timing belt tensioner

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tonkatoy189
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timing belt tensioner

Post by tonkatoy189 » Sun May 28, 2006 11:07 am

ok, im sure this question has been asked before.

i have the standard timing belt tensioner on my 82 gtv6. even after a rebuild it still makes a mess. the engine i had in the car previously had the mechanical tensioner from IAP in it. it seemed to work fine. recently i read somewhere on the web that these mechanical tensioners often fail. i read something about retanining the origional hydraulic tensioner, pluging the oil holes and filling it with grease. whats the story with this? what's peoples opinion on timing belt tensioners?

thanks
david
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Peab
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Post by Peab » Mon May 29, 2006 10:48 am

I started a thread on this topic a few months ago. Turns out there are many different opinions on this subject.

You have the three possibilities as you mention. Hydraulic, mechanical and the plugged hydraulic type. I had the same experience as you with the hydraulic tensioner. Leaking even after fresh rebuilds. So personally i don't like this. But the true believers will tell you this is the best detensioner you can have when it is working properly. It seems to me that the plugged hydraulic type is the one that have caused the least of problems for the users. I used this before and never had any problems with it. But it will require some rework on your engine to convert to this type. I have now the mechanical type on my engine, and so far so good. I think this is the easiest to install. But some people here will tell you it is worthless crap, that is prone to failure. So it is really your call to make your choice.
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dcefali
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Post by dcefali » Sat Jun 03, 2006 7:57 am

It seems that the general consensus is that a plugged hydraulic tensioner is the way to go, so when I plugged mine and went with it. No problems. Mine had a mechanical tensioner on it when I bought it, and it was broken of course. Because it had the mechanical type, the conversion was easier since the oil gallery was already plugged.

Doug
1986 GTV6 3.0
1991 Spider
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x-rad
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Post by x-rad » Sat Jun 03, 2006 10:53 am

The purpose of the hydraulic tensioner is to actually 'decrease' tension as the engine block expands from heat absorption. Several solutions are as mentioned above. Also, someone designed a set tensioner (set it and forget it) but the belt is looser cold than when the engine is warm (cam slip?).

I have a plugged oil type in which I have replaced the original internal spring with a firmer spring (~25lbs). I was hoping to create a constant tension device. As the block expands, the force of the timing belt should compress the tensioner pulley.

However, the physics of the tensioner arm allow much more leverage for expansion rather than compression. And, the throw of the arm is limited. It is possible to design a constant force tensioner (many vehicles have them) but add the block and head expansion and this becomes more difficult. There needs to be an almost direct acting system so that the belt is tight when engine is cool and the force of the belt on a heated engine can compress the system, while it maintains fairly constant pressure. I have been trying to adapt other common junk yard tensioners (Ford, etc..) but have had no luck yet.

If you use a fixed tensioner, I would think that setting it while engine is warm is better. I have set a fixed system while engine cold and checked it hot and there is a significant timing belt tension difference.

Anyone else???
tonkatoy189
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Post by tonkatoy189 » Sat Jun 03, 2006 2:18 pm

thanks for the tips. i think i'm going to keep the oil type and block off the oil passage. first i get to replace all the drive shaft guibos. more fun.

thanks
david
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Post by x-rad » Sat Jun 03, 2006 2:21 pm

Here is my latest thought:

old 'new' style thermo tensioner for Milano, gtv6, and new (mid 1990s)thermo tensioner for the 156,166, etc..

Dimensions are similar. Slightly increased arc in newest style. There is a belt guide on the pulley, too. I know the newest style tensioner is for the x4 cam 24v, but looks like the belt path is over top of the pulley like on the older 2.5, 3.0's. Or, maybe it runs below the pulley??? I know Alfa made a few changes to the new block but maybe, the newest (mid 90's) tensioner is an improvement????

The quality of this 'made in Canada?' piece appears pretty good....
Attachments
aa.jpg
Older style thermo tensioner
aa.jpg (22.53 KiB) Viewed 3339 times
8c_1.jpg
Newer style thermo tensioner
8c_1.jpg (25.14 KiB) Viewed 3340 times
cf_1.jpg
Newer style thermo tensioner
cf_1.jpg (22.46 KiB) Viewed 3339 times
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Post by x-rad » Fri Jun 09, 2006 8:49 am

Anybody try the newer (see above post) tensioner on the older 3.0L's?
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