Dismiss Notice

Welcome To CK5!

Registering is free and easy! Hope to see you on the forums soon.

Score a FREE t-shirt and membership sticker when you sign up for a Premium Membership and choose the recurring plan.

Rebuilt motor is knocking- Update, If you're interested

Discussion in '1973-1991 K5 Blazer | Truck | Suburban' started by FWP, Jan 3, 2002.

  1. FWP

    FWP CRS

    Joined:
    Oct 11, 2000
    Posts:
    3,845
    Likes Received:
    3
    Location:
    Prescott Valley, AZ
    Rebuilt motor is knocking- Update, If you\'re interested

    1100 miles into my rebuilt motor (pre-emissions 350), it's knocking. Sounds like the bottom end in the back of the motor. Utmost care was taken when I bolted the machined parts together. All bearings were plasti-gaged, all torques on all bolts correct. Cam was degreed in and piston clearances and rings checked. Motor was pre lubed before starting (2000 rpm- 20 minutes).

    Ran it real easy driving the first 500 miles, then changed oil and filter. Ran motor normal driving for another 500 and changed oil and filter again.

    Now at 1100 miles, I can hear knocking from the block, I think? Sound increases with engine speed, load or not. Oil pressure is the same as when I first started it, 15-45 psi.

    Here's what I have done so far:

    Took a stethascope to the motor, sound coming from the bottom rear, hard to isolate.

    Pulled 1 plug wire at a time (thinking a rod)- no changes.

    Disconnected torque converter from flex plate (maybe tranny or TQ conv noise), ran motor- no changes

    Removed all belts from accessories (just in case sound was transmitted down)- no changes

    Removed fuel pump (weak spring in pump might cause rod to slap cam lobe)- no changes

    Checked crank end play, no problem there.


    HEEELLLPPP, I really don't wan't to take the motor back out, but I will if I have too<img src="http://coloradok5.com/forums/images/icons/mad.gif">, I figure it will cost about 100 bucks just for fluids and gaskets- not including my labor. I hope it turns out to be something stupid<img src="http://coloradok5.com/forums/images/icons/blush.gif"> and cheap<img src="http://coloradok5.com/forums/images/icons/wink.gif">. Somehow, I doubt it though........

    Any other ideas????????

    Update-
    <font color=red>Thanks for the ideas guys. ....Something is really screwy with the main bearings[​IMG]or crank. I get wear marks (shiney- not the usual grey colored wear) on one half of a bearing and none on the other half. For example- The bottom half front bearing has one wear area towards the rear of the motor, and no wear on the front, the top half is shiny all around except for 3/8 inch on the sides. Almost like the bearings are the wrong size, or the crank was ground wrong (It was supposed to be 10/10)

    The mains plastigaged to spec (1.5-3) when I first put it together......It's really bizarre.......I've never seen anything like it......Anyway, I'm taking the bearings to my machinist for further evaluation. </font color=red>
     
  2. DesertDueler

    DesertDueler 1/2 ton status

    Joined:
    May 23, 2001
    Posts:
    3,106
    Likes Received:
    0
    Location:
    Phoenix, AZ
    Re: Rebuilt motor is knocking, any other ideas before I pull it???

    Turn the stereo up :) Were the rods new, or resized?

    86Jimmy 4"&35"MTRs,87 burb 4"&33"MT,69Firebird w/525 hp,and 70GTO live in PHX,AZ<a target="_blank" href=http://www.geocities.com/modifierperformance>My vehicles</a>
     
  3. Liberator

    Liberator 1/2 ton status

    Joined:
    Jul 16, 2001
    Posts:
    276
    Likes Received:
    0
    Location:
    Communist California
    Re: Rebuilt motor is knocking, any other ideas before I pull it???

    <blockquote><font class="small">In reply to:</font><hr>

    Utmost care was taken when I bolted the machined parts together. All bearings were plasti-gaged, all torques on all bolts correct. Cam was degreed in and piston clearances and rings checked. Motor was pre lubed before starting (2000 rpm- 20 minutes).

