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| My VM motor. http://www.lostjeeps.com/forum/phpBB3/viewtopic.php?f=5&t=81547 |
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| Author: | lacabrera [ Wed Mar 11, 2015 1:43 pm ] |
| Post subject: | My VM motor. |
I decided to inspect the rockers and camshaft on my motor, it always sounded a bit to noisy for my liking. Removed the camshaft/inlet manifold and was quiet surprised all the rockers look in fairly good condition, maybe 1 or 2 had a bit more play in the roller but not enough to cause a problem. Well I have already purchased a full set so new rockers and hydraulic adjusters so they have gone in. The one issue I have nether been happy with is, the cam sprockets and the lack of keys to lock them on to the camshafts. So I decided to modify this and cut a key way on the sprockets and made a pair of keys. Actually was much simpler than expected. I will now sleep with ease knowing that those sprockets are not going to turn on the camshafts. I would post pictures but I can not find how to load photo's to this forum. The only reason I can see why VM Motori nether fitted keys to the cams, is to make assembly easier? With cam sprockets fixed to the camshaft and the pins fitted to prevent camshaft from moving makes fitting the timing belt that much more time consuming. |
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| Author: | Mountainman [ Wed Mar 11, 2015 8:49 pm ] |
| Post subject: | Re: My VM motor. |
some wise person said that not all timing belts are exactly the same, so it makes sense that the cams will be better aligned without a key. The belt goes on, gets tensioned, and then the cam sprockets are tightened which keeps the cams setup perfectly to that particular belt. I'd like to hear how your next belt feels with the cams locked. Maybe the same manufacturer is almost exactly the same. I thought it was a terrible design before I read that, now I think it's a wonderful design 
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| Author: | GreenDieselEngineering [ Thu Mar 12, 2015 5:47 am ] |
| Post subject: | Re: My VM motor. |
VM had to go with the press fit cams due to the stack up of tolerances in the timing system. If belt alignment is off by just a tad you can realize very accelerated wear on the belt cogs. Timing belts are now a thing of the past on most diesel engines. |
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| Author: | lacabrera [ Thu Mar 12, 2015 12:14 pm ] |
| Post subject: | Re: My VM motor. |
Thanks for you thoughts, however I have worked on many twin cam diesel engines (common as water here) the VM is the first I have seen with no keys fitted to the cam sprockets. All timing belts are manufactured to exact tolerances, yes its possible they can stretch and move the timing of the valve opening times but than the belt should have been replaced before than. As for no timing belts? Most small production engines use them. The old fashion push rod engine tend to use gears but there designs back date to the fifties. |
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| Author: | lacabrera [ Thu Mar 12, 2015 12:21 pm ] |
| Post subject: | Re: My VM motor. |
GreenDieselEngineering wrote: VM had to go with the press fit cams due to the stack up of tolerances in the timing system. If belt alignment is off by just a tad you can realize very accelerated wear on the belt cogs. Timing belts are now a thing of the past on most diesel engines. I know you are an experienced person but come on? It will put no more stress, just move the timing of the valve opening and closing times. With the friction fit the same applies. If those sprockets move on the shaft you will have serious problems? I have worked on many race engines Cosworth/Lotus twin cams all with keyed shafts? We developed one of first adjustable cam sprockets to adjust valve timing. |
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