The 340 is out....again.....

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340_dart_power said:
Latest rebuild resulted in the same damage to the camshaft bearings after being run for awhile, so the block and heads are back at the machine shop. The current suspicion is that the Edelbrock Performance heads may be to blame in some fashion. No end in sight at this point....
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Damn..whos building your engines???
 
Cam bores in block are not straight is my guess. Pretty common on SB Mopars.

Heads won't have squat to do with the cam bearing issue. It's poorly assembled and not paying attention to the cam fit. Whether the builder know that or not, it's on them if it's two strikes.
 
crackedback said:
Cam bores in block are not straight is my guess. Pretty common on SB Mopars.

Heads won't have squat to do with the cam bearing issue. It's poorly assembled and not paying attention to the cam fit. Whether the builder know that or not, it's on them if it's two strikes.
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This^^^^^^^^^^^^^^^^^^^^^^^^^^^



There is nothing special or trick to building a Chrysler. Straight is straight and round is round. Whoever is working on it needs to stop and take a breath and look at what's going on. It ain't that hard. If nothing else, get a factory service manual and look at what the factory specs are.

I hate to see this happen. People think because it's a Chrysler it's some voodoo bullshit and it ain't. The oil goes from the pickup, to the pump, out to the filter, back into the block, turns vertical and goes up to the passenger side lifter gallery, turns horizontal and runs to the front of the block. The mains feed from drilled passages up from the main bearings. From the mains the oil goes out to the rods. Also, the number 2 and 4 main bearings have vertical holes drilled up to the cam line. There is a hole drilled from the deck down to the cam bearing. There are two holes in the cam journal of number 2 and 4. When the holes in the cam line up with the hole that comes up from the mains and the hole drilled down from the deck, you get oil to the rockers. Chrysler designed the system to limit oil as RPM goes up the time the feed holes are lined up is less and less oil goes to the rockers.

I mention all this because the oil system is really simple. It's not complicated. It only has issues when someone who doesn't get it starts dicking with it, or you start spinning high RPM's. The oil timing to the rods bearings is not where it should be. This is why full groove mains are essential to a performance build. Any time you can get oil to the rods you are helping them. For high RPM use, you have to correct the oil timing to the rods.
 
Gentlemen, thank you all for your input. I am the first to admit that I do not have the technical expertise that I'd like to have, and in this area I appreciate any and all relevant input. FYI, I've taken your comments to my garage guys in printed format and have asked them to review your opinions as to what has and is going wrong. For all I know, they missed something simple and by reading your comments the light bulb may go off and they'll realize where things went south.
I'll keep you all posted.
 
340_dart_power said:
Gentlemen, thank you all for your input. I am the first to admit that I do not have the technical expertise that I'd like to have, and in this area I appreciate any and all relevant input. FYI, I've taken your comments to my garage guys in printed format and have asked them to review your opinions as to what has and is going wrong. For all I know, they missed something simple and by reading your comments the light bulb may go off and they'll realize where things went south.
I'll keep you all posted.
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I hope you get it figured out. Things like this take the fun right out of stuff like this. I hate it when it happens to me and I hate it when it happens to other people.
 
340_dart_power said:
Gentlemen, thank you all for your input. I am the first to admit that I do not have the technical expertise that I'd like to have, and in this area I appreciate any and all relevant input. FYI, I've taken your comments to my garage guys in printed format and have asked them to review your opinions as to what has and is going wrong. For all I know, they missed something simple and by reading your comments the light bulb may go off and they'll realize where things went south.
I'll keep you all posted.
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I feel your pain I just had to rebuild my 416 because of shitty sloppy work done by a professional mopar builder who will take no responsibility for his shitty work . at least your guys will work with you I hope they get this figured out soon .
 
Good luck on round 3. If it were mine they would have to show me in absolute certainty the problem or it would not be put back together and further more I would find someone who can find the problem. The process is no more than logical thinking.....

However if they say it could be the heads I would question them however life is about learning something new and quite frankly your cylinder heads being the problem would be something I have never seen...

JW
 
So, it appears we have diagnosed and identified the problem.
The camshaft bearings which were used were too narrow for the application in my 340.
They are 1/4 inch smaller/narrower than the ones which should have gone into the build.
Instead of riding on the layer of oil, the camshaft as it spun dug down into them because there wasn't enough metal on the bearing surface to hold the oil and create a protective layer; instead the oil ran off both sides of the bearing surface instead because each bearing wasn't wide enough.
The shop has ordered the correct wider bearings and we will see how this rebuild goes.
I found out about this yesterday, and the answer came after consultation with a number of people and entities, including Hughes Engine and Comp Cams. Enough people were contacted and the issue described to where someone was found who had seen this before and was able to comment on it.
 
So both engine failures came from Cam Bearings? And this was built in 2 different shops, correct?

JW
 
I didn't know there was more than one cam bearing for LA engines.

Never heard of a wide or narrow bearing.


Doesn't make sense to me.
 
