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  #1  
Old 05-14-2008, 05:44 AM
coronetcustom coronetcustom is offline
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Default help needed with engine noise

i thought i could figure this out by myself, but again looks like i need advice from more experienced people. problem´s here: knocking coming from nr.4 cylinder. noise disappears after pulling wire off. gets worse when turn idle down. disappears if i turn advance on distributor. most noticeable when engine cold. i thought it would be piston pin, but well known and recommended shop checked rings, piston, connecting rod+bearing and piston pin, no problem there. lifters seem to be ok and rocker arms+pushrod aswell. cam (hydraulic) looks good too. cylinder´s exhaust valve was darker than others when i took head off. no problems with compression test. car was tuned in dyno. i use high octane gas. any idea
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  #2  
Old 05-14-2008, 06:29 AM
darktone darktone is offline
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what engine is it?
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  #3  
Old 05-14-2008, 07:25 AM
coronetcustom coronetcustom is offline
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Default engine specs.

oops, sorry.
it´s 1971,383, engine rebuilt 700miles ago, stock heads, edelbrock performer intake, 750edelbrock carb, new mopar performance 272 hydraulic cam, mopar electronic ignition, cylinders honed, old pistons but new rings. all new bearings. new lifters and pushrods. crankshaft milled, polished and balanced. no visible damage in piston i took out, it was measured ok
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  #4  
Old 05-14-2008, 09:38 AM
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rumblefish360 rumblefish360 is offline
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Double check the wires on the distrib and make sure there not cross fireing. Check plug.
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  #5  
Old 05-14-2008, 10:23 AM
thatwasfunny thatwasfunny is offline
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Sounds like a piston rocking back and forth.
Too much clearance, scuffed maybe?
Some mopar distributors have bad cap/rotor phasing which can cause misfire and scuff piston/s.
[not to say this is your problem] but u can find out by looking at the contacts
to see if there burnt off to 1 side.
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  #6  
Old 05-14-2008, 10:29 AM
coronetcustom coronetcustom is offline
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just did:new dist.cap, new plugs, new coil, no cross wiring, already checked wires for cracks, just got dyno tuned. could low oil pressure cause this? few months back shop installed cam bearings, they´re not perfectly alligned with oil passages. all of ´em are open but some passages about 1/3rd overlapping. somebody might remember that from my earlier posts. i think i might just get new piston/pin/rod bearing before i put the engine back together. if it still knocks, i´ll take car to shop. only thing is that i´d like to fix it myself rather than have someone else do it for me.
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  #7  
Old 05-14-2008, 10:34 AM
aarracer aarracer is offline
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Coronetcustom

When did this begin? Right after tuning?

Sounds like TOO MUCH timing advance causing detonation at idle?

Check for correct timing!!! (total advance)
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  #8  
Old 05-14-2008, 10:48 AM
coronetcustom coronetcustom is offline
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ì´m not experienced about timing, it was tuned for me and i think guy who did it said it´s 30`to 40`advance on full throttle(i´m not sure how them degrees work and i could be wrong here, how much should it be?). funky thing being that when turning distr. to advance takes the knock away. turning retard no effect. sound is most clear when engine is cold and i adjust low idle. when engine warms up and there´s more revs, there´s less sound. car was driving great and no audible sound in cockpit when driving/accelerating/high
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  #9  
Old 05-14-2008, 10:54 AM
aarracer aarracer is offline
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Default Counterclockwise

Coronet custom

Are you sure you are turning the distibutor for advance?

Big blocks distributors rotate counterclockwise, so advance increases with a clockwise rotation of the distributor!

