Datsun Roadster Forum-311s.org

I pulled my upper tensioner last night with the intention of shimming to eliminate the death rattle and dropped the entire assembly (outside of the car). The spring popped out and I can't find it anywhere. I was trying to decide if I should shim or get a stiffer spring (or both) but my error may force me to replace the spring.

I ordered a bunch of compression springs from Amazon last night in varying sizes from .3 to .42 inches in diameter from 1.5 to 2.0 inches long and different spring rates but was wondering if someone on the forum might have one lying around and could take the measurements for me. If someone has an extra they are willing to sell, I'd be interested in that too.

I can guarantee that I will find the old spring the minute my replacements arrive!

Bummer!

Thanks in advance.

Shannon

I am missing one as well. If you find replacement info, please share!

Are you 500% sure it's not in the motor?
I used an oil pump spring for a 70's to 80's Buick 231 v6. Cut it down until you have 25 pounds pressure installed, about in half. any similar spring would work. The tensioner, with 70psi oil pressure would exert about 25 pounds against the tensioner. I'll check the parts pile, see if I have any more springs, the other half of the first one, or a stock 2000 tensioner. Reminds me, I have to check the tensioner in the new engine (I didn't build it, so who knows what's in there)
Other option is to use a spring that fits and has some pressure, and shim it up close, as many others have done successfully.

Yes Sid, I'll save you a spring, but I won't send it until my 1500 parts arrive

dbrick wrote:Yes Sid, I'll save you a spring, but I won't send it until my 1500 parts arrive

Check's in the mail, I'm from the government and I'm here to help you, this will only hurt a little bit, I will still love you in the morning...

spl310 wrote:.....................this will only hurt a little bit, I will still love you in the morning...

OK, time for that restraining order.

OK you guys . . . you need to focus! Think springs.

Somebody has an upper tensioner for sale on ebay for a starting price of $179 . . . ouch! He had a photo with the spring in it and, scaling from the photo, it looks like the spring is longer than I thought. I'd ordered springs from 1.5 - 2.0 inches but the actual length may be more like 2.5 -3.0 but I can't be sure.

My spring assortment will arrive tomorrow so I can start playing.

Another search of the garage for the original spring was unproductive.

sfdaugherty wrote:OK you guys . . . you need to focus! Think springs.

Sproing!

I think they have ADD...LOL
Have you tried using the magnetic pointer tool to hopefully find it in the hiding places on the car?
Worth a try.

Linda

The spring measures 2 7/8" long .417" diameter and is .040 gauge and according to Dave has 25 lbs pressure.

Gary

Hold on there, boys. The installed pressure is nowhere near 25 lbs. I just reached into my engine and pushed the tensioner back into it's bore...took maybe a few pounds of pressure. The tensioner plunger's inside bore measures .433", so at 70PSI, you would get about 10 pounds of pressure( .433x.433x.7854x70=10.3)...not counting the leakage through the oil feed hole for the chain. If you had 30 pounds pushing on that rubber pad it would fail in no time. These tensioners are carbon copies of the ones used in my old Jag, and I have several to look at. The spring is about 2.6" long in those.

Gary: Thanks for the dimensions. As I suspected, the sample springs I ordered are too short (max 2") so I'll have to order some more to play with.

Lee2000: When I was playing with the tensioner (before I dropped it) it didn't require much force to push the plunger in so I think your estimate of the tension might be very close.

Linda: I was standing in front of my tool box when I dropped the tensioner, my 1600 was about 10 feet away and 7 feet up in the air on a lift so the chances of it landing there are small but probably worth a look. The 2000 was about 25 feet away and also on a lift but the lift was on the ground so again, chances are slim but I'm willing to look just about anywhere at this point.

Thanks for all the help guys. If I can't find the spring, I think I can find one that will work.

Shannon

As soon as I find my spring rate calculator formula, I'll calculate the spring rate of the Reynold (Jaguar) tensioner spring. I'm sure it's rate will be very close to our U20's.

Lee2000 wrote:Hold on there, boys. The installed pressure is nowhere near 25 lbs.

Sorry, I was unclear. What I meant to say was the total pressure exerted by the spring and running engine oil pressure calculated to about 25 psi, if my math and measurement was correct.
IIRC, I was calculating on a .625 piston and 80 psi, got 24.5 pounds force. Measured with my trusty Rapala fishing scale at about 25 pounds installed.
If the piston is indeed .433, then Lee's figure is correct and I have too much tension.
BTW, Where did the .7854 come from? I did {Pi x (Radius squared) for piston area }x pressure= force and got the same result.
Must be some College engineering shortcut?


My goal was to have the static pressure of the tensioner the same on start-up as under full running oil pressure, but not to be rigid, like shimming it tight..

Been 25 years since I rebuilt an E-Type, but didn't the Jag have a ratcheting chain tensioner?

The .7854 is the constant to find the area of a circle, diameter squared x .7854. It is Pi divided by 4. Story is, it came from a calculation/measurement made eons ago by a guy who actually laid out a grid of 10,000 equal squares, (100 x 100), drew a circle using some kind of compass, then counted the squares inside the circle...which came to 7854. I actually read this in "Marks Standard Handbook For Mechanical Engineers", years ago.

Forgot to mention, yes, the Jag style tensioner DOES have a ratchet system to take up the slack as things wear. Wish our engines had that same feature...no more death rattle, and no need for spacing washers.