    <hr></blockquote>

    That's why I hate working on motors! You can do everything by the book, but something still goes wrong. Lets take installing a harmonic balancer on my 350 for instance. All I wanted to do was put on a new balancer. Easy, right? Not if the threads are thrashed in the crank nose! And the worst part is, it's a stinkin cast crank and can't be re-threaded. The only way to fix it is with one of those heli-coil or whatever kits. And in order to do that I have to take everything apart again just to get the crank out! I'll throw it, the new performer intake and the new 4x4Extreme cam that's on it and toss it all in the dumpster before I take apart any lower end!
    Ok, I feel a little better now! Sorry! All I can say is, engines frustrate me!

    Bo

    If it breaks, it wasn't good enough!
    http://coloradok5.com/gallery/liberator
     
  4. FWP

    FWP CRS

    Joined:
    Oct 11, 2000
    Posts:
    3,845
    Likes Received:
    3
    Location:
    Prescott Valley, AZ
    Re: Rebuilt motor is knocking, any other ideas before I pull it???

    Hehehe, very funny, I'm not real fond of getting stuck in the middle of the desert- In August[​IMG] ....

    Recon'd rods

    <a target="_blank" href=http://coloradok5.com/gallery/75K5>http://coloradok5.com/gallery/75K5</a>
     
  5. FWP

    FWP CRS

    Joined:
    Oct 11, 2000
    Posts:
    3,845
    Likes Received:
    3
    Location:
    Prescott Valley, AZ
    Re: Rebuilt motor is knocking, any other ideas before I pull it???

    I feel your pain dude...[​IMG]

    <a target="_blank" href=http://coloradok5.com/gallery/75K5>http://coloradok5.com/gallery/75K5</a>
     
  6. juanblzer

    juanblzer 1/2 ton status

    Joined:
    Sep 12, 2001
    Posts:
    1,614
    Likes Received:
    9
    Location:
    Chandler, Arizona
    Re: Rebuilt motor is knocking, any other ideas before I pull it???

    hey fred,
    when I bought my goodwrench 350 from Tyrell Chevrolet in Flagstaff lastyear I thought everything was set. 4months later I was treated to a sudden fluxuation of oil pressure and then a knocking that was unbelievable. As I was trying to get back to a McDonalds so I could use the phone the engine siezed. The motor was torn down at Lou Grubb Chevrolet (they had to warranty it) and found that I had spun two main bearings and broke the crankshaft. They replaced the motor.
    Anyway. I hope everything is ok. That sucks something awful. As you can see, even factory stuff gets messed up. God it seems like you did everything by the book. If you need an extra hand let me know.

    chrome sucks
     
  7. DesertDueler

    DesertDueler 1/2 ton status

    Joined:
    May 23, 2001
    Posts:
    3,106
    Likes Received:
    0
    Location:
    Phoenix, AZ
    Re: Rebuilt motor is knocking, any other ideas before I pull it???

    Id say the rods are probably junk. I know thats not what you want to hear though.

    86Jimmy 4"&35"MTRs,87 burb 4"&33"MT,69Firebird w/525 hp,and 70GTO live in PHX,AZ<a target="_blank" href=http://www.geocities.com/modifierperformance>My vehicles</a>
     
  8. mpascino

    mpascino 1/2 ton status

    Joined:
    Jan 1, 2001
    Posts:
    557
    Likes Received:
    0
    Location:
    Connecticut
    Re: Rebuilt motor is knocking, any other ideas before I pull it???

