Datsun Roadster Forum-311s.org

Saw this on Ebay, for another Datsun model. The bolt through he back sets the tension. I doubt this exact part will interchange, but this might be a do-able modification for the U20 upper tensioner, instead of shims etc. Food for thought.

http://cgi.ebay.com/ebaymotors/Racing-A ... 0215257076

Certain Mazda engines have a hydraulic tensioner that has a rachet built in that would perform the same function without having to manually adjust it (and probably much cheaper). Now whether it can be made to work is another question, but would be sweet if it could.

Mark

Here the passage from the FJ manual...LOL

Apparently the 1980-81 series 626 RWD with a 1300 cc SOHC motor had a rachet tensioner and it fits the FJ with minor modification to the back profile (compare your mazda tensioner with the nissan one to see what you have to remove with a file or die grinder). The mazda part number for this is 3953-12-500A, but make sure you bring your FJ top tensioner with you to the mazda parts store to check out its the right one before you hand over the $. Then get out of there real quick just in case other mazda parts are infectious....

They have raised the price on these tensioner to over $100.
I got two when the were under $10 each.

Dave, I got this in a box of stuff for the U20 I bought. Head was off so dont know much about it. Is this the same thing only different? Also got this nice tool, also in the box. Something to do with timing chain? Inquiring minds want to know.

Thanks
Richard

That is certainly a chain tensioner, but the piston looks pretty rough…more important is how bad is the wear on the ‘foot’ …if the grooves are deep in the face of that large black foot , the tensioner can’t tighten the chain as designed (look to Gordon’s site for installing it…the zip tie trick is a lifesaver). I have never used that second tool on any Roadster, but I did have a small wedge tool close to that for my 510’s L series…you simply stuck the wedge into the chain to hold it into position and then you could remove the head and then use the tab to pull it out. (not necessary on the U20 as the “evil L” holds the sprocket and chain in place). That is only a guess on the tool, but someone on this board is certain to know.

v/r
Buddy

Thanks Buddy,
The foot is groovy....like mm, but may never use It anyways. May use the crank and stuff for my 1600 engine. The tool...well may just be nice add to the tool box.

Richard

Richard, I'm sorry...my explanation might have made you worry...there are small grooves like you described (even in a brand new tensioner), now if there are deep grooves or if the edges look like they are chipping in the grooves or the material is brittle replace it (but it sounds like you're leaning towards a stroker anyway). Good luck with the project.

v/r
Buddy

Has anyone explored the possibility of modifying the tensioner with the set screw as shown in the top photo?

There's also the Austin Healy/Triumph TR7 lower tensioner, I've been told it's a dead on fit for the Datsun part in both motors, and it ratchets. I haven't had a U20 apart that far as of yet, so haven't dug too deep into it, but the photo looked interesting.

dbrick wrote:There's also the Austin Healy/Triumph TR7 lower tensioner, I've been told it's a dead on fit for the Datsun part in both motors, and it ratchets. I haven't had a U20 apart that far as of yet, so haven't dug too deep into it, but the photo looked interesting.

Is this for the upper tensioner you are talking about? The lower R16/U20 look the same, only the U20 one has a hole drilled in it. I'm running a R16 lower tensioner currently and it hasn't blown up yet. There should be lower tensioners for a long time since the fork lifts use them. The U20 uppers are the tricky one. What do the Triumph tensioners run?

Will

I was referring to the lower tensioner. Fits many British cars in the 60's, and defiantly was on a TR7. they are under $20.00