Jump to content

l20b spun bearing...


superbee

Recommended Posts

So I've been tearing apart the l20b that will be going in my truck, noticed that the #3 pushrod had some play, and by some, I mean, a lot...

 

IMG_0485.JPG

 

IMG_0486.JPG

 

Seems like I'm definitely not the first one here to have run into this issue, does this kind of damage require having the crank repaired?

 

Thanks

Link to comment
  • Replies 17
  • Created
  • Last Reply

Top Posters In This Topic

Top Posters In This Topic

So I've been tearing apart the l20b that will be going in my truck, noticed that the #3 pushrod had some play, and by some, I mean, a lot...

 

IMG_0485.JPG

 

IMG_0486.JPG

 

Seems like I'm definitely not the first one here to have run into this issue, does this kind of damage require having the crank repaired?

 

Thanks

YUP!  gt it to a machine shop and have it turned, have the mains checked too.

Link to comment

This is not common at all. Neglect is what causes this. Like not checking the oil enough even though you know it uses a lot. Keep filled with oil and water and this will never happen. The good news is the rod didn't weld to the crank and get thrown through the block but it made a lot of noise for a long time. Previous owners..... idiots.

 

It may be cheaper to find another crank. All L20B and Z20 cranks are the same so look for a U60 casting on the first throw forward of the flywheel. http://community.ratsun.net/classifieds/category/4-engine/?sort_key=date_added&sort_order=desc

  • Like 3
Link to comment

I tend to not be especially fussy about most things, but an engine with a spun bearing is a case where I would error on the side of doing too much rather than too little (which may involve spending a little more money than is absolutely necessary). The crank needs to go to an automotive machine shop for a regrind. You should have them inspect and measure the connecting rod where the bearing spun. The big end where the bearing sits must be perfectly smooth and round (measured with a micrometer, not just looks round). Otherwise there is a good chance the close clearance between the rod bearing and the crank journal may not be proper. The last time I had an L20 with a spun rod bearing (and my crank didn't look quite as bad as yours) the machine shop just replaced that rod with a used one rather than reconditioning the old one. It would be good to have them measure all 4 con rods. Replace the rod bolts on the rod with the spun bearing. The shop may go ahead and do this, but ask them to be certain.

 

I would be concerned with bits of the spun bearing getting into the engine oil galleys, so I would have the block hot tanked by the shop (which doesn't cost very much). I would pull the camshaft out of the head and look at the cam bearings closely, then blow through the oil passages in the head to be sure there are no metal flakes in there.

 

A shop may recommend a couple of other things I'm not remembering. If this is a street engine you don't need to over do it with balancing and blueprinting, but you want to end up with a clean engine and everything more or less back to factory tolerances. You may decide you are better off buying a good used engine instead of rebuilding what you have, and that may depend on the condition of your pistons and head. Often engines that spin a bearing tend to run hot before the inept owner realizes there is something seriously wrong and shuts it down, so have the head checked for flatness.

 

The thing with buying a used engine is finding a good one, hopefully from someone that you can trust - like someone on Ratsun taking out a good L20b to replace it with a KA24 or similar. The L20b I'm running in my 510 is a used engine I got off craigslist for $75 and it has been fine. But I don't drive many miles a year and don't rev it very high. I bought it from a guy who was heavily into 620s and after talking to him for awhile felt I could trust him when he said this was a good engine. Even so, I replaced the bearings before I stuck it in the 510 since that is a cheap thing to do and good for peace of mind.

 

Final thought - some machine shops are better than others and I don't know how to find a good one in your area. Probably just ask any car guys you know. You don't need the best shop in town than builds racing engines since they may be expensive, but you want a shop that is competent.

 

Len

  • Like 1
Link to comment

The oil filter will catch the bearing particles however the oil pump will almost certainly be ground up. Found a KA and pulled the pump. Woot woot I thought! Very stiff to turn by hand. Took it apart and it looked like it had been pumping sand. Went back and rolled engine over on the other side. Hole with rod sticking out.

 

To find a reasonably good shop talk to sprint car racers or hobby stock car racers and see where they go to get work done. These places don't exist if they do shitty work but it won't be the cheapest and if they are good you'll have to wait in a long line.

Link to comment

datzenmike - Good point on the oil pump. When I wrote my post I was pretty sure I was forgetting to mention something important. I'm trying to teach myself to cut threads on the lathe and this is taxing my limited mental powers. :lol: Nothing very difficult about thread cutting except the thinking involved!

 

I'm dubious about the oil filter catching all the particles. The couple of spun bearing engines I've opened up have had the oil pan coated with a mixture of bearing chunks and a kind of slurry of the late departed bearing particles and oil. I'm theorizing this could clog the oil filter completely then the particle laden oil would be pumped through the engine through the bypass valve. But I have no proof of this.

 

Several months ago a friend had me look at a 1998 4-cylinder Camry engine that had spun a rod bearing due to lack of oil. It would have been the perfect chance to autopsy the oil filter. However it turns out the reason for lack of oil is the oil filter wasn't tightened after an oil change and all the oil was pumped out on the road in a short time. Likely little or none of the contaminated oil got into the filter.

 

The L20b I had with a spun bearing - in hindsight I realize I should have pulled the camshaft out just to see what damage (if any) there was to the bearings.But I had another head (peanut) for rebuilding and I used the head from the blown engine for a core at Pull n Save. So maybe superbee can post pics of his cam and cam bearings so we can see if bad oil damaged them.

 

Final random thought - I've never seen it, but I have heard of cases where an inept owner ran an engine out of oil, then changed the oil and filter in hope of "fixing" it. Something to think about when buying a non-running engine with perfectly clean new oil.

 

Len

  • Like 1
Link to comment

The oil pump doesn't seem to be in bad shape. I have found a source for a new crankshaft if all else fails, but sounds like it would be a good idea to get that, the conrods and pistons at the same time. I'm still searching for a local shop, but that will have to wait for a week while I am in SFO for Intel Developer Forum...  thanks for all the advice guys.

 

 

IMG_0410.JPG

 

IMG_0409.JPG

Link to comment
  • 3 weeks later...

Join the conversation

You can post now and register later. If you have an account, sign in now to post with your account.
Note: Your post will require moderator approval before it will be visible.

Guest
Reply to this topic...

×   Pasted as rich text.   Paste as plain text instead

  Only 75 emoji are allowed.

×   Your link has been automatically embedded.   Display as a link instead

×   Your previous content has been restored.   Clear editor

×   You cannot paste images directly. Upload or insert images from URL.

Loading...
×
×
  • Create New...

Important Information

By using this site, you agree to our Terms of Use.