‘87 5.7 top end rebuild develops knock n shake

Discussion in '1973-1991 K5 Blazer | Truck | Suburban' started by Dont fake it break it, Mar 21, 2020.

  1. Dont fake it break it

    Dont fake it break it Registered Member Premium Member

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    Hello, Long time first time. I’m missing something and could really use some help. Just did a mild top end rebuild with new rod bearings, crank bearings, and rings. Stock pistons n rods and re-honed the cylinders. Never touched cam n crank. Pistons got mixed up at the machine shop where I had the heads resurfaced and the valvetrain assembled. I had them hot tanked with the heads to clean them up. No they weren’t marked I just had them in order in their wash basket thinking I would also unload them when they were done. My bad. Kept the rod caps intact and correct so could at least distinguish driver side front passenger side.Installed new standard crank bearings one at a time. When they were all in then I torqued them in order. Hod to tap the crank forward a hair to get the last pistons in. Didn’t tap it back because it seemed it would bind up on the rod. Did my best to check end play clearances with feeler and plastic gauged all the bearings. Needed standard bearings in all pistons except one and two, they needed .010. No binding issues and the engine rotated with a torque wrench at about 55 pounds. Sometimes it’s tough to get it to begin to rotate by hand but once I do it’s usually smooth until I stop and have to start again. Mechanically it looks like it’s put together correctly with no identifiable binding. I was liberal with the assembly lube and pre-oiled before start up. Set distributor by plugging number one hole and check for compression, then rotating timing mark to zero. Rotor pointed at number one and I can see the piston at tdc, and assembled plug wires accordingly. Start up resulted in some pretty significant shaking and a very consistent knock. It will idle steady but the knock seemed lower and light smoke from tbi. Could my timing be 180 off? Could my harmonic balancer have rotated or something? I found a similar thread that referenced a spun balancer but looks dead on so I’m looking for new info. I’m at a loss now. Any and all input welcome. Thanks in advance.
     
  2. frankin5

    frankin5 Super Mall Crawler Premium Member

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    Check timing and there should not be smoke out of the TB. Make sure the wire on firewall is disconnected to check timing. Sounds like it could be 180 out. Should not have a knock.
     
  3. 1-ton

    1-ton 1/2 ton status Premium Member

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    My guess is some serous out of balance issues. If the rods where not put back in in the same order as they came out this would create a serious balance issue. The pistons could be installed up-side down as well causing piston slap. If the the engine was put back together incorrectly then my guess is that the installation of the distributor met the same fate.
     
    Last edited: Mar 23, 2020
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  4. yblow

    yblow 1/2 ton status Premium Member

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    Did you set the thrust bearing and check end play within specs? Or just did your best and called it good. Your engine shouldn't be hard to turn without the heads on. Who honed the cylinders? Did you check the cylinders and pistons within spec?
     
  5. Dont fake it break it

    Dont fake it break it Registered Member Premium Member

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    Thanks for the response. I have actually failed to check the timing at all thinking the computer would just adjust it for me.
     
  6. Dont fake it break it

    Dont fake it break it Registered Member Premium Member

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    Thanks for the input. I actually came across a photo I had texted to my son with all the pistons lined up in a box or used to transport to the machine shop. I believe I can actually reassemble the persons in the correct order based on the slight imperfections in the manufacturing process. They all look similar but certainly have distinct characteristics.
     
  7. Dont fake it break it

    Dont fake it break it Registered Member Premium Member

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    Thanks yblow. I actually searched for a while for some visual instruction on how to do that and couldn’t find anything. Everything was in dialogue but when it’s a foreign subject, it might as well be in Greek. I wasn’t even sure how I would check the end play without removing the crank. I did the cylinders with a three stone hone. I checked ring gap and it seemed OK but that was it. No real specialty tools to work with except a feeler gauge and a torque wrench.
     
  8. Dont fake it break it

    Dont fake it break it Registered Member Premium Member

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    I think you’re all right. The mismatched pistons I suspect would create some drag resistance when rotating. It was also my first attempt with plastic gauge. Not an exact science. The timing was certainly off because I was so shocked by the knocking, I never even adjusted it. Setting the thrust bearing is still something of a mystery to me so if someone could elaborate, that would be much appreciated. I’m gonna tear it all down and start over and I’ll probably find where I went wrong along the way. As if there was just one thing wrong. LOL.
     
  9. yblow

    yblow 1/2 ton status Premium Member

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    Unless you take your motor to a good machinist your going to need some measuring tools. Even if taken to a machinist you still want to check a few clearances. Your going to need caliper, micrometer, dial bore gauge and for end play the easiest way is with a dial indicator and magnetic base.

    There are lots of videos on checking clearances and end play. I've had to shave main bearings to get proper clearance. A little trick once crank is installed snug up main caps, with a rubber mallet tap on each end of the crank. This will help in setting the bearings in. End play, place dial indicator on front of block, move crank to one side(front or rear) with a pry bar, set dial on indicator to zero, move crank to other side of block, read dial indicator. Check that it's in spec. Feller gauges can be used if you have correct ones.

    You should be able to pick up those measuring tools for around $500, or borrow from friends family.

    Did you separate the rods from the pistons? If so are you sure you installed the rods facing each other in the correct orientation on the crankshaft?
     
  10. Dont fake it break it

    Dont fake it break it Registered Member Premium Member

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    Thanks for the response. I get it about the importance of checking those clearances so I’ll look into borrowing some advanced tools. No, never separated the rods from the Pistons. They looked in decent enough shape so just ran with them as is.
     
