Well crud...are these solid chain tensioners?

[75 911s]

Hey guys,

I think I opened a can of worms. I picked up the chain tensioner safety collars, new ramps and a gasket kit. I've been chasing a bit of noise that I thought was a valve ticking, but after adjusting the valves many times, I still had noise. I decided to check out the chain tensioners and make sure they weren't about to blow my motor up.

The motor had a partial top end rebuild in '83 and I think I know now why. My theory is the chain tensioner failed, which ended up bending a few of the valves on the right side. I think one piston was replaced as well.

Fast forward to today when I took off the cam housing covers and saw these...



You can see someone has modified the tensioner to be "solid"



I found some information saying that this doesn't allow the chain to flex and basically stretches out the chain.



Of course the fix is hydraulic tensioners but the full kit is not in the budget right now. I was thinking of just buttoning it back up. Just wondering if anyone can tell if my chain is stretched.

I have no idea how long this has been like this. The chain ramps look good, there is a little wear on the sprockets but not much.

What do you think? Anyone have experience with this mod?

[stownsen914]

There's nothing fundamentally wrong with solid tensioners, but they do need to be adjusted from time to time, which is why you see them mostly on race cars. If your chains have loosened over time, there could be some slack and cause the noise you heard. Any slack in the chains?

Scott

[75 911s]

Scott,

Thanks for the info. There is about 1-3mm of slack in the chain currently. By slack I mean I can press down firmly here and the chain can move about 2mm. It's a firm press, and the chain moves a bit - it's not like the chain has slack like a bike chain.

[ossiblue]

Originally Posted by stownsen914

There's nothing fundamentally wrong with solid tensioners, but they do need to be adjusted from time to time, which is why you see them mostly on race cars. If your chains have loosened over time, there could be some slack and cause the noise you heard. Any slack in the chains?

Scott

This^^.

When you say the hydraulic tensioner "full kit is not in the budget", it sounds like you are speaking of the carrera pressure fed kit rather than basic hydraulic tensioners. What you have are hydraulic tensioners which have been converted to "solid." I've never heard of an issue with solids causing chains to stretch, but I'm no expert either. The major issue with solids is, as mentioned before, the necessity of adjusting to take out slack.

[75 911s]

Thanks L.J.,

You're right. I thought mine were only spring loaded. I take it they originally had oil inside before the solid mod?
And, yes, I was referring to the Carrera pressure fed kit.

[Daves911L]

Its not about allowing the chain to flex. Its about thermal expansion of the various components. The hydraulically damped tensioner (either sealed or pressure fed) allows the chain to be under proper tension at all times from cold start to fully hot. The solid tensioner can apply the correct tension at only one particular temperature, and it is either too loose or too tight at every other temperature. If too loose it flops around a little, can make some noise, and allow slight variations in can timing. If too tight it accelerates wear of the chain sprockets, intermediate shaft bearing, and cam nose bearing. In theory the solid tensioner can be adjusted to correctly tension the chan at normal operating temperature. But there is a lot of subjectivity to the adjustment. The solid tensioners will not destroy an engine (unless extremely mal-adjusted), but the hydraulically damped factory units are preferable. It is not just the chains that "stretch" (not really stretching, but wearing) the sprockets are all wearing too.

[Jack Stands]

I don't know the cost of new tensioners (not the hydraulic Carrera ones), but posting a WTB ad in the classified section may turn up some used ones from folks that have converted to the pressure fed tensioners. The old style can be rebuilt as well if needed (assuming the kits are still available).

[75 911s]

Thanks guys I was offered a good deal on original sealed hydraulic same part number tensioners.

Do you think it would be worth the trouble to swap them and put the collars on that I already bought? Or would you leave well enough alone as I plan a rebuild in a few thousand miles anyway and at that point I'll upgrade to the Carerra style.

Motor is in still in. I would clamp the chain and have already marked the sprockets and chain.

[pmax]

Originally Posted by 75 911s

Hey guys,

I think I opened a can of worms. I picked up the chain tensioner safety collars, new ramps and a gasket kit. I've been chasing a bit of noise that I thought was a valve ticking, but after adjusting the valves many times, I still had noise.

I suggest posting a video of the engine noise before you go "updating" the engine.

[DanielDudley]

Originally Posted by Daves911L

Its not about allowing the chain to flex. Its about thermal expansion of the various components. The hydraulically damped tensioner (either sealed or pressure fed) allows the chain to be under proper tension at all times from cold start to fully hot. The solid tensioner can apply the correct tension at only one particular temperature, and it is either too loose or too tight at every other temperature. If too loose it flops around a little, can make some noise, and allow slight variations in can timing. If too tight it accelerates wear of the chain sprockets, intermediate shaft bearing, and cam nose bearing. In theory the solid tensioner can be adjusted to correctly tension the chan at normal operating temperature. But there is a lot of subjectivity to the adjustment. The solid tensioners will not destroy an engine (unless extremely mal-adjusted), but the hydraulically damped factory units are preferable. It is not just the chains that "stretch" (not really stretching, but wearing) the sprockets are all wearing too.

THIS. ^^^^ And what will screw you is if the intermediate shaft bearing wears, and you get low oil pressure when hot.

If you have good oil pressure at temp, you probably dodged that bullet, and most likely the others as well.

[DanielDudley]

Originally Posted by pmax

I suggest posting a video of the engine noise before you go "updating" the engine.

I've heard it said that a tappy engine is a happy engine. It may not be totally good, but it doesn't have to be bad. Some engines sound a little thrashy, especially at idle.

Your adjustments could be a little loose, you could have a leaky exhaust at the heat exchanger to cylinder head, you could have a bunch of other scarier things (unlikely), or you could just be an excitable boy. I know I am.

[75 911s]

Oil pressure seems good from what I've seen. Here's a video. You can hear a little chattering around the revs... Nothing to write home about, but like you said, sometimes you get a little excitable.

[Flat6pac]

The mechanical tensioners, when adjusted, are only correct at the adjusted setting. As the motor warms the chain stretches and is out of adjustment. The chain stretches with heat and you need the hydraulic adjustment or you get the rattle.
Bruce