    I was in your shoes about a year ago..... Just finished building my motor, ran great at first. Soon after I noticed my oil pressure dropping day by day along with a strong knock apearing. To make a long story short and to keep my blood pressure down turns out my crank way defective. It checked out perfect when installed but after running somehow it literally broke down. It was pitted across the entire crank. Only thing I can think of is that I was sold a resurface crank as new and it was just not done right. I would pull the pan down again and check the conditions of your bearings.
    Good luck,
    Mike

    The jeep eater ......[​IMG]
     
  9. BorregoK5

    BorregoK5 1/2 ton status

    Joined:
    Sep 7, 2001
    Posts:
    2,457
    Likes Received:
    0
    Location:
    San Marcos, Ca USA
    Re: Rebuilt motor is knocking, any other ideas before I pull it???

    Sounds kinda like a wrist pin but I would bet one of your rod bolts has loosened up. I've seen this happen several times before where it was hard to pin-point where the origin of the knock came from and it sounds exactly like the items you have checked (like the fuel pump rod). Pull the pan and go over your rod caps. Most people who have had this tend to think it can't be what it is and eventually throw a rod through the side of the pan. Eat the cost of oil and a new gasket and drop the pan before its too late, even if it is something else, a bottom end knock is usually a warning of inevitable failure. Good luck.

    I started with nothing and I still have most of that left! - <a target="_blank" href=http://24.55.50.76:81/k5/> Pictures</a>
     
  10. RedDwarf

    RedDwarf 1/2 ton status

    Joined:
    May 9, 2001
    Posts:
    816
    Likes Received:
    0
    Location:
    North Central Florida
    Re: Rebuilt motor is knocking, any other ideas before I pull it???

    Look for exhaust leaks.
    Then check the torque convertor bolts/ pressure plate bolts, and the bellhousing bolts.
     
  11. arq

    arq 1/2 ton status

    Joined:
    Jan 17, 2001
    Posts:
    2,017
    Likes Received:
    0
    Location:
    Imperial Valley/Maricopa
    Re: Rebuilt motor is knocking, any other ideas before I pull it???

    i second reddwarf, you'd be surprize at how close the exhaust sounds like a bad rod.

    ARQ

    offroad baja!!!
    72 4x4 CST Blazer
    71 4x4 CST Blazer
    <a target="_blank" href=http://coloradok5.com/gallery/ArqDennis>My Pics</a>
     
  12. FWP

    FWP CRS

    Joined:
    Oct 11, 2000
    Posts:
    3,845
    Likes Received:
    3
    Location:
    Prescott Valley, AZ
    Re: Rebuilt motor is knocking- Update, If you\'re interested

    Updated on original post.....

    <a target="_blank" href=http://coloradok5.com/gallery/75K5>http://coloradok5.com/gallery/75K5</a>
     
  13. K5 NUTT

    K5 NUTT 1/2 ton status

    Joined:
    Feb 17, 2000
    Posts:
    1,611
    Likes Received:
    0
    Location:
    Grand Junction Colorado
    Re: Rebuilt motor is knocking- Update, If you\'re interested

    Thats what it sounded like fred....seems like somebody made a boo boo on the crank machining....my old 383 did the same thing...but at least i got 1.5 years outa it. Hope you can get this resolved...hope to still see you in the yellow p/u on the 12th bud! BTW...ran into Jaunblazer at the autoshow today....nice guy!

    Azblazer

    1979 K5 350 TBI
    1976 K5 Chalet
    If it ain't got arizona pinstriping.....you ain't wheelin the pee outa her!
     
  14. mpascino

    mpascino 1/2 ton status

    Joined:
    Jan 1, 2001
    Posts:
    557
    Likes Received:
    0
    Location:
    Connecticut
    Re: Rebuilt motor is knocking- Update, If you\'re interested

    Sounds like your crank is toasted........Sorry buddy, keep up updated.
    Mike

    The jeep eater ......[​IMG]
     
  15. FWP

    FWP CRS

    Joined:
    Oct 11, 2000
    Posts:
    3,845
    Likes Received:
    3
    Location:
    Prescott Valley, AZ
    Re: Rebuilt motor is knocking- Update, If you\'re interested

    You bet, Mike, I'll keep you guys updated. I hope some one can learn something. I know I'm learning as I go .....

