HELP! knock in engine

Discussion in ''Da Nailhead' started by cobravii, Oct 20, 2015.

  1. cobravii

    cobravii Well-Known Member

    have a 1964 425 dual quad engine. My father rebuilt it 20 years ago and put about 10 miles on it test driving it before he parked it. I got the car and the engine was seized from sitting. I pulled the heads, cleaned up the cylinders and got the engine turning again. I stripped the heads down. 2 valves were badly stuck one so badly the guide broke taking it apart. I replaced the valves and installed a new guide. I also drained the oil and replaced the fuel pump. After reassembly I fired the engine up and for the first while had a lot of blow by. it eventually went away and the engine ran smooth with no noise. Once I knew the engine was ok i took it (and the transmission) out. Just before wrapping it up for storage I pulled the oil pan and found 3" of jello like oil in the bottom. I cleaned it all up and put it together.
    2 years later the frame is restored and I put the engine back in but this time with a transmission adapter and a 700R4 transmission. When I fired it up again I had huge blow by again and there was a fairly solid knock. I thought maybe when I broke it loose I broke a piston or spun a bearing because of the jello oil. I bought new pistons, rings, lifters, pushrods and rod bearings along with all new gaskets. I disassembled the engine except for the crank and cam. I found the rings stuck but the pistons were immaculate. The rod bearings were like new, the lifters looked new but because I had new ones I used them. Because I bought new pistons I decided to use them and had the pistons installed by a very reputable machine shop. After installing the new parts I fired it up and it ran well but slowly over an hour of running the knock came back. The engine ran smooth, the oil pressure is great but at an idle there is a knock that I just can't pin point to where it is coming from. When I pull #3 plug it seems to get a lot better. The knock goes away when idle is raised. It is only at a low idle that I hear it and is really pronounced when in gear. I unbolted the torque and the noise went away but I have no way of putting a load on the engine.
    I tore it down again and replaced the cam and rechecked the rod and main bearings... all good. I did notice that the valve lifter on the same valve I replaced the guid on had small cracks on the face the contacts the cam. I replaced it. I also replaced the fuel pump again thinking the arm was hitting the timing cover. just in case I also replaced the oil pump. fired it up again ran it at 2000 rpm for about 20 minutes to break in the new cam it sounded awesome! smooth, no noise and solid. after bringing it back to an idle I have the same EXACT knock i have had all along.
    I am at a loss. good oil pressure, idles and runs smooth, lot's of power. only knocks a low idle and under load.
    The only thing I can think of now is that I didn't drive the valve guid in enough and the top of the valve spring is hitting the guid when the valve opens.

    Please... any thoughts would be appreciated.
     
  2. Bigpig455

    Bigpig455 Fastest of the slow....

    Could it be a cracked flex plate?
     
  3. 56buickboy

    56buickboy Well-Known Member

    If the valve spring retainer was hitting the guide I would think the noise would be there constantly?

    If the noise disappeared when the torque converter was unbolted then I would also be looking at the flexiplate or an issue inside the torque converter.
     
  4. ttotired

    ttotired Well-Known Member

    I kind of agree about the flex plate/torque converter

    I also have a knock in mine that I am trying to track down, but I am at the start (old engine that I freed up)

    I do wonder what can knock after the engine though, maybe the guts of the torque converter falling apart?

    I wouldnt have thought you would have loose bolts, considering you have had it apart a couple of times

    I wish you the best of luck

    Mick
     
  5. 8ad-f85

    8ad-f85 Well-Known Member

    If you had the valve guide contacting the retainer, it would probably bend a pushrod or at least leave a witness mark at the point of contact.
    Some quick measuring before assembly would prevent those questions.
    Sorry I can't be more helpful.
     
  6. cobravii

    cobravii Well-Known Member

    Ok, so it looks like either the toque converter/area or the valve guide. The torque is brand new but doesn't mean it isn't faulty.
    What does a broken crank sound like? How do I diagnose?


    Any other thoughts?
     
  7. 8ad-f85

    8ad-f85 Well-Known Member

    Various methods of inspection like stethoscope (or wooden dowel) while running can be used. Isolating components or cylinders can narrow down things.
    Is the noise at engine speed or half engine speed? Move a timing light around to synch the noise?
    Basic diagnostic charts can really steer you better than blind internet guessing.
    Run the engine with the valve covers off and feel anything while handling the rockers?

