Ok heres another diagnose my noise thread.

I get a knocking sound - different from and exhaust tick - and deeper in tone than detonation. It occurs in the following conditions.

1>under load only - or heavy decelleration
2>after warming up it is most noticable, not so when cold
3>it varies with engine rpm

The noise seems to be coming from the drivers side of the engine as it is almost unnoticable on the passenger side - unless you drive by something that reflects the sound back into the car.

A few of my thoughts.

1> it isnt an exhaust leak at the headers (I know what this sounds like) and besides they tend to be worse when cold and get better as things warm up, which is opposite to what is happeneing
2>It isnt a belt driven accessory, these items should not tell the difference between load and no load conditions - its just rpm to them and as such I would expect them to make their noise regardless of temperature or loading.
3>It isnt a fuel pump pushrod or lever as that is on the passenger side of the motor and hence it should be at least as audible in the passenger seat.

anybody want to chime in?

 

CHeck your mail, I'm having a problem with IM.:D

 

I just became a unfortunate recent expert at rod knock, having my own rod knock disaster. I haven't fixed it yet but I found out it was in the bottom end - which means probably a new engine rebuild.
Some pointers of what I went through:
1.) Use some kind of stethescope to isolate the sound - I used a rubber hose with one end to the ear the other end to the engine. I think a long screwdriver will work too. Put your head under the car and see if it is louder under the car (near the oil pan).
2.) Take the valve covers off and make sure it isn't the valve train - make sure it isn't the rocker arms ticking. Adjust them if needed. Make sure pushrods and lifters are OK.
3.) Remove spark plug wires one at a time. If sound changes then you know where the problem is - probably in the reciprocating parts for that cylinder - rods or bearings.
Good luck. If it is unoticable from passenger side it doesn't sound too bad, maybe it is just the valve train. Mine you can hear from inside the car with the windows closed.

 

My 73 has the same problem.
It sounds fine when it is cold, but starts knocking louder as it warms up.
It is much more noticeable when driving past a building or a wall that reflects the sound.
I am 99.9999% certain that mine is a wrist pin, and I am 100% certain that it is the #1 wrist pin because when I remove the #1 spark plug wire the knock ceases.

The Bubba I bought it from 2 1/2 years ago said he "rebuilt" the engine, but after more questioning he said that he thought he had spun a bearing that he had only reground the crank and replaced the bearings and the cam (with a "higher performance one", although he had no idea what it was). He added that the "pistons were fine so we didn't replace them".

After chasing the knocking sound in my engine for months I found a bunch of things that he thought were "fine" and didn't replace, like the timing chain that allowed at least 10 degrees of crank movement before the cam caught up with it!!! and the distributor that had was so worn the shaft could move up and down at least 1/4 inch.

So I summized that Bubba had not spun a bearing, but had mis-diagnosed the knocking sound that I am still hearing as a spun bearing, made the wrong repairs, and reassembled the engine with the worn parts that were causing the problem in the first place.

I have replaced, and fixed most of the things that Bubba missed or screwed up on my car now (except the wrist pin) and other than the knock (and the mismatched cam) it runs very good. I am still waiting to aquire the $$ to rebuild the engine properly, but since it hasn't gotten any worse in the last 2 years I am not in too much of a hurry. I just try to keep the rpm's down to keep from doing any more damage.

 

Kevin_73

I was reading a book last night that gave some tips on diagnosing knocking sounds and by description mine sounds much like a collapsed lifter, the description for wristpin knock didnt seem to fit but Iwill borrow that book and re-read.

I will be checking this weekend to see if I can find the problem - I have already resigned myself to rebuilding the motor, in fact my hope was to start on this after christmaqs anyway - so a month early isnt any big deal - although in truth - i was hopoing to build a completely new motor while still driving the car.

Rebuilding the existing motor offers some nice economies, such as not having to acquire a block, steel crank or quality rods - since an L-82 has all those things to begin with - so I will be able to spend that saved money on other good things.

The downside is that engine machining is bloody expensive in San Diego. Estimates for complete block prep range between 560-800 bucks :eek:

part of that is my fault for deciding to stud the bottom end - thus incurring at the very least a line hone for the mains. Line bore is very expensive.

