Serpentine Belt / Pulley Conversion?

A regular run of the mill 1.6 sohc 8 valve engine uses a multi rib drive belt... the parts will all interchange with a regular run of the mill 1500 sohc

grainy, but large cutaway pic of a 1581cc sohc, showing drive belt/pump/alternator and tensioner...

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After 5 years the tensioner pivot arm failed. Back then, I had no TIG, and had braised the pivot attaching flange nut to the arm (bottom of pic)

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The braise failed & the tensioner dropped this past Wednesday evening. Fortunately, just before I was pulling into a parking lot & not on the highway to or from work. I extracted the arm from the engine bay & drove the car the mile home off the battery. Short enough drive that the engine coolant temp only started to go over normal as I pulled into the driveway & shut it down.

I remade the tensioner pivot, and TIG welded the flange nut this time. Replaced the belt, and it's all good for now. Options for 5 rib belts are not great however, so I'm gettting a 6 rib NASCAR 3.33" pulley to replace the 5 rib I installed some years back. All the other pulleys I used are 6 rib, so this will give me more options in terms of belt quality/price options. I prefer the 'softer' Conti belts to the "hard" shell Gates, etc., available in the 5 rib variety, which seem to be very noisy. I'd really like to devise a way to incorporate an auto tensioner for this, but I cannot see any way for that to happen given the space limitations with AC. Obviously, I don't need to do any of this since I'm pulling the motor this year, however I'd like it to be good for more than 5 years at a time for whomever I sell it all to.

No pics of the replacement pivot.
 
Glad you were able to get it sorted without a lot of problem. That actually lasted quite well for a brazed joint with a rather considerable load and vibration on it. I know you've done a number of excellent brazed pieces and you do a good job of it. For some reason I've never been extremely successful at things like brazing or soldering. I always try to get too much filler in there or too hot or something, and it ends up a mess. :oops:
 
3.33" OD pulley arrived. Finally had time to swap out the 3.25" for my original 4" 5 rib pulley, so I can keep driving it. I'm now curious what OD the old v belt pulley is considered, it's 4" OD, but the belt doesn't ride the outer rim, so I'm wondering whether the seat of the VBelt in the groove is a more appropriate depth to gauge running diameter. If so, it would be closer to 3.5", IMO.

The reason for my questioning lies in the fact that with the 4" serpentine, the speed/stop/idle temp rises (in summer weather), vs. the 3.25" which runs evenly regardless, which would suggest the pump runs too slow at idle with 4" OD.

Anyway, I'll get the 6 rib 3.33" pulley machined & bolt pattern drilled to match the 3.25", and switch over to the wider belt.

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I would be fun to do some real testing of pulley drive ratios, to see the effect on engine temps.

On a related note I find it very interesting that on the A/C version, Fiat opted to run not only a smaller water pump body, but also a smaller crank pulley - further reducing the water pump's output. And that's on a engine that has to work harder just to drive the A/C compressor. Not to mention the A/C condenser is sitting in front of the rad, blocking it's airflow plus adding hot air to the mix. Poor guy never had a chance.
 
Dr.Jeff said:
I would be fun to do some real testing of pulley drive ratios, to see the effect on engine temps.

On a related note I find it very interesting that on the A/C version, Fiat opted to run not only a smaller water pump body, but also a smaller crank pulley - further reducing the water pump's output. And that's on a engine that has to work harder just to drive the A/C compressor. Not to mention the A/C condenser is sitting in front of the rad, blocking it's airflow plus adding hot air to the mix. Poor guy never had a chance.
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Non AC W/pump has a larger (than AC version) pulley - so smaller AC setup crank pulley & smaller w/pump pulley prolly cancels out....
 
And in New Mexico heat I noticed no special tendency to get hot with the stock set up. So something went right with that set up
 
LarryC said:
And in New Mexico heat I noticed no special tendency to get hot with the stock set up. So something went right with that set up
Click to expand...

But.... you have to deal with nasty old v-belts :D for that. I think it's funny that a few members who live in hot year-round climates have had no cooling system issues. Maybe it's the up & down climates that screw with it.
 
lookforjoe said:
Non AC W/pump has a larger (than AC version) pulley
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I did not realize that. I assumed they were the same diameter on the water pumps, but I had not compared them to see. If the ratio between the water pump and crank are the same for both engines (A/C and non-A/C), then the smaller A/C style (underdrive) crank pulley could be a very minor performance upgrade for non-A/C cars that are not cooling challenged like A/C cars are. :D
Or vice-versa, modify the smaller A/C style water pump pulley to fit on a non-A/C pump (while retaining the larger crank pulley) to increase its cooling performance.
One thought I've had for my A/C car is to rework the whole water pump / alternator / compressor arrangement to allow the use of the regular size water pump (while retaining the A/C). Not just because of the cooling system losses the A/C brings (condenser/rad, engine load, etc), but because of the extreme climate I'm in.


lookforjoe said:
I think it's funny that a few members who live in hot year-round climates have had no cooling system issues.
Click to expand...
It may be possible that living in a really hot climate you know that proper maintenance and function of your cooling system is vital to survival. So you make sure everything is in top condition, service/maintain it regularly, and keep an eye on things. Those steps might not be as critical to others and easily neglected, relatively speaking. With a cooling system design that is somewhat marginal to begin with, it wouldn't take much to push it over the edge. ;)
 
It could be that running the stock set up right down to a maximum of 10 degrees of initial advance is the secret. Once you bump up the power out put, advance the timing, and do other performance things, things get hotter real quick. That requires some sort of upgrade to the cooling capacity. I will bet that super high output fans and a well-maintained cooling system could be the way to resolve the issue.
 
Larry, do you also find that in the simmering heat of our summer weather, most drivers seem to behave as if their brains have been fried and putt along at a annoyingly slow pace? The slower speeds with reduced RPM's may also reduce operating temps. :D
 
Got the machine work done on the pulley, sleeve inserted.


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I had to then install it, check the sleeve depth to get the correct offset, remove it again, weld the sleeve, then reassemble.

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The 6 rib belt (6PK1355) I ordered is longer than it's 5 rib counterpart, even though it's listed as the same length. As a result, I has to switch out the idler pulley for a 3" to get the proper range

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The issue now is that with the larger idler, the reduced gap between crank pulley and AC compressor has effected the belt alignment/acceptable deflection. Belt is riding on the outer ridge of the clutch & making a hell of a racket. I thought the water pump was shot, it sounded so bad. I may need to move the compressor out another 1/16-3/32" to resolve that, or get a shorter belt (6PK1335) & switch back to the smaller (2.5") idler. I'm leaning toward the latter. 3" pulley options are limited, for DTR servicing.
 
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New shorter belt is not coming til tomorrow, so I moved the AC compressor out 1/8", and had the machine shop clean up the inner pulley seat, which I had compromised in terms of pulley runout in the welding process. With those two things, the belt rides nice & true and is quiet :D I'll save the new belt as a spare, it can be used with the smaller pulleys I have plenty of.


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