I believe 35 degrees advance at 2000 rpm is a baseline for big blocks total mechanical advance.
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  #10  
Old 05-14-2008, 02:54 PM
thatwasfunny thatwasfunny is offline
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Yea pretty much if u retard the timing the piston knock [if thats what it is]
will go away.
Thats funny about the ignition kits these days, they tell you dis rotation is clockwise. When I helped a friend of mine break in his 440 we were debating over which way was advance, when he showed me the instruction sheet I couldn't believe my eyes when it said ,from mopar, clockwise.
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  #11  
Old 05-14-2008, 03:11 PM
coronetcustom coronetcustom is offline
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yep, i knew timing works counter clockwise/how to retard-advance timing.
i think i will replace all moving parts on problem area. 2lifters, 2rocker arms, 2pushrods, piston/rings, wrist pin, connecting rod/bearing.
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  #12  
Old 05-14-2008, 03:18 PM
thatwasfunny thatwasfunny is offline
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For shts & gigls check the rod journal on crank and the rod for straightness and the big end correct size and if pressed make sure the piston flops back and forth easily cause if pins too tight it will hurt the skirt/bore.
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  #13  
Old 05-14-2008, 04:07 PM
dgc333 dgc333 is offline
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An exhaust leak at the cylinder head to manifold / header can sound an awful lot like a metallic noise. Pulling the wire off you no longer have pressure there and cold things tend to be looser and they get tighter when hot.
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  #14  
Old 05-14-2008, 06:20 PM
rampage_82 rampage_82 is offline
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Check to make sure you don't have a vaccum leak on that cylinder... of course if you have the motor apart, IDK how this could be verified.
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  #15  
Old 05-14-2008, 07:45 PM
bobr bobr is offline
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"cylinders honed, old pistons but new rings."


My guess is you have too much piston to wall clearance which allows piston to rock and make a hollow knocking sound. The fact that you reused old pistons with a rehone of already worn cylinders makes this much more likely. -Bob
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  #16  
Old 05-15-2008, 01:55 AM
Mecki Mecki is offline
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Quote:
Originally Posted by coronetcustom View Post
cylinder´s exhaust valve was darker than others when i took head off. no problems with compression test
I would recommend checking out what causes this first. The exhaust gases have been hotter in this cylinder for some reason. Good compression indicates that the valve is not over heated due to the seat leaking. Also the piston rings are sealing tight. Piston slap could be the reason for the noise, but then the bore would be really loose. I have re ringed many engines and haven't had a problem with this so far. A rod bearing noise again is so obvious and increases with revs, that you would not like to run your engine at all. It should also be visible.

Whether it is the reason for the noise or not, the exhaust valve has been running hot and that's an issue. Lean mixture caused by intake air leak would look like this. On engines where exhaust temperatures for each cylinder are constantly monitored this is easily observed before the valve is burnt. Could the valve be occasionally hanging due to a bad lifter, causing by pass and heating? I haven't seen it on these engines, but a burnt valve is normally the result of this kind of an issue. Fix the found issue first, the noise could just disappear.
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  #17  
Old 05-15-2008, 04:07 AM
coronetcustom coronetcustom is offline
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hello Mecki,
i can send you short videoclip with engine noise. you sent me picture of steering unit few weeks back. could i use same email address?
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  #18  
Old 05-15-2008, 06:15 AM
Mecki Mecki is offline
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Yeah, thats OK!
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  #19  
Old 05-15-2008, 07:14 AM
Mecki Mecki is offline
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Sounds like a ticking lifter to me, but it's hard to recognize exactly from a video. Regular clicking noise witch decreases when revs increase? Low oil pressure at idle? Did you check the pump, old or replaced, when you assembled the engine?

You have had the piston, rod and bearing checked. Check the piston to bore clearance when you put it back together.

Still have the miss coloured valve. Is it the material that has turned dark or is it deposits on the metal surface?
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  #20  
Old 05-15-2008, 09:12 AM
RacerHog RacerHog is offline
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Fuel Pump ...????? Knock......Cam Speed Knock

Sounds like Piston slap or Wrist Pin to me...... Crankshaft speed knock.

Keep Digging....You will find it.
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  #21  
Old 05-15-2008, 09:28 AM
bobr bobr is offline
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"I have re ringed many engines and haven't had a problem with this so far."


