This has not really been a known problem area. I'd say if it ain't broke, don't fix it in that area... Just my
though!
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| needle bearing the cams http://www.lostjeeps.com/forum/phpBB3/viewtopic.php?f=5&t=77758 |
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| Author: | diesel_guy86 [ Wed Dec 18, 2013 8:25 am ] |
| Post subject: | needle bearing the cams |
I'm in the process of doing a lot of work to my 05 kj. Got the top cover off the engine and set aside to take to the machine shop to get hot tanked, along with a valve job on the head. Met a fellow crd owner last night that only lives 4 miles from me ( thanks LOST!) and he said the cams aren't in any type of bearing. I haven't looked at mine close enough yet, but I worked on a 2000 ford focus that didn't have cam bearings either. So I'm wondering if while everything is at the machine shop, have him line bore the cam holes and press in some needle bearings. Its common practice on the Cummins B motors to squeeze a Lil more efficiency out of it. I'm thinking it would lessen the burden on the timing belt also. Thoughts?? -Joe |
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| Author: | flash7210 [ Wed Dec 18, 2013 10:32 am ] |
| Post subject: | Re: needle bearing the cams |
It SOUNDS like a great idea! Dont know if it will work though. I dont think there is enough material in the cam journals to machine away space for some fancy bearings. The Cummins B motors are a cam-in-block design. They have a lot more CAST IRON material to work with. |
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| Author: | diesel_guy86 [ Wed Dec 18, 2013 10:53 am ] |
| Post subject: | Re: needle bearing the cams |
My thoughts exactly, but remember that the can sees pressure in one direction. I'll try to get a look tonight. The Cummins motors also have 60lb valve springs, these do not. I can relatively easily push a valve down with one hand. Still some research to do yet. Just wanted to get others thoughts/ opinions first. -Joe |
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| Author: | EAB [ Wed Dec 18, 2013 3:40 pm ] |
| Post subject: | Re: needle bearing the cams |
Wont work. The cam journals you speek of are smaller than the lobes so ther is no way to get a small needle bearing setup on the journals. |
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| Author: | diesel_guy86 [ Wed Dec 18, 2013 3:51 pm ] |
| Post subject: | Re: needle bearing the cams |
Then how do the lobes get through? |
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| Author: | EAB [ Wed Dec 18, 2013 5:38 pm ] |
| Post subject: | Re: needle bearing the cams |
Uh oh, I'm thinking of the clamping style, I dont know why that popped in my head. At any rate, I wonder how you could tell if there was a benefit or not when done. |
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| Author: | diesel_guy86 [ Wed Dec 18, 2013 6:35 pm ] |
| Post subject: | Re: needle bearing the cams |
Performance wise, probably not a whole lot. But durability wise it would make a difference. Should run smoother, quieter, and with less stress on the belt, in my opinion. |
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| Author: | MRausch82 [ Wed Dec 18, 2013 11:19 pm ] |
| Post subject: | Re: needle bearing the cams |
This has not really been a known problem area. I'd say if it ain't broke, don't fix it in that area... Just my though!
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| Author: | diesel_guy86 [ Wed Dec 18, 2013 11:44 pm ] |
| Post subject: | Re: needle bearing the cams |
I understand and do agree with what your saying. And it may not be do-able. But I asked myself this, why are good quality timing belts getting chewed up and stressed/worn in such short order? Why aren't the cams in any sort of a bearing? Are these 2 issues related? Generally, maintenance schedules are setup to be well within the rated life of that component. For instance changing engine oil. The oil isn't going to breakdown and ruin your engine at 6,500 miles when it should have been changed at 6,000. There's usually a safety factor of at least 2 or 3 calculated in. Meaning the oil is actually good for 12,000 miles, but to be safe the factory says to change it at 4,000 or maybe 6,000 miles. That being said, everyone knows the 100,000 mile service interval of the timing belt. Mine made it to 146,000 miles, some more some less, but seems like a lot are even before the 100,000. What the heck? The belt should be changed at 100,000 but could go 200,000-300,000 before failure. All this is my opinion though and is open for discussion. It just seems like something is playing hell on our belts, and its not like were using a wal-mart special belt either. I might be jumping into a hornets nest trying to improve this, but I'm willing to sacrifice another set of rockers to see if it works. I looked at the cams/cover and I think there's enough meat there to do it. Just need to get the cams out so I can measure them better, then talk with my machinist to see what he thinks. If its gonna be one of those, machine this to fit that so this will clear, kinda deals I'll accept defeat. 
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| Author: | MRausch82 [ Wed Dec 18, 2013 11:48 pm ] |
| Post subject: | Re: needle bearing the cams |
Who would go beyond 100k on a timing belt?! Rubber wear out, plain and simple. The only real timing belt issues seem to be as a result of rocker arm issues or tensioner/roller/water pump issues. I don't think the cam plays any role in that. Just my thoughts on the subject. 
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| Author: | Glend [ Thu Dec 19, 2013 2:19 am ] |
| Post subject: | Re: needle bearing the cams |
There are plenty of high mileage VM 2.5 and 2.8 CRD engines that have never had any problems with cam bearing surface wear. If your breaking belts its due to something else, like ignoring the service interval. |
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| Author: | diesel_guy86 [ Thu Dec 19, 2013 9:46 am ] |
| Post subject: | Re: needle bearing the cams |
I only ignored mine because I was told it had the 100k mile service done when I bought it. I just fine it odd that this motor has replaceable liners, yet doesn't have anything for the cams. What's one suppose to do when it is wore out? Replace the whole top? What if in 15 years those aren't available? I have a couple 86 Isuzu trooper diesels. Timing belt interval is 100k but its not uncommon to see one with 200k+ on it. But the biggest pain is that Isuzu stopped making parts for them years ago. Forget finding oversize pistons, you can get stock size pistons new from China, but most of them motors are now into the 300k-500k mile range and the bores are wore out. Maybe I'm just looking too far into this. I just am planning on keeping this and I don't want to be kicking myself later on down the road. |
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| Author: | Hexus [ Thu Dec 19, 2013 2:31 pm ] |
| Post subject: | Re: needle bearing the cams |
diesel_guy86 wrote: I just am planning on keeping this and I don't want to be kicking myself later on down the road. LOL, you might as well just start the kicking now.... 
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| Author: | diesel_guy86 [ Thu Dec 19, 2013 3:08 pm ] |
| Post subject: | Re: needle bearing the cams |
Lol Your probably right. |
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| Author: | Glend [ Thu Dec 19, 2013 6:12 pm ] |
| Post subject: | Re: needle bearing the cams |
I've known people that have had cams resurfaced on older engines and that's an option. If your worried about availability of replacement parts in the future why not buy a second hand engine now and start rebuilding it at your leisure (assuming you have the space); you can also buy new head assemblies from VM Specialists in the UK ( ship it be sea freight as your not in a hurry). My plan is to eventually rebuild my engine, simply because I doubt I would find a better looked after one anywhere else. BTW if your looking for a future replacement, try getting your hands on a second generation JK or KK (export) CRD engine with the upgraded head and injectors - these would be available in europe and Australia. These engines put out over 500 nm of torque with a basic Eco tune, and yes GDE has tunes for them. |
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