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Are My Pulleys Wrong


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Got a v-belt to connect Bosch alternator on my v8.

The belt (ETC7394) seems to be a perfect fit for the alternator pulley but looks a bit small for the waterpump and crank pulleys.

To be honest I would rather use a wider belt, as in one that would better fit the waterpump pulley, especially as the alternator is 120A. But this would mean I would need a wider pulley for the alternator. Hmmmm.

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You need to use the correct belt and pulleys, if you use a belt too narrow it will ride in the gulley of the groove, rather than on the cheeks of the belt

Or to put it another way, you are better off using a wider belt than a narrow belt with mismatched pulleys

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Fair enough. The thing is my belt part number is what's listed for a v8 so I don't know why it would be too small for the standard pulleys?

Also, if I were to buy a wider belt (which I would like to do for reasons I mentioned above) what alternator pulley do I need??

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Looks to me as if you're trying to drive a 3.9 style alternator pulley using an early 3.5 setup. Your chances of getting this working on a 3.5 setup are slim, to say the least and also pretty risky given that you have a single belt driving everything. The biggest issue is that the length of belt makes it difficult to tension and prone to being thrown. With a high output alternator there's a good chance that you'll melt the belt and it's better if that only effects the alternator rather than also losing your cooling. I had a team mate who ran a similar setup and, on average, we'd have to fit a new belt maybe 3 or 4 times a day during competitions. Having said that, getting an alternator pulley for an early 3.5 should fix the immediate problem. I have a feeling that it's also a bigger diameter pulley than the one you have which may help with traction.

The 3.9 setup uses multiple belts rather than a single one with the water pump and power steering having their own belts from the crank and then the alternator driven off a second groove on the power steering pump pulley. The alternator uses a narrower belt than the other two and it looks to me as if that's the pulley you have. The main advantage of this configuration is that you can continue driving from the battery if the alternator belt dies - in the winter when SWMBO had everything turned on including the heated windscreen we'd occasionally lose a belt and she knew that as soon as the alternator light came on she had to turn everything off and head for home so I could fit a new one :)

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Thanks for the lengthy reply Dave.

I think the problem is there are so many different v8 configurations and I've tried to utilise the parts I have. I think the 3.9 setup you mention where the alternator had a separate belt to the power steering pump was where the alternator is mounted on the passenger side, whereas I have the power steering pump mounted there.

I really don't fancy having to change belts that often. If you were me how would you modify my setup to be more reliable? Other than going serpentine which I can't really afford right now.

Edit: I noticed that the pulley on my steering pump has a 2nd groove but I just assumed it was for air-con or something.. :(

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The late V belt setup had the power steering pump mounted in the same place and, as you say, the alternator mounted further out with a small belt between the power steering pump and the alternator. I may be wrong but I believe that Land Rover moved the alternator to the passenger side to make way for the air con pump which was fitted to the driver side in place of the alternator. Not sure of the exact changeover but all the EFi 3.5 and 3.9 engines I've seen have this setup, the carb V8s have the alternator on the RHS.

I think I'd look at driving the alternator off the power steering pump if it has the spare pulley as a sort of hybrid version of the two. If nothing else it means that if you do overload the belt the effect will be constrained to the alternator. On the later setup the alternator and power steering pump mounts were combined. An adjustable bar was then taken from the top of the alternator to a water pump bolt to provide the tension.

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..I think I'd look at driving the alternator off the power steering pump if it has the spare pulley as a sort of hybrid version of the two. If nothing else it means that if you do overload the belt the effect will be constrained to the alternator...

Sounds like a sensible idea but I've no idea how I would implement it. The alternator is mounted on the wrong side for that. The waterpump is completely in the way.

Edit: Sorry Dave, reading the last bit of your reply suggests I need to mount my alternator on the other side. Would the mount that I've attached be the one I need. Baring in mind I have the old style steering pump..

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I can't really make out your 2nd picture too clearly but my setup looks similar to this in so far as it has the alternator on drivers side and steering pump on passenger side.

If you look at the pics in my op you will see what I have. And if you take a look at the 2nd pic in my post above you will see what type of steering pump I have. It's just not shown in the pics as I took it off to paint the mounting bracket.

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Ok Dave I will pick up one.

So with the alternator and my steering pump both on the passenger side, please remind me what belt goes where?

Am I right in thinking the waterpump will have a belt all to itself from the crank, and the alternator and steering pump will be connected together with another belt?

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don't know if these will help, 3.5V8 Vee belt routing on pages 262/263 in http://www.retroanaconda.com/landrover/parts_books/110/3_engine_200TDI_300TDI_V8_p168-299.pdf

page 248 shows Alternator upper right as your is located

Yes that is exactly how I've done mine Ralph. The problem I have encountered though as I mentioned in OP, is the fact that the alternator belt I've got seems to narrow for the waterpump and crank pulleys. But strangely it's perfect for my alternator pulley.

If I could find a pulley that would fit my Bosch alternator and would allow for a belt that matches the waterpump and crank pulleys that would suffice until I change to a serpentine setup..

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I think your misunderstanding me Ralph. It isn't the belt that's the problem. If I get a belt that properly fits the waterpump and crank pulleys, it will be too big for the alternator pulley.

My alternator pulley is a smaller diameter than my waterpump and crank pulleys.

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With you on the belt width, for example there are 10mm & 11mm wide Vee belts for 200tdi engines

alt pulley has to be certain diameter to allow the alternator to work at the optimum rpm, suspect the groove width is the same for all.

found 3 different alternator pulleys common to 3.5 V8 & 4 cylinder engines & Tdi's

RTC5686 http://www.lrseries.com/shop/product/listing/10956/RTC5686-ALTERNATOR-PULLEY.html?search=rtc5686&page=1

568788 http://www.lrseries.com/shop/product/listing/1406/568788-ALTERNATOR-PULLEY-SINGLE-GROOVE.html?search=568788&page=1

ERC8986 http://www.brit-car.co.uk/product.php/144430/0/pulley

pretty much all seem to use similar size belts

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My apologies. I've been saying pulley diameter when I should be saying groove width.

It's the width that seems wrong. The groove width of my waterpump and crank pulleys are way too big for my belt. Yet it seems perfect for the alternator. See my 1st pic in OP. The belt fits the alternator groove perfectly but not the waterpump and crank. I'm stumped here :(

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