Re-ringing a race motor that may have only a hundred 1/4 mile passes is one thing. Re-ringing a street motor that has several thousand miles on it is just not good mechanics. I don't see how, after rehoning an already worn engine, your piston to wall clearance is anywhere near decent spec. Horrible practice IMO and could easily be the cause of what is happening. -Bob
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  #22  
Old 05-15-2008, 05:33 PM
Chiphead Chiphead is offline
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Yeah, what is the skirt to wall clearance? Could be piston slap, if over about .005".

How did the upper half of the rod bearing insert look? If it shows copper, it's detonation.
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  #23  
Old 05-15-2008, 08:25 PM
Mecki Mecki is offline
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Quote:
Originally Posted by bobr View Post
Re-ringing a race motor that may have only a hundred 1/4 mile passes is one thing. Re-ringing a street motor that has several thousand miles on it is just not good mechanics. I don't see how, after re honing an already worn engine, your piston to wall clearance is anywhere near decent spec. Horrible practice IMO and could easily be the cause of what is happening. -Bob
How about 200k miles, then ridge reaming, honing and new rings. 50k miles after still going strong and not eating oil. Bad practice? Maybe in your opinion, but I knew exactly what I was doing and what to expect and I already got more. Of course, the cylinders were not too worn, out of round and tapered and cleaned up pretty easily with straight stones. The pistons were also good with minimal skirt wear as usual in a well lubricated cylinder. I ended up with an average of about .004" bigger bores. (By the way, the service limit for taper according to FSM is .01", compare that to a slightly big bore but with improved straightness.) This is just a cruiser, not a daily driver any more. Come on, these engines are really not so sensitive to piston clearance at normal driving and you can't say that there is some hi tech in the factory clearances either. Tapper and out of round is much worse than clearance for durability (the clearance will of course result in a faster wear of out of round and taper).

Can you say at what clearances you have experienced noisy piston slap? I haven't, but .008 has still been working fine. I'm not saying that I'm happy with loose clearances, but a garage fix good for 10 or 15 more years for a hobby car is pretty cost efficient, especially if I already have all the measuring and honing tools needed.

IMO bad practice is if you don't know what you are doing and what to expect. If I can run our wheel loader over the winter and get the snow job contracts fulfilled with a similar weekend home workshop fix for pocket money instead of taking it out of service with all the consequences of that I'm happy, the customer is happy and my bank manager is happy. It can be horrible practice, but I dont give a f**k.
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  #24  
Old 05-15-2008, 08:47 PM
bobr bobr is offline
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"IMO bad practice is if you don't know what you are doing and what to expect. If I can run our wheel loader over the winter and get the snow job contracts fulfilled with a similar weekend home workshop fix for pocket money instead of taking it out of service with all the consequences of that I'm happy, the customer is happy and my bank manager is happy. It can be horrible practice, but I dont give a f**k."


Some people are satisfied with nothing but the best and some don't really care what they have. Sounds like you fit in the latter. For someone with your expertise why are you posting on this board looking for answers? Remember, you are the one with the engine noise that stems from something not being correct. Running a motor 200,000 miles, reaming the ridge(which had to be more than .004 by the way or you wouldn't have needed to do it) then honing and installing the same pistons and calling that good enough-well you(or someone else) can solve the problem because I have better things to do. -Bob
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  #25  
Old 05-15-2008, 09:46 PM
Mecki Mecki is offline
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Dear Bob!

Different problems need different solving methods. Some times getting a job done within a certain time for a certain goal with a certain cost and in a location where you only have what you have with you put some limits on what is "good enough".

Funny that you are saying that I don't care about what I have. All the people who knows me are saying that I'm a perfectionist who is newer satisfied and always wants better and demands too much quality. That's true, I know my self and I like to execute that on my hobbies too. But I have also learned that the world does not work that way and to get things done, some short cuts must be taken and you can't press your employees to be perfect either. Life is just compromising all the time. The most important IMO is that you know the risks with the decisions you make and are ready to take the responsibility for that action too. OK, this is not about an engine, but I think you should not make conclusions about me so fast.

