The blowby coming from the oil dipstick tube and the oil filler cap are the signs of a damaged ring(s).
What Does A Tapping Valve Sound Like? 
dne' here,
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