Mechanical Tensioners

jjone20 · jjone20's Garage

My 79SC has a Dymo label in the drivers door jamb that reads: "MECH TENS INSTALLED 18K" I asked the local P-car mechanic what that meant, and he said "Oh, full mechanical tensioners. Get them out or you'll stretch your chains". Having not heard of this before, I thought I'd ask you-all. Thoughts?

David · David's Garage

Yes, you should replace them. They will overstretch your chains unless they were set very loose and then you'll have other problems. You can save the tensioners for setting your cams if you do a rebuild.

jjone20 · jjone20's Garage

Trying not to sound too ignorant, but given the installation at 18 K miles, I'm now at 102K, is the stretching progressive? The mechanic also said that the full mechanicals will not fail like the stock ones. I was planning a conversion to Carrera tensioners at some point soon, but I guess I need to know how critical the stretching issue is. Thanks.

David · David's Garage

Sounds like with that many miles any damage has already been done. You could pull the covers off and check them. If you don't hear anything you may be fine for a while. You'll just have to put new chains with a masterlink in when you change tensioners.

jjone20 · jjone20's Garage

Thanks. I don't hear anything now with the old screw driver, but I'll keep an eye (ear) on it. What's the effect of the stretched chains - accuracy of cam timing?

David · David's Garage

I would think just cam timing until it slips a tooth. I think it would have to be very loose to actually jump a tooth. I've never heard what a loose one sounds like so I couldn't say if you'll hear it or not.

erobinson · 10:56 AM

I second what 125 shifter says about these. Even though I have a set in my current engine, its only temporary. The chains are near end of life and the tensioners helped the situation. They adjusted out a little further than the mechanicals. If you continue forth with the mechanicals, make checking their tension and the chains a regular service procedure. Also keep a good eye on the ramps, a loose chain can cause havoc with an old brittle chain ramp. And become familiar with the chain replacement procedure

Jeff Higgins · 10-04-2005, 10:46 AM

There is a difference between "mechanical" and "solid" tensioners. It sounds like there may be some confusion over this regarding your car. I would pop a cam chain cover off and take a look. Just drop the muffler, the tin that is fastened to to covers, and one of the covers. It should take all of half an hour to check. Oh - and make sure you drain the oil first.

If it has "mechanical" tensioners I wouldn't worry; just make sure they have either the collars or the Woods mod (bushing in the bottom to prevent total collapse).

If they are in fact true "solids" I would replace them with the mechanicals. If they were set up loose enough they should not have damaged anything at all. Too tight is what does the damage - it puts one hell of a side load on the layshaft and cam bearings on the sprocket ends that they are not designed to take, plus it eats up the sprockets.

I would be surprised with 102k on the motor if it turns out it actually has solids in it. If they were put in at 18k, one would assume (hope?) that they have had several checks/adjustments since then. If not, they would be pretty darn loose and noisy by now and your screwdriver check should pick that up. So, I would verify what's in there before you go much further.

erobinson · 10-04-2005, 10:58 AM

I hadnt even thought of that...I just assumed if they put a sticker in the door jam they would be the solid tensioners.