I'm sorry if I have insulted you, I dont know what kind of a guy you are and what your experiences are. I was just telling what I have experienced about piston slap and what I got out from one of my engines by re ringing it. I was surprised that the result was so good with those measures. Other results also confirms that out of round and taper is more critical than clearance if you are not aiming for an engine that will last 200k miles more.

FYI I'm posting at this board asking questions and reading other threads to get information. I want to get as much information on a subject as possible before I evaluate it and then decide what to do. This is a great place to collect facts and info. My experiences and skills are what they are and only doing more will increase them. It's obviously better to keep them to my self.

BTW, it's not me having the trouble with engine noise, I was just stupid enough to get involved in this discussion.

Have a nice day!

M. Eriksson

PS. I asked a question I honestly would like to get answered. By anybody who has experienced it. At what clearances has piston slap noise occurred?
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  #26  
Old 05-16-2008, 12:13 AM
RacerHog RacerHog is offline
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Answer.....When the clearance becomes enough to make the noise....
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  #27  
Old 05-16-2008, 12:14 AM
RacerHog RacerHog is offline
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Custom,
The only way to fix this is to open it and find the problem....
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  #28  
Old 05-16-2008, 01:02 AM
rampage_82 rampage_82 is offline
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Wait I have to chime in here again. This sounds eerily similar to a noise I was chasing in my 440. Does the motor get sluggish or hard to start (by this I mean does the starter have a hard time turning the engine over?) when it gets up to operating temperature. I finally tracked down my noise, it was caused by a vacuum leak. The valley-pan had a crushed spot, and it was causing detonation on #8 cylinder only. Unfortunately for me, it had already ruined the piston (crushed ring lands, and scored cylinder wall, and piston skirts) by the time I found it. See if you can check for this. Cause like you I was attributing the noise to loose tolerances, because I had forged pistons. My noise was worse when it was cold, or when you would barely rev the motor, like in the 1500 - 2200 rpm range. I also didn't have any signs of detonation on my spark plug, it wasn't until I seized the motor and tore it down, when I found the problem. Hope my tragedy can help someone else. BTW I didn't have a problem with piston slap. I have heard the "piston slap" diagnosis multiple times, I for one however have not seen a single instance of this actually occurring. Everytime I hear of this diagnosis, I cover my head, because inevitably there is fixing to be a thrown rod. Also another dead giveaway for me, is that valve that is different than all the others, this is the exact thing that happened in mine too. See when the ring lands crushed it allowed that cylinder to let oil pass by, which turned straight to carbon. All my other exhaust valves were a nice brown color, that one however was black black black. BTW my compression test revealed nothing unusual with any of the cylinders.
That's just my experience though.
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  #29  
Old 05-16-2008, 03:55 AM
Mecki Mecki is offline
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Quote:
Originally Posted by RacerHog View Post
Answer.....When the clearance becomes enough to make the noise....
Very accurate answer and correct. LOL, that's like my replies to my kids.

But really, have you had this problem and could you give some figures? I think it would help coronetcustom too to have some figures to compare his observations with.
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  #30  
Old 05-16-2008, 04:33 AM
Mecki Mecki is offline
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Quote:
Originally Posted by rampage_82 View Post
BTW I didn't have a problem with piston slap. I have heard the "piston slap" diagnosis multiple times, I for one however have not seen a single instance of this actually occurring.
Sorry to having hi jacked your thread coronetcustom, but what Rampage is saying about piston slap is exactly what I have experienced too and nobody has been able to give any facts and figures on the subject. Would be great to see some figures about when this issue could be expected and confirming this diagnosis.

Rampage, I enjoy reading your posts, your observations and facts have given me a lot of information before also. You don't mix facts and quesses and you don't make premature conclusions. You must have been writing a lot of reports in your job.
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