 

That is definately a rod bearing knock. Save the crank by rebuilding now,or trash it and stroke the hell out of it!!!!!!!!!!!!!!!!!!!!!!!!Been there done that. :cry


[Modified by The Money Pit, 10:57 PM 11/16/2002]

 

Eric,

Sorry to hear about that "knock" or "noise". I went through that last May...... Anyway, I should be able to fire up the BB next weekend if I get the new Griffin radiator and spal fans by the end of next week.

Are you going to keep it a "355"?

My buddy and I went to a local junkyard here in Phoenix and picked out TWO 350 motors- one turned out to be a 4 bolt main with a steel crank and the other was a 2 bolt with a cast crank. BOTH motors were STANDARD bore!!! Awesome!

Good luck with your small block project. Keep us updated on the camshaft specs/compression ratio you go with...

Bob
:cheers:

 

Exhaust leak right. I assume your e-mail was made after this thread.

David

 

Yes I must admit. :rolleyes: :rolleyes: With all my hyper intelligent theories and self confidence that I know what an exhaust leak sounds like and lo and behold - cruddy ol paper gasket burnt through in 3 places and brittle like a saltine. :rolleyes: Every bolt on the drivers side was loose - one had backed out completely......I'm just gonna shut my stupid know it all mouth from now on :rolleyes:

Well fortunatly I had a set of copper header gaskets hangin on the wall just waiting to be installed - so I put that side on and the noise went right away. Well I'm feeling very IQ challenged right now.

Whats really odd is I have mixed feelings about the result - in a bizarre sort of way I was hoping for some sort of internal problem - it would give me all the impetus I need to start a new engine. Funny.... Still it will be very nice Driving the vette to work on Monday instead of my miserable little mazda 4 door. :cool: :cheers: :yesnod:


[Modified by fauxrs, 7:42 PM 11/16/2002]

 

Eric no problem. If you ever need someone to bring to light your ineptitude I'll be right there for you. :jester I'm so glad it wasn't something internal, now you have a perfectly working block to rebuild, not a guestimate of why am I spending all this time to tear apart a trashed/ useless block when I could get a turn key no worries crate block for little more. Now you know your old block is okay and she will purr like the day she was new. Good for me to since it has taken weeks to get all your carbon off my hood/ windshield.

:lol: :lol:

kidding of course
David

 

The downside is that engine machining is bloody expensive in San Diego. Estimates for complete block prep range between 560-800 bucks :yesnod: :yesnod:

Mine is being built right now, as we speak by Total Performance in Santee on Prospect Ave

Stop on by and while you are there, visit me across the street at The Dyno Shop! :cool: :D

 

Paul obviously you can't go but I'm leaving PB at 0700 tommorow morning hangover and all and meet RHill and gang at 0800 at the Carlsbad mall.

David


[Modified by Cali,77,L-82, 11:02 PM 11/16/2002]

 

Ouch, boy Its gonna take me awhile to live that one down :lol: BTW you were behind SDpacecar - so it must be his carbon :lol: :jester

 

I just may have to do that. Used to work out in that part of town.

 

Well see my post on the Peterson Museum. Can you say tow truck?

 

part of that is my fault for deciding to stud the bottom end - thus incurring at the very least a line hone for the mains. Line bore is very expensive.
-----------------------------------------------------------------------------------

Studding with correct TQ shouldn't alter the line bore. I had all my blue printing done and I ask if they wanted my stud kits. They told me no. Because a seasoned block Tqed with stock bolts would be the same.


I thought that I had bad rod knock. Only it was strange and seemed to be much higher in the block. It turned out to be just smeared aluminum from a KB hyper piston.

I had some friends listen and it stumped them because it still had normal oil pressure and pulling the number one plug made it much quieter.

 

Kinda like I felt when I blew the engine that came in my vette. Everyone was telling me how sorry they where but I just felt it was a good reason to get a 383 stroker. :) Don't ask me how that turned out. :cuss :mad

 

Well, I suppose thats possible, everything I have ever read and any machine shop I have spoken to said that in all likelyhood a line hone would be required. TQ values for studs are greater than that of bolts and thus they can cause minute distortions in the block necessitating the line hone or in extreme cases bore.

My problem was I specifically stated I wanted the line hone so the prices I quote included that, it the machine shop called me up and said that that procedure wasnt required then the price would be about $120 lower.