Jump to content

Photo

Rod bearing failur

- - - - -

  • Please log in to reply
14 replies to this topic

#1
edge04

edge04

    Junior Member

  • Members
  • Pip
  • 6 posts

Number 4 went on my 1993 1.6 SM. No idea how many miles, laps, etc. I don't race it but it is my secondary track car. After replacing all the bearings there was an immediate knock again. So I'm guessing it went due to some kind of oiling issues. I know very little about these engines other than they are easy to work on. Can you help by pointing out where or what I should be looking at? Thanks for your help. 



#2
Tom Sager

Tom Sager

    Veteran Member

  • Members
  • PipPipPipPipPip
  • 1,546 posts
  • Location:Chicago Suburbs
  • Region:Central
  • Car Year:2001
  • Car Number:94

Did you inspect and measure the crank journals when disassembled?  Did you plastigauge or otherwise measure bearing clearances with new bearings before finishing assembly? 


Donor - Made PayPal donation Bona fide - A bonafide Spec Miata driver We have a Winnah! - Won their 1st race... Congratulations! Make it Rain - Made Paypal donation of $100+

#3
edge04

edge04

    Junior Member

  • Members
  • Pip
  • 6 posts

Did you inspect and measure the crank journals when disassembled?  Did you plastigauge or otherwise measure bearing clearances with new bearings before finishing assembly? 

Yes. 2 and 4 were slightly oversized and the others were close to stock clearances. Thanks 



#4
Steve Scheifler

Steve Scheifler

    member

  • Members
  • PipPipPipPipPip
  • 2,261 posts
  • Location:St. Louis

Did you take pictures of the old bearing shells? How did the others look?

Any idea of the history of the engine; stock, old pro shop like Sunbelt or RE, ...?
Bona fide - A bonafide Spec Miata driver

#5
edge04

edge04

    Junior Member

  • Members
  • Pip
  • 6 posts

So its number 4 again which tells me there's an oil blockage somewhere



#6
Steve Scheifler

Steve Scheifler

    member

  • Members
  • PipPipPipPipPip
  • 2,261 posts
  • Location:St. Louis

That seems reasonable but it’s not very common, and short of an obstruction in the passage in the crank to that journal, it wouldn’t hit just one. Others should show at least some signs of unusual wear. I assume you confirmed that the rod was not damaged.
Bona fide - A bonafide Spec Miata driver

#7
Jim Drago

Jim Drago

    East Street Racing / 2 Time National Champion

  • Administrators
  • 6,211 posts
  • Location:Memphis, Tn
  • Region:Mid South
  • Car Year:2005
  • Car Number:2

did you change the rod? is it round?


East Street Auto Parts
Jim@Eaststreet.com
800 700 9080

NASA Champs Winner - NASA Champs Winner Hoosier Super Tour points Champion - Hoosier Super Tour points Champion ARRC Champion - Won the ARRC Race in a Spec Miata Series Champ - Won a points based series in a Spec Miata BFG Supertour Winner - Majors Winner - Circuit of the Americas Winner - We have a Winnah! - Won their 1st race... Congratulations! June Sprints winner  - June Sprints winner June Sprints winner  - June Sprints winner June Sprints winner  - June Sprints winner June Sprints winner  - June Sprints winner SCCA National Champion - Won SCCA Runoffs at Road America SCCA National Champion - Won SCCA Runoffs at Road America

#8
edge04

edge04

    Junior Member

  • Members
  • Pip
  • 6 posts

have not checked the rod yet as I was hoping replacing the bearings would do the trick. Now I need to decide if I want to do a complete rebuild or buy a used engine.



#9
Jim Drago

Jim Drago

    East Street Racing / 2 Time National Champion

  • Administrators
  • 6,211 posts
  • Location:Memphis, Tn
  • Region:Mid South
  • Car Year:2005
  • Car Number:2

have not checked the rod yet as I was hoping replacing the bearings would do the trick. Now I need to decide if I want to do a complete rebuild or buy a used engine.

if it is the same rod, it was likely distorted the first time and failed quickly the second time around


East Street Auto Parts
Jim@Eaststreet.com
800 700 9080

NASA Champs Winner - NASA Champs Winner Hoosier Super Tour points Champion - Hoosier Super Tour points Champion ARRC Champion - Won the ARRC Race in a Spec Miata Series Champ - Won a points based series in a Spec Miata BFG Supertour Winner - Majors Winner - Circuit of the Americas Winner - We have a Winnah! - Won their 1st race... Congratulations! June Sprints winner  - June Sprints winner June Sprints winner  - June Sprints winner June Sprints winner  - June Sprints winner June Sprints winner  - June Sprints winner SCCA National Champion - Won SCCA Runoffs at Road America SCCA National Champion - Won SCCA Runoffs at Road America