So putting aside the explanation (there are not narrow or wide bearings for an LA small block... I'd ask them what the part number they are getting is)...
Why did the lower end bearings fail?
 
moper said:
So putting aside the explanation (there are not narrow or wide bearings for an LA small block... I'd ask them what the part number they are getting is)...
Why did the lower end bearings fail?
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The OP is saying they were losing oil from the cam bearings being too narrow.
 
the clevite cam bearing set for the 340 is sh875s-width- 1=.900", 2=.770", 3=.757", 4=.770", 5=.950", also listed for 318s and 360s up to 1978. for 1979+ they have sh1112s-width- 1=.900", 2 3 4 =..630", 5=.950". so bearing 1 and 5 are the same, and 2 3 4 are about 1/8" narrower, not 1/4". I believe the 1979+ blocks are about 1/8" narrower-lighter weight-for gas mileage. some shops only stock the sh1112s, if they work fine in a 1979+ 318 and 360, the theory is they should be fine in the earlier blocks. I agree, but in my 340 I run the sh875s, why not
 
Interesting - learn something new every day. Thanks Marco! Some companies do list separate bearings for pre-79. Some use the same number for all years. Never noticed that before - Durabond seems to only list the wider ones (PD-16) and that's what I use.
 
Marcohotrod said:
the clevite cam bearing set for the 340 is sh875s-width- 1=.900", 2=.770", 3=.757", 4=.770", 5=.950", also listed for 318s and 360s up to 1978. for 1979+ they have sh1112s-width- 1=.900", 2 3 4 =..630", 5=.950". so bearing 1 and 5 are the same, and 2 3 4 are about 1/8" narrower, not 1/4". I believe the 1979+ blocks are about 1/8" narrower-lighter weight-for gas mileage. some shops only stock the sh1112s, if they work fine in a 1979+ 318 and 360, the theory is they should be fine in the earlier blocks. I agree, but in my 340 I run the sh875s, why not
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This is true^^^ OP it wasn't the cam bearings that caused your problem. I've used these two cam bearing numbers with reckless abandon over the years and never observed a lower end problem. With that being said I have had problems when the main oil feed wasn't drilled completely in mains 2,3,4. Might wanna look at that. J.Rob
 
No way a narrow bearing caused that, it's fairly common to use narrower bearings in certain applications to reduce friction. Your engine builder is probably missing something very basic, like the oil hole location mentioned
 
I agree RAMM. Hence my comment in post #86.
The cam bearings are not the issue. My feeling is a blockage in the passage(s) between the junction of the cam oil feed and the main oil feed from the lifter galley. I drill those out on all my builds anyway but I've seen some very narrow factory ones in doing that. Especially in later LA blocks. Thing is the oil does not flow around the cam, but to the mains under the cam bearing shell. I can't see potential leakage at the cam killing bearings such as yours. Not with a camshaft of some sort in place and not flopping around in the bearings.
 
RAMM said:
This is true^^^ OP it wasn't the cam bearings that caused your problem. I've used these two cam bearing numbers with reckless abandon over the years and never observed a lower end problem. With that being said I have had problems when the main oil feed wasn't drilled completely in mains 2,3,4. Might wanna look at that. J.Rob
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I don't want to read the entire thread again so maybe the OP will jump back in and answer this.

I can buy the oil holes not being drilled, or partially drilled BUT I thought the OP said this was a running engine he rebuilt. The only possible way the oil galleries not being drilled would be if the block always had these issues and the OP bought someone else's problems.

I didn't realize there were two widths of cam bearings. I don't have a durable catalog here but that's all I've ever used and I don't remember two numbers in that catalog.

I'm not a big fan of using a narrower cam bearing to save power. As the spring loads and RPM goes up, taking away bearing area is the wrong way to go. Who knows, maybe they were used to save fuel. You never know.
 
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yellow rose said:
The only possible way the oil galleries not being drilled would be if the block always had these issues and the OP bought someone else's problems.

I didn't realize there were two widths of cam bearings. I don't have a durable catalog here but that's all I've ever used and I don't remember two numbers in that catalog.
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Without re-iterating a very long story--I had a problem with a 360 and a 340 block in the same timeframe. The mains are drilled but NOT the full diameter so yes the mains received oil but were starved and would wipe the bottom end if 5000+ RPM was approached. The hole in the main saddle will appear correct but I had to take a 9/32" extra long bit and drill 'till I intersected the lifter oil galley. They both took 4 inches yes 4 inches of drilling to correct. I just took this pic of an Early 80's 318 block I have sitting here and as luck would have it--this one will take 2 inches of drilling or more. The flutes on the drill bit almost become flush with the saddle when drilled all the way properly. FWIW the early blocks seem to be the worst with the Magnum's never needing this. If you didn't know this and have never been burned by it then consider yourself very lucky. J.Rob

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Oh and DuraBond only lists one cam bearing width set while Clevite offers the two versions. J.Rob
 
I've seen the holes partially drilled myself. As common practice (and it appears it is common practice for you as well) I drill all the feed holes to 9/32 just to make damn sure they are done. I have heard of, but never seen an oil feed hole not drilled at all, as in no oil hole at all. I'm sure that is possible, but it would seem that by this time, all that stuff would have been flushed out. Is it possible the OP's block was incorrectly drilled for all these years? I'm sure it is. Maybe he is making more power now, or using more RPM to make the issue show up.

It's always something that bites you in the ***. I'm sure the OP is double sick of it.
 
in the 340 era mopar drilled the holes in steps, to a max diameter of 1/4", so part of the hole may be less than 1/4". I have heard of a broken fluted end of a drill bit being left in there. all oil passages should be checked! federal mogul cam bearings : 1451m-.760" width center bearings, 1484m-.615" width center bearings. I save old catalogs-better than the interweb. Do not just install the wider bearings and hope and pray for success
 
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