  11. yblow

    yblow 1/2 ton status Premium Member

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    It sounds like piston knock/slap to me. Could be caused by timing or improper fitting of piston to cylinder clearance.
     
  12. 1-ton

    1-ton 1/2 ton status Premium Member

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    I am thinking a piston or two could be in up-side down. If the pistons have two valve reliefs make sure the reliefs are on the bottom. If they are dish pistons with no valve relief then there may be a small divot in the piston crown indicating the bottom of the piston. The piston divot would go on the bottom like the valve reliefs would.
     
  13. Dont fake it break it

    Dont fake it break it Registered Member Premium Member

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    I hear u on that. 4 valve reliefs with clear arrows pointing front. Best I can tell by sorting them from the picture I found is that 3 were in the correct cylinders. Also when I carried them in and sat em down on the table to study, I was missing 1 bearing half. :dunno:. I’m hoping I dropped it to save some face but hoping I didn’t to solve a mystery. Fml.
     
  14. 1-ton

    1-ton 1/2 ton status Premium Member

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    If that was the case then the big end of the connecting rod would show definite damage on it from not having 1/2 of the bearing at all.
     
  15. Dont fake it break it

    Dont fake it break it Registered Member Premium Member

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    Hmm. I didn’t notice anything but that certainly makes sense. So I got it all back together last night, turn the key and it fired on the first crank and ran good! However it started to sputter after a minute or so and died out. Got it to turn over and fire up a couple more times Each time being harder to start and sputtering and dying. Pulled all the plugs and every one is fouled, but at least the knock and shake is gone. Keep in mind that I did not get a chance to set the timing and did the valve adjustment myself. Zero lash, three-quarter turn but my technique is unchecked. Thoughts?
     
  16. Dont fake it break it

    Dont fake it break it Registered Member Premium Member

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    Latest update: After repeatedly fouling plugs, I reset the distributor and that did the trick. Not sure how it was off but it fired right up. At tdc, the rotor looked between two terminals so I rotated them all 1 position. It didn’t fire. I moved them back and it fired right up. Figure I had played with the timing on previous attempts and got it too far off. Still has a faint knock and maybe a lifter tick but at least that’s progress. Oil pressure gauge never worked befor and now it does but reads quite low. 15 at idle and 30 at about 2500rpm I’m guessing. Oh also recapped plugs from 045 to 035.
     
    Last edited: Mar 28, 2020 at 12:26 PM
  17. dyeager535

    dyeager535 1 ton status Premium Member

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    Did you by chance put a new oil pump in and I missed that? I suspect it's the springs that give up the ghost, but it seems fairly common for a new pump to raise the pressure even on old engines. As cheap as they are, not a bad idea.

    Not that 15 is dangerous, but it's only going to go down from there.
     
  18. Dont fake it break it

    Dont fake it break it Registered Member Premium Member

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    Thanks for asking but no I never did replace the oil pump. I thought about it but the receipts are adding up. I did have the transmission worked on when the TV cable had failed on me a while back and The guy told me that my pick up was just laying in the oil pan so he welded it back on. I sort of suspected maybe it wasn’t at the factory angle so I added half a quart and it came up considerably. There’s noise I still have I really can’t tell if it’s a knock or a tick but I hear it mostly at the rear of the engine underneath at the flywheel. I hooked the timing light and listen for the sound and it was in sync so I thought it was valve train related based on something I read but I just can’t deny I hear it louder underneath that I do above which leads me to think it’s a rotating assembly related. I was planning on pulling the valve covers and running it to check my valve adjustment since I can’t run it with the oil pan off which I would love to do. Any thoughts on that? Thank you.
     
  19. diesel4me

    diesel4me 1 ton status Premium Member

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    The oil pump is pretty cheap,been about 10 years since I last bought one for a SBC from Autozone (Melling pump),it was $12.99 !

    I also replaced the nylon p-o-s oil pump drive sleeve with a steel one,that was about $5...that nylon thing can fail and let the oil pump drive shaft flop around and even come off the other half of the shaft that is driven by the distributor..you don't want the oil pump to stop turning with the engine running!..

    A friend had a '70 Impala with a 350 years ago,that had an intermittent clickity-clack noise coming from the flywheel area--we checked the torque converter bolts,they were tight,and we didn't see any cracks in the flex plate where it bolts to the crank...he drove it like that awhile,but it kept getting louder..we thought maybe the torque converter had something bouncing around inside it..

    One day he decided to install a set of mechanical gauges,after he saw the oil idiot light flicker a few times when the noise came around--we watched the oil pressure gauge,every time the clicking noise started,the pressure dropped below 10 psi,then it would fade away and the gauge rose right back up to 35 psi again,and it would repeat this about every 15-30 seconds..

    He decided to replace the oil pump--had to lift the engine off the mounts to get the oil pan off--we found that nylon drive sleeve in pieces ,in the sludge in the bottom of the pan!..he bought a new oil pump and steel drive sleeve and installed it,and the oil pressure went up to 40+ psi at idle,no more scary noises..he was lucky it didn't spin a bearing running it that way..
     
  20. dyeager535

    dyeager535 1 ton status Premium Member

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    Are you sure it's not the TBI injectors ticking? My ears suck, with a stethoscope (super cheap on ebay) I can hear but not pinpoint a ticking in mine. I figure it's the injectors or aftermarket roller rockers for some reason. Its run with that noise a long time, so I'm leaving it alone lol.
     

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