    I feel bad that it's been torn down a couple times and still has noise, but some way better opportunities have been overlooked.
    Like inspect things while they are apart.
    You're not going to like this, but you might be better off installing a different engine or tearing down this one and really going through it.

    You mentioned "properly installing new pistons" at a shop...how about properly inspecting a likely out-of-round rod from being hammered out of shape from knocking, or crack checking it?
    Some shops never re-use a knocked rod, despite passing an initial magnaflux test.
    How are you inspecting the bearings? Did you put new bearings into out-of-round bores? That often leads to trouble.

    Piston slap from too much clearance? I see this one often from home-built engines not inspected.
    Cracked cranks MAY ring or throw belts, as the crack opens up or flexes.
    Oil filters collect material from failures as they shed material.
    A single rocker on it's way to failure?
    External accessory maybe?
    Slight exhaust leak would act the exact same way.
    Trans adapters loosening make noise and leave marks at the mating surface.
    I've seen cheap, import lifters arrive new with cracks on the face.
    Valve job after guide replacement? Could a valve leak?
    Noise follow a vacuum gauge?
     
  8. telriv

    telriv Founders Club Member

    Could be a variety of things. If it got better when #3 was removed I would concentrate on that cyl. after checking the fly wheel/torque converter bolts & look closely at the flywheel for cracks. Could be the piston is making contact with the head which happens, usually, when .020" or more is removed from the head, not so much so if a composite head gasket was used because they are "Thicker" compressed. Also seen where the wrist pin wasn't "Squarely" pressed in damaging the pin bore of the piston. Have also seen cam bearings that look to be good, ARE NOT. Did you check to make sure the cam turned "Smoothly" when installed??? Had an instance where after the installation of the 3rd. cam bearing the cam would not go in without force, which I didn't do. Used the original cam & slipped in like "Butter". Put the replacement cam in the lathe & checked, it was BENT .008"!!!! This was new out of the box.


    Tom T.
     
  9. 8ad-f85

    8ad-f85 Well-Known Member

    I know you meant from the deck...sorry to be a nazi!
     
  10. cobravii

    cobravii Well-Known Member

    WOW! Lot's of great insight here.

    I will add some more info based on the last two responses.

    Firstly, a little insight to my education... I am a journeyman red seal automotive mechanic with a fair amount of engine rebuild experience albeit not on nailheads.

    -I have used a dowel, steel rod, stethoscope and a rubber tube to try to narrow down the noise but just haven't been able to pin point.
    -The noise is only at an idle or while under load at other RPM's.... I haven't tried using a timing light and switching wires, that's a good idea.
    -I have run the engine without the valve covers on but was unsuccessful in pinpointing the noise. I was, however, successful in lubing the engine bay.
    -I am not interested in changing out a numbers matching engine and the engine has been torn don three times now.
    -When the engine was rebuilt by my father he had it bored .030 with new pistons. When I installed the second set of pistons I trailed them without rings and the gaps were very good.
    -The rods were checked when the new pistons installed.
    -I'm not sure if the crank is cracked and I'm not sure how to check it without removing it. The belts are running true though.
    -I swapped the rocker arms side to side when I ran it without the valve covers on and the noise stayed the same. I think this rules out the rockers.
    -I have run it without the belts on, no difference.
    -no exhaust leaks
    -I have just installed the transmission and adapter but would be willing to recheck.
    -One lifter did have fine cracks on it on the cylinder I pulled the spark plug wire on. It was a new lifter an hour run time earlier. I have since replaced it and same issue.
    -I'm not sure how a valve leak causes a knock... anymore insight you could give me on that one?
    -not sure what you mean by noise following a vacuum gauge... anymore info you could give me on that item?
    -If the piston is contacting the head would it not knock all the time? Also, there were no marks on the piston or head from contact. In addition, the pistons are Egge brand and historically are lower compression than stock.
    -The cam I removed was a new 1360891 dual quad cam and installed a new T/A dual quad cam. It fit in very nicely. it was run at 2000 rpm for 20 minutes right at start up.

    Thank you all for your thoughts and for taking the time to type it all out, Very much appreciated. I have lot's more to ponder.

    Larry
     
  11. telriv

    telriv Founders Club Member

    It seems to happen when the head is cut rather than the deck.
     
  12. 64 wildcat conv

    64 wildcat conv Silver Level contributor

    Could it be the cam lobe that this lifter runs on or have you replaced the cam as well? Seems like you issue is on #3 if pulling the plug wire improves the noise.
     
