Chain noise

[Aurel]

Lately, my engine developed a distinct chain noise at high mid to high rpms. It is especially frustrating since I rebuilt it with upgraded chain idler arms and pressure fed tensioners only two years ago. So, I did a partial engine drop for valve adjustment, and removed my chain covers to investigate. The passenger side was nice and tight. But on the driver side, I found the chain not as tight, could lift it about 10 mm from the ramp. And also, the idler arm can move back and forth on its axis by at least 1mm. Questions: 1. How can I tell for sure if my tensioner is bad? 2. Is the back and forth play on the idler arm axis normal or not?

[Aurel]

OK I did a little search, and the play on the idler arm is normal. We are only left with a possibly bad tensioner. I noticed it is less extended than on the other side.

[snbush67]

Check to make sure the nipple didn't come detached.

[Aurel]

Originally Posted by snbush67

Check to make sure the nipple didn't come detached.

The nipple is still there. But the tensioner is extended only 7 mm on the drive side, versus 11 mm on the passenger side. Shouldn't they be the same? Also, I was wondering if the tension increases when oil pressure gets to them? If not, then the chain is definitely too lose on the driver side.

[Aurel]

I removed the tensioner, and I can compress it fully by hand! I really think it is toast. My plan is to revert back to my old setup with safety collars. I still have the old chain covers and the old tensioners, which are very strong. No way I could compress those by hand.

[snbush67]

It may not be toast, compare it to the resistance from the other tensioner. The running resistance is greater as they have the pressure from the oil.

I believe that you can disassemble and repair it as well, I haven't had one apart in a while. This would be a good time to bullet proof them by doing the "Jerry Woods Mod". Quoted below for your convenience;

Originally Posted by aigel

All right folks, I thought I should write this up, since I have done this to my engine and believe that it is an easy and highly valuable upgrade: Fail safing the pressure fed tensioners, the "Jerry Woods mod". I'll be happy to submit this as a tech article if it is desired:

Jerry Woods uses a special tweak to limit travel on the oil fed tensioners. According to Jerry, oil fed tensioners can see very rare failures caused by oscillations of the chains if an engine runs at very high rpm and then abruptly drops to low rpm. Timing can jump and this can lead to terminal engine damage.

For this modification, disassemble the chain tensioners by taking out the grenade pin and then the c clip retainer pin. Remove the spring. (Figure 1) Put it back together with the spring removed and install the tensioner. Measure the total travel between the collapsed tensioner and the fully tensioned idler arm as indicated in Figure 2.

Now remove the tensioner again and limit the total available travel to 1/8" by installing a piece of tubing into the bottom of the tensioner that is 1/8" shorter than the measured total travel. The tubing has to be 5/8" outer diameter and about 1.5 mm wall thickness. This has to be a hollow cylinder, becase oil is flowing through it and the spring has to go through it also, to keep the forces the same. Hydraulic tubing is a good choice but I had found bronze bushings at the hardware store that had the perfect dimensions. Figure 3 shows this limiting tubing cut to length, together with the piston and spring, before it is installed back into the tensioner housing.

Throw away the grenade pin and the C clip retainer because they will not fit with the limited travel, and are not needed once the tensioner is installed. In the unlikely case that you ever have to take apart a Jerry Woods assembled engine, you will notice that the tensioners have the c-clip missing and the tensioner piston travel is limited. According to Jerry, all his engines (even the stock rebuilds) get this final tweak to race proof oil fed chain tensioners.

Figure 1


Figure 2


Figure 3

[snbush67]

Here is a link to the thread:

Shops that don't recommend Carrera Tensioner Update?

[Aurel]

Thanks Shane, I was just looking at this thread. In fact, I already dismantled my tensioner, and unlike the old style tensioners, there are no o-rings that can fail. The only part that could fail is the spring, and mine looks fine. So, my new plan is to refresh them by adding grease on the piston, and do the Jerry wood modification for peace of mind. Then, if the chain noise is stil there, I have bigger problems...