#10
Steve Scheifler

Steve Scheifler

    member

  • Members
  • PipPipPipPipPip
  • 2,261 posts
  • Location:St. Louis

That seems reasonable but it’s not very common, and short of an obstruction in the passage in the crank to that journal, it wouldn’t hit just one. Others should show at least some signs of unusual wear. I assume you confirmed that the rod was not damaged.


See, there I go assuming, You did plastigauge but didn’t check for round?
Bona fide - A bonafide Spec Miata driver

#11
steveracer

steveracer

    Blue Eyes, Aquarius, hates being squeezed to the grass in SowDiv

  • SMembers
  • PipPipPip
  • 404 posts
  • Location:Austin, Tx
  • Region:Lone Star
  • Car Year:1999
  • Car Number:92

have not checked the rod yet as I was hoping replacing the bearings would do the trick. Now I need to decide if I want to do a complete rebuild or buy a used engine.

 

I have NEVER seen nor heard of just putting a new bearing back in work.

Damage to the crank journal and rod end would indicate that machining or replacement is necessary.


  • Jim Drago likes this

Steven Holloway

Artist formerly known as Chief Whipping Boy for Lone Star Region

Donor - Made PayPal donation Bona fide - A bonafide Spec Miata driver

#12
edge04

edge04

    Junior Member

  • Members
  • Pip
  • 6 posts

I have NEVER seen nor heard of just putting a new bearing back in work.

Damage to the crank journal and rod end would indicate that machining or replacement is necessary.

I went the cheapest, easiest route and that didn't work. So now its a question of rebuilding or swapping in a used engine. 



#13
Dave D.

Dave D.

    Member

  • Members
  • PipPipPip
  • 140 posts
  • Location:New Jersey
  • Region:NASA Northeast
  • Car Year:2002
  • Car Number:14

Not really cheap or easiest, how did you change the rod bearings? Either dropped the subframe to get at the pan or pulled the engine. Either one is enough effort and expense to drive home the point of doing it right the first time WILL be the cheapest and easiest way.


  • steveracer likes this

#14
edge04

edge04

    Junior Member

  • Members
  • Pip
  • 6 posts

Not really cheap or easiest, how did you change the rod bearings? Either dropped the subframe to get at the pan or pulled the engine. Either one is enough effort and expense to drive home the point of doing it right the first time WILL be the cheapest and easiest way.

Pulled the engine, it comes out, on the stand and pan off in less than a hour. Anyway, question now is rebuild or swap. Do SM uses stock bottom ends? Would it be best to just try and find a short block? I see complete drive trains out there between $800 and $1200 but those are stock and who knows what kind of miles. Thank you



#15
Jim Drago

Jim Drago

    East Street Racing / 2 Time National Champion

  • Administrators
  • 6,211 posts
  • Location:Memphis, Tn
  • Region:Mid South
  • Car Year:2005
  • Car Number:2

Pulled the engine, it comes out, on the stand and pan off in less than a hour. Anyway, question now is rebuild or swap. Do SM uses stock bottom ends? Would it be best to just try and find a short block? I see complete drive trains out there between $800 and $1200 but those are stock and who knows what kind of miles. Thank you

 

If you have run the bearings to metal twice already?  You need to take the head apart as well and clean it or you will be doing this a third time. 


  • steveracer likes this

East Street Auto Parts
Jim@Eaststreet.com
800 700 9080

NASA Champs Winner - NASA Champs Winner Hoosier Super Tour points Champion - Hoosier Super Tour points Champion ARRC Champion - Won the ARRC Race in a Spec Miata Series Champ - Won a points based series in a Spec Miata BFG Supertour Winner - Majors Winner - Circuit of the Americas Winner - We have a Winnah! - Won their 1st race... Congratulations! June Sprints winner  - June Sprints winner June Sprints winner  - June Sprints winner June Sprints winner  - June Sprints winner June Sprints winner  - June Sprints winner SCCA National Champion - Won SCCA Runoffs at Road America SCCA National Champion - Won SCCA Runoffs at Road America




0 user(s) are reading this topic

0 members, 0 guests, 0 anonymous users