  13. 8ad-f85

    8ad-f85 Well-Known Member

    OK, Telriv...I now know what you mean, thank you! The chamber changes shape when enough is machined off, possibly hitting the dome of the piston!

    1. Thanks for the detailed response, it's now much easier to know where you might be at as well as how you look at things.
    2. You've tried some clever things to isolate noise :)
    3. My comment on leaky valves was more along the lines of how an exhaust leak or loose spark plug might sound like a knock, "Ticking" heard up the intake, or exhaust...combustion noise.
    4. This can also coincide with the movement of the needle on a sensitive vacuum gauge. They can pick up the less obvious things sometimes.
    5. I've noticed that at maybe 2000 rpms, what would eventually become a rod knock might not be detected without varying speeds up and down as the piston begins to just hit the head and load changes along with inducing piston rock. No...it might not knock all the time. Most of the time when you hear a rod knock, it's actually way past that and hitting the head, even if barely... depending on piston rock, etc.

    6. I've also seen the opposite, makes noise exactly under the conditions you describe.
    7. I never implied that a numbers matching engine should be discarded, but if the objective was to keep it on the road it could certainly be set aside for proper and thorough inspection, which had not taken place all 3 times torn down.
    8. I'm only approaching the suggestion of a teardown as the most methodical, certain way and yes...it sucks. It's already gotten by you a few times.
    9. Can you swap anything like flexplates?
    10. I've street driven cars with poorly designed trans adapters and when they begin to loosen they sound just like a rod knock. They are aluminum and move around some. They usually need attention at some point, although maybe not so much on the rather robust nailhead adapters.
    11. Verify the bore clearance? Piston slap? Pins "pressed" in?
     
  14. telriv

    telriv Founders Club Member

    Another thing. Is the snap ring behind the cam in the rear of the block installed??? And, installed properly. The rounded part goes towards the cam. The flat is to the rear.
     
  15. wkillgs

    wkillgs Gold Level Contributor

    I did have a '79 Buick V6 that made a knocking noise. When I tore it down everything looked decent. But when I rotated it, I saw the cam would move slightly forward, then slap back against the block..... and that was my 'knock'. Was likely due to the way the lobes were ground. I wouldn't expect this issue on a Nailhead, but it may be worth checking at some point. You never know.

    Clearance between crank and oil pump can be a problem.
    Flex plate bolts that are too long could hit the block.
    If the transmission isn't concentric with the crankshaft, or plumb/square to the block, something will have to give... a flexplate will only flex so much.
     
  16. Mister T

    Mister T Just truckin' around

    This is right out of left field, but how about the dust cover for that 700R4 trans? Could it be slightly warped causing it to hit the flexplate? I have heard of this happening, albeit rarely
     
  17. John Codman

    John Codman Platinum Level Contributor

    I was thinking the same thing.
     
  18. 69GS400s

    69GS400s ...my own amusement ride!

    Im no mechanic but I do have lots of experience with failure analysis - to me, the above is clearly a clue to the root problem. The lifter developing cracks certainly may not be the cause of the knock but the fact that it happened to the same lifter location not once but twice is statistically WAYY beyond coincidence.

    I'll leave it to the mechanics to tell you why this may be happening and where to look for the root cause.
     
  19. cobravii

    cobravii Well-Known Member

    TONS of great info guys! I really appreciate all of you taking the time to respond.

    Here's what my plan of action is next time I get some 'me' time.

    I am going to pull the passenger valve cover (pain in the a$$ with A/C) and rotate the engine till both valve springs on #3 are depressed and see if I can see in there. I want to see if it looks like the top of the valve spring is touching the guid. If it is I will move forward from there. If it isn't I am going to pull the 700R4 and put the T400 back in and run it.

    I'm still feeling in my gut that it's the guid that's giving me trouble.

    Thanks again all
    Larry
     
  20. wkillgs

    wkillgs Gold Level Contributor

    Larry, There was a thread last week where a video camera was used to help find valve noise on a 455. It was recorded and then played back at a very slow speed to try to synchronize the noise with a particular noise. It was a 455.
    http://www.v8buick.com/showthread.php?303056-How-to-find-the-noise-from-the-valve-train

    As Tom suggested, put a timing light on each plug wire and see if the noise coincides with a particular valve event.
     

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