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Custom serpentine belt tensioner

Old 08-18-2017, 09:49 AM
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Custom serpentine belt tensioner

So.. I have my blower on the passenger side. Right now I have a tensioner over there, but I want to change to a double plate blower mount and that would stack it out too far to run an idler or tensioner for the serp.

So I was thinking of running a standard rotation water pump, and running the routing like the attached diagram.

I need to make a tensioner that will bolt to the top two bolts on the alt bracket, and attach an idler pulley that I can make go up and down.

Similar to how a procharger tensioner is setup. I kinda think I know what I need, I think, but I don't know what those parts are called.

-- Joe
Attached Thumbnails Custom serpentine belt tensioner-serp_routing_modified.jpg   Custom serpentine belt tensioner-img_20170818_171743.jpg  

Last edited by anesthes; 08-18-2017 at 04:26 PM.
Old 08-18-2017, 07:49 PM
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Re: Custom serpentine belt tensioner

You might have a problem with not enough belt wrap on the water pump pulley.
Instead of using the 1 serpentine belt, could you add an additional belt?
Old 08-18-2017, 09:19 PM
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Re: Custom serpentine belt tensioner

Originally Posted by NoEmissions84TA
You might have a problem with not enough belt wrap on the water pump pulley.
Instead of using the 1 serpentine belt, could you add an additional belt?
I was thinking if I make a bracket of some sort for the tensioner, I can run it real low like this:




I'd think that would be enough?

Basically, I need a bracket that will allow the pulley to go up or down.

-- Joe
Old 08-18-2017, 11:59 PM
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Re: Custom serpentine belt tensioner

That would do it if you can fit it in there.
Old 08-19-2017, 09:57 AM
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Re: Custom serpentine belt tensioner

Originally Posted by NoEmissions84TA
That would do it if you can fit it in there.
I wonder if making a bracket to mount a tensioner to these bolts would be a good idea..

-- Joe


Old 08-19-2017, 07:08 PM
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Re: Custom serpentine belt tensioner

It looks like you don't have many mounting options.

See if you like this. Your current tensioner would have to become an idler pulley, you still have to find a way to mount the tensioner on the right side by the alternator, but you could still use the CCW rotation water pump. This setup gives you terrific belt wrap on all pulleys, and frees up the entire left side for your blower. If you could design 1 plate that mounts both the tensioner and idler pulley.......
Attached Thumbnails Custom serpentine belt tensioner-serpentine-2.jpg  
Old 08-23-2017, 08:09 PM
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Re: Custom serpentine belt tensioner

Originally Posted by NoEmissions84TA
It looks like you don't have many mounting options.

See if you like this. Your current tensioner would have to become an idler pulley, you still have to find a way to mount the tensioner on the right side by the alternator, but you could still use the CCW rotation water pump. This setup gives you terrific belt wrap on all pulleys, and frees up the entire left side for your blower. If you could design 1 plate that mounts both the tensioner and idler pulley.......
Ive been thinking about doing something similar to this too. wouldn't swapping out the existing tensioner with one the works the opposite direction work?
as is the belt runs under it with smooth side running on wheel. replace it with a grooved wheel and run belt over it with grooves running on wheel. if the belt was short enough the tensioner should still work or would it need to apply tension the other direction too?

but i guess this way you would have to leave that bracket that holds the AC and smog pump or fab up a new mount for the tensioner
Old 08-23-2017, 08:36 PM
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Re: Custom serpentine belt tensioner

Originally Posted by sid 91RS
Ive been thinking about doing something similar to this too. wouldn't swapping out the existing tensioner with one the works the opposite direction work?
as is the belt runs under it with smooth side running on wheel. replace it with a grooved wheel and run belt over it with grooves running on wheel. if the belt was short enough the tensioner should still work or would it need to apply tension the other direction too?

but i guess this way you would have to leave that bracket that holds the AC and smog pump or fab up a new mount for the tensioner
My supercharger is on the passenger side, and I have a miniram intake so I can't put any pulleys on the passenger side of the water pump.

