Mechanical Chain tensioner DIY. Recycle those tensioners!

[whackit]

I made a set of mechanical tensioners out of my old tensioners. It's simple.

With all the carrera upgrades out there I thought this would be a useful DIY as they are imperative to setting cam timing properly. Why spend $90 when you probably have everything you need.



Gut your old tensioners as follows:

1. Remove the circlip from around the inside of the tensioner. A small screwdriver in the slot on the side will pop it right out. You may need to rotate the circlip a little. Wear glasses!

2. Remove the inner sprins and stuff that falls out.

3. remove M6 bolt on side

4. Pull center plug out by grasping on either side of piston shaft with needle nose pliers. Grab the bushing. not the actual shaft. it should pull out easily.

5. Undo the circlip in the middle by inserting a screwdriver in the bore where the M6 bolt was. Hold tensioner away from you as a bunch of springs and stuff will eject when circlip pops.

Fabricate center:
1. Using a 1 1/4" hole saw drill a piece of 1/4" steel. The resulting "donut" that comes from the cutout is a perfect fit for the gutted tensioner.

2. You can either thread the center of the donut or weld a nut onto the back.

3. Weld or JB weld Donut into top of center.

4. Insert Bolt

5. You can use a longer M6 Bolt in the old hole as a locknut.

Voila. Hope this helps some people as so many have helped me here.

[Henry Schmidt]

Perhaps even simpler.
Threaded aluminum insert. These were made to press fit in for secure operation.
Note that the tensioner housing has been trimmed down about 8 mm ( simple grinder will do). That is so when you install new chain you will have enough clearance for a lock/jam nut.
The tensioners above may offer a challenge with new chains.

[whackit]

they actually work fine with new chains. you bottom out the bolt and use the m6 hole on the side as the locknut... like a set screw.

although it's no surprise that you came up with something better Henry! I was going for the ghetto approach....

[Henry Schmidt]

Necessity is the mother of invention & sometimes inventions need tweaking.
Back in the eighties when we started playing around with solid tensioners we tried the set screw method.
We found after hard driving and heat cycles that it was common for the 8 mm center bolt to come loose. That is why we changed to the jam nut method.

[whackit]

For sure yours are better if you are going to run them to run them! I intended mine solely for use as tools.

[Henry Schmidt]

Originally Posted by whackit

For sure yours are better if you are going to run them to run them! I intended mine solely for use as tools.

Originally Posted by Henry Schmidt

.....edit......We found after hard driving and heat cycles that it was common for the 8 mm center bolt to come loose. That is why we changed to the jam nut method.

The information is cautionary. When items / new ideas are posted it is important to vet/ examine them so others may succeed with a modicum of aggravation.
Keep up the innovative thinking and please don't be discouraged by advise forged with experience.

BTW: it will be a challenge to get the adjustment correct on the first time. Remember the a mag case engine will grown in magnitudes faster than the chain. This means that when adjusting the chains they must be very loose. We use the finger nail method. Turn the engine in reverse, go to the exposed chain rail and lift the chain off the rail with your finger nail. It should lift about 12 to 13 mm. This is a subjective measurement that requires time to master. If the chain is too loose it will slap when the engine is cold. If it is too tight the engine will whine and you will experience premature chain and sprocket wear. I have see them so tight that the case distorted at the intermediate shaft bearing.
Setting them loose with the intention of adjusting them after the chain settles, is a great Idea. Generally 15k-20k miles. The necessity for adjustment is why we rarely use solid tensioners on a street car. With a race car you rarely see enough miles to necessitate an adjustment. Race cars are generally wormed up before running which make the slight occurrence of chain slap less bothersome. They rattle a little until the engine worms up and the assembly grows.
Good luck..

[SCrescue]

I'm going to take your advice Henry and shave them down as you recommend. I installed new chains and it definitely doesn't look like there'd be enough clearance to allow adjustment.

Mike...