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Grizzly

timing belt tensioner assembly

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Hello,

I've stripped and cleaned my timing belt automatic adjuster. Despite taking pictures of it on the car engine and whilst being stripped on assembly I'm left with a bit over!! It is the bush in the attached picture and I cannot for the life of me see where it fits.

Any help gratefully appreciated as always

 

Brian

 

R&R161.jpg

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Hello. It fits between the tensioner body and the bracket in the picture. You should have 2 of them though.

The middle hole on the bracket fits on a stud on the block, then the spacer. The bottom hole has a bolt through tensioner body, spacer, bracket into the block.

Don't forget the earth wire between the tensioner body and the block. It cuts down of radio interference.

Cheers

Jason

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Hello Jason,

Thanks for the quick reply.

I understand what you are saying, but (there is always a but) the middle and bottom holes on the tensioner body are 10mm diameter and the hole through the bush is 8 mm. And there is only one of the bushes.

I say bushes but on closer inspection the face of the bush not shown in the picture. ie face down,  is cupped or dished as if to mate up to a round something - which makes me think it might be a roller and not a bush.

It also came off a 1978 907 engine which might account for the difference.

 

On another part the tensioner has two springs, one fitting inside the other. A note on SJ Sportscars web pictures of same has "Not HC" next to the inner spring. Does this mean that an HC engine tensioner requires only the larger spring?

 

Brian

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Hi the HC is the 912 engine and they use an eccentric bolt to tension the belt ,the early 912 LC has the same as yours

cheers  Ian

Edited by pompey ice

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Have you taken to lower guard off. There should be a spacer on that ? 

 

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Hello 

A bit of explanation may be of use. My original 907 engine was damaged when the timing (cam) belt snapped. My original Elite chassis was shot. So I decided to go down the hybrid Elite body onto an Excel chassis. I also decided to upgrade to a 912HC engine. My donor Elite provided the chassis but not an engine. I bought a 912HC engine on ebay that turned out have an obsolete "+15" block (I didn't know they existed). I bought a standard block and this is being built up now. So I haven't actually seen a complete 912HC engine. I know I will end up with a Heinz 57 engine in a dog's breakfast of a car, but that's the challenge. Now your telling me there is more than one type of belt tensioner? Lotusbits offer a tensioner like mine for all Lotus engines. SJ have a picture of an eccentric component. My Excel Notes ignores this item altogether. Guess I'll investigate some more. 

Thanks 

Brian 

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Ahhh. Yes. The 912 HC  engine has a manually tensioner. It uses the same bearing which fits onto a eccentric hub and is adjusted by twisting the hub until the correct tension.

The only problem is,looking at the parts manual I can't find a spacer that looks like that.

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I just discovered that early JH engines use different bearings in the tensioner. Ours (Lotus engine) use the complete bearing from a Ford auxilary belt tensioner, the early JH setup was a separate tube thatb ran on the belt, with two sealed bearings pressed into that tube.

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I converted mine to use a modern Ford focus tensioner bearing and plastic outer roller.

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This is what I have found

The Lotus Elite Workshop manual only describes the removal and replacement of the Driving BelytTensioner - no mention of type

Later Service Bulletins describe  for all cars fitted with auto tensioners  B907E0885K a service replacement (B-type) A907E0893K. - a C-type C907E0885K which is oil filled and fitted to Elite / Eclat from engine number 15049 onwards which can also be replaced by the B-type which I think became the "standard" belt tensioner used on Excel and Esprit 912 engines.

Lotusbits offer refurbished cam belt tensioners for all 907,911,and 912 and 910LC engines from 1977 to 1986 - note no mention of HC for 912 engines -  see their  website https://lotusbits.blogspot.com/2009/11/refurbished-cam-belt-tensioner-lotus.html which is the one I have.

Lotus Marques have an expanded view of the tensioner https://lotusmarques.com/parts/catalogue/lotus/50-excel-parts/450-excel-timing-belt-tensioner-parts which goes along way to helping me understand what is going on.

And finally I found this on ebay

Listed in category: 

 

the eccentric hub tensioner  "a popular conversion for high performance engines".
 
On the one hand it suggests that the manual tensioner is the way to go on an HC engine - but I would have to buy one, and then what would I do with the one I've got - sell it on ebay?
or fit it as I'm not going to take the car on track days. An auto - adjuster should mean I don't have to check the belt tension every week - all for that - but is more to maintain to keep it working.
 
I think I'll stick with what I've got until it start to give trouble
 
Now this one or two springs business.............
 
Advice always welcome (except "Don't do it" - gone past that point)
 
Brian
 

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There would be nothing to refurbish int he same way for the HC cars, the tensioner bearing (same one as the LC) simply sits on an off-centre circular piece of steel, whereas the LC has castings with nylon bushes, earth strap, spring piston etc.

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I have an HC engine and had the same discussion about the benefits of fitting an auto tensioner with Lotusbits. I think it basically came down to the fact that if you buy a decent belt and tension it correctly to start with then you shouldn't need to retension it anyway until it is due for replacement. Auto tensioners, I guess, can wear and themselves be a source of problems.

ATB Richard

Edited by rjwooll

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To conclude - there is no perfect answer - it's a matter of choice. As I stated above I'm going with auto tensioner ( for now). 

Looking at the expanded diagram from Lotus Marques I am missing two spacers as Jason said and the maverick Bush is the bearing that holds the ignition sprocket on. 

Brian 

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