I'm fabricating a tensioner bracket based on Eclipse alternator tensioner. (screw type).

Hopefully I'll have some time this weekend to finish it.

-- Joe
Old 08-23-2017, 09:21 PM
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Re: Custom serpentine belt tensioner

Joe, just for brainstorming, look at the BMW tensioner used on an E36? 6 cyl. M3, a I think it is. There is a rotational spring style. Then, there is a "hydraulic" which, if I had to describe it, is a short, fat chihuahua trunk strut on a triangle bracket.

If you turned those two bolts into the driver's side head into studs and made up a plate / platform mointed to those, would a tensioner similar to the third gen 88-92 V8 tensioner have space to bolt up? If not, would a tensioner with the pulley side-by-side with it fit better?

Ever think of making the alternator act as a tensioner? Maybe ditch the as-is DS bracket, create a bracket that can pivot (and be acted upon by a tensioner, instead of a pulley,) and the alt. bolt to the custome bracket? Tough to make elegant, but it would reduce the need for idler and tensioner pulleys.
Old 08-24-2017, 03:42 AM
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Re: Custom serpentine belt tensioner

Originally Posted by jmd
Ever think of making the alternator act as a tensioner? Maybe ditch the as-is DS bracket, create a bracket that can pivot (and be acted upon by a tensioner, instead of a pulley,) and the alt. bolt to the custom bracket? Tough to make elegant, but it would reduce the need for idler and tensioner pulleys.
Now there is another good idea.
Old 08-25-2017, 04:59 AM
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Re: Custom serpentine belt tensioner

Originally Posted by NoEmissions84TA
Now there is another good idea.
So I did this. I think it will work:
Attached Thumbnails Custom serpentine belt tensioner-img_20170824_160920.jpg  
Old 08-25-2017, 05:59 PM
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Re: Custom serpentine belt tensioner

That will work.
Now if there were a way to put a spring inside of that adjuster to turn it into a tensioner.....

I found these. Does this give you any good ideas?


http://www.hutchinsontransmission.co...near-tensioner
http://www.hutchinsontransmission.co...ulic-tensioner

Last edited by NoEmissions84TA; 08-25-2017 at 06:10 PM.
Old 09-04-2017, 06:44 PM
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Re: Custom serpentine belt tensioner

I recently noticed the new LT1 Camaro and othe Gen V engine applications have a "shock absorber" type tensioner design as well.

Joe, nice belt wrap. That upper bolt location makes me nervous it may NVH itself to death some day, so thanks for being a guinea pig.
Old 12-30-2017, 11:07 PM
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Re: Custom serpentine belt tensioner

Man allot of engineering going on here. Pic of mine. Never had a problem. Cut the alternator bracket and added an adjustable helm joint.
Attached Thumbnails Custom serpentine belt tensioner-img_0738.jpg  
Old 12-31-2017, 08:21 AM
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Re: Custom serpentine belt tensioner

Originally Posted by grover85
Pic of mine. Never had a problem.
Grover, You have almost no belt wrap on the water pump. I'm surprised you don't get slippage and have overheating problems.
Old 12-31-2017, 09:14 AM
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Re: Custom serpentine belt tensioner

Originally Posted by MoJoe
Grover, You have almost no belt wrap on the water pump. I'm surprised you don't get slippage and have overheating problems.
Had over 10k miles on this setup cooling a 406ci engine. Never saw over 180 degrees ever. Had a t56 behind it that I would shift at 6-6500 rpms spraying a 150 shot. I would say it had enough belt wrap. You have to remember water pump drag is not that heavy.
Old 12-31-2017, 11:42 AM
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Re: Custom serpentine belt tensioner

Here is how I did mine:




Standard rotation water pump.

-- Joe


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