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| Timing belt question https://www.ausmini.com/forums/viewtopic.php?f=2&t=58920 |
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| Author: | mini-dunger [ Fri Nov 20, 2009 12:25 pm ] |
| Post subject: | Timing belt question |
hello I am putting a honda head on my mini. I was just wondering how any accuracy is maintained with a dohc engine with a long belt and a belt tensioner? The way I see it, you line up the marks or what ever and then slip the toothed belt on. This part of the process is the same as a chain I understand that, but what happens when you tighten the belt tensioner? do the marks move around and you have to pull it off and move this or that a couple of teeth to "even it out" or am I a complete idiot? any help would be appreciated.. |
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| Author: | awdmoke [ Fri Nov 20, 2009 12:31 pm ] |
| Post subject: | |
Quote: "a couple of teeth"  That's quite a lot of angle you're talikng there.
The tensioner is on the "slack" side of the belt, so the distance between the crank and the cam pulleys on the driven side is not affected. There is virtually no stretch in the belts, so tightening the tensioner will affect the cam timing by four fifths of fudge all. This is how millions of modern engines are set up. |
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| Author: | mini-dunger [ Fri Nov 20, 2009 12:40 pm ] |
| Post subject: | |
awdmoke wrote: Quote: "a couple of teeth" That's quite a lot of angle you're talikng there.The tensioner is on the "slack" side of the belt, so the distance between the crank and the cam pulleys on the driven side is not affected. There is virtually no stretch in the belts, so tightening the tensioner will affect the cam timing by four fifths of fudge all. This is how millions of modern engines are set up. thanks mate.....clear as crystal.. what defines the slack side? the side that's on the down side of the rotation? |
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| Author: | mini-dunger [ Fri Nov 20, 2009 12:44 pm ] |
| Post subject: | |
So in this pic you would put the belt on the left hand side with as much tension as you can and work clockwise in a similar fashion so that all the slack was left in the vicinity of the tensioner? does belt length make and difference at all...apart from more slack on the tensioner? 
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| Author: | mini-dunger [ Fri Nov 20, 2009 12:53 pm ] |
| Post subject: | |
this dude put a tensioner on the other side too... is it worth it? 
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| Author: | awdmoke [ Fri Nov 20, 2009 1:00 pm ] |
| Post subject: | |
In that picture, the crank rotates anticlockwise so the tensioner must go on the right hand side. There will be no benefit of a tensioner on the other side. It is more important to position your tensioner so that you get a good wrap around the crank pulley. This will stop rapid belt wear or possibly stripping a belt. |
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| Author: | drmini in aust [ Fri Nov 20, 2009 3:06 pm ] |
| Post subject: | |
Keep oil away from the belt, it degrades the poly coating on the teeth, THEN they strip... How do I know so much about stripped timing belts? I owned 3 Fiat 124AC sports coupes. 
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| Author: | gafmo [ Fri Nov 20, 2009 9:16 pm ] |
| Post subject: | |
3rd time I'v moved a Thread from General to Chat 
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| Author: | mini-dunger [ Fri Nov 20, 2009 10:52 pm ] |
| Post subject: | |
gafmo wrote: 3rd time I'v moved a Thread from General to Chat
I thought it was more of a general type thing... no biggy tho. you keep doin ur thing and I will keep doing mine
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| Author: | david rosenthal [ Sun Nov 22, 2009 9:33 pm ] |
| Post subject: | |
mini-dunger, have a look at the pic of the front of the last engine I built up[thread on here, or pics on my website] the F4 head cams are closer together than F3. the belt I run is 8mm pitch HDT type[round tooth like the engine pic you posted]. the cam pulleys are 30 tooth and crank is 15 tooth. the small bore block has 115 tooth belt[ std for nissan rb30 engine in commodore] and the 1275 is 120 tooth. the only place to get them is from RYDELL at cavan. I run a inside pully on the l/h side to guide belt past water pump, and a outside tensioner pully on the r/h side. with this set-up there is NO belt stretch and the original v belt system can also be used. the cam pullys I make [vernier type] although some blokes have used a water pump pully off a honda engine and bored it out and fitted to a vernier type shaft. If you make the pullys check out the info on net for dimensions etc to cut the teeth. IE pitch dia, root dia and diametrical pitch. If you do not get them absolutely spot on the the belt will ride side ways or climb the teeth on the pulley |
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