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Discussion Starter #1
Upon teardown of the '65 GTA engine, it was noted that the lower chain had a LOT of backlash. Mounted a degree wheel and found there was 5 degrees of backlash, which to most is a LOT.

While looking at Alfaholics parts offerings, I noticed they offered a "Rolon" brand tensioner for the lower chain. I did a search about this brand, and there seemed to be many issues with the rubbing block delaminating from the metal and causing damage.

Are any folks here using these, or a similar solution ??? Read one account of folks using a Jaguar tensioner with good results.

Thanks !
 

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That tensioner is an MGB part, available anywhere for a fraction of the price. It's been discussed elsewhere, make a search on "ROLON", and the consensus seems to be that it is an answer to a question that wasn't asked.

The backlash may obviously result form a loose chain, but I would bet the block was line bored deeply which raised the crank in relation to the middle pinion. There are ways to cure this that involve advanced machining.
 

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Discussion Starter #5
Yes, ... the build sheet from the shop that built the engine previously states it was "align bored". Further, as an experienced engine machinist I know that align boring and align honing are two different things. I can align bore a block and not sink the crank into the block, however an align honing will sink it. I suspect this one was honed from what i see.

I want to use a lower tensioner, it's just that my research has found that the ROLON brand has issues with the rubbing block de-laminating and falling off. It is obvious that new oil galleys need to be drilled as well as a flat surface milled for it to sit on and holes drilled and tapped to mount. All things I have the machinery to accomplish. Just looking for insight on the best brand to work with from someone's past experience.
 

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I think Alfaholics suggest to use the MG tensioner without oil feed. The lower chain is short, spring tension should be enough. I remember seeing another thread which described the use of a TR4 tensioner which is just a leaf spring.
 

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There was also a type with a roller sproket but can't find the link. Sorry.

Ken
 

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You can purchase gearsets to replace the lower timing chain if you really want to get rid of backlash, but easier and cheaper (?) to just move the middle sprocket up to get the relationship with the crank corrected. Just need to do some machining. The top chain doesn't care, as it has an adjuster

Pete
 

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Norman Racing does this, move the idler up, if the block has been align-honed and the crank moved up. I wonder, does that mess up the tach drive alignment in the water pump? Does it need remachining too?
Andrew
 

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Norman Racing does this, move the idler up, if the block has been align-honed and the crank moved up. I wonder, does that mess up the tach drive alignment in the water pump? Does it need remachining too?
Andrew
Yep. Or replace with electronic rev counter

Pete
 

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I did a search about this brand, and there seemed to be many issues with the rubbing block delaminating from the metal and causing damage.
True about te rubber block unsticking from the metal but again you can modify it and add 2 bolts ( or ribets) to hold the rubber element in place preventing it to move or unbonding from the metal part, just an idea
 

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I made a search based on the idea that there must be a better quality MG tensioner than the Rolon one ($8.19 from Moss - Rockauto even cheaper at $5). I found quickly what I wanted from this very informative MGA site, not the first time I find great info there.

In short:
  • It confirms quite frequent and early separations of the Rolon tensioner, even recently
  • Jaguar XK use the exact same part
  • A better quality tensioner is available from Jaguar under the original part number EAC3269
  • Another better quality substitute is Massey-Ferguson part 826113M1
  • And some Jaguar builders that say your are better off with a used original tensioner!

Brought me to find this which leads to the very similar Toyota part 13540-38012 that you can order from your local dealer with no surprises on the quality.

Let me know if you want to pursue the Jaguar ones and have a problem finding one, I have a couple Jaguar specialists amongst my friends.
 

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I wouldn't use that tensioner. The reason being, while English engineering can be wonderful, they went through a phase, especially British Leyland, where it was more about saving cost that making a good product.

I would look at what modern engines, or 80-90's Toyotas did and see if that can be engineered in ...
Pete
 
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That tensioner has been around since the 50s, when Britain was still proud and was a major player in the automotive industry.

And note that indeed Toyota and Datsun did copy that tensioner. As a matter of fact some Datsun engines are directly derived from BMC engines.
 

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I think teflon would be better than the rubber pad

Pete
 
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