    <a target="_blank" href=http://coloradok5.com/gallery/75K5>http://coloradok5.com/gallery/75K5</a>
     
  16. FWP

    FWP CRS

    Joined:
    Oct 11, 2000
    Posts:
    3,845
    Likes Received:
    3
    Location:
    Prescott Valley, AZ
    Re: Rebuilt motor is knocking- Update, If you\'re interested

    I'll know tomorrow what the deal is, or at least what I should do next.

    I'll be out there on the 12th-Like you said, probably in the K10

    Yep, Juan is a decent fellow. Was he in his K5? Pretty cool setup he has there[​IMG]

    <a target="_blank" href=http://coloradok5.com/gallery/75K5>http://coloradok5.com/gallery/75K5</a>
     
  17. K5 NUTT

    K5 NUTT 1/2 ton status

    Joined:
    Feb 17, 2000
    Posts:
    1,611
    Likes Received:
    0
    Location:
    Grand Junction Colorado
    Re: Rebuilt motor is knocking- Update, If you\'re interested

    Didn't get to see his K5..just met him and his mechanic...lol.

    Azblazer

    1979 K5 350 TBI
    1976 K5 Chalet
    If it ain't got arizona pinstriping.....you ain't wheelin the pee outa her!
     
  18. txoneway

    txoneway Registered Member

    Joined:
    Sep 21, 2001
    Posts:
    20
    Likes Received:
    0
    Location:
    texas panhandle
    Re: Rebuilt motor is knocking- Update, If you\'re interested

    i got the same thing in my 400. i pulled it outa my old pick up cuz i heard it knockin. a few yrs later i rebuilt it an put it in my ugly suburban. at first there was no noise. then after 1000 or so miles ya could here it knock slightly at an idle but it would go away at higher rpm. i kept drivin it. gave it hell actually. if its gonna go, itd gonna go.never has. but nown at round 4000+miles its stillknockin, louder, an the oil pressure drops as the rpm goes up. but its still runs like a raped ape. i figered the pick up on the oil pump mighta fellor moved. ill check it out when i gotta nice day AND the time to do it. ill letcha know the outcome as soon as i figer out what the deal is. lotsa luck to ya with yers.

    hell yeah, im drunk! what do ya think, im a stunt driver??
     
  19. mudddog91

    mudddog91 1/2 ton status

    Joined:
    Dec 28, 2000
    Posts:
    471
    Likes Received:
    0
    Location:
    north carolina
    Re: Rebuilt motor is knocking- Update, If you\'re interested

    Just a question.Are you guys having your mains aligned honed when you take it to the machine shop?Im not trying to be a smartass but it sounds like the mains are worn or warped causeing bearing failure.Just a thought.
     
  20. Ddragggon

    Ddragggon 1/2 ton status

    Joined:
    Apr 25, 2001
    Posts:
    2,657
    Likes Received:
    0
    Location:
    Hartford, WI (formerly Etiwanda, SoCal)
    Re: Rebuilt motor is knocking- Update, If you\'re interested

    in my C20, I had the 454 in it for about a week, when suddenly I got a VERY loud and irregular knocking on the freeway... just out of the blue, and so, I dove off the freeway, and parked it, ( the knocking becaome regular, and louder) and had my friend Nate come haul me home. pulled the engine, took it back to the shop it came from, they pulled it appart, and determined that one of the middle main bearings collapsed for no reason, did warranty on it, and returned it to me. since then, its run perfectly for me, although I need a new Pan seal, since I misread the torque settings, and had the pan too loose...

    good luck with it,

    -Rich

    My truck isn't ugly, you have a skewed sense of beauty

    <font color=blue>2007 Ford XLS++ intrepid Ram Superduty 7000 R-type's suck</font color